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FINAL REPORTBOMBAY SEWAGE DISPOSAL PROJECT

BHANDUP AND GHATKOPAR

SPONSORMUNICIPAL CORPORATION OF GREATER BOMBAY

0~~

National Environmental Engineering Research InstituteJanuary 1995

FOREWORD

Munidpal Corporation of Greater Bombay (MCGB) is in the process ofimplementing wastewater treatment and disposal schemes with the World Bankassistance. These schemes are planned under the Bombay Sewage DisposalProject and envisage disposal of preliminary treated sewage from Colaba, Bandraand Worli drainage zones through marine outfalls into the Arabian Sea, treatedwastewaters from aerated lagoons at Versova and Malad into Malad Creek, andfrom aorated lagoons at Bhandup and Ghatkopar into Thane Creek.Implementation of the proposed facilities is expected to significantly improvebeaches dnd coastal water quality in and around Bombay. The large scaleconstruction activities, however, have potential adverse environmental impacts.

MCGB reained the National Environmental Engineering Research Institute(NEERI), in September 1991, for assessing the potential impacts of theconstruction and operation of the proposed facilities. The first report on the studyBombay Sewage Disposal Project Marine Outfalls, submitted in October 1993.provided exhaustive baseline water quality data for west coast of Bombay andpresented water quality scenarios for different lengths of outfalls, developedthrough mathematical models. The second report, submitted in October, 1994,dealt with environmental issues related to construction and operation of aeratedlagoons at Versova and Malad and presented plan for assinilative capacity basedwater quality management of Malad Creek. The findings of these studies led tomajor modifications in proposed disposal and treatment schemes.

This report, the last of three reports envisaged on the project, deals withenvironmental issues related to construction and operation of aerated lagoons atBhandup and Ghatkopar. The report presents the existing environmental status ofThane Creek; and details the methodology and results of matlwmatical. modellingwhich formed the basis for assimilative capacity based water qualitvmanagement of the creek.

The cooperation and assistance rendered by Er. l.C.Gandhi, Deputv MunicipalCommissioner: Er. MX.CGokhale, Deputy Municipal Commissioner (Retd.); andoter staff of MCGB in the preparation of this report is gratefully acknowledged.The contributions of Binnie & Partner and the World Bank towards review of thedraft report are sincerely appreciated. Thanks are also due to officials of a numberof agencies who readily fumished information for the study.

*January, 1995 a Klanna)

- ~~~~~CREDBITS

Proect Coordinator

Dr. P. Kuanma

OPERATION PHASE STUDIES

Project Leaders

Dr. Vijay JoshiMr. Rakesh Kumar

Prject Scientists

NEER, BZL NEERI, HQMs. Chandorkar A.A. Mr. Apte V.RMr. Deshpande S.U Mr. Bhide A.DMs. Dhage SS. Dr4Mrs) Cadkari ASMr. Kulkami A.L Dr. Chsh T.K.Dr4(Mrs.) Lala K. Mr. Pentu Saheb S.DrX(Mr) Padiyar V Dr. Shekadr A.UMs. Pathi M.M.Ms. Patkie S.A.Mr. Rosurio K.E.Ms. Subramaniam J.Mr. Thakur S.C.Mr. Iipnis S5.

Scieintific Assistauce

NEERI BZLMs. Divekar N.

Ms. jalota S.Ms. Joshi P.Ms. Kale V.

Secretarial Assistance

NEERl BZLMr. Chaudhari V.

Mr. Chinchulkar R1D.Mr. Joshi A.KMr. Sawant S.

Mr. Shidbaye S.V.Ms. Siddhu JJC

CONSTRUClON PHASE STUDIES

Project LeadenDr. Badrinath S.D.

Dr. Chalapati Raut C.V.

Project Sdenist

NEERI HQ

Mr. Apte V.R. Dr. Kale C.K.Mr. Oaakradhar B. Mr. Khadakkar S.N.Dr(Mrs) Chiakavarti C. Dr. Kondawar V.K.Dr. Charkarvarti T. Mr. Mahajan A.U.Dr. Deshpande V.u. Dr. Olaniya MS.Dr. Gadkari SIC Mr. Pawan Kumar

Scientic Assitace

Ms. Aluwala V. br.(Ms) Pradhan S.Ms. Bhanja A. Mr. Raman NS.Mr. Dabir P. Dr. Ramesh Kumar G.Dr. Dhaneshwar RS. Mr. Sen M.K.Ms. Huddar P. Ms. Shah V.Dr. Iyer V.N. Ms. Sharna A.Mr. jushi M.W. Mr. Sharma N.Ms. Joshi T. Dr. (Mrs) Sharma S.Ms. Khan S. Mr. Shukla 5.5.Mr Kundalia AK Mr. Siracoumer R.Mr. Manglurkar A.D. Mr. Sunil Kuumar CSiMr. Manuel A.C Mr. Talkchande A.UMs. Mudalar SiL Ms. Uma TS.Mr. Murthy V.R. Ms. Vadini V.Mr. Narayanan Raa N. Ms. Verma B.

EXTERNAL STUDIES

Pwf. SJKGuha

Secrel Assistance

NEER[ HQ

MS. Awale M. MrMKhan A.Mr. Anturkar PS. Mr. Kunte 1J3.Mr. Deshpande D.C. Mr. Labhe S.T.Mr. Dhawale A.H. Mr. Negi SS.Mr. Dighekar D.B. Mr. Ojha S.N.Mr. Iyer V.V. Mr. Palnchpatkar S-IMs. Kalyankr D. Mr. Raman M.VMr. Kasture PA. Ms. Sarkar K.

Contents

Page No.

List of Figures. ivList of Tables. viExecutive Summary. viii

CHAPTER IINTRODUCrION

1.1 Preamble 1.11.2 Objectives. 1.31.3 Organisation of the report. 1.4

CHAPTER 2PROJECT SIING

2.1 Preamble. 2.12.2 Bombay : the city, its genesis and growth. 2.12.3 Geography. 2.22.4 Regional geology and structure. 2.2.5 ClLmatology . 2.4

2.6 Demography. 2.42.7 Environmental setting. 2.42.8 iaJor envirorunental concerns. 2.5

CHAPTER 3BOMBAY SEWAGE DISPOSAL PROJECr

3.1 History of the project 3.132 Development Plant 1 323.3 Development Plan II 323.4 Review of Development Plan II 323.5 Development Plan m 3A3.6 First phase facilities 3.73.7 Present status 3.10

CHAPTER 4AERATED LAGOONS

4.1 Prenmble 4.14.2 Salient featues of aerted lagoons 4.24.2.1 Types and Design Features 4242.2 Construction features 44

AWDLAOONS

4.3 Lagoorn. effluent characteristics 4.74.4 Environmental repercussions 4.845 Environmental safeguards 4.84.6 Proposed aerated lagoons at Bombay 4.94.6.1 Design specifications 4124.7 Inference 4.15

CHAPTER 5METHODOLOGY AND DATA GENERATION FOR ENVIRONMENTALMANAGEMENT PLAN

5.1 Preamble 5.152 Scope of field studies 5.25.3 Methodology and findings 5353.1 Air quality 53532 Noise studies 5.55.32.1 Sound level measurement at Bhandup lagoon site 5.5532.2 Sound level measurent at Ghatkopar lagoon site 555.33 Land envirnment 5.95.33.1 Land use 5.95.33.2 Soil characteristics 5.12533.3. Terrestrial Ecosystem 5.155.3.4 Water quality 5.1753.4.1 Reconnaissance survey 5.1753.42 Summer water quality survey 52353.43 Wmter water quality survey 5355.3.5 Biological parameters 5.4353.6 Trace metal levels 5.455.3.7 Nutrients in sediments 5.5253.8 Detergents 5.5553.9 Wastewater characterization 5.5853.10 Solid waste characterization 5.635.4 Condusions 5.64

CHAPTER 6NUMERICAL MODEL FOR THANE CREEK

6.1 Preamble 6.162 Model selection 6.16.3 Thane creek model 6A6.4 Model calibration for water quality parameters 6.96.5 Condusions 6.14

AJi.IED UCGOONS -

CHAPTER 7PREDICTION OF IMPACTS

7.1 Preamble 7.17.2 Construction phase impacts 7.1.7.2.1 Impacts of mangroves redamation 7.17.2.2 Noise impacts 7.27.2.2.1 Noise impacts on construction workers 7.672.3 Air quality impacts 7.67.24 Water quality impacts 7.67.3 Operation phase impacts 7.773.1 Air quality impacts 7.77.3.2 Water quality impacts 7.97.3.21 Prposed treatment 7.97.3.2.2 Analvsis of alternatives 7.117.3.2.3 No action scenario 7.117.324 Augmentation of wastewater management effort 7.127.4 Socio economic impacts 7.2473 Conclusions 7.24

CHAPTER 8RECOMMENDATIONS FOR MANAGEMENT PLAN

8.1 Preamble 8.18.2 Management options for Thane creek 8.28.3 Mitigation plan 8.58.3.1 Construction phase 8.58.3.2 Operation phase 8.108.3.3 Environmental monitoring 8.10.8.3A Public participation 8.1183.5 Institutional needs 8.11

AEATU COONS

List of Figures

1.1 Proposed wastewater disposal/treatment schemes underBombay Sewage Disposal Project 1.2

2.1 Geographical setting of Bombay city and its suburbs 233.1 Physical boundaries of service areas 3.34.1 Layout of facultative aerated lagoon 4.34.2 Layout of aerobic flow through lagoon 4.54.3 Tlypical layout of aerobic lagoon with solids recyde 4.64h. Schematic layout of treatment units Bhandup 4.164.5 Schematic layout of treatment units Ghatkopar 4.175.1 Observed noise levels at Bhandup lagoon site 5.652 Observed noise levels at Ghatkopar lagoon site 5.55.3 Sampling transects for reconnaissance survey of 20.03.93 5.195.4 Sampling locations dunng reconnaissance survey of 13.04.93 5.215.5a Intertidal water quality at Transect 2 of Thane creek 5.36

(Summer spring tide)5.5b Intertidal water quality at Transect 2 of Thane creek 536

(Summer neap tide)5.6a Intertidal water quality at Transect 3 of Thane creek 5.37

(Summer spring tide)5.6b Intertidal water quality at Transect 3 of Thane creek 537

(Summer neap tide)5.7a Intertidal water quality at Transect 4 of Thane creek 5.38

(Summer spring tide)5.7b Intertidal water quality at Transect 4 of Thane creek 538

(Summer neap tide)6.1 Bathymetric features and wastewater discharge location in

Thane creek 6362 North and south boundaries for Thane creek model 6.563 Tidal elevations ard open boundaries of Thane creek model 6.76A Locations of current and water quality observations 6.86.5 Hydrodynamic calibration of Thane creek model (inner region) 6.106.6 Hydrodynamic calibration of Thane Creek model (outer region) 6.116.7a Predicted DO distribution 09.00 hrs. on 06.02.93 6.156.7b Predicted DO distribution 11.00 hrs. on 06.02.93 6.156.7c Predicted DO distribution .0 hrs. on 06.02.93 6.166.7d Predicted DO distribution 14.00 hrs. on 06.02.93 6.166.8a Predicted BOD distribution 09.00 hrs. on 06.02.93 6.176.8b Predicted BOD distribution 11.00 lrs. on 06.02.93 6.176.8c Predicted BOD distribution 12.30 hrs. on 06.02.93 6.186.8d Predicted BOD distribution 14.00 hrs. on 06.02.93 6.18

AERAlED UOONS

7.1 Predicted noise levels at Bhandup lagoon site 7.47.2 Predicted noise levels at Ghatkopar lagoons site 7.573 Predicted DO in Thane creek during high tide for management

scenario 1 (Single cell aerated lagoon with 2005 flows) 7.167.4 Predicted DO in Thane creek during low tide for management

scenario 1 (Single cell aerated lagoon with 2005 flows) 7.167.5 Predicted DO in Thane creek during high tide for management

scenario 2 (Single cell aerated lagoon with 2005 flows afterdiverting 50 mld for industial use at Ghatkopar) 7.18

7.6 Predicted DO in Thane creek during low tide for managementscenario 2 (Single cell aerated lagoon with 2005 flows afterdiverting 50 mid for industrial use at Ghatkopar) 7.18

7.7 Predicted DO in Thane creek during high tide for managementscenario 3 (hree cell aerated lagoons with 2005 flows afterdiverting 50 mld for industrial use at Ghatkopar) 7.19

7.8 Predicted DO in Thane creek during low tide for managementscenario 3 (Three cell aerated lagoons with 2005 flows afterdiverting 50 mid for industrial use at Ghatkopar) 7.19

ARME LAGOONS

List of Tables

3.1 Wastewater treatment and disposal facilities proposed under . rDevelopment Plan mIl 3.5

3.2 On-Line pumping stations planned under first phase ofDevelopment Plan m 3.8

33 Projected and revised estimates of average dry weather flow(mild) 3.11

4.1 Tolerance limit for water quality after receiving discharges(IS :7967 1976) 4.10

4.2 General standards for discharge of effluents 4.114.3 Design specifications of proposed aerated lagoons 4.135.1 Sound levels at Bhandup aerated lagoon site 5.752 Sound levels at Ghatkopar aerated lagoon site 5.753 Land use pattem around the aerated lagoon site at Bhandup 5.105A Land use pattem around the aerated lagoon site at Ghatkopar 5.115.5 Proposed quarry site 5.135.6 Physical properties of soils at the aerated Lagoon sites 5.135.7 Chemical properties of soils at the aerated lagoon sites 5.145.8 Cation exchange properties of soils at the aerated lagoons sites 5.145.9 Reconnaissance survey of Thane Creek on 28.03.93; physico-

chemical parameters 5.205.10 DO values in Thane creek on 13.04.93 5.225.11 Schedule for sampling in Thane creek during summer 5.245.12 Observations on water quality indicators in Thane Creek

during summer 5.255.13 Phytoplankton observations in Thane creek (summer) 5.285.14 Intertidal variations in water quality of Thane creek (summer):

Transect 2 5.295.15 Intertidal variations in water quality of Thane creek (summer):

Transect 3 5.315.16 Intertidal variations in water quality of Thane creek (summer):

Transect 4 5335.17 Schedule for sampling in Thane creek during winter 5.395.18 Observations on water quality indicators in Thane creek

during winter 5.405.19 Phytoplankton observations in Thane creek (winter) 5.445.20 Zooplankton observations in Thane creek (winter) 5.46521 Total heavy metal concentration in Thane creek during summer 5.485.22 Total heavy metal concentration in Thanu creek during winter 5.505.23 Heavy metals in Thane creek sediments during summer 5.53524 Ratio of trace metal concentration inThane creek sediments to

Bombay urbal soil and World shale backgrounds 5.54

ASAE lAGOONS VI

EXECUTIVE SUMMARY

Preamble

1. Bombay 'is the hub of commercal and industrial activities and haswitnessed a rapid growth during past few decades. According to 1991census, 9.93 million persons reside within the municipal limits of GreaterBombay which has a land area of 603 square kilometers.

2. The infrastructural development, however, has not kept pace with thegrowth of population. As a result, the city suffers from shortage of all basicamenities including housing, water supply, sanitation and transport.Amongst these, sanitation is perhaps the mnost neglected sector. Only aminiscule proportion, 22.5 mld out of approximately 2000 mid municipalwastewater generated in the city, receives treatment before disposal toadjoining coastal and creek regions. Discharge of such large quantity ofuntreated sewage into the marine environment has resulted in widespreadimpairment of coastal and creek water quality.

Bombay Sewage Disposal Project (BSDP)

3. The first integrated wastewater management scheme for the city wasplanned in 1970. The scheme envisaged disposal of screened wastewaterfrom entire Bombay municipal area thmugh two marine outfalls at Worliand Bandra.

4. The plan, since then, has undergone many revisions. The most recentDevelopment Plan III, divides the Bombay municipal region into sevenservice areas. The plan provides for disposal of wastewater afterpreliminary treatment through marine outfalls at Colaba. Worli and Bandrainto coastal sea and after treatment in aerated lagoons at Bhandup andGhatkopar in Thane creek and at Malad and Versova in Malad creekrespectively (Figure 3.1).

The proposed facilities

Aerated lagoons

5. The proposed lagoons. are combination of aerobic and facultative lagoons.Each lagoon comprises of four identical streams of three cells of averageresidence time of 1A, 1.8 and 1.1 days respectively. Out of three cells, thefirst cell is designed to operate as a flow-through aerated lagoon and thefollowing two cells as facultative aerated lagoons. The over-all removalefficiency of the treatment system is expected to be 80 percent for'Biochemical Oxygen Demand (BOD) and 70 percent for Suspended Solids

-E ULAOONS a

S -

(55). The salient design details of the aerated lagoons are presented in Table 4.3.,

6. Due to fimancial constraints the original plan of implementation has beenmodified and implementation has been divided into two phases. During thefirst phase activities, the first cells of four streams are being constructed andwill be operated as facultative aerated lagoons with expected BOD removalefficiency of 50 per cent. Figures 4.4 and 4.5 describe the layouts of theaerated lagoons at Bhandup and Ghatkopar, respectively, The shadedportion in these figures indicate the facilites proposed to be built during thefirst phase.

Need for present study

7. The present study has been undertaken in keeping with the World Bank.policy and procedure for the environmental assessment of bank lendingoperations with respect to Bombay Sewage Disposal Project, DevelopmentPlan IIL Procedures as listed under Operational Directive 4.01 have beenfollowed during the assessment. The study also meets the requirements ofthe State of Maharashtra and the Government of India for environmentaldearance of development projects.

Objectives of environmental assessment

8. The objective of this environmental assessment study has been to evaluatethe impact of proposed first phase facilities at Bhandup and Ghatkopar onthe water quality in Thane creelk The study also envisaged to ascertainwhether thie facilities when augmented to three cell lagoons would beadequate to provide the desired water qualitv benefits and it niot. wlhatmodifications in the form of higher degree of treatmnt and mode ofdisposal would be necessary. The design period iur the pnmarvrecommendations has been kept upto the year 2005

9. In view of the need to defne water qualitv management framework bevondthe year 2005, the study was also expected tf. evaluate wastewater treatmentoptions for the year 2015 and after. The objective for such extension was toprovide broad guidelin for future wastewater management in the creek.As the project involves large scale construction activities, the study, alsoaimed at assessing the potential negative impacts during the constructionphase of the project and delineation of necessary mitigatory measures.

ARAWED AOONS

10. With the above objectives, the study was planned to cover the folowingenvironmental aspects:

* Assessment of environmental impacts of proposed aerated lagoons onwater quality in Thane creek with special emphasis on improvement of

Dissolved Oxygen (DO) levels.

* Evaluate the existing water quality in Thane creek and the adequacy ofproposed single and three cell aerated lagoons at Bhandup andGhatkopar to achieve the acceptable DO levels of the creek water.

FeFld investigations and data collection to set up appropriatehydmdynamic arnd solute transport model for Thane creek to enablewater quality predictions.

B* ased on the modeLing studies, broadly delineate possibleaugmentatiors of proposed scheme with respect to additionalwastewater treatment/ transport/disposal measures for planninbeyond the year 2005.

Assessment of impacts on air, noise, land, water and socuo-economicenvironment due to construction of aerated lagoons and delineation ofmitigatory measures.

Environmental Standards

11. Environment (Protection) Act, 1986 vests in Central Government. thepowers to lav down standards for environment protection. Central and StatePollution Control Boards are responsible for compliance of these standards.The Boards, based on local conditions, have power to stipulate morestringent location specific standards.

1L For protection of coastal water quality, two standards apply in lndia. Thefirst of these stards is in the form of receiving water quality and is basedon best designated use of the water body such as for bathing, fishing ornavigation. The creek and coastal waters used for recreational purposes orfising, accordingly, should always have BOD less than 5.0 mg/L, totalcoliforms not more than 1000/100 ml and DO more than 3.0 mg/L

13. The second is in the form of effluent standards for discharges into marinecoastal area. According to this standard, effluents with BOD and SS up to100 mgJL each and amnmoniacal nitrogen up to 50 mg/L can be dischargedinto the creeks.

MAEDLAGOONS

14. The standards for receiving water and effluent discharges do notcomplement each other as the latter does not take into account theassimilative capacity of the receiving waters. If the effluent volume is large,'discharges in compliance with the effluent standard may still lead to severedeterioration of receiving water quality. Also, for smaller water bodies, evena very high degree of treatment of municipal discharges may fail to complywith bacterial quality prescribed by the receiving water stadard. A rationalview, thus, would be to take decisions which ensure DO levels necessary toachieve minimal conditions to sustain a healthy creek ecosystem in thereceiving waters. The water quality management objective for Thane creekwas, therefore, aimed at achieving a minimum DO level of 2 mg/L.

Methodology for environmental assessment

15. In order to assess adequacy of proposed treatment facilities at Bhandup andGhatkopar, the existing water quality status of Thane creek was determinedthrough elaborate field surveys. As inputs to water quality model,hydrodynamic and bathymetric data on Thane creek were also collected.

16. Water quality predictions were carried out mainly for DO and BOD, usingmathematical models. These models were calibrated for local environmentalconditions through in-situ and laboratory experiments.

17. For processes involving highly complex interactions such as nutrient.enrichment, bioaccumulation and ecological transformations, the approachof observations at and inference from the regions which have been receivingsimilar wastewater discharges over a long period was adopted.

18. For estimation of construction phase impacts. field investigations onambient air quality, noise levels, creek and coastal waler quality wereconducted. Land-use pattern and soil characteristics near the constructionsites were also studied. Area under mangwve cover in entire Inner Thanecreek was determined through satellite imageries.

19. The observations and model predictions were used to examine the efficacyof proposed single and thre cell aerated lagoons in achieving the desiredenvironmental benfits. Probable augmentations of te proposed treatmenteffort catering to increased flows by the year 2015 and after, in the form ofhigher treatment and options for wastewater disposal at new locations inthe creek, were evaluated. The scope for additional field observations andmodeLing work to fmalise such optiors was also highlighted.

AT UW OONS xi

Existing environmental status

20. The major impacts of present wastewater discharges are creek water qualityimpairment in terms of low DO, high BOD, SS and total coliforms. Thanecreek, in its inner regions, receives approximately 400 mid untreatedwastewater from Bhandup and Ghatkopar service areas. Due to shallowdepths and narrow cross-section, the creek in this region does not havesufficent capacity to assimilate these discharg As a result, about 10kilometers long stretch along the west bank of the aeek exhibits poor waterquality characterised by low DO and high BOD levels,

21. Concentrations of BOD as high as 7 mglL and total coliforms exceeding10'/100 ml are frquenty observed in the creek. Observations on biologicalindicators present a picture similar to those of physico-chemical parameters.The creek sediments also show high concentration of nitrogen, depictingaccumulation of nutients due to large wastewater discharges.

22. Ambient air quality analyses at Bhandup and Ghatkopar aerated lagoonsites indicate that present air quality in terms of NO2 and SO2 at both sitesfall within Indian standards for ambient air quality.

23. Observations on noise levels at the lagoon sites are within the limitsprescribed for urban residential areas.

Environmental impacts of proposed project

Construction phase impacts

24. The major construction activities for the project are sate .:aranme. landfilling, earth work and material transfer. The most impi rtant impict ot theseactivities is the loss of about 40 hectares of mangrovIe ; Jtwr mstuntang to 5per cent of total mangrove forests in inner Thaln .rnwi. Quantitativeestimationof impact of suchredamationonThane creek wVtr rquaiztt IS notpossible. However, considering the role of mangroves in sustenance ofcoastal ecosystem, it is essential to compensate for the lost mangrove cover.

25. The other prominent impacts during the construction are rise in ambientnoise levels and marginal increase in air borne pollutants like SPM at theconstruction site. The higher SPM levels would be witnessed for shortperiods orny during peak periods of construction activities. There will beinsignificant increase in the gaseous pollutants such as SO and NOx.

AU= LAGOONS ,.

26. Predictions of noise levels at the sensitive locations, located at more than 1kilometer distance from the aerated lagoons, indicate an addition of 40 dBAto a similar background noise level at the time of construction activities. Thenoise due to constructions, thus, wilt be attenuated to the backgrund levelsat sensitive locations.

27. With the exception of the effects of mangrove loss (see para 24.),construction of aerated lagoons will not have any adverse impacts on creekwater quality or fishing interests as all construction activities except foreffluent chanel will be restricted to land. The construction is not expectedto have significant impacts on drainage characteristics of the regionLHowever, it will be necessary not to block any natural drainage channel inthe vicinity of lagooas.

Operatiinal phase impacts

28. The pLanned treatment level at Bhandup and Ghatkopar aerated lagoonsalong with the present and projected flows for the year 2005 are presented inTable 73. Thane cek water quality projections developed through ngoroushydrodynamic and water quality modeUling, indicate that the proposed firstphase treatment effort through single cell aerated lagoons would notprovide significant improvement in creek water quality. Suchimplementation would, however, arrest rsing trend of water qualityimpairment.

29. The present design capacity of Bhandup lagoons is only 180 mtd against theestimated flows of 280 mld. If built to the design flows, Bhandup lagoonswiLU be considerably over loaded. It will, therefore, be necessary to redesignthe Bhandup lagoons for the new flows.

30. HFS emission in the event of malfunctioning of the aerators could lead tosignificant odour nuisance within 1 kilometer radius of the lagoon on atypical stable winter day. However, impacts would not be significant inareas which are beyond 1.5 to 2 kilometers distance from the lagoon.

Analysis of altematives

No action scenario

31. Tie murncipal wastewater discharges from Bhandup and Ghatkopar serviceareas are presently esfimated at 400 mid and are expected to rise to 515 mldby the year 2005. A further steep rise in wastewater generation in theseservice areas is expected due to planned augmentaton of water supply. By2015, wastewater generation in these areas is expected to reach 1000 mid. Ifno wastewater treatment facilities are implementd, creek water quality

AENAEDLAGOONS N.

I~~~~~~~~~~~~~~~~~~

which already exhibits widespread impairment during the low tides, wouldbe considerably further degraded.

-Augmentation of wastewater management effort

32. When augmented to three cell aerated lagoons designed to achieve 35 mg/Lor lower BOD in the effluents, the proposed wastewater treatment wouldprovide adequate level of pollution abatement ili the affected creek regionuntill wastewater flows exceed the projected flows for the year 2005.

33. Water quality scarios developed to examine the benefits of further raisingthe treatment level at Ghatkopar to activated sludge process indicate thatsuch augmentation for 2005 flows would give rise to only a marginalimprovement of 0.3 mg/L in aeek dissolved oxygen over three cell aeratedlagoons optionL Shifting effluent discharge location to center of the creekalso does not yield any significant improvement in creek DO.

Long term water quality perspective

34. When extended to 2015 flows, the simulations indicated that it was notfeasible to discharge effluents beyond projected flows for the year 2005 atBhandup and Ghatkopar even after nitdfication of effluents. For futureflows, it will thus be necessary to build additional wastewater treatmentfacilities and discharge the effluents at new locations in the creek. Thenalrysis indicates, that, if one were to discharge within the inner Thanecreek, it would be possible to discharge upto 260 mid after secondarytreatment near Vikhroli. To cater to entire excess flows of 520 mnid betweenthe year 2015 and the year 2005, however, such option would entail tertiarylevel treatment. The simulated creek DO levels for management scenanrosdescribed above are summarised in Table 7.4.

3S. Considering the high cost of tertiary treatment and also the need to plmneven beyond the year 2015, it is desirable that options for discharging thewastewaters in other regions of the creek be explored. Under such case, itmay be adequate to treat the effluents only upto secondary level and cost of

* transporting the wastewater may be off-set by savings in the cost of itstreatment.

Socio-economic impacts

36. The project area for Bhandup and Ghatkopar lagoons is uninhabited anddoes not involve any displacement of people. The project, during theconstruction, is expected to generate some employment which would have

AU LAGOON5 xlv

marginal positive impacL The operation of aerated lagoons does not requirea large workforce and therefore, no large scale residential development inthe region, is expected, due to the implementation of thie project. Theimplementation of the project, may result in beneficial impacts in terms ofhigher fish yield thereby increasing fishing activities in inner Thane creek.

bitigation plan

Co38. ton phase

37. Loss of about 5 per cent of the total mangrove cover in the inner Thane creekdue to land relamation for lagons, is the most important constructionphase impact of tuhe prjecto To compensate for the uravoidable loss ofmangrve area, MCGB should designate about 200 hectas of mangrovearea along the creek as protected area and take measures agaist furtherclasmationor unauthorized cutting. Alternatively, MCGB shouldundertake friesh planting of mmangrove forests of area equivalent to thereclaimed area in the inner Thane cmeek region.

35. Anothe potentiay negative impact of aerated lagoon construction is a risein the ambient noise and dust levels. This impact can be prevented byadherence to good construction and housekeeping practices. Measures suchas avoidance of unnecessary idling of construction machinery and spiLlageof fuel and ol and adequateen of constructin machinery to'ensure efficient and trouble free operation should be provided for in theconstruction contracts.

39. Analysis of the noise levels at the site and surrounding areas indicate thatthe effect of construction activities during the day, is not felt outside theconstruction site due to the local noises. At night, however, the constructionactivities, can raise the noise levels and the nearby iresidential locationsbeyond the ight tim standards for such areas. The nise generatingcomtrucdion activities thereforeshouLd be resticted only to day time hours.

40. Air quality analysis at the sites indicates the air quality in terms of SPM,NO, and SO, are well within the Indian Standards for ambient air quality.Hiowever, the SpM levels may, on some occasions, surpass the standards atthe time of site clearing and construction activities. Provision of waterspraying on all haul roads at the construction site should be made to

miniizethe dust Also, green belts should be developed around theboundary7 of the lagoon sites on the sides facing habitation to safeguardagainst aesthetic impaiment An inventory of requsite mniigatory-measures is provided in TAble &1.

AIVM1LASoOOI

Operation phase

41. If the facilities are limited to single cell lagooms, water quality in the affectedregion of the creek will remain below the level necessary for a healthyecosystem. An adequate mitigatory measure, therefore, would be toconstruct three cell aerated lagoons at this stage itself or to augment thesingle cell lagoons to three cell configuration as soon as possible. Withrespect to the treatment facilities care should be taken to extend the effluentdischarge point upto 20 meters beyond the low water line in the creeldets toavoid formation of sludge mats in the inter-tidal zone.

42. In order to achieve acceptable environmental conditions in the vicinity ofthe creek proper functioning of aerators is of prime importance. Adequateback up systems should be incorporated in the design stage itself to ensuretheir continuous and trouble free operation.

Recommendations

43. Construction of properly designed single cell aerated lagoons at Bhandupand Ghatkopar is the munimum admissible treatzent effort necessary tomeet the currnt effluent discharge stndards. Construction of suchwastewater treatment facilities at Bhandup and Ghatkopar would be apositive step towards the objective of overall water quality improvement in

.Thane creek and is strongly recommended.

44. For significant improvement in creek water quality, it would be essential toaugment the aerated lagoons at Bhandup and Glatkopar to a three cellconfiguration designed to produce effluents with BOD below 35 mg/L.Considering that such augmentation would remain effective only upto theyear 2005, subject to funds being available, consider implementation of thisconfiguration could be considered at the present stage.

45. The recommended long term waler quality management option for theThane creek is to build three cell aerated lagoons at Bhandup andGhatkopar and to develop additional treatnent units with facilities todischarge the effluent at new locations within the creek. One of the suitabledischarge locations has been identified near Vikhroli and has potential toreceive about 260 mid of effluents after secondary treatment.

46. Additional water quality modelling studies are recommended to assessassimiative capadty of the creek south of Trombay as possible new effluentdisage aras for expected wastewater flows in Bhandup and Ghatkoparservice areas by the years 2015 and after.

ASR<AlD LAOONS

47. The conclusions of this assessment are limited to the study of municipalwastewater loads from Bhandup and Ghatkopar service areas. For achievingthe full water quality benefits of the investments in treatment that MCGBplans to make, it is imperative that a comprehensive management plan bedeveloped for the creek, with comparable treatment levels applied to otherdischarges. Because this involves multiple jurisdictions, it may be bestaccomplished by Government of Maharashtra. Considering the probableenvironmental impairment due to delays, It is desirable that immediatepriority be assigned to planning and implementation of such a managementscheme.

Environmental monitoring

48. A systematic water quality monitoring effort within the creek slould beinitiated before and after commissioning the aerated lagoons at both thedischarge locations. At the post-commissioning stage, the morLtoringshould be aimed at an evaluation of water quality projections andvaiidating the water quality model used in the present study. Suchvalidation will be useful for future planning.

49. A regular effluent monitoring program to establish the performanceparameters for the treatment system should, lwwever, be undertakenimmediately after commisioning ithe treatment systems and continuedduring the entire operation period of the treatment systems. Guidelines forsuch monitoring are provided in Table 8.1.

50. Creek water quality morntoring along with observations otl hydrodvnamicparameters slhould, however, be initiated by Government of Mlaharashtra todevelop a comprehensive water quality model for the entire Thane creek. aprerequisite for developing the overall wastewater matuagpment plan forthe region. The exercise should aim at developing location secific dischargestandards for various industrial discharges into the creek to ensure that theoverall pollution load to the creek are within its assimilative capacity.

51. A limited monitoing at the creek may also be undertaken to document theimprovement ir the creek ecosystem comparing the pre and post-projectwater quality conditions (Table 8.1).

Public participation

52. The proposed wastewater management effort along Thane creek involves* significant investment of public funds. The findings of the study indicatethat even more comprehensive treatment efforts wilU be necessary to

AEWE LAGOONS Xv

safeguard the creek water quality in the not-too-distant future. It is,therefore, desirable to create public awareness for the project activities tofacilitate their involvement in the decision making. ¶Ibwards this end,findings of tIuis study should be placed for public discussions amongrepresentatives of fishing communities, general public and local NGOs. Thereport summary should alos be translated in local languages anddistributed among the fishing communities.

53. A comprehensive awareness program on the need for the project, majortechnical and social issues and the environmental benefits should beundertaken through local media., The coverage should include discussionson TV and radio by panels comprising eminent citizens and officialsconnected with implementation and environmental assessment of theproject. An outline for envirorunental awareness program has also beensuggested.

Institutional needs

54. There is a need for substantial institutional development within the MCGBfor effective operation of aerated lagoons and the additional treatment ariddiversion options which will have to be developed later. Training programsfor various levels of assodated staff of MCGB should be conducted forefficient operation of the project On certain environmental aspects such-asuse of water quality models for effective water quality monitoring in thecreek, evaluation of long term post project environmental impacts andplanning for wastewater management of future discharges it may benecessary for MCGB to take recourse to the expertise available with theresearch Institutes active in these areas.

55. For effective implementation of the recommended environmentalmontitoring, it will be necessary to develop adequate facilities fur samplingand analysis. It will be desirable to operate an environmental monitoringcell, with adequate taining and instrumentation support for coastal waterquality monwtoring and analysis related to the aerated lagoon project.Government and private laboratories with adequate infrastructural facilitiesand expertise may also be identified to assist in these activities.

AWIED LAGOONS

Chapter 1INTRODUCTION

1.1 Preamble

Rapid growth of Bombay city over past few decades has given rise toinnumerable problems of diverse nature and of significant dimensions. Oneof the major problems is the deterioration of water quality in creeks andcoastal regions around the city, due to more or less unrestricted disposal oflarge volumes of domestic and industrial wastewaters. Loss of cleanrecreational beaches and sea fronts, and probable damage to coastalecosystem are some of the manifestations of such pollution that has causedserious concern to planners and the residents alike.

Regardless of the wastewater treatment method, Bombay, being an islandcty, warrants discharge of the effluents to Thane creek on the east coast andto the Arabian sea on the west coast. In the late seventies, M/s. Metcalf &Eddy carried out detailed hydrodynamic and water quality studies in Thanecreek and in Arabian sea to examine the impact of such discharges on waterquality. These studies indicated the feasibility of discharging the primarytreated effluents into the sea through marine outfalls and secondary treatedefluents directly into the creek. The findings and recommendations of these*udies culminated in the formulation of Development Plan III of the BombaySewage Disposal Project. It comprised construction of primary treatmentfacilities followed by marine outfalls at Ba.dra, Colaba and Worli; andaerated lagoons to provide secondary treatment prior to disposal ofwastewaters from Malad and Versova into Malad areek and Ghatkopar andBlhandup into Mhane creek (Figure 1.1). The Municipal Corporation of GreaterBombay (MCGB) was to undertake the implementation uf these worksthrough a series of large scale co-ordinated pollution abatemenit programmes.

Before implementing the above works, MCGB desired to ascertain theenvironmental impacts of construction and operation of the proposedfacilities in keeping with the World Bank policv and procedure for theenvirorLmental assessment of Bank lending operations. In September 1991,MCGB retained NEERI to undertake the environmental assessmentt studiesfor all wastewater disposal and treatment schemes envisaged under theBombay Sewage Disposal Project. The study also meets the requirements ofGovernment of Maharashtra arnd Government of India for environmentalcdearance of development projects.

Disposal of untreated/partially treated municipal wastewater could have avariety of impacts on the receiving marine environment. The most prominentof these are water quality impairment due to depletion of dissolved oxygenand bacteriological contamination, probable build-up of nutrients in sea

AED LAGOONS 1.1

Figure: 1.1

Proposed wastewater disposal I treatment schemesunder Bombay Sewage Disposal Project

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DUGOONS 1I

AERAMIELAGOONS 12

water giving rise to algal blooms under adverse meteorological coinditions,and accumulation of metals and trace orgapics in sediments and benthosthrough the process of biomagnification. Construction activities associatedwith the project implementation could also lead to negative impacts onenvironment in the vicinity of the construction sites.

Although, marine outfalls and aerated lagoons are designed to achieveimprovement of coastal water quality around Bombay, their operationalmechanism is radically different. Marine outfalls are designed to carry thewastewater to open coastal regions of adequate assimilative capacity torender the discharges environmentaily safe, whereas aerated lagoons aim atreducing the pollution load before disposal to match the limited availableassimilative capacity in the receiving creeks.

Due to differences in hydrodynamic characteristics, physical extent andambient water quality of open coastal areas and creeks, different approacheswere required to evaluate the impacts of wastewater discharges into therespective regions. The investigations and reporting on envirornentalimpact assessment for marine outfalls and aerated lagoons were, therefore,segregated. The field studies related to marine outfalls were completed bythe end of 1992 and a final report on the environmental impact assessmentafter the requisite review was submitted in October 1993.

Studies on environmental impacts of discharges from proposed aeratedlagoons into Malad and Thane creeks were subsequently undertaken. Thepreliminary investigations indicated that discharges into Malad creek werepotentially more sensitive due to their widespread negative impacts in theregion. The Malad creek studies, therefore, were undertak-en ahead of Thanecreek studies and the final report after reviewing the findings was submittedin October 1994. Finally, the environmental impact assessment of proposedmunicipal disclarges into Thane creek has been completed and forms thesubject matter of this report.

1L2 Objectives

Thane creek extends northward from the Bombay harbour and segregates theisland fmm the main land on the east. At its northern end, the creek receivesan outlet from Ulhas river but with very little discharge as the river flowspast the creek head. In its upper region, the creek is narrow and only a fewmeters deep. It, however, spreads to more than 5 kilometers as it opens intothe harbour. The total length of the creek is about 25 kilometers with anaverage depth of about 5 meters. The creek is dominated by diurnal tideswhich range from approximately 1 to 4.8 meters during thie neap anid spring

AERATE LAPOONS1.

tides, respectively. The creek provides natural drainage to the easternsuburbs comprising Bhandup and Ghatkopar service areas and receivesabout one third of the total municipaL wastewater generated in Bombay. Dueto inadequate dilution, these discharges give 'rise to significant water qualityimpairment in the inner region of Thane creek.

In order to ease the onus of pollution on the creek, construction of aeratedlagoons having disign capacity of 176 mid at Bhandup mnd 386 mld atGhatkopar, is planned. The aerated lagoons are expected to reduce theorganic loading to the creek by approximately 60 percent. The proposeddegree of treatment, was determined based on the studies conducted byMetcalf & Eddy on Thae creek in 1976. The revised wastewater estimates,however, indicated a significant variation in wastewater generation andentailed a fresh scientific study to assess the adequacy of the proposedtreatment schemes.

Considerable advances in creek water quality modelling have also takenplace since 1976. The present study makes elaborate use of advance waterquality models in conjunction with comprehensive field investigations toestablish the impacts of proposed treatment schemes on creek water quality.The major areas of investigations under this study are:

* Assessment of envirornmental impacts of proposed aerated lagoons onwater quality in Thane creek with special emphasis on improvement indissolved oxygen levels

* Field investigations and data collection to set up an appropriatehydrodynamic and solute transport model for Thane creek to enable waterquality predictions

* Delineation of additional wastewater treatment /storage /transportmeasures, if required, to ensure a safe level of dissolved oxy gen in Thanecreek based on the modelling studies

* Assessment of impacts due to construction of aerated lagoons on air,water, land and socioeconomic components of the environment.

13 Organisation of the report

This report addresses all environmental issues, delineated under section 1.2,pertaining to the impacts of construction and operation of proposed aerated'lagoons at Ghatkopar and Bhandup. The report comprises of eight chapters,the subject matter of which is briefly described below.

ADM=EDLGOONS IA

Chapter 11 of the report provides the project setting with brief description on city ofBombay with respect to its growth, geography, climatology, demography andenvironment. The chapter also summarizes the major envirounental problems,which need immediate attention, for betterment of quality of life of large sectionsof population in Bombay.

Chapter III describes the history of Bombay Sewage Disposal Project and thepresent status of project implementation.

Chapter IV highlights the salient features of aerated lagoons, repercussions on thecoastal environment due to lagoon effluents and presents the design features ofthe proposed lagoons.

Chapter V details thLe methodology and inferences of investigations on existing.envirnmnental quality in Thane creek, construction sites and neighbouring areas.

Chapter VI provides an overview of methodology of field surveys forhydrodynamic and water quality observations. It also details the depth-averagehydrodynamic and solute transport model used for predicting the water qualityimpacts and use of hydrodynamic and water quality observations in nodelcalibration.

Chapter Vnf highlights the inferences drawn from the environmental impactpredictions. It describes the overall environmental impacts of the proposedproject and underscores the areas of deficency. This chapter also provides thepossible management alternatives to achieve desired water quality improvementafter a comprehensive examination of feasible options.

Ciapter VIll is the conduding chapter of the rtlx)rt .. nd i,rse2ntsrecommendationis of the study. It delineates the environimenti. I mualln.Vnlet ptai.for construction and operation phases of the project and 'nr- iids .%auent leaturesfor future monitoring programme in the project area.

AEMD LAGOONS 1.

Chapter 2.PROJECT SETTING

2.1 Preamble

A small cluster of islands burgeoning into a megapolis sounds incredible.However, this is the story of the growth of Bombay, within a span of aboutten decades. Bombay has witnessed unprecedented industrial andcommercial growth in this period and has emerged as the industrial capital ofIndia. The industrial growth of Bombay has been accomparnied by an equallyphenomenal rise in population. The infrastructural development, however,could not keep pace with the growing population. This has led to sihortage ofwater supply, lack of proper sanitation facilities, proliferation of slums,inadequate transport facilities etc. in the city.

Disposal of untreated wastewater into the coastal regions has led todeterioration of water quality in the adjoining areas and poor beachaesthetics. In order to curb the increasing environmental impairment, dcvicauthorities have planned large scale waste management schemes in the city.Construction of aerated lagoons to provide secondary treatinent, prior todisposal of wastewaters from Ghatkopar and Bhandup service areas intoTbane creek, is one such scheme envisaged under the Bombay SewageDisposal Project.

An environmentally sound design for the proposed lagoons, however, entailsconsiderations of local coastal environment, socio-economic and otherinfrastructural conditions. In the context, this chapter describes Bombay city,its geological and demographical characteristics and the relevantenvironmental setting.

22 Bombay: the city, its genesis and growth

Bombay, situated at 1855°N latitude and 72.540E longitude was originally acluster of seven islands of Colaba, Fort, Byculla. Parel, Worli, Matunga andMahim Now Greater Bombay is extended upto Mulund and Dahisar. It is nomore an island but a sort of peninsula. Its early inhabitants were Kolis orfishermenL Bombay was a part of the Mauryan Empire (273 -232 BC). It wasunder the Silara Kings (810 AD 1260 AD). On Dec. 23,1534, Bombay wasceded to D. Joans m, King of Portugal by Sultan Bahadurshah.

In 1549, the islands of Bombay were handed over in perpetuity to Dr Praciada Orfa. In 1625, an Anglo-Dutch fleet captured Bombay fort by a surpriseattack They looted the island and left. On June 23, 1661 King Charles H ofEngland married Princess Catherine Le Breganza of Portugal and the islandof Bombay was given in dowry to King Charles II Thus, Bombay went to the

AAED LAOONS 21

British by an alliance of marriage. In 1668, Bombay was handed over to EastIndia Company by a Royal Charter. Sir George Oxender was the firstGovernor of Bombay.

Decades of development and reclamation resulted in the expansion of thecity area to 70.2 square kilometers in 1950, to which the area of BombaySuburban District was added in 1951, bringiLg a total aren of 235 squarekilometers under Greater Bombay. In 1957, more villages were added and thearea increased to 4663 square kilometers.

2.3 Geography

Greater Bombay comprises of the isLand of Bombay, Trombay and major partsof Salsette. In the north, the Salsette island is separated from the main land byBassein creek on the west, and by Thane creek on the east Figure 2.1. TheMahim creek, on the south of Salsette island separates it from the island ofBombay, while the wester margin is further indented bv Manori and Maladcreeks. The island is bounded on west and south sides by Arabian Sea andhas a natural deep water harbour protected by the island of Bombay on thewest coast and the main land of Konkan on the east. Bombav is the largestport along the west coast of Idiia.

City of Bomtbay, on the southern side of Mahim creek is highly overcrowdedwith unplanned growth. The suburban development on the northem side, is-relatively better planned and is aligned to the two railways, the western andthe central, dividing this area into western and eastern suburbs. Suburbs onCentral railway comprise the main industrial belt of Bombav. Th-e importantindustries include paints and varnishes, miscellaneous chemical productsmanufacturing, machinery and electrical appliances etc.

2v4 Regional geology and structure

The regional geological setting of westem India and in particular of Bombay,may be termed Deccan Trap as described in both Geology of Intia chapterXVI pp 275-286 and in Geology of India and Burma chapter XV pp 405-421.The basaltic rocks extend over an area of some 500,000 square kilometers andthe thickness of the Deccan Trap may be as much as 2,000 to 3,000 metersalong the present western margins, where the rocks dip 5-15 degrees to thewest; the only sea where the rocks are not effectively horizontaL

The Traps are divided into 3 sub-units; Lower, Middle and Upper TraPs. TheBombay area (Upper Traps), is noted for its intcr-trappean sedinmntary beds,lava flows and ash deposits.

MM IAGOO 12

Figua : 21

Geographical setting of Bombay city and its suburbs

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The basaltic rocks have been erupted from vents and along fissures. Theindividual flows vary between 10 and 30 meters thick, although compositeflows of a number of smaLer units, which are difficult to differentiate cangive rise to apparenty thicker flow sequences. The lavas can, and often do,show sedimentry 'coercing-downwards' like differentiation within theflows, giving rise occasionally to brecciated deposits. Two major flowformation mechanisms (each of whichcan be subdivided into two types) areseen altough breccias, tuffs and other variations due to minor changes in themagma mneralogy are also noted.

ZS Climatology

The climate of Bombay is fairly equable with average annual maximum andmimmum temperature of 31.40C and 22.90C respectively and the averageannual maximum and minimum Relative Humuidity of 95.7 per cent and 34.0per cent respectively. The average annual rainfall is around 2000 millimetersoccurng mostly during July to September. Strng land and sea bxeeze effectis observed, particulaady during monsoon. Prominant wind directionsduring monsoon are north-west and west.

2.6 Demography

In a little over a century, the population of Bombay has almost increased byhundred folds to about 10 million. The rise in population has been caused bylarge scale migration from various parts of the country on account of betteremployment opportuities in Bombay. The most commondy spokenlanguages are Hindi and Marathi. The city of Bombay is divided into 23wards and its population according to the 1991 census is 9926 1.khs.

Inadequate housing has forced a large number of people in Bombay to residein slums. According to 19B1 censu, more than 30 per cent of Bombay'spopulation lived in slum areas. The present estimates indicate thatapproximately 5 million people live in slums. Marine produce was the mainsource of income for inhabitants of Bombay before it developed into anindustrial centre. F6ing in the coastal waters of Bombay however, is stilU animportant economic activity.

2.7 Environmental setting

Bombay is endowed with a natural harbour, beaches and hilU ranges, lakesand river It was estimated in 1959, that the area of mangrove foests inBombay and adjacent coastal districts was about 24,70 ha. The revisedestimates indicate that the same was around 20,000 ha in 1975.

AERAIESSD OONS 'a2

There are turo major forest areas in Bombay. It has few good national parksand a small bird sanctuary that has been preserved. Vegetation cover in thecity of Bombay is not very good. The suburban areas, however, are mudcgreener than the man area of Bombay city. The mangrove swamps ofBombay are worst affected by human interferences. The principal cause fortheir degradation, is large scale reclamation of mangrove swamp areas forhousing due to increasing population pressure.

2.5 Major environmental concerns

The evironmental problems in Bombay have been caused due to highpopulation pressure and intensive industrial and commercial activitieswithin a small physical area. Discharge of large quantum of untreated wastewater into the surrounding coastal and creek regions, formation of pockets ofacute air poltution due to industrial and vehicular emissions, inadequatedisposal of solid wastes, congested roads and overcrowded trains, noisepollution, enroachment of forest area and open spaces and aestheticimpairment are some of the consequences of Bombay's phenomenal growthThe solution of these problems entails an integrated and well coordinatedeffort considering the problem as a whole. The wastewater managementplan undertaken by Municipal Corporation in the form of Bombay SewageDisposal Project is an important and positive step towards restoration ofenvironental quality in and around Bombay.

L

Chapter 3BOMBAY SEWAGE DISPOSAL PROTECT

3.1 History of the project

Wastewater management fadlities in Bombay, date back to the 1860'sfolowing the inauguration of the Vihar Lbke scheme to provide Bombaywith the first piped water supply. Following a Government Cmmiionreport in 1872, the Worli outfall discarging wastewater into the Arabian Sea,was completed in 1880. Lack of funds, however, prevented tLie constructionof the outfalL as initly proposed to discharge below the low water leveL

Wastewater cllection facilites within the city continued to expand, and by1900 all wastewater was directed to Love Grove from where it was pumpedto sea hrough the Worli outfalL Problems of pollution in this area had starwdto become evident even at this early date.

By 1905, the basis of the present wastewater coUection, treatment anddisposal system within the cty, had been established. Subsequent demandswere met by the duplication of sewers, provision of overflows to relievesurcharfng in- developed areas, addition of new sewers in developing areas,constuction of additional failities at Love Grove, and the construction ofnew treatment facilities at Banganga, Dharavi and Dadar.

Following the second World War, the rapid increase in population of the cityrendered many of the wastewater facilities completely iruadequate. To correctthis situation extensive relief works were sanctioned in 1948 under the ReliefSewerage Scheme. Unfortunately, because of the length of time taken tocomplete these works, and because population forecasts prepared in 1948proved to be far too low, the relief works did little to alleviate the problems.

In 1950, the Municipal Corporation boundary was extended to include whatare now Wards HKL,MN, and part of P Ward. The boundary was further

extended in 1957 to its present position. Wastewater facilities within thesesuburbs and extended suburbs were very limited during that period.

A High Level Committee of Experts (appointed by the MunicipalCorporation) to advise on water supplies and wastewater facilites for theGreater Bombay area, submitted its report in 1963. This report maderecommendations for expansion and upgrading of the wastewater facilitieswitin the city and th suburbs to meet the demands of wastewater flowsexpected from population prcected for 1981.

Aw~iMtAUoous 3.1

Although some minor improvements were carried out; the collection,treatmert, and disposal facilities continued to be completely inadequate todeal with the increasing quantities of wastewaler.

3.2 Development Plan I

In May 1970, M/s. Binrie & Partner (India) Ltd. were reained to advise onwater and wastewater problems in the Greater Bombay area. Their study ofthe wastewater problems culminated in the prepatimon of Development PlanL This plan set out a programme for exparsion of existing facilities to meetthe demands of the projected population in 1991. The plan r nddisposal of screened wastewater frm the entire Greater Bombay areathrough two marine outfalls at Worli and Bandra.

3.3 Development Plan I

on instructions of the Deputy Municpal Cmmisioner- (Special.Engineeing), an alternate plan for the treatment and disposal of wastewaterfrom the Greater Bombay area, as per the proqection for 1991, was prepared.This plan was referred to as Development Plan II

Development Plan H recommended the disposal of screened wastewaterfrom Malabar, Worli, and Mahim drainage zones through marine outfahs atWorli and Bandra (Figure 3.1). Wastewater flow from Chembur drainagezone was planned to be treated in plants at Bhandup and Chembur prior todcharge into Thane creek, and the flow from Marve zone at a treatmentplant at Marve followed by discharge into Malad creek. In this plan. theDadar treatment plant was to be retained and expanded to meet the needs ofDadar. Sludgs from all treahnent plants were planned to be disposed intothe Arabian Sea through the marine outfalls.

3A Review of Development Plan II

The Municipal Corporation proceeded with some of the sewerage proposalscontained in Development Plan IL and the detailed design of eight pumpingstations and feasibility studies of eleven more pumping stations. However,no work was carried out, on the treatment and disposal aspects of the plan.

Befre proceeding with design and construction of facilities to augment thetreatment and disposal of wastewater, the Municipal Corporation inconsultation with the Intenational Development Association, decided on afesh review of the recommendaions ained in Development Plan IL Totlis end, the services of M/s. Metcalf & Eddy Inc of Boston, U.SA. and M/s.

AERAIDULAOONS 32

Figure: 3.1

PhMical boundaries of service areas* _ .o* ,..I.*:Ie:l...l...l...lt'".:.l. : 1.... I12;_.'A..MV. I- I .!I?,

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AOUMLAGOONS ~ ~ ~ * ~' :

Envirnmental Engir Consultants of Bombay, were retained with theview to solve the immediate and mid-term wastewater problems of Bombay.The prime objectives of the review were:

- To produce a wastewater treatnent and disposal plan for Bombay(Development Plan 111) for the period tirough 2005 that would achieveand maintain satsfactory levels of public health and environmentalquality

- Determination of the wastewater assimilation capacities of Thane creekand coastal waters around Bombay for thir optima utiLization fordisposal of municipal wastewater

- To prepare feasibility studies, preliminary designs and cost estimates fora first-stage progamme catering to the wastewater flows for 1981

- To outline furte envirmental or related studies required for thedevelopment of a long-range environmental quality improvementProgramme

M/s. Metcalf & Eddy submitted an Interim Report in 1977, setfing out eirproposed solution to te problems of treatment and disposal of wastewatergenerated in the Greater Bombay Area. Ts proposed solution wassubsequently revised in consultation with MCGB engineers and became thebasis of Development Plan IlL

3.5 Development Plan III

Under the Development Plan lL the design period for the wastewatermanagement fahcilities was extended to the year 2005. Under the scheme. itwas envisaged that the sewage generated in the municipal boundaries of cityof Bombay shall be treated and disposed into the coastal and creek regionsthrugh seven different works.

The drainage zones envisaged in the earlier plan were reorganized to formseven service areas. Prvision for the treatment/disposal of entirewastewater generated in an area, was made at the works within that areaitself. The physical boundari of the service areas and location of thetreatment/disposal works designated for each of those are presented inFigure 3.L The salient features of these works are presented in Table 3.1 andaxe summariz belw.

*MM LAGON 3

Table: 3.1

Wastewater treatment and disposal facilitiesproposed under Development Plan III

SL Service Area Facility Design FRow Present StatusNo. (mld)

1. Colaba Madne outall 41 12 km. length fadlityin operatAonsine 1988.

2. Uve Gmve Maine outfal 757 498 m outfal inoperation since 1990.

3. Glatkopar Aerated lagoon 386 in planning stage

4. Bhdup Ae lag 178 in planning stage

5. Ba Maxine outfall 797 200 m outfall laid(not in operation)

6. Versova Aerated lagoon 131 under revision

7. Malad Aerated lagoon 280 under revision

AIRAME LAGOONS

Colaba service area

Disposal of 41.1 mld by the year 2005 into the harbour, after 1 hoursedinentation at an expanded and upgraded Colaba Treatment PlanL

Love Grove service area

The existing treatment plant at Dadar to be relained as a training andresarch establishment. Prvision for expansion and upgradation of facilitiesto provide secndary treatment for a flow of 22.5 mid, in year 2005.

Wastewater generated within the remainder of Malabar zone and all of Worlizone to be conveyed to the Love Gro'e site for treatment and disposaLReo end facilifies for the design flow of 757 mld in 2005 to comprisescreening, grit removal, one-hour sedimentation and chloination beforedisposal to the Arabian Sea thrugh a marine outfall. Sludge processn bygravity thickening and vacuum filtration before disposal to landfill sites orapplicaton to agricultural land. Sceing and grit from preliminarytreatment facilities to be disposed off hirough landfill.

Bandra service area

Disposal of wastewater fEm the Mahim zone to the Arabian Sea through anoutfall The design flow of 796 mid to be subjected to screening, grit removal,one-hour sedimentation and chlorination before disposal to the Arabian seathough a manine outfalL Processed sludge after gravity thickening andvacuum filtration for .landfill or agricultural application. Disposal ofscrening and grit from preliminary fadilities through landfill.

Gbatkopar service area

Disposal of wastewater from South Chembur zone, to the tune of 3S6 mld in205, to Thane creek after treatment in aerated lagoons at Ghatkopar.Pretreatment to consist of screening and degntting, with provision fordisposal of seenings and grit to a landfill. Removal of stabilized sludgefrom the lagoons required at approimately ten-year intervals. The sludge tobe used for land application or landfllig.

Bhandup service area

Disposal of wastewater from North Chembur zone, to the tune of 176 mild in2005, to mane crek aft treatment in aerated lagoons at Bhandup.Pretreatment to oonsist of screening and degritting, with provision for

AM=IE LArwOONS 3A

disposal of screenings and grit to a landfill. Removal of stabilized sludgefrom the lagoons required at approximately ten-year intervals. The sludge tobe used for land application or landfllUing.

Malad service area

Disposal of wastewater from North Marve zone to the tune of 280 mld in2005, to Malad creek after treatment in aerated lagoons situated at Malad.Pretreatment to consist of screeng and degritting, with provision fordisposal of sceenings and grit to a landfill. Removal of stabilized sludgefrom the lagoons required at approximately ten-year intervals. The sludge tobe used for land applicadon or landflling.

Versova service area

Disposal of wastewater from South Marve zone to the tune of 131 mid in205, to Malad ceek after biological treatment in aerated lagoon situated atVersova. Pretreatment to consist of screening and degritting, with provisionfor disposal of screnngs and grit to a landfill. Removai of stabid sludgefrom the lagoons required at approximately ten-year intervals. The sludge tobe used for land application or for landfilling.

Concurrently with the studies by M/s. Metcalf & Eddy, MCGB had alsoauthorized Tata Consulting Engineers, to investigate the feasibility forupgrading eleven existing pumping stations and to undertake preliminaryengineering on eight new stations, who submitted the reports on theseproposed works in 1978! The service areawise description of thcse pumpingstations is given in Table 3X

3.6 First phase facilities

In order to reduce initial capital requirements, the Municipal Corporationdecided to implement Development Plan m in two phases. Phase Iprogramme which was targeted to be completed by 1984, included thefollowing components in addition to upgrading and construction of pumpingstations

Colaba treatment works

In0uent pumping staion, screns, aerated grit chambers and 1.1 km longoutfall with a design flow of 41 mid, will be provided for disposal ofwastewater in the Bombay harbour.

AUMD WS~OONS 3.7

Table : 32

On-line pumping stations planned underfirst phase of Development Plan III

Sr. Collection Area Pumping Station Ultimate CapacityNo. (Approx.) (mld)

New Pumping Stations1. Colaba Kitridge Road 22

N.F. Road 22

2. L.ovegrove Dadar 220Carrol Road 30

3. Band Kalina 32Saki.Naka 160

Pumping Stations to be Uprated

1. Lovegrove Jacob Circle 250Globe Mill Passage 145TuLsi Pipe. 170Tank Bunder 16

2. Bandra Matunga 150Wadala 125Sion Koliwada 22Mahim 120

AVUMLOZOONS 3i

AEAlC AOONS . 6

-~ ~ ~~~

Love Grove treatment works

Iluent pumping station, screens, aerated grit chamber and a 3 km longoutfall with a design flow of 757 mld will be provided for disposal ofwastewater into the Arabian Sea.

Bandra treatment works

Irdluent pumping station, aerated grit chambers and a 3 kon long outfall,with design flow of 796 mld will be provided for disposal of wastewater in toArabian Sea.

9.0 kilometers of tunnel to collect sewage from within the Mahim zone andconvey it to the Bandra influent pumping station.

Versova treatment works

Iluent pumping station, screens, aerated grit chambers and aerated.lagoons, with a design flow of 131 mld, will be provided at Vcrsova.

2.93 kilometers of force main to convey sewage from pumping station toaerated lagoon site.

Malad treatment works

nuent pumping station, screens, eaerated grit chambers and aerated lagoonswith a design flow 280 mid, will be provided at NIalad.

2.23 kilometers of force main to convey sewage irom -univing !-tation toaerated lagoon site

Ghatkopar treatment Works

Influent pumping station, screens, aerated grit chlmbers and aenrted lagoonswith a design flow 386 mld, will be provided at Ghatkopar.

2.4 kilometers of sewer tunnel to collect sewage from the south part of theChembur zone and convey it to the Ghatkopar influent pumping station

0.95 kilometers of force main to convey sewage from pumping station toaerated lagoon site

A DM LAON

Bhandup treatment works

Influent pumping station, screens, aerated grit chambers and acrated lagoonswith a design flow of 176 mid, will be provided at Bhandup.

1.15 kldometers of force main to convey sewage from pumping station toaerated lagoon site

3.7 Present status

Due to techno-econoiuc reasons and logistic constraints, the executionschedule of the first phase facilites has been considerably delayed. Further,recent observato on wastewater genraion m the seri ars haveindicated deviations from the onginal estimates. For instance, the presentwastewater flows in Worli, Bandra and Ghatkopar seri areas have beenfound to be considembly less than the prqected wastewater flows for theyear 1992. Whereas the wastewater flows already reaching the pumpingstations at Bhandup, Malad and Versova are considerably higher than the-estimates.

Ln view of the above and the findinp of ongig envimmental impactassessment stuhdies, the design for Bandra and Worli outfalls, and aeratedlagoons at Malad and Versova are under review. Importanty, the 3 kilometerlong outfalls at Worli and Bandra will now be constructed with the option foraugmenting their length in future. The option of constructing an outfallinstead of aerated lagoos catering to Malad and Versova service areas is alsobeing currently evaluated. The design period for these schemes has also beenextnded to year 2015 in view of considerable delays on the project.

The revised estimates of wastewater flows for the years 1992, 2005 and 2015,along with the original estimates of MJs. Metcalf & Eddy and percent changewith respect to those, have been presented in Table 33. Al calculations in thisreport for assessment of enviromental impacts of Bhandup and Ghatkoparaerated lagoons are based on the revised esimates for the year 2005. Thereprt also highlights possible additional wastewater management options tocater to estimated wastewater flows for the year 2015.

Regarding the progress of work on the pumping stations, at both KitridgeRoad and N.FIhoad, in Colaba service area, new pumping stations have beencommissioned. n Love Grove servce area also all pumping stations asenvisaged in phase I, have been commiid.

AEDtELAGOON3.10

Table 3.3

Projected and revised estimates ofaverage dry weather flow (mld)

Drainage 1992 2005Zones

AsperMeklf As calculated Vaiation AsperMetcaf As caluated Viationand Eddy from water and Eddy from water

prtections supply data proections supply datafrom His rin H£Vs

DepL Dept

Colaba 38 32 -15.50 41 37 -10.07

Love Gwve 687 315 -54.20 757 511 -32A6

Bauira 619 492 -30.0 797 552 -30

Versova 97 115 19.06 131 164 24.92

Mad 203 193 -5.00 28) 364 29.75

r ' 30m1 250 -2L77 386 321w -17.00

Dhanldup 125 150 430 176 208 1&00

Total 2070 1547 2568 2157

* - These flows are expected to be 674 dld and 345 mlId for Ghatkopar and Bhandup tervice areasespectively by the year 2015 (August, 1994 esfimates)

T- hese flows have been further revised to 285 mId for Ghatkopar and 280 mld tor Hhandup service areasrspectively, (November 1994, esmates)

ALUM LOONS '

In Bandra service area, among the four pumping statons to be upgraded inthis area, Mahim and Wadala pumping stations have been commissioned.For Sion Koliwada and Matunga pumping stations, the work is i differentstages of progress and the stations are expected to be commissioned by theend of 1995 and 1996, respectively.

AAJED LAOONS 3.12

Chapter 4AERATED LAGOONS

4.1 Preamble

Major cities, all over the world, have witnessed accelerated rise inpopulation under the onslaught of urbanisation and industrialisation. Asthe cities struggled to develop the infrastructural facilities to keep pace withthe growing needs, environmental priorities were invariably neglected. Allmajor cities, thus, faced environmental crsis at one point or the other duringthe process of iteir development, the most common being widespread-pollution of the nearby water bodies. Very poor water quality in riverThames, downstream London, and in river Seine, downstream Pans, upto

; middle of 60's are examples of such neglect in the two major cities ofEurope.

As the true dimensions of ecological damage due to inadequate treatmentand disposal of wastewater became apparent, town planners began to paymwre attention to wastewater management The sustained effort towardsbetter management of water resources, in the developed countries, hvas lcdto appreciable success in contml of water pollution due to disposal ofdomestic wastewater. Developing countries, however, are still witnessing

g pollution of inland and coastal aquatic resources due to low key anidsporadic efforts in the area of wastewater management.

In the control of domestic wastewater pollution, wastewater treatment hasbeen the key element. For such treatment, naturally occurring biologicalprocesses have been exploited the most, wherein microorganisms utilize theorganic matter in the wastewater as substrate and thus reduce the pollutionload in effluents. Biological degradation is carried out b! microorganismsunder either aerobic or anaerobic environments. Aerobic biologicalprocesses have been more popular for treatment of domestic wastewater.These processes include a wide spectrum of treatment technology options,starting from simple oxidation ponds to technologically advanced optionssuch as activated sludge systems running on pure oxygen

The processes, however, greatly differ in their land, power and maintenancerequirements. For instance, power and maintna need of stabilizationponds is virtually nil. These, however. entail very large land area. On theoher hand, activated sludge process requires negligible land area incomparison to stabilization ponds but is highly energy intensive anddemands sskilled operation and maintnan Aerated lagoons fall in themiddle of the two extremese. The land requirement for aerated lagoons ismuch less than the stabilization ponds. The energy requirements although

AWM OOMNS AI.

are comparable to activated sludge process, the process is almostmaintenance free. Availability of sufficient land in the four service areas andlow skilled maintenance needs perhaps were the prime factors for selectingaerated lagoons as the sewage treatment technology for Bombay.

4.2 Salient features of aerated lagoons

421 Types and Design features

Aerated lagoons are earthen basins generally 2.5 to 5.0 meters deep,provided withmecharical aerators installed on floats or fixed columns. Rawsewage is fed from one end into the lagoon after preliminary treatment andleaves from the other end after a desired period of aeration. Dependingupon the power input per unit lagoon volume and the provision orothrwise of a recirculation arrangement, the solids in the system eithersettle, flow-through or build-up. Thus, based on the way solids are handled,the aerated lagoons could be cassified as:

1. Facultative2 Aerobic, flow-through, or3. Aerobic, with solids recyde

The different ways of handling the solids have a substantial effect onefficiency, power requirement, detention time, sludge disposal etc. and the.design methods have to take these differences into account although thebasic princples of biological treatment apply equally well to all the threetypes.

In facultative aerated lagoons the power input per unut v,olume is onlysufficient for diffusing the required amount of oxygen into the liquid to keepthe dissolved oxygen in the lagoon at about 1-2 mg/L. The aeration,lwwever, is not sufficient for maintaining all the solids In suspensionConsequently, some of the suspended solids entering the lagDon and someof the new solids produced in the lagoon as a result of substrate removal,tend to settle down and undergo anaerobic decomposition at the bottomThe activity in such a lagoon is, therefore, pardy aerobic and partlyanaerobic which gives it the name 'facultative'. These are also sometimesreferred to simply as 'aerated lagoons'. Such lagoons generally provide70-90 per cent BOD removal effidency for domestic sewage. A typical layoutof a facultative aerated lagoon is shown in Figure 4.1.

Aerobic, flow-through lagons are hose where the power level is highenough not only to diffuse enough oxygen intD the liquid but also to keep

AAEDLAGOON 42

Figure: 4.1A mechanically aerated facultative lagoon.

FLOa rNs oa

reXgo pTyP VCRTIC&L

A11$ AERATOR

INLTn CNA BER &ERB- TWoosP *trIPUENT

WItH V NOtCN OUTLETANAEROBIC

SECTION

PLAN

A,, A LAGOONS 4'3

all solids in suspension as in an activated sludge aeration tank. Nosettlement of solids, therefore, occurs within the basin. In these lagoons thewastewater leaves along with solids under aeration. Thus, efficiency of BODremoval attained in these lagoons is only in the range of about 50 to 60percent. Additional treatment is necessary if better BOD and solids removalis desired. In fact, these lagoons are generally followed by facultativestabilization ponds or aerated lagoons or are designed with the intention ofconverting them eventually to aerobic lagoons with solids recyde. As theentire lagoon contents are aerobic, these lagoons are also sometimes referredto as 'aerobic lagoons' to distinguish them from 'aerated lagoons' a termused for facultative lagoons. A typical layout of an aerobic flow-throughlagoon is shown in Figure 4.2.

Aerobic lagoons with solids recycle are just like activated sludge orextended aeration systems. The power input level is sufficient to meet theoxygen requirements and keep all solids in suspension. But the solidsconcentration in such a lagoon is quite high, since the system is designed toprevent the solids from escaping out with the effluent by the incorporationof some form of solids settlement and recycle. In such lagoons, BODremoval efficiencies can be as high as 95 to 98 per cent and nitrification canalso be achieved. A typical layout of aerobic lagoons with solids recycle isshown in Figure 4.3.

42.2 Construction features

Lagoons are generally built 2.5 to 5 meters in liquid depth in earth workwith the slopes partly or fully pitched in stone and the inlet and outletlocated on opposite banks.

Where fixed aerators are used, it is essential that the liquid level in thelagoon is maintained constant so as to ensure the required degree ofsubmergence of the aerator blades. This implies (a) watertight conditions inthe lagoons, and (b) dischrge of effluent over a weir located at the desiredleveL To avoid percolation, the lagoon has to be located in relativelyimpervious soil or suitably lined or constructed in masonry or concrete. Thelatter is generally avoided owing to the volume involved. Control ofpercolation is also to be considered from the point of view of ground waterpollution

Where floating aerators are used percolation does not affect aeration sincethe aerator submergence always remains the same. Hence, the lagoon can beconstmcted easily and inexpensively in earthwork and provided withpitching, if necessary. This is the main advantage of using floating aerators.

AMiEDLAGOONS 44

S~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Figure: 4.2A mechanically aerated flow-through lagoon.

rFLOATING Ot FrixD TYPEV tnTlCAL AXIS -AERATOR

INLET CHAMUEN R UC PiPe crFLUENTWITH" SCRfX--- OUTLETAND v NOTCH

SECTION

PL AN

a~ ~ ~~~~~EAI UCOONS - -5

Figuw : 43Aerobic aerated lagoon with solids recycle.

rLOAntEG ORfIl toC - JrPc

. / V~~~~WETCALC AXIS

INLgT CNMAMIERI% L TOP CpIP ENTWIlTH SCREEN OUTTAND V mrc M SLUDCEE E- XCESS

SECUiON aRTURN - SLUDGE

. O--tI

N SUjPUMP i SLUDGE

"f TU"" SLUOCE , *RCO

--.

The floats or pontoons should be fabricated from non-corrodable material toensure durability. The steel ropes used to anchor the aerator to the sidebanks also serve to carry the cable connections. For repairs or maintenancethe aerator can be pulled or dragged in water to a corner of the lagoon wherea small loop or arm can be provided to 'wet-dock' the aerator or enable itslifting for inspection.

Aerated lagoons are often rectangular in shuape aLthough they could be builtin any shape to conform to natural typographical features. In case of unevenshape, the number and disposition of aerators are designed to ensureuniform oxygenation.

It is preferable that the inlet pipe is submerged to avoid odours andshort-circuiting, while the outlet weir is provided of sufficient length toavoid heading up at peak flows which would change the aeratorsubmergence in the case of fixed aerators. The outlet weir should beprovided with a stiLlng baffle to avoid the sewage splashing over the weir-due to agitation in the lagoons.

In the design and construction of these lagoons, the usual principles of goodcivil engineerng practice apply as for waste stabilization ponds, particularlywith regard to embankment slopes, compaction of earth work, pitching,flood irrigation etc.

The water level in the lagoon may be so kept as to enable flow by gravity toadjoining fields for irrigation or to the receiving water body at the time offlood or high tide as applicable.

4.3 Lagoon effluent characteristics

As is evident from description of various types of aerated lagoons, BODremoval efficiency in such systems (aerated lagoons) could varv over a widerange between 50 - 98 per cent. Also, effluent from lagoons with or withoutrecycle could significantly differ in ammoniacal-N and nitrateconcentrations. Wide range of coliform removal is also observed subject tothe lagoon design.

In view of above, the lagoon effluent characteristics can not be a prioriprecisely defined. For facultative aerated lagoons treating domestic sewage,however, 80 per cent BOD removal, 90 per cent coliform removal and noreduction in ammowracal-N may be assumed as reasonable. Under theseassptions, a raw sewage of about 200 mgJL BOD, 1x07/100 ml totalcoliforms and 20 mg/L ammnoniacal-N is expected to yield an effluent

AEED LAGOONS

having 40 mg/L BOD, Wx106/100 ml total coliforms and 15-20 mg/Lammoniacal-N.

4.4 Environmental repercussions

The impact of aerated lagoon effluents on the receiving water body isgoverned by the available dilution and assimilative capacity. For effluentcharacteristics described above, approximately 12 times dilution would benecessary to bring down the BOD and ammoniacal-N levels sufficiently toavoid an adverse depletion of dissoved oxygen. A few hours of travel timebefore the effluent reaches the sensitive locations, however, will benecessary for total coifonms to decay to a level of about 10000, 100mi whichmay be considered safe for bathing. For discharge of effluents into creeks,available dilution at the low tide slack period could be of overridingimportance as during the fiood tide, pollutants are pushed into inner regionsof the creek and may cause significant dissolved oxygen depletion. In theabsence of adequate dilution, bacterial contmdition of water andsediments may also occur in the water body.

The impact of lagoon effluents on the receiving waters, however, is closelylinked with the performance of the aerated lagoons. Inadequate lagoonperformance can also lead to odour problem due to formationl anddispersion of hydrogen sulphide. AMother aspect of lagoon operation isperiodic desludging of facultative lagoons. Adequate measures are alsonecessary for proper disposal of sludge to safeguard against ground watercontamination due to formation of leachates at the sludge disposal sites.

Environmental repercussions may also arise due to the civil wvorks activitvduring the Canstruction of the lagoons. These impacts are primarily, air andnoise pollution at the construction and quarrying sites, due to materialhauling and operation of construction machinemr

4.5 Environmental safeguards

Environmental safeguards for regulating the beneficial uses of receivingwaters against industrial/municipal discharges are achieved throughcompliance with the environental standards. In India, Environment(Protection) Act, 1986 vests in Central Govemment, the powers to lay downstandards for environment protection. Central and State Pollution ContolBoards are responsible for ascertaining compliance of these standards. TheBoards, based on local conditions, have power to stipulate more stringentlocation specifc standards.

AELiAGOONS a.

For protection of coastal water quality, two standards apply in India. Thefirst of these standards is in the form of receiving water quality and is basedon best designated use of the water body such as for bathing, fishing ornavigation. Details of these standards (IS:7967-1976 ) are provided in Table4.1. The creek and coastal waters used for recreational purposes or fishing,.accordingly, slhould always have BOD less than 5.0 mg/L, total coliformsless than 1000/100 ml ( 95 per cent of observations) and dissolved oxygenmore than 3.0 mg/L.

Another set of standards in the form of effluent standards for discharges intotidal creeks, however, is also applicable to Thane creek (Table 4.2).According to this standard, effluent with BOD and suspended solids of 100mg/L each and ammoniacal-N upto 50 mg/L can be discwarged into thecreek and form the basis for the discharge consent given by the MalharshtraPollution Control Board (MPCB) to MCGB for discharging treated sewageeffluent into Thane Creek from proposed Bhandup and Ghatkopar lagoons.

On careful consideration of these standards, a possible incompatibilitybetween the receiving water and effluent standards becomes apparent. Forconcurrent compliance of effluent and receiving water standards, aminimum dilution of about 20 times is necessary within the creek. Suchdilution may be attainable for small discharges but is extremely difficult foreffluents of the order of 12 m3 /s, the combined estimated discharges from,Bhandup and Ghatkopar service areas in the year 2015. Further, thereceiving water standards entail that if the creek waters are used for fishing,95 percentile total coliform levels should be less than 1000/100 ml. Theeffluent standards, however, do not specify a bacteriological standard andtotal coliform levels in Thane creek as a result of expected discharge of 12m3/s with total coliforms levels of about 10"/100 ml shall certainly remainabove 10,000/100 ml.

A rational envirorunental objective with respect to effluent discharges inThane creek, therefore, would be to safeguard the ecological role of the creekas the breeding area for a variety of coastal marine fauna. Such an objectivemay be achieved if the dissolved oxygen in the creek is maintained above 2mg/L for the entire tidal cycle and accumulation of toxic substances in thesediments is avoided.

4.6 Proposed aerated lagoons at Bombay

The important factors affecting choice of type of lagoons for a particular.application asre teir power and land requirement vis-a-vis theirperformance and operating characteristics. Generaly, the choice lies

AD LAGCOONS A.9

Table : 4.1

Tolerance limits for water quality *after receiving discharges (IS : 7967-1976)

SL CharacteristiCs Tolerance limits for bathing, recreation,No. commercial fish cultre and salt

manufacture(1) (2) O)

1. Color and odour No noticeable color or offensive odour

2. Floating material No visible floating matter of sewage orindustrial waste origin

3. Suspended solids No visible suspended solids of sewage otindustrial waste origin

4. pH value 65 toD85

5. Free ammonia (as N), mg/LT Max 12

6. Phenodic compounds (as C6HOH), 01ng/L, Max

7. Dissolved oxygen, Min 40 percent saturation value or 3 mg/Lwhichever is higher

8 Biodcemical oxygen demand (5 days at 20C) 5.0mg/L Max

9. Coliform Bacteria, MPN index per 1,00010D nl, Max

Abridged

"mm .10

Table : 4.2

General standards for discharge of effluents*+

Sr. Parameter StandardsNo. _

Marine coastal areas

1. Suspended solids, mg/L, Max 100

2. pH value 5.5 to 9.0

3. Temperature, aC Max 45 at the point of disLcharge

4. Oil and grease mg/L, Max 20

5. Total residual chlorine, mg/L mU

6. Amniial nitrogen (as N), mg/L, Max 50

7. Total Ijeldahl nitrogen (as N), mg/L Max 100

& Free ammorna (as NH3 , mg/L, Max 5.0

9. Biocemical oxygen demand (5 days at 20 °C)mg/L, Max 1(0

10. Chemical oxygen demand, mgIL, Max 250

* Abridged+ Ref.: Environment Protection Act, 19B6, Schedule 11. Amended as per Notification dated 19thMay 1993 as schedule VI.

AE-E LA'U 411

between a facultative type aerated lagoon and an aerobic lagoon with solidsrecycle. A flow-through type lagoon is often considered in stagewisedevelopment leading eventually to recycle of solids or is followed by othertreatment to obtain a better quality effluent.

Lagoons with solids recyde are mostly of the extended aeration type asthese avoid the need for sludge digestion units which would be necessarywith conventional activated sludge systems. Extended aeration typelagoons, though relatively easy to operate, do require a greater degree ofattention compared to the facultative lagoons, which are, in fact, thesimplest to operate as their extent of mechanization is truly minimal. Withregard to power and land requirement, the two types of lagoons haveopposite characteristics: the extended aeration lagoons require more powerbut much less land, the facultative lagoons require more land but lesspower.

Facultative lagoons may be favoured for a large number of situations underwnich the oxidation pond may not be acceptable owing to its high landrequirement, and the other methods like activated sludge may not bedesirable either owing to their technological requirements or simply becausea higher quality effluent is not essential. Both these factors have beenresponsible for favouring a treatment system based on facultative aeratedlagoons at Bombay.

4.6.1 Design specifications

The wastewater generated in Bhandup, Ghatkopar, Malad and Versovaservice areas is proposed to be treated in aerated lagoons before itsdischarge into the adjoining Thane and Malad creeks. Initially, all theproposed four lagoons were to comprise of four streams of three cells eachThe wastewater after primary treatment was to be divided into four equaland identical streams comprising of three lagoons or cells with averageresidence times of 1.4,1.8 and 1.1 days respectively. Out of the three cells, thefirst cell was to operate as a flow through aerated lagoon and the followingtwo cells as facultative aerated lagoons. The overall removal efficiency of thetreatment system was expected to be 80 per cent of BOD and 70 per cent ofsuspended solids respectively. The salient design details of the aeratedlagoons are presented in Table 4.3.

Due to paucity of funds and low effluent standards prescribed by MPCBentailing about 50 - 60 per cent BOD and suspended solids reduction, theoriginal plan of implementation has been modified. The first phase activitiesat Bliandup, Ghatkopar and Malad are proposed to be restricted to

ANAID LAGOONS 4.12

Table 4.3

Design specifications of proposed aerated lagoons

Lagoon type and Lagoonsdesign parameter Versova Malad Ghatkopar Bhandup

Aerobic

Retention period (d) 1.40 1.40 1.40 1.40

Volume of pond liquor (tcm) 256.26 326.88 326.88 256.26

Soluble BOD loading (kg/tcm/d) 128.69 128.60 150.00 150.14

BOD loading (kg/d) 32,978.10 42,036.77 75,375.00 38,474.88

Soluble BODs reduction (% / 100) 0.65 0.65 0.72 0.72

BOD reduction (kg/d) 21,435.76 27,323.90 54,270.00 27,701.91

First faciltative aerated

Retention period (d) 1.80 1.80 1.80 1.80

Volume of pond liquor (tcm) 32037 420.28 420.28 320.37.

Soluble BOD loading (kg/tcm/d) 33.03 35.00 32.67 32.60

BOD loading (kg/d) 10,581.82 14,709.80 20,843.46 10,444.06

Soluble-BODs reduction (% / 100) 0.66 0.66 0.71 0.71

BOD reduction (kg/d) 7,015.75 9,708.47 14,798.86 7,415.28

Contd..

AEJTED LAGOONS 4.13

Table 4.3 (Contd.)

Lagoon type and Lagoonsdesign parameter Versova Malad Ghatkopar Bhandup

Second facultative aerated

Retention period (d) 1.10 1.10 1.10 1.10

Volume of pond liquor (tcm) 199.68 256.84 256.84 199.68

Soluble BOD loading (kg/tcm/d) 18.94 19.47 15.50 15.15.

BOD loading (kg/d) 3781.94 6234.00 6334.08 3025.15

General

No. of lagoon sets (No.) 4.00 4.00 4.00 4.00

No. of lagoon per set (No.) 3.00 3.00 3.00 3.00

Overall BOD reduction (Y / 100) 0.80 0.80 0.80 0.80

Detertion period (d) 4.30 4.30 4.30 4.30

AWTED LAGOONS 4.14

construction of only first cell of the four streams. While at Versova, twostreams of the originally proposed three cell lagoons are proposed to beconstructed. Further, based on recent findings of environmental impactassessment of Malad and Versova lagoons (Malad and Versova Aerated.Lagoons- Final Report,NEERI 1994), the proposed construction of aeratedlagoons at these sites is being reviewed and marine outfalls are beingconsidered as alternative option.

During the first phase of implementation at Bhandup and Ghatkopar, thesingle cell lagoons are proposed to be operated as facultative aeratedlagoons instead of flow through aerated lagoons allowing the settlement ofsuspended solids. These modifications will also considerably reduce theoperating costs of the lagoons. Figures 4.4 and 4.5 describe the layout of theaerated lagoons at Bhandup and Ghatkopar respectively. The shadedportion in these figures indicates the facilities proposed to be built duringthe first phase of project implementation.

4.7 Inference

Aerated lagoons provide a robust system for treatment of domesticwastewater. If the land availability is not a constraint, lagoons provide goodoption for wastewater treatment specially for the developing countries due.to their lower capital costs, favourable environmental conditions and easeof operation. Facultative aerated lagoons can achieve treatment efELcienciesupto 90 percent removal of BOD and can, therefore, provide desirable levelsof treatment for most conditions.

The effluents from the proposed aerated lagoons at Bhandup and Ghatkoparwill be discharged into Thane creek. Certain discrepancies between theeffluent discharge standards and receiving water quality standards for thecreek are apparent and the proposed treatment level may not be adequateduring the later part of the design period to maintain desired water qualitvin the creek. The water quality response of creek regions to pollutantsloading is primarily governed by their hydrodynamic behaviour under tidalforcing. Comprehensive hydrodynamic and associated waste assimilationconsiderations are, therefore, necessary to assess the impact of effluentdischarges in Thane creek and to delineate water quality management planfor the region.

A* AED lAGOONS 4.15

0~~~~~~~~~~~~~~~~~~~~~~~~~~

/~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

la FRO INFUEN Antcvza <\ C z PUNPING STAtION FAL -FACULTATIVE AERAT EDmU Lsw1 AGON *

fl ~~~~~~~~~1s\011 213 g i |1 t ==+I ______________________________ I__)______FAL_AL a_ ;|_I

'-F l FAL ,/

NALLA PROPOSED UNODR PHASE I

.~~~~~~~~~ L

W . .

Figure: 4.5

Schematic layout of treatment units - Ghatkopar

.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

cc0

'IL

IL0 0.

.~~~~~~~~~~~~~~~ zc c__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ~ .. i . ,

ABLATED LAGOONS 4.17~~~*~~

Chapter 5METHODOLOGY AND DATA

GENERATION FOR ENVIRONMENTALMANAGEMENT PLAN

5.1 Preamble

The wastewater drainage scheme of Bombay comprises of seven serviceareas. About 60 percent of the total wastewater generated in the cityreaches the west coast either through direct discharges into the coastalregions or through other adjoining surface water bodies such as Maladcreek and Mahim bay. The remaining 40 percent wastewater is dischargedinto on the east coast of Bombay through a marine outfall at Colaba anddirect discharges of Bhandup and Ghatkopar in Thane creek Disposal ofsuch large quantities of wastewater into the coastal regions aroundBombay, despite the significant assimilative capaity of receiving coastalwaters, has led to serious impairment of aquatic environment of certainregions.

Thane creek at the north-east coast is one such affected region. It is atriangular mass of brackish water which forms the eastern boundary ofisland of Bombay and widens out and opens to Arabian sea in the south.It receives an outlet from Ulhas river at its northern end but with verylittle discharges as the river flows past the creek head. Thus except duringhigh tide, its connection to Ulhas river is rarely effective. The creek isdominated by diurnal tides. The maximum tidal range in the creek isabout 5 meters. During an average spring tide the water level rises byabout 4.7 meters above the low tide level. The tidal elevation for anaverage neap tide is about 1 meter.

During an average spring tide the creek stores about 126x1' m3n of waterat the time of low water which increases to about 2'3x10" m3 at highwaters. At an average neap low tide the volume of water in the creek isabout 1.74 xl') m3 which rises to about 1.92 x10" mr at the time of hightide. During the spring tide the average water exchange in the creek,therefore, is about 5.4 times that of neap tide.

Due to the natural ground slopes, the creek receives municipal andindustrial wastewater discharges through a number of channels from theeastern suburbs. The sewage pumping stations at Ghatkopar and Muiundwhich discharge municpal wastewater from Ghatkopar and Bhandupservice areas, however, form the principal pollution loads to inner Thanecreek. Combined discharges from these two sources exceed 400 mid and

ADIWLAGOONS S1

are slated to increase to above 1000 mid by 2015. As the wastewaterdischarged into the creek remains entrapped in a confined volume andmoves back and forth with the tidal action, their continued discharge has.given rise to considerable water quality impairment in inner Thane creek.

In order to mitigate the adverse impacts of municipal wastewaterdischarges in Thane creek, construction of aerated lagoons of designcapacities of 170 mid and 385 mld is planned at Bhandup and Ghatkopar,respectively. Though, the treatment of sewage through the aerated lagoonsis expected to alleviate the pollution stress on the creek, a scientific studyis necessary to estabLish its adequacy for desired water qualityimprovement in the region. Such an investigation can be carried outthrough a dual approach of predictive modelling and field investigations.The present chapter discusses the methodology adopted for delrieatingthe existing environmental condition in these areas and summanzes thepresent status of the environment.

5.2 Scope of field studies

The construction and operation of aerated lagoons are expected to havesignificant environmental impacts. During the project implementation, air.and noise pollution at the construction and material excavation sites arethe major construction phase impacts. The change in hydrodynamiccharacteristics of the creek due to reclamation of part of the inter tidalzone for construction of the lagoons and consequent possibility of floodingof nearby areas during the monsoon is another concern needinginvestigation. Field investigations on ambient air qualityv, noise levels,tidal current pattern, meteorology and sources of noise and air pollutantsduring the construction work were undertaken to generate requisite datafor assessment of these impacts.

The major environmental impacts of the project, however, are thoseassociated with the operation of aerated lagoons and are largely beneficial.Most pronminent of these is expected to be the widespread improvementin the water quality in Thane creek due to reduction of pollution load onthe creek.

It is also necessary that extent of mixing of industrial discharges with thesewage in the drainage area is investigated, as such, disposal in marine.environment could have certain additional impacts due to the presence ofpotentially hazardous substnces. These impacts are reflected in the formof direct toxicity to aquatic life or through biomagnification. The latter

AERJD LAGOONS 52

could also have health impacts on the human population tluoughconsumption of contamtinated sea food.

The magnitude of water quality impacts arising from aerated lagoon'soperation, are governed by a variety of physico-chemical and biologicalinteractions in the creek environment and are substantially influenced bythe ambient tidal currents. Due to the variable hydrodynamic conditionsin the creek and complex nature of water quality transformations, ondythose variations which primarily depend on physical processes orsimpler bio-chemicaL processes are amenable to mathematical modelLng.The relevant processes indude advection and dispersion of pollutantswith tidally driven currents, reaeration due to surface oxygen transfer anddecay of organic matter due to microbial activity. For processes involvingmore complex interactions such as altered nutient balance insediments and ecological transformations in the creek, it is necessary toadopt the approach of observation and inference on the regions whichhave water quality similar to the expected quality in Thane creek afterimplementation of the schemes.

In view of the above, the sampling and data generation on coastalenvironment had two distinct objectives. One set of activities wereundertaken to define the existing water quality in Thane creek andobservations on ecological status in areas which currently have conditionssimilar to those aimed to be achieved in Thane creek later. Other set ofdata was collected to obtain ambient environmental conditions and localestimates of model coefficients needed for quantitative predictions of theimpacts using mathematical models. Sampling and characterization ofraw wastewater in the Bhandup and Ghatkopar service areas were alsoundertaken during the course of the field studies.

Methodology and findings of the field studies for defining the ambientenvironmental conditions are described in the following sections. The fieldmonitoring progammes to establish model coefficients for predictivemodeling are presented in chapter 7.

53 Methodology and findings

5.3.1 Air quality

To establish the baseline status of air quality near the construction sites ofaerated lagoons at Bhandup and Ghatkopar, air quality monitoring wascarried out at two locations for each site. Samples for gaseous pollutantsviz. NO. and 9°2 and suspended particulate matter(SPM) were collected

AE ZLAGOONS

as 8 hourly averages. As winter season is generally considered criticalperiod for air quality, the observations were made during February, 1992.The monitoring was carried out continuously for one week at each site.Concurrent to air quality monitoring, site direction micrometeorologicaldata viz. wind speed and direction were collected at 8 meters above theground level through an automatic computerized weather station. Therecorded data was used to draw wind roses for both the sites.

The wind roses for Bhandup and Ghatkopar sites indicate that thepredominant winds are from NW and NNW directions for Bhandup andfrom NW, NNW and NWW directions for Ghatkopar respectively. Theobservations have been found to be in conformity with the climatologicalnormals of the region for the month of February. The wind speed wasobserved to be in the range of 1-5 kmph for 10 and 21 percent of theduration at Bhandup and Ghatkopar respectively The wind speeds of6-10, 11-15 and 16-20 kmph occurred for 29, 13 and 8 percent of the surveyperiod respectively at Bhandup and 18, 15 and 9.7 percent at Ghatkopar.Calm conditions (below 1 kmph) prevailed for about 40 and 36 percent ofthe times at Bhandup and Ghatkopar, respectively

During the air quality morutoring survey, 8 hourly samples were collectedat two locations for each lagoon site. Round the clock observations werecarried out for a period of seven days resulting in 42 observations at eachsite. The samples were analyzed for SO2, NO2 and SPM levels. The averageSO2, NO, and SPM levels at Bhandup lagoon sites were observed to be 3.5,12.2 and 246 pg/m3 respectively. The maximum and minimum observedconcentration for these parameters were 9 and 3; 42 and 3. and 51S and 1=2p1g/m3 , respectively.

Observations at Ghatkopar indicated that the average Ilvdls * SO.. NO.and SPM were 63,15.6 and 339 I.g/m3 respectiveh. fln maximum andmirimum observed concentrations were m22 and 3 pg. m fr S,0- 34 and 3jig/&m for NO, and 677 and 86 4g/m3 for SPM, respectively.

According to the Development Plan for Bombay, Bhandup and Ghatkoparare designated as residential areas. Comparison of the observed air qualitylevels at Bhandup and Ghatkopar aerated lagoons sites with the ambientair quality standards prescribed by Central Pollution Control Board forresidential urban areas, indicates that the levels for all air pollutants atthese sites are well within the prescibed limits for such areas.

AEMDLAGOONS SA

5.32 Noise studies

The objective of field observations on noise levels was to generate noisedata for estimating the rise in ambient levels due to constructionactivities at those residential areas (sensitive zones) which are in closeproximity of the proposed sites. The observations, therefore, includedmeasurements on ambient sound levels at lagoon sites and nearbysensitive areas. In addition, inventory of construction machinery assources of noise and their operation pattern during the constructioln wasalso determined.

5.3.2.1 Sound levels at Bhandup lagoon site

Sound level measurements at Bhandup aerated lagoon site were carriedout at various locations as depicted in Figure 5.1. No excavation orconstruction activity at the site is in progress as the proposed lagoons arescheduled to be constructed only in 1996.

Sound level measurements were carried out around the periphery as wellas at the centre of the site. The observed sound levels are presented inTable 5.1 . The observations indicate that the ambient noise levels at thelagoon site are in the range of 45 to 50 dBA which occasionally rise to 54dBA due to the blowing of wind, chirping of birds etc.

As no construction activity was in progress and the nearest humansettlements are located beyond 1 kilometer from the lagoon site, soundlevels at these locations are unlikely to be affected by constructionactivities. No sound level measurements were, therefore, conducted atthese localities.

5.322 Sound levels at Ghatkopar lagoon site

During the survey, the construction of aerated lagoons was not inprogress. The wastewater treatment facility construction was nearlycomplete with some metalling activity being carried out at the time of.survey.

Sound level measurements were carried out around the periphery andcentre portions of the lagoon sites. The measured sound levels along withthe description of prominent activity at the point of observations ispresented in Table 5.2 . The observations indicate that the ambient noiselevels at the lagoon site are in the range of 41 to 45 dBA which occasionallyrise to 60 dBA due to the vehicular traffic on the highway (Figure 5.2).

AERWED LAGOONS

Figure : 5.1

Observed noise levels at Bandup lagoon site

NVO DEVELOPMENT ZONE

N.~~~~~IN

:~K _

* 1. .7

AERATZO LAGOON

3

AERATED AGOONS Si

Table : 5.1

Sound levels at Bhandup aerated lagoon site

Point No. Sound level ActivitydBA

1 41.8 - 51.2 Nil

2 43.8 - 46.0 Nil

3 44.1 - 54.2 Nil

4 42.4 - 52.0 Nil

5 46.8 - 53.2 Nil

6 45.0 - 49.0 Nil

7 41.0 - 45.0 Nil

8 39.2 - 43.0 Nil

Table: 52

Sound levels at Ghatkopar aerated lagoon site

Point No. Sound level ActivitydBA

1 45.0 - 603 Metalling of surtace in tront ofwastewater treatment facility

2 41.0 - 57A Nil

3 37.0 - 41.6 Nil

4 40.1 - 44.4 Nil

5 39.3 - 43.4 Nil

6 38.8 - 42.9 Nil

7 38S - 43.0 Nil

8 392 - 44.1 Nil

9 402 - 45.6 Nil

ASAED LAGOONS

a~~ -

Figure 5.2

Observed noise levels at Ghatkopar lagoon site

I LAGOAR * t E LAGOON X.l

ATEDWLAGOONS Ss

9~~~~~~~~~~~~~~~~~~~~~~~~~~

As the nearest human settlements are located beyond 1 kilometer from thelagoon site, sound levels at these locations are unlikely to be affected byconstruction activities. No sound level measurements were, therefore,conducted at these localities.

53.3 Land environment

533.1 Land use

The baseline data on land environment pertains to present land usepattern in and around the aerated lagoon sites and properties of soils. Theland-uses have been recorded around each lagoon site in eight directions,keeping the specific site in the centre with necessary discretion for areacoverage in each direction It may be noted that most of the residentialand commercial areas are located in South-East, North-East, East, South,West and South-West directions in the same order. Some of the playgrounds and gardens are also located in these directions with respect tolagoon site.

The data on land use pattern around Bhandup lagoon site is presented inTable 5.3. The proposed site is being developed by reclaimingapproximately an area of about 40 hectares partially covered bymangroves on the west bank of the creek. There is no municipal park,national highway or residential area in the immediate vicinity. The nearestresidential and commercial areas are located on north-west, west,south-west and north of this lagoon. A BEST bus depot is located on thewest and a MSEB sub-station in the north west direction of the lagoon site.

Land use pattern amund Ghatkopar lagoon site is presented in Table 5.4.The area of this lagoon site is considerably bigger than that of Bhandup.The proposed site is being developed by reclaiming approximately 90hectares of land partially covered by mangroves on the west bank ofThane creek near Ghatkopar. Most of the residential and commercial areasare concentrated towards the.west, north west, south-west and northsides.

In view of significant requirements of construction mcaterials such as,murum, boulders and bricks for the project and consequent environmentalimpacts of quarrying operations, two of the quarry sites were alsostudied for ambient environmental quality.

Land use pattern around all the identified quarry sites, within 1 kilometerradial distance, is more or less similar. All the quarry sites are accessibleby roads. They are either located on no development zones or beyond 500

AUATED LAGOONS A9

Table: 5.3

Land use pattern around the aeratedlagoon site at Bhandup

(area in hectares)

SL Type of land use Direction (wzt. lagoon site)No. E S-E S S-W W N-W N N-E

1. Lagoon area - - - 58 - - - -

(Approximate)

2 Creek 622 400 158.3 16.6 21.0 Nil Nil 6

3. Munidpal park Nil Nil Nil Nil Nil - 70 91

4 National highway Nil Nil Ni£ 13.0 10.3 3.3 92 Nil

5. Residential and Nil Nil Nil 72.6 140.0 397 40 Nilcommercial areasincluding roadretwork and saltpans

6. No development 92.8 Nil 21.7 302 89.4 Nil 9.5 32zone

7. Recreational/play Nil Nil Nil 17 28 - 1o Nilgrounds

8. Oders - - _ _ 4+ 7+_

+ RS receiving station++ B.E.S.T bus depot and MS.E.B. sub-statiorL

AIWALED AGOONS LID

Table:5.4

Land use pattern around the aeratedlagoon site at Ghatkopar

(area in hectares)

Sr. Type of land use Direction (wit lagoon site)No. E S-E S S-W W N-W N N-E

1. Lagoon area - - - 108 -

(approximate)

2. Creek 55 8 Nil Nil Nil Nil Nil 40

3. Municipal park Nil Nil Nit Nil Nil Nl Nil Nl

4. Nationalhighway Nil Nil Nil 6 11 Nil 13 Nil

5. Residential and Nil Nil 89 213 227 390 209 Nilcommerial areasincluding roadnetwork and saltpaw'

6. No development 223 287 9 30 5 Nil 98 280zone

7. Reaeational/play Nil Nil 9 27 15 10 28 Nil-nds

8. Others Nil 62 100 4' 13 Nil Nil Nil

Part of IVth railway terminal

AMIRAED O 5.11

meters from the nearest residential and commercial areas. Railway lines,water reservoirs and public gardens are located at safe distances from thenew quarry sites. The proposed sites are as listed in Table 5.5.

Since general principles of reclamation, rehabilitation and environmentalmanagement are basically similar for all quarrying operations, it is feltadequate to study two quarry sites which are in operation. These areOshiware/ Ambivali quarry in Andheri Taluka and Damupada quarry inBorivili Tehsil. The first quarry is mainly surrounded by slum hutments.with stone crushers located at several places. The area is devoid of treesand vegetation. The surrounding areas mainly include residential andcommercial developments along the S.V. Road, encroachments by slumsand a few multistoreyed buildings. In the case of Damupada quarry site, 8hectares are covered by the quarry, 30 by Sports Authority of India (SAI)and 242 hectares by slums. The SAI campus has a number of trees plantedwithin their area. The remaining area has no vegetation.

5.3.3.2 Soil characteristics

Considerable portions of the areas dose to the construction sites have to bereclaimed from the creek. Irrespective of the refill material used, due to itsexposure to marine water owing to capillary action the soils in the regiontend to become saline which can retard the growth of many plant species.A number of soil samples were collected covering the regions surroundingthe lagoon sites with the view to examine the nutrient levels aredexchangeable properties. Such information is necessary for the design ofthe green belts around the sites to mitigate the negative aesthetic impactsdue to the construction of wastewater treatment schemes in closeproximity to residential areas.

Surface soil samples were collected from the lagoon sites. The mainobjective of sampling was to assess the soil properties relevant to plantgrowth on the refilled lagoon sites, in their immediate vicinity and alongthe sides of major roads. In the case of lagoon sites at Bhandup andGhatkopar, the major road is Eastem Express Highway (EEH). Surfacesamples were collected from 4-6 different locations in each case andcomposited. Two composite samples were collected at each lagoon siteand analysed for relevant soil properties. The data is presented throughTables 5.6, 5.7 and 5.8.

The data on physical properties of the soils indicate high soil pomsities'along the EEH and at Ghatkopar lagoon site (Table 5.6). At Bhanduplagoon site the soil porosities are relatively less. The soil texture is loamy.

AERED LAGOONS 5.12-

Table :5.5.

Proposed quarry sites

Sr. District SiteNo.

I Bombay Borivali

2 Thane VasaiTIhaneKalyanUlasngarBhivandi

3 REigah AlibagUranKa#atPanvelKhalapurPet

Table :5.6

Physical properties of soils at the aerated lagoon sites

Sr Site/ Sample Density, Porosity Particle size distribution SoilNo. particulars (g/ cc) (per cent) (per cent) texture

Particle Bulk May Silt Fine Coarsesand sand

1 BhandupEEH-sides 1.128 2487 54.6 14.5 1Z0 8.0 65.5 Loam

Lagoon site 1.247 2.079 40.0 10.0 28.0 12.0 50.0 Silty8loam

2. GhatkoparEEH-side 1.113 2.578 56.8 14.0 8.5 9.7 67.8 Sandy

loam

Lagoon site 1246 2709 54.0 7.5 115 11.0 70.0 Loamy~~~~~ sate~~~~~m d -

EEH -Eastem express ighway..

AAED LAGOONS 5.13

.

Table: 5.7

Chemical properties of soils at the aerated lagoon sites

St. Sitel Sample pH Conductivity Cadons AnionsNo. particulars ,L mhos/ cm (Meq/1) (MeqI 1)

Ca++ Mg++ Na+ K U a- HCO3- SOC2

L UhandupEEH-side 730 7.60 0 30 1.12 14 .ll 8.60 0.20 4.30Lagoon site 7.60 8S90 40.00 62.00 67.00 0.20 10.50 15.00 49.00

2. GhatkoparEN-side 820 1.50 130 0.80 0.45 0.08 128 0.15 .00Lagoon site 7.70 4720 38.00 2320 33.00 020 70.00 850 1550

EEH - Eastern express highway

Table :5.8

Cation exchange properties of soils at the aerated lagoon sites

SY. Site/ Sample Exchangeable cations ExchangeableNo. Particulars (meq/ 100g) Sodium

per centCa++ Mg++ Na+ K (ESP)

L BhandupEEH-side 9.0 3.0 21.8 25 60.0

Lagoon site 32.0 24.0 11.6 2.1 16.6

2. GhatkoparEEH-side 27.0 2.1 2.7 2.0 8.0

Lagoo site 8.0 5.2 7.1 2.0 31.8

EH - Easten express highway

AWED UGOONS ~~~~~~~~~~~~~~~~14

Physical properties of these soils would not normally pose problems forplant growth unless chemical properties, such as dissolved salts, or

- exchangeable properties such as exchangeable sodium percent (ESP) of thesoils impose their influence on plant growth.

The 1:2 soil-water extract analysis presented in Table 5.7 indicates that thesoils have a pH range usually encountered in the case of normal soils (pH6.5-8.5). However, the dissolved solids as revealed by the electricalconductivity (EC) values, are very high for the lagoon sites . In sites withhigh EC values the concentration of divalent cations and sodium are quitehigh and in comparble concentrations. Similarly, amongst the anions,concentrations of ciloride and sulphate ions are high and comparable.

The cation exchange properties of the soils (Table 5.8), indicate thatexchangeable sodium percentage is more than the maximum permissiblelimit in all soils except at EEH near Ghatkopar lagoon site.

5.33.3 Terrestrial ecosystem

The tenrestrial ecosystems at the lagoon sites constitute a habitatconsisting of shrubs which mostly include mangroves and halophytesalong estuarine shores and mud flats . Mangrove formation and zonationare influenced by several factors like tidal range, temperature, salinity,rainfall, landwash, substrate characteristics, nature of the shore etc. Thedifferent systems followed for making zonation patterns mainly dependeither on the frequency of inundation, salinity of the soil or dominant treespecies. The species that are found at the lower levels are inundated by seawater twice daily during semidiurnal tides, whereas those found at thehigher levels get submerged in water only during high tides. Thevegetation and fauna occupying the swamp get adapted to varying levelsof salinity and show tolerance to the fuctuations in saline concentrations.

It was estimated in 1959 that the area of mangrove forests in Bombav andadjacent coastal districts is about 24,870 ha. The revised estimates indicatethat the same is around 20,000 ha in 1975 .The mangrove swamps ofBombay are worst affected by human interference. The main factorsinclude increase in population pressure and consequent large scalereclamation of mangrove swamp areas for housing, indiscriminrate cuttingof plants. According to recent sateLlite imageries the total mangrove areaavailable in inner Thane creek is approximately about 750 hectares.Significant mangrove areas have also been redaimed for salt panconstruction. Baseline studies on vegetation with reference to speciescomposition, diversity, abundance and distribution have been carried out

AEIWED LAGOONS

in the study areas at the two lagoon sites viz; Bhandup and Ghcatkopar.Quadrat method was adopted for sampling in approachable areas.

Most of the mangroves have adapted themselves to their environmentthrough development of required parts for attachment to soft or loosesubstrata, formation of respiratory roots and aerating devices, evolutionof vivipcary, use of specialised means for seed dispersal and developmentof xerophytic structures. Usually they are shallow rooted and lack.well-developed tap roots due to high salt concentrations,water saturationand anaerobic substratum whiLch is organically rich. A number ofadaptations in root morphology are typical of most of the mangroves. Theroots may be 'prop' (from lower part of the stem) or 'drop' (from upperpart of the stem) type that terminate after growing for few centimeters inthe ground (e.g. Rhizophora sp.). In other cases, 'surface' (1-5 centimetersdeep) horizontal roots grow out from the stem base and producenegatively geotropic, erect, aerial roots called pneumatophomes (eg.Avicennia sp.). All these roots act as ventiation systems by havingspeciaLsed air space systems, and they further produce anchoring andfeeding types of roots, which help in absorption.

Bhandup

The most dominant speces at this site were found to be Avicennia marina,followed by Sailvadora persica and Ceiriops sps. with an linportance ValueIndex of 81.90, 12.21 and 5.89 respectively. It was again observed here thatAziicennia were dwarfed with an average height of 0.61 meter as comparedto the other plants with an caverage height of 1.08 and 0.72 meterrespectively . The total mangrove area being reclaimed for lagoonconstruction is 608 meters x 574 meters. The area is partially covered bymarshy grass Acluropus villosus along with Scsuwiuin portulu:custlri. Mudflats were also observed in patches at some places. Aviccnnia species wasabundantly found at some places whereas the same were found to beabsent in some areas. This may be due to human interference for firewood/fuel wood and other purposes.

Glatkopar

The most dominant species observed at this site was again Avicnujiaexhibiting monoculture vegetation with an Importance Value Index of 100.The plants were taller as against the observations made at the other sites,with an average height of 1.34 meters. Other species observed here includeSalvadora persica. Nearly 90 hectares of land partially covered bymangroves is expected to be needed for lagoon construction out of whichabout 50 percent has already been reclaimed.

AERA EDLAGOONS - 5.16

The fauna present in mangrove forests were also studied. A number ofinsects especially mosquitoes and midges were present. Water.accumulates in the rot holes of branches and these are the ideal habitats forthe mosquitoes and midges larvae. Mudskippers from the chnunels fliptheir way across the soiL Hermit crabs were also observed in these foresLAmong thle mammals fox, jackal, fishing cat, dog, rat and mongoose weref6tind witlhin Lhlc sLLEdy area of two) lagoon sites. Differelit tyles (if birdpopulationis were also observed in marshy areas around these sites. It wasreported that some common migratory birds visit the marshy areas in theDecember-January and stay till March-April of each year.. They feed onsmall fish, floating garbage and waste materials which adhere to themarshy land especially during low tide. These birds are often called as'scavengers'.

5S.4 Water quality

Water quality in creeks which receive significant wastewater discharges, isintricately linked with the tidal conditions. The water exchange with thecoastal sea is far greater during the spring tide in comparison to the neaptide. The volume of water retained in the creek at the low tide is, however,.more during the neap tide than the spring tide. Identification of criticaltidal conditions in a creek with respect to the creek water quality,therefore, is not straight forward and requires water quality investigationswhich cover both spring and neap tide conditions of differing tidalstrength

Also, the regions of water quality impairment due to wastewaterdischarges shift with the tidal conditions. Delineation of such regionsalong with quantification of the extent of water quality impairmentnecessitates repeated observations for different tidal conditions extendingpreferably over one full tidal cycle. Water quality observations on Thanecreek which receives wastewater from a number of domestic as well asindustrial sources along both of its banks was initiated in the summer of1993. As the first step towards selection-of sampling stations to identifythe impacts of major municipal discharges reaching the creek throughBhandup and Ghatkopar creeklet, a reconnaissance survey was conductedon March 28, 1993 during a spnrng tide.

5.3.4.1 Reconnaissance survey

During this survey it was established that Bhandup and Ghatkuparmuricipal discharges were the only major sources of pollution along thewest bank of Thane creek within about.20 kilometers stretch beginning

AEJED LAGOONS 5.17

from Thane rail bridge * and extending upto about 6 kilometersdownstream Vashi bridge. The creek was observed to receive significanitindustrial wastewater discharges along its eastern bank but due to thesignificant width of the creek these did niot overlap with th e domesticdischarges coming from the western bank.

To establish the spatial extent of region of impact of Ghatkopar andBlimidup discharges water quality samples were collected at six transectsfrom 1 kilometer downstream Vashi bridge to 3 kilometers upstreamBhandup creeklet (Figure 5.3). The sampling times were adjusted so as tocollect the samples at the time when the wastewater flow from theadjacent discharge point directed towards the respective transects. Forinstance, at transect 1 below the Ghatkopar creeklet, samples werecollected at the fag end of ebb tide. The transects above Ghlatkopar andBhandup creeklet were sampled during the flood tide. At each transecttwo samples, one near the west bank and one at about 500 meters insidethe creek fom the west bank were collectedL The samples were analyzedfor physico chemical parameters and the results are presented in Table 5.9.-The observations indicated that most portions of inner Thane creek weresignificantly polluted up to a minimum of 500 meters from the west bnLk.Observed dissolved oxygn levels in these regions were at many timesabout 2 mg/L or below with concurrent BOD levels of about 5 mg/L andnitrogen levels of up to 4 mg/L. Total coLiform concentration alsoindicated polluted creek conditions.

To confirm above observations and to compare the pollution levels duringthe spring tide with the neap tide conditions, another survey wasconducted on April 13, 1993 and both these surveys constituted thereconnaissance survey. During thissurvey,effort was primartly k'cused atthe west bank of Thane creek. The sampling was carried *ult at fiv fixedpositions along the west bank, 100 meters inside the creek from the lowestlow tide line (Figure 5.4). Sampling at the outer locationm was conductedduring the ebb tide and at the inner locations during the flood tide. Theregions above the Bhandup discharge were sampled by allowing a boat todrift with the current during ebb as welL as flood tide. The samples werecolected at regular half hourly intervals. The observations on dissolvedoxygen levels indicated that the neap tide conditions were more critical incomparison to the spring tide conditions. It was further established that inthe outer creek region about 1/3 width of the creek on the west washeavily polluted due to discharges from the west bank. In the upper creekregions, however, the creek substantially narrows and entire cross sectionof the creek exhibits heaviiy polluted conditions in this region during neaptide (Table 5.10).

AERM;ONS 5.18

Figure : 5.3Sampling transects for reconnaissance survey of 20.03.93

/ ~~~~

ShandupW

tI'

1,- Gha01k-Pv

AEIRAED LAGOONS 5.19

Table: 5.9

Reconnalsance survey of Thane creek on 28.03.93;physico-chemical parameters

Sr. Mle in Sample pH liibidlty DO BOD Chlorides Nitrates Total Ammnonacal SolubleNo. lacation as Cl as N Kjehldal Nitrogen phosphate

Nitrogen as N as Pas N

houi NTU mg/L muglL mg L mg/ L mg/ L mg/ L mgl L

1 8.00 Tr I(A)* 7.6 15.0 2.6 3.1 22,500 1.84 2.4 1.90 0.10

2 8.00 Tr l(B)" 7.4 12.0 2.2 4.2 20,000 1.76 3.5 1.54 0.12

3 9.00 Tr 2(A) 7.4 15.0 2.2 3.6 19,300 1.84 2.8 130 0.09

4 10.00 Tr 3(A) 7.4 15.0 1.2 5.7 19,900 1.56 4.2 130 0.16,

5 11.30 Tr 4(A) 7.4 12.0 1.8 4.5 20,000 1.26 35 1.10 0.12

6 11.30 Tr 4(6) 7.2 14.0 1.8 6.5 2,000 1.34 4.2 1.60 0.13

7 1230 Tr 5(A) 7.5 14.0 23 4.9 21,500 1.94 35 232 0.10

8 12.30 Tr 5(B) 7.5 12.0 2. 3.6 22,000 1.50 2.8 1.30 0.12

9 13.30 Tr 6(A) 7.8 10.0 3.6 2.8 21,700 1.68 2.1 0.50 0.10

A sample collected at 500 m from the west bankB sample collected at 100 m from (he west bank

0 Transect

Figure : 5.4Sampling locations during reconnaissance survey of 13.04.93

. , U,,

Sampling Locatlons Ouring ( bld'

o Ebb Tide 6Fl VICod Tide

eShandup ; / f

ni X

i0 dCAa 0

...

~~~~~~~3 - krn1

Ghmtkopar

l'S

se 71~~~~~~~~~~~~~~~~~~0 1

AE 02LGON

Table : 5.10

DO values in Thane creek on 13.04.93(LT-10.18 hrs.; HT-17.34 hrs.)

Sampling location

rime in 4 km downstre.n 500 m downstream 1 km downstreamhous Ghatkopardischarge Vaihi Bridge Bhadup discharge

West Centre Eant

A. Ebb tide sampling

8X30 2.8 1.39.00 1A 1.0 2. 13 2.09.30 2.0 0.9

10.00 0 0.8 1.61030 - 1.1 1.5 15 1S

Sampling location

Timein 500mupstrm 4Imupstream Boatallowedtodriftnorthhours Ghatkopardischre Chatkopardischarge of Bhandup discharge point

B. Flod tide sampling

11.00 2.8 2.31130 1.4 1.6 -I2t00 1. 03 1.91230 2.6 1.5 2.413.00 28 0.6 2.41330 3.0 2.6 2.614.00 2.5 2.8 2.614.30 3.0 2.2 2515.00 2.9 23 2.91530 32 23 2716.00 3.2 2.5 3.31630 3.6 25 2.91700 3.4 2.6 3.41730 3.6 2.6

Values expressed as mg/L

AEAED LAGONS- 5:i22-

5.3.4.2 Summer water quality survey

To establish summer water quality conditions in the creek two detailed V

surveys on April 25 and 29 representing spring and neap tide conditionsfollowed the reconnaissance survey. During these surveys, samples werecollected across the entire creek width. A description of the samplingdetails, highlighting time and locations of sampling is provided in Table5.31. The samples were analyzed for physico-chenmcal, bacteriological andbiological parameters and the analytical results are presented throughTables 5.12 and 5.13.

It is observed from results on physico-chemical parameters that at low tideslack for spring as well as neap tides, water quality conditions at transect 4do not indicate significant presence of pollutants. This indicates that theimpact of wastewater discharges into the creek remains confined to aregion less than 7 kilometers south of Vashi bridge. The main mechanismof assimilation of pollutants in the creek, therefore, is biodegradation - _ rather than dilution due to water exchange with the coastal region. Theobservations on bacterial parameters, however, indicate that impact of.wastewater disc4arges reaches upto Transect 4 during the spring low tide(Table 5.12). It appears that bacterial contaminations travel considerabledistance during spring ebb tide due to swift tidal currents and high initialcontamination levels at the point of discharge.

Observations in the inner portion of the creek (Transects 1 and 2) indicatethat the regions along the west bank of the creek are heavily pollutedspecially during the low tide. The high pollutant levels are, infact,observed up to the middle of the creek at these transects whichoccasionally extend to the east side of the creek also. The typical dissolvedoxygen and total coliform concentrations in this region of creek are 1.5-3.0mglL and 104-10s per 100 ml, respectively (Table 5.12). BOD values as highas 7 mg/L have been observed on the west bank of the creek. Similarwater quality conditions have been observed for spring and neap tidesduring these surveys. The reason for the similarity in observations may beattributed to the fact that the difference in tidal elevation of 2.5 metersduring the neap tide was not very significantly low in comparison to thatof 4.0 meters during the spring tide. These differences were much less than.possible range of about 0.5 meter during the neap and 5 meters during thespring tides, respectively.

The intertidal observations on creek water quality at transects 2, 3 and 4for DO, BOD, NH--N, total coLiforms and other relevant physio-cheMicalparameters are presented in Table 5.14 to 5.16, respectively. The

AE:L.ED rOONS. -,

Table :5.11

Schedule for sampling in Thane creek during summer

Sampling locations

Sampling 3 In north of 4 in north of 1 km south of 7 In south ofDate Blandup discharge Ghatkopar creek Vashi bridge Va;li bridge

arm near Trombay(Trmsect 1) (Trmasect 2) (Transect 3) (Transect 4)

A. Spring tide (2504.93)

L Watr samplesLow tide Centre Centre, east and Centre east and Centre, east and

west shore west shore west shore

Intertidal period - Two samples at Near west shore Centre 1, 2 andafterlowtide centre1,2 1,2&5hsafter 45hrafter

45 hrs after low tide slack low tide slacklow tide slack

High tide Centre, east and Centre, east and Centre Centrewest shore west shore

2 Sediment Centre, east and Centre, east and Centre, east and Gentrewest shore west shore west shore

B. Neap tide (29.04.93)

L Water samples

Intertidal period - 2, 1 hr before 2 hr before low 2 1 hr beforebefofe low tide low tide tide at west shore low tide

Low tide Centre Centre, east and Centre. east and Centre, east andwest shore west shore west shore

Interfidal period - 1, 2 and 4.5 hrs Near west shore 1, 2 and 45 hrsafter low tide after low tide at 2 45 and 6 hrs aFter low tide at

centre after low tide centre

Hih tide Centre, east and Centr east and Centre Centrewest shore west shore

EAIAED LAGOONS

: . 8 ' ~~~~~~~~~~~~Table :5.12

Observations on water quality indicators in Thane creek during summerDissolved oxygen Biochemical oxygen demand Total colifonvs

- . ; (mg/ L) (mgl 0 (countsl looml x lo1o)

.5 ;FLT HT LT HT LT HT

Location W C E W C E W CE W C E W C E W C E

Tidal condition: Spring tide (25.04.93), Range: 4 m, Time LT-07.25 ha.,; HT-14.25 hrs.

. Transect I - 2.7 - 2.4 2.7 3.1 - 3.2 - 5.3 3.9 2.7 - 238 - - 0.7

Transect 2 15 2A4 25 - - 3.2 5.9 4.3 3.7 4.1 3.7 3.8 120 - - 1.8

Transect 3 2.8 2.0 3.7 4.0 3.9 5.1 4,7 2.8 2.2 3.0 - 16.2 65 - 1.2 1.1

Transect 4 4.7 5.0 5.3 - 4.9 1.6 1.7 1.2 - 2.8 - 114 124 - _ 1.2

Tidal condition: Neap tide (29.04.93), Range: 2.5 mn, Tme LT-10.30 hMs.; HT-17.45 his.

Transect - 2.6 - 36 40 3.5 -4.8 - 1.9 4.2 3.6 - - -_ _

Transect 2 2.9 - 2.8 46 45 47 7.5 2.5 3.3 2.9 3.6 3.9 - 1.9 _ - 0.5

Transect 3 2.1 4.5 2.6 - 5( - 2.5 3.0 2.2 2.6 - 94 -- - 2.1 - _

Transect 4 4.7 5.5 4.8 - 4.4 - 2.3 2.2 2.5 1.0 - - 45 - - 0.2

Tabke: 5.12 (Contd...)

Soluble Phosphale as P Amnmonlacal Nitrogen as N Total KJehldal Ni_ugen as N Nitrate Nit agen as N(mgl L) (mg/ Li (Mg/ l (mg L)

LT HT LT HT LT HT LT HT

Location W C E W C E W C E W C B W C E W C E W C E W C e

Tidal condition : Spring tide (25.04-93), Range: 4 m, Time LT-07.25 hrs.; HT-14.25 hrs.Transect 1 - 040 - 0.27 0.27 0.30 - 35 - 1.70 1.30 2.10 5.1 - 21 2.1 23 - 0.50 - 0.55 0.59 058

Transect 2 0.27 0.28 0.32 0.17 0.18 0.16 2.2 14 4.0 0.48 0.77 080 2.8 3.1 11.2 2.4 1A 1.4 0.39 0.47 0.62 0.62 0.93 0.58

Transect 3 0.20 0.28 0.18 0.18 0.17 - 1.0 1.3 0.7 0.20 0.40 - 63 3,5 1.7 1.7 1.4 - 0.42 0.40 0.56 0.69 0.76 -

Transect 4 0.18 0.05 0116 -0,10 - 0.6 0.4 0.6 - BDL - 1.I 3.8 1.4 - 7.0 - 0.74 0.59 0.59 - 0.55-

Tidal condition: Neap tide (29.0.I.93), Range :2.5 nm, Time LT-10.30 hrs.; [HT-17.45 hts.

Transect I - 0.44 - 0.28 0 27 038 - 4.14 - 3.5 2.40 1.80 - 5.6 - 3,80 3.5 3.2 - 0.30 - 0.29 0.29 0.3

Transect 2 0.34 0.52 0.40 0.24 0 25 0.24 3 7 3.00 4.6 BDL 1.32 1.06 4.2 3.5 4.8 1.05 2.1 2.1 0.59 0.29 0.29 0.42 0.35 0.3

Transect 3 0.07 0.12 0.11 - 005 - 06 0.56 1.4 - 0.71 - 1.4 1.4 2.8 - 1.4 - 0.31 0.39 0.30 -0.36-

Transect 4 0.05 0.05 0.09 -012 0 (2 BDL. 0.2 - DL - 1.4 4.9 4.2 - 1.4 - 0.44 0.35 0.38 -0.42-

Table : 5.12 (Con td..)

Temperature pH Tblmdlty Chlorides as Cl

IC) (NTU) (mg/ L x 1f0)

LT HT LT HT LT HT LT HT

Location W C E W C E W C E W C E W C E Wc C E W C E W C E

a I

Tidal condition: Spring tide (25.04.93), Range: 4 mn, Time LT-07.25 hrs.; HT-14.25 his.

Transectl - 28 - 30 30 31 - 7.3 - 7.3 7,1 7.3 - 31 - 55 45 45 - 183 -- 198 200 200

Transect2 28 28 27 31 30 31 76 7.5 7.5 7.7 7.6 7.7 38 32 50 42 48 45 188 190 196 200 204 198

Transect3 27 28 28 31 31 - 7.6 7.5 7.6 7.7 7.8 7.7 50 21 23 25 23 - 204 190 204 195 195 -

Transect4 27 27 28 - 30-- 7.8 7.8 7.8 - 7.8 - 38 73 100- 72 - 202 205 206 - 202 -

Tidal condition: Neap tide (29.04.93), Range: 2.5 m, Time LT-10.30 hru.; HT-17.45 hrs.

Transect I - 32 - 32 31 32 - 7.3 - 7.6 7.6 7.6 - 12 - 15 18 12 - 226 - 180 196 187

Transect 2 32 33 32 32 32 33 7.6 7.7 7.7 7.1 7.7 7.7 18 15 16 32 28 27 173 189 188 200 204 198

Transect3 31 33 32 - 32 - 8.3 7.5 8.1 - 8.1 - 13 12 15 - 36 - 200 212 204 - 207 -

Transect 4 32 31 31 - 32 - 7.7 7.8 7.7 - 7.1 - 20 17 20 32 - 211 210 212 - 207 -

Tale: 5.13

Phytoplankton observations in Thane creek (summer)

TiLdal Sampling Total Per cent composition in groupscondition station counts .

per Bacilaria- CIIIOrO- CyanJo- CInjso- Diuo-ILOO ml plmyceae phyccae phyccac phyccac phtyccac

A. Spring tide (25.04.93)

High tide Transect 1 2457 87.13 - 7.69 5.12

Transect 2 1800 91.62 5.55 2.77 -

Transect 3 1450 100.00 - - - -

Transect 4 900 94.42 - - - 5.55

Low tide Transect 1 3750 91.98 - 8.00 - -

Transect 2 3087 95.89 2.04 2.04 -

Transect 3 2079 93.93 - 6.06 -

Transect 4 1200 100.00 - - - -

B. Neap tide (29.04.93)

High tide Transect 1 2995 94.45 - 5.54 - -

Transect 2 2709 90.67 - 930 - -

Transect 3 1150 86.89 4.34 8.69 - -

Transect 4 1008 95.81 - - - 4.17

Low tide Transect 1 4252 88.24 - 11.76 - -

Tan.sect 2 3541 94.11 - 5.87 - -

Transect 3 2350 8932 - 6.38 4.25 -

Transect 4 1350 96.20 - - 3.70 -

AUAlED .OON -

Table : 5.14

Intertidal variations in water quality of Thane creek (summer)

Sampling Tune DO BOD Total ColiformsLocation hours (mg l L) (mg/ L) (counts/ 100 ml)

ridal condition: Spring tide (2S.0493), Range: 4 m, rune: LT-07.25 hrs.; HT-14.25 hrs.

Transect 2 8.15 2.4 43 1.2 x 105

930 2.7 5.7 9.7 x 106

12.15 2.8 5.5 1.6 x 105

1430 3.7 3.2 1.8 x 103

ridal Condition: Neap tide (29.04.93), Range: 2.5 m, Time: LT-10-30 hrs.; HT-17.45 hrs.

Transect 2 8.30 2.8 2.6 1.90 x 103

9.30 2.6 3.5 7.25 x 103

10.30 - 2.5 2.16 x 10'

1130 3.2 3.7 3.62 x 105

12.15 3.8 43 131 x 104

15.30 5.5 35 Z.09 x 104

17.00 4.5 3.6 1.0Sx 103

At the centre of the creek

AERAlED LAGOONS .. S2

Table: 5.14 (Contd...)

smphing Trme Temp. pH Turbidity Chlorides Total Ammoniacal Nitrate SolubleLocation* as Cl Kjeldahl nitrogen nilrogen phosphate

nitrogenhours eC NTU (mg/L) (tmgJL) (ng/IL) (mgiL) (mg/L) (mglL)

Tidal condition: Sprins tide (25.04.93), Range: 4 m, Tume: LT-0725 his.; HT-14.25 his.

Transect 2 8.15 28 7.5 32 19000 3.1 IA 0.47 02B

9.30 29 7.4. 55 19200 3.1 2.4 0.65 031

12.15 30 7.5 33 19400 2.8 1.8 0.48 0.27

14.30 30 7.6 48 20400 1A 0.8 0.95 0.18

Tidal condition: Neap ride (29.0493), Range : L5 m, Trme LT-10.30 hrs; HT-17.45 hrs.

Transect 2 8.30 28 7.6 12 18800 3.5 3A 0.25 033

9.30 30 7.8 13 19000 4.2 4.1 0.24 0.20

1030 32 7.7 15 18900 3.5 3.0 0.29 0.52

11.30 32 7.5 14 18400 3.6 3.5 024 0.28

12.15 32 7.5 15 18500 3.6 35 0.34 034

15.30 32 7.7 35 20000 2.8 1.3 0.30 0.27

17.00 31 7.7 28 20000 2.1 1.3 0.35 025

At centre of the creek

AmED LAGOONS 530

Table : 5.15

Intertidal variations in water quality of Thane creek (summer)

Sampling Time DO BOD Total ColifonmsLocation hours (mg/ L) (mgl L) (counts/l 0O ml)

ridal condition: Spring Tide (25.04.93), Range: 4 m Time: LT-07.25 hrs.; HT-14.25 hrs.

Transect 3 9.00 2.8 5.1 6.50 x 104

9.30 2.8 4.7 1.62 x 104

10.40 3.4 2.8 1.78 x 104

12.05 3.8 2.3 1.22 x 03

14.30 4.0 2.2 1.22 x 103

ridal condition: Neap Tide (29.04.93), Range: 2.5 m, me: LT-10.30 hrs., HT-17.45 hs

Trnsect 3 8.30 3.8 2.3 9.40 x 104

11.10 2.1 2.5 3.70 x 103

12.30- 5.7 4.3 1.66 x 104

15.10 63 2.0 6.60 x 103

17.00 5.6 3.9 1.13 x 104

'Near the west shore of the creek

A- D LAAGONS

S

Table: 5.15 (Contd...)

Sampling Tnne Temp. pH Turbidity Chlorides Total Ammoniacal Nilrate SolubleLction: as Ca Kjeldahl nitrogen nitrogen phosphate

nitfogenhours C NTU (mg/ L) (mg/ L (mg/IL) (1mg L) (m&gL) (mg/ L)

Tidal condition: Spring tide (2504.93), Range: 4 m, rume: LT-07.25 hrs.; HT-1425 hrs.

Transect 3 9.O0 29 75 50 20400 63 h. 0.42 Ol

9.30 29 7.6 28 200D0 2.1 0. 0.50 0.18

10.40 30 7.7 30 20200 1.7 05 0.53 0.16

12.05 30 73 60 20000 1.0 0.2 054 0.17

14.30 30 7.7 25 195O0 1.7 02 0.70 0.18

iLdal condition: Neap tide (79.04.93), Range: 2.5 m, Time: LT-10.30 hrs. HT-17.45 hrs.

Trawne 3 830 29 7.7 36 20700 2.1 0.9 036 0.10

11.10 30 83 13 20000 1.4 0.6 031 0.07

1230 31 82 26 20400 1A 03 031 0.06

15.10 32 8.0 17 21900 1.0 0.1 0.42 0.15

O7.00 31 7S 30 20900 1.0 02 0.51 0.05

Near the west shore of the creek

AIC AGOONS-

Table : 5.16

Intertidal variation in water quality of Thane creek (summer)

Sampling Thi! DO BOD Total ColifomsLocation* hours (mg/ L1 (mg/ L1 (counts/ 100 ml)

rtdal condition: Spring tide (25.0493), Range: 4 mt, rume: LT-07.25 hrs.; HT-14.25 hrs.

Transect 4 8.30 5.0 1.7 1.24 x 105

930 4.9 1.0 1.61 x 105

12.30 4.9 - 5.50 x 104

14.00 4.9 2.8 1.16 x 103

ridal Condition: Neap tide (294.93), Range : 25 Ml, Time: LT-10.30 hrs.; HT-17.45 hts.

Transect 4 8.30 4.7 4.0 -

9.30 4.9 1.2 4.50 x 104

10.45 4.7 2.3 320 x 102

11.30 5.9 1.7 5.45 x 103

12.30 5.9 2.9 2.54 x 104

15.00 5.9 1.9 1.20 x 103

17.30 4.4 1.0. 2.10 x 102

At centre of the creek

Ap,MwpLou O.S33

B~~~~~~~~~~~~~~~~~~~~~~~~

Table: 5.16 (Coultd...)

Sampling Time Temp. pH Tutbidity Chloridis Total Amnoniacal Nitrate SolubleLocation as Cl Kjddahl nitrogen nitrogen phosphate

nitrgenhouts *C NTU (mgIU l iu (Mg/lLI (mgIL) (ig(L) Im*IL)

Tidal condition: Spring tide (25.04.93), Range: 4 m, rme: LT-07.25 hrs.; HT-14L25 hrs.

Transect 4 8.30 28 7.8 73 20500 3.8 0.4 0.60 0.06

9.30 28 7.8 35 20400 5.1 0.3 0.45 0.08

1230 30 7.8 64 20200 1.7 03 0.60 0.09

14.00 30 7.7 72 20200 7.0 BDL 0.55 0.10

Tida condition: Neap tide (29.04.93), Range: 2.5 m, rune: LT-10.30 hrs.; HT-17.45 hrs.

Transect 4 8.30 28 8.0 22 20700 2.8 02 036 0.08

9.30 30 7.0 17 20400 2.8 0.1 0.38 0.05

10.45 31 7.8 17 21000 4.9 0.1 035 0.06

11.30 32 7.7 18 21000 1.7 0.1 0.35 0.09

1Z30 32 7.2 17 20700 1.0 BDL 0.58 0.12

15.00 32 7.6 23 20900 1.0 BDL 0.38 0.13

17.30 31 7.1 32 20700 1.4 BDL 0.42 0.12

At centre of the creekBDL - Below detectable limit

AEED LAGOONS - 4

observations indicate that water quality conditions at the iLuner transect 2remain poor for at least two hours before and after the low tide slack (Figure 5.5). During the ebb tide pollutants from Bhandup discharges moveand spread towards the transect 2 whereas during the flood tide'Ghtatkopar discharges move up and pollute the inner middle regions of.the creek. It is observed that it may take upto 4 hours before relativelydean sea water from outer Thane creek reaches this portion.

The regions near the west bank of creek at outer transect 3 also exhibitelevated concentration of total coliforms and low dissolved oxygen levelsduring the ebb tide (Figure 5.6). This transect is orly about 2 kilometersaway from the mouth of Ghatkopar creeklet and the pollutants emanatingfrom the creeklet flow along the west bank of the creek in this region. WLththe flood tide, however, water quality conditions at this transect rapidlyimprove. Water quality conditions at the outer most transect (transect 4)remain unchanged during the low and high tides, indicating that the creekportion at this transect are away from the region of immediate impacts ofwastewater discharges. The bacterial contamination levels at this transect,however, are high during the ebb tide and indicate that the pollutantsfrom the discharges do reach this transect but are observed only in termsof microbial parameters due to their high initial concentration (Figure 5.7).

5.3.4.3 Winter water quality survey

In order to have complete representation of water quality with respect toseasonal variation sampling was also planned during the winter. Surveyswere conducted on January 28 and February 6,1994 to studv winter waterquality variations under spring and neap tidal conditions. respectivelv.During these surveys, samples were collected across the entire creek widthat low and high tide slacks at three transects. The sampling -.chedule andlocations for these surveys are described in Table 5.17. Thie samples wereanalyzed for physico-chemical, bacteriological and biological parametersand the analytical results are presented through Tables 5.18 to 5.'0,respectively.

The observations on physico-chemical parameters as presented in Table5.18 indicate that at tidal slacks creek dissolved oxygen is generally higherduring the spring tides in comparison to the neap tides. Under the neaptidal conditions water quality remains unaffected by the wastewaterdischarges in regions downstream Vashi bridge. This indicates that due toweak tidal currents during neap tides wastewater discharges remainconfined within relatively short distances (about 5 kilometers) from thepoint of discharge. At low tides transects 2 and 3 show marked water

A- ED UMLAGOONS. 5.35

Figire: 5.5

Intertidal water quality at transect 2 of Thane creek(Summer-Spring tide)

6

5

4 -

2

1

7 a 9 10 11 12 is 14. 15- Sampling Time in hrs.

-- DO (mg/) C SOD (mg/I) --x- Log of TC ctB/100 ml

LT * 14.25 hr. HT * 20.11 hri.

Intertidal water quality at transect 2 of Thane creek(Summer-Neap tide)

6~~~~~~~

5 -

4 -M

S.

2-

'0 I 9 10 -1 12 19 14 15 16 17

Sampling Time In hrs.-6i DO (m/O S BOD (mg/O -- x Log of TC cts/100 ml.

-T *lO.O hir. 14T 17.45 -'

ABED LAGCOONS 536

Figure : 5.6Intertidal water quality at transect 3 of Thane creek

(Summer-Spring tide)

5.

0a 9 10 11 12 13 14 16

Sampling Time In hrs.-DO (mO/Il SOD (mg/I) -- Log of TC ate/100 ml

LT 14J.5 hm NT * 0.011 r.

Intertidal water quality at transect 3 of Thane creek(Summer-Neap tide)

7 -

5

2- ,

09 10 In 1 S 14 1 15 17

Sampling Time In hrs.DO (mog/I BOD (mgll) --x Log of TC ate/100 ml

LT U 10.50 hr. HT 17.4 hrs.

AERAlED LAOONS 53

S ~ ~ -

Figure: 5.7Intertidal water quality at transect 4 of Thane creek

(Summer-Spring tide)

x~~~~~~~~~~~~~~~~~~I

2-

1

* 9 10 11 u2 18 14 15Sampling Time In hrs.

-DO (mg/) ODD (mg/S -x-- Loa of TC ts/10O mlT * 14.2 hrf. NT w 30.11 hr.

Intertidal water quality at transect 4 of Thane creek(Summer-Neap tide)

76 .-

4 q * --

a~~~~~~~

* 9 10 n1 t2 1i 14 15 1s 17 18Sampling Time In hrs.

- U DO (mg) o oD (mgAO --K-' Log of TC atmllOO mlLT 10.80 hr. MT * 17.4 hr.

ARMED LAGOONS 5,S3

Table : 5.17

Schedule for sampling in Thane creek during winter

Sampling location

Sampling 4 In north of I kn South of 7 an south ofDate Ghatkopar aeek am Vauhi Bridge Vach Bridge

nea Trombay(Trnsect 2) (Trmsect 3) (Transt 4)

A. SpFing tide (243194).

L Water samples

Low fide Centre, East and West Centre, East and West Centre, East and West

High tide Centre West Centre Centre

- Sediment Centre Centre Centre

B. Neap tide (062.4).

i Water samples

Low tide Centre, East and West Centre, East and West Centre, East and West

High tide Centrp, East and Centre, and West CentreWest

L Sediment Centre - Centre

ARTE LAGOONS

Table: 5.18

Observations on water quality indicators for Thane creek during winter

Dissolved oxygen Biochemical oxygen demand Total colifonms(mot L) (mg/ L) (counts/ 100 ml x 100)

LT HT LT HT LT HT

Location W C E W C e w c W CE W C E W cC E

Tidal condition: Spring fide (28.01.94), Range: 3.75 m, Time IT-S8.32 hbs.; HT-12.28 hra.

Transect 2 3.0 30 5.0 5.8 6.8 6.1 4.0 4.0, 3.4 3.8 3.9 4.4 340 110 18 13 5 8.6Transect 3 3.2 4.4 4.5 - 5.5 - 2.8 2.7 BDL - 2.0 105 340 - 10 10Transect 4 43 5.0 6.6 - 6.3 - 3.3 3.1 4.2 - 2.9 - 840 22 7 - 25

Tidal condillion: Neap tide (06.O0.94), Range: 2.5 m, Time: LT-14.32 hrs.; HT-07.4S hr.

Transect 2 1.5 1.5 6.3 3.1 3.0 3 8 3.0 2.6 4.7 2.0 3.7 2,1 374 430 500 220 196 97Transect 3 35 2.0 4.8 5.3 4.9 - 2.9 5,2 BDL 1.7 1.9 - 88 84 9 106 0.8

Transect 4 3.2 4.4 4.7 - 4.2 - 1.5 2.9 6.3 - 1.9 - 49 . 48 21 - 1.4

DDL - Below detectable limit

Table :5.18 (Contd..)

Tidal conditlon: Spding fide (28.01.94), Range: 3.75 m, Time HT-12,28 hug.; LT-18.32 ha.

Soluble phosphate as P Ammoniacal nikrgen a N Total kjeldahl nitiogen as N(md LI (mgt LI (mg! L)

LT HfT LT HT LT HT

Location W C e W C E I C E W c H w c e W C E

Ttansect2 0.27 0.28 0.26 0.26 0.14 0.15 23 23 1.5 09 1.2 0.6 4.2 4.2 2.8. 4.2 2.8 2.8

Transact3 0.15 0.30 0.05 - 0.11 - 1.4 0.9 0.6 - 03 - 2.8 2.8 1.A - 2.8 -

Transect4 0.10 0.10 0.05 - 0.10 - 0.7 0.7 0.4 - 1.0 - 4.2 4.2 4.2 - 2.8 -

Tidal condition: Neap tide (0642-94), Range :2.5 m, llme HT.07.48 hbs.; LT.1432 hrs.

Soluble phosphate as P Ammoniacal nitrogen as N Total kieldahi nittogen as N(mg/ LI (mgl L) (mg/ L)

LT Hff LT HT LT HT

Location W C e w C E B C E W C E W C E W C E

Transect 2 0.33 0.29 0.19 0.18 0.20 0.14 1.5 2.4 1.20 0.2 1.40 1.2 4.2 3.9 3.4 2.8 4.20 3.40

Transect 3 0.23 0.25 0.07 0.08 0.08 - 1.9 2.1 0.35 0.7 0.40 26 3.6 * 4.3 8.2 1.7 0.23 0.25

Transect4 0.10 0.13 0.11 - 0.08 - 1.2 0.5 0.70 - 0.15 - 1.2 2.8 2.8 - 1.10 -

6 6

Table: 5.18 (Contd...).

Temperature pH Turbidity Chlorides as Cl

QC NTU (mg/L x 100)

LT HTT HT LT HT LT HT

Location W C E W C E W C E W C E W C E W C E W C E W C .E

Tidal condition : Spring tide (28.01.94), Range : 3.75 m, Time HT-12.28 hrs.; LT-1832 hrs.

Transect2 26. 26 26 27 27 27 7.2 7.2 7.4 7.6 7.5 *7.7 45 55 63 20 15 12 180 178 182 *185 184 187

Transect 26 25 26 - 27 - 7.3 7A 7.7 - 7.6 - 65 90 28 - 32 - 180 183 184 - 192 -

Transect 4 26 25 25 - 27 - 7.4 7A 7.6 - 7.7 - 80 13 27 - 26 - 180 188 193 - 200 -

Tidal condition: Neap tide (06.02.94), Range: 2.5 m, Time HT-07.48 hrsa. LT-1432 hts.

Transect 2 28 28 27 25 26 26 7.3 7.3 75 7.3 7.4 7.5 14 5 11 13 14 11 181 210 204 208 194 208

Transect3 26 25 26 - 27 - 73 7.4 7.7 - 7.6 - 65 90 28 - 32 - 180 183 184 - 192 -

TransectV28282- 2 5 - 7.67.5 7.4-7.6- 181415-30- 19 197189-205-

quality impairment in considerable transverse section of the creek,presumably the regions which fall in the path of wastewater plumesflushing out of the creek with the ebb tide. Water quality at transect 3,however, significantly improves during the high tide with influx ofrelatively dean water from outer Thane creek. Bacterial counts in the creekalso present a scenario similar to physico-chemical parameters.

The nutrient parameters analyzed for water samples collected from thevarious transects included ammoniacal nitrogen, total nitrogen andsoluble phosphates. The observations were taken with respect to seasonaland tidal variation and are presented in Tables 5.12 to 5.19. Higher nutrientconcentrations are observed in the inner transects as compared to the outertransects thereby indicating hier pollution. The total nitrogen valuesranged from 2.8 mg/L to 63 mg/L in the inner Thane creek.

5.3.5 Biological parameters

Phtytoplankton

Phytoplankton levels and its compositions were estimated inside theThane creek at four different transects stretching from Vashi bridgedownstream to a distance of about 7 kilometers to 3 kilometers upstreamBhandup discharge and are presented in Tables 5.13 cand 5.19.

For all sampling conditions, phytoplankton counts show a decreasingtrend from inner to outer transects. The observation indicates higherproductivity in the creek compared to the outer coastal region. Low tidecounts are also found to be higher than that of high tide. The observationsfurther indicate higher counts in summer than in winter. Lower waterexchange with coastal regions during the neap tide, as observed from thephysico-chemical observations, is further confirmed by the higherphytoplankton counts observed during neap tides in comparison to springtides. The over all phytoplankton counts in the creek, however, are fairlylow and range below 5000 per 100 ml in all observations.

Bacillariophyceae was the prominent group of phytoplankton at alltransects. A noteworthy feature was the presence of Dinophyceae attransect 4 for all tidal conditions in winter and during high tide in summerthus indicating deaner regions at locations further south. The above factcan be further reaffirmed by the absence of Cyanophyceae the indicatorgroup of organic pollution at transect 4 for all tidal conditions both insummer and winter.

ARE LAGOONS54

Table: 5.19

Phytoplankton observations in Thane creek (winter)

Tidal Sampling Total Per cent composition in groupscondition station counts

per Bacilaro- Chloro- Cyano- Chryso- Dino-1O ml phyceae pilyceue phyceae phyceae plhyceae

A. Spring tide (28.01.94)

High tide Transect 2 1650 93.90 3.03 3.03 - -

Transect 3 1310 94.17 - 359 217 -

Transect 4 850 92.08 - - 5.26 2.63

Low tide Transect 2 2196 85.32 6.14 5.16 3.33

Transect 3 1600 93.71 - 4.74 1.51 -

Transect 4 1176 92.67 - - 3.64 3.64

S. Neap tide (06A3.94)

High tide Transect 2 1820 89.8 3.64 6.50 - -

Transect 3 1314 93.47 - 5.02 1.47 -

Transect 4 1230 92.89 - - - 7.07

Low tide Tramnsect 2 2275 90.08 3.92 4.73 1.25 -

Transect 3 - - Sample not collected - -

Transect 4 1590 94.14 - - - 5.83

AERATED LAOONS

Zooplantkton

Zooplankton is a very important group in the aquatic ecosystem acting asa major source of link between the phytoplankton and the primarycarnuvores. Zooplankton levels and its compositions were estimatedinside Thane creek at locations stretching from south of Vashi bridge tonorth of Bhandup discharge (Table 5.20). Samples were collected andpreserved in buffered formalin' solution. Copepods followed by Ciliateswere the most predominant species observed which may be attributed tothe presence of abundant phyt6plankton, decaying organic matter andbacteria in the creek. The number of groups observed during high tide aremore as compared to low tide. The total zooplankton counts are observedto be higher during the spring ti le in comparison to neap tides due tohigher flooding and drying of mangroves which act as breeding areas forzooplanktor.

5.3.6 Trace metal levels

Thane creek receives significant inputs of heavy metals due to the influxfrom the surrounding basaltic terrain as well as through domestic andindustrial wastewater discharges. The dissolved trace metals addedthrough these influxes get immobilized into creek sediments due toalkaline pH of creek waters and related transformations. A partialresuspension of precipitated metals is possible due to strong tidal currentsbut a rise in dissolved metal levels in the creek water is not expected, dueto resuspension. Due to established high cation exchange capacity ofThane creek sediments, the metal pollutants are most likely to beaccumulated in creek sediments.

In order to examine the status of trace metal contamination in Thane creekstudy area creek water and sediment samples from a number of locationswere analysed for total and dissolved metals. The municipal wastewatersamples were also analysed for total metals to assess tthe load of tracemetals through such discharges into the creek. The water quality surveywas conducted in summer and winter seasons and covered high and lowwater conditions during the spring and neap tides. Sampling locations forthe creek surveys during the two seasons were identical.

The results of creek water analysis for Zn, Cu, Ni, Mn, Cr, Cd and Pb forsummer and winter surveys are presented in Tables 521 and 5.22. Theseresults indicate that the total metal concentrations were higlher dturingsummer in comparison to winter. These levels, however, do not indicatesignificantly higher metal levels as the observed concentrations are only

AERATED LAGOONS 5S

Table: 5.20

Zooplankton observations in Thane creek

Location Tolui Pemcent compuWn In gwups ShannonZooplanklon _Veaverper 100 m3 Diviiseiy

0 U ~~~~~~~~~~~~~~~~Index

WMloteo spuing tide (28.01.94)

Tr -2C/t 1H61T3 076 152 29 038 - 251 076 - 6 U 151 0.6 =6 229 - 38 1I1

Tr- 2CdLT 1,419 - -0 - 16S 76 55 1 - 63 - - 3.41 - - - --10 - 173

Tr -4CjHr 457.29 - -145 09 - 17 3.6 241 483 12 603 120 622 - - 36C - 957 240

Tr -4C/LT 86312 0.46 -- - Ohb 0.46 083 813 - 74.9 0.46 - 0.13 7 - - 0.93 0.62 I41 1.40

C -Cemb

Table: 5.20 (Contd...)

Location Total Percent compuifan In groups Shannan

Zooplankton . Weaver

per 100 m3 IDuunityIndex

u I~~~~~~~~~~~~~~EuU

Winter, neap tide (06.02.94)

Tr-2C/HT - 958 - - 1 1m - .0 - - 3m

Tr-2cIULT 8926 - 27.M 1391 5105 - - A1

Tr -4IHT 10A21 ISO15 2511 469 361 118 14.41 7.22 Isis 397 - 27

Tr 4CiLT 14.693 1123 33.70 - _ 32% - - 1123 1123 - - 2.

*h.

Table 5.21

Total heavy metal concentration in Thane creek during summer(spring tide)

Location Ni Mn zn Cr Cu Cd Pb

(mg/ L)

Tr 1 LTC 0.05 1.19 0.26 0.11 0.06 BDL 0.08.

Tr 2 LT W 0.06 1.65 0.22 0.30 0.17 BDL 0.11Tr 2 LT C BDL 0.80 0.12 0.25 0.30 0.01 0.08Ti 2 LT E 0.05 0.62 0.11 0.15 0.26 BDL 0.20

Tr 3 LT W 0.02 0.72 0.19 0.20 0.17 BDL 0.09

Tr 3 LT C 0.06 0.43 0.28 0.17 0.24 BDL 0.99Tr 3 LT E 0.30 0.40 0.14 0.20 0.06 BDL 0.02

Tr 4 LT W 0.08 0.57 053 0.10 1.48 BDL 0.06Tr 4 LT C 0.06 0.87 0.35 0.18 0.75 BDL 0.09Tr 4 LT E 0.08 0.54 0.38 0.22 1.12 BDL 0.10

Tr 1 HT W 0.04 1.73 0.18 0.14 039 BDL 0.05i 1 HIT C 0.04 .OA7 0.29 0.06 035 BDL 0.03Tr 1 HT E 0.01 2.15 1.04 0.25 053 BDL 0.13

Tr 2 HT W 0.02 1.30 0.26 0.04 0.06 BDL 0.11Tr 2 HI C 0.06 0.71 0.11 0.20 BDL BDL 0.08Tr 2 HT E 0.04 130 0.09 0.17 BDL BDL 0.03

Tr 3 HT C 0.05 0.39 0.17 0.06 0.03 BDL 0.06

Tr 4 HT C 0.03 0.62 0.43 0.19 0.13 BDL 0.08

* - TransectC - centre; W - west; E - eastBDL - Below detectable limit

AERATED LAGOONS SA

Table : 5.21 (Contd.)

Total heavy metal concentration in Thane creek during summer(neap tide)

Location Ni Mn Zn Cr Cu Cd Pb

(mgl L)

Tr*1 LTC 0.12 1.30 0.75 0.03 1.21 BDL 0.04,

Tr 2 LT W 0.09 2.22 0.37 0.02 1.46 BDL 0.02

Mr 2 LT C 0.11 153 036 BDL 038 BDL BDL

Tr 2 LT E 0.08 1.45 0.34 BDL 0.28 BDL 0.03

Tr 3 LT W 0.06 0.39 0.29 0.14 0.59 BDL 0.18

Tr 3 LT C 0.09 0.43 0.25 BDL 1.95 BDL BDL

Tr 3 LT E 0.09 1.14 0.27 BDL 0.48 BDL BDL

Tr 4 LT W 0.09 1.82 0.22 0.05 0.25 BDL 0.02

Tr 4 LT C 0.06 0.37 0.28 BDL 0.32 BDL BDL

Tr 4 LT E 0.12 0.19 0.34 0.20 0.36 BDL BDL

Tr 1 HT W 0.8 0.78 0.23 BDL 0.56 BDL BDL

Tr I HT C 0.03 0.79 0.42 0.17 0.47 BDL 0.06

Tr 1 HT E 0.08 2.01 0.21 0.08 2.77 BDL 0.01

Tr2HTW 0.05 0.62 0.31 0.07 0.23 BDL BDL

Tr 2 HT E 0.10 1.27 0.27 BDL 0.30 BDL BDL

Tr 3 HT C 0.04 030 036 0.21 0.32 0.01 0.05

Tr 4 HT C 0.05 0.61 0.25 0.13 0.37 BDL 0.01

*- TransectW - west, C - centre, E - eastBDL- Below detectable limit

_NRIEDLAGONS sA9

Table -5.22Total heavy metal concentration in Thane creek during winter

(spring tide)

Location Ni Mn Zn Cr Cu Cd Pb

(mg/ L)

Tr*2 LT W 0.08 0.87 0.24 0.34 0.05 BDL BDLTr 2 LT C BDL 0.49 0.14 0.19 0.02 BDL BDLTr 2 LT E BDL 0.55 0.10 0.4 0.01 BDL BDL

Tr 3 LT W BDL 0.34 0.10 0.45 0.02 BDL BDLTr 3 LT C BDL 0.51 0.04 0.43 BDL BDL BDLTr 3 LT E BDL 0.28 0.08 024 0.01 BDL BDL.

Tr 4 LT W BDL 0.17 0.07 0.31 0.03 BDL BDLTr 4 LT C 0.02 0.24 0.10 0.09 0.02 BDL BDLTr 4 LT E BDL 0.54 0.07 0.30 0.02 BDL BDL

Tr 2 HT W 0.02 0.10 0.34 0.21 0.03 BDL BDLMr 2 HT C 0.13 0.03 0.05 0.26 BDL BDL BDLTr 2 HT E BDL 0.04 0.01 0.22 0.02 BDL BDL

Tr 3 HT C BDL 0.12 0.17 0.48 BDL BDL BDL

Tr 4 HT C BDL 0.45 0.04 0.31 0.07 BDL BDL

- Transect

W-west,C-centre,E-eastBDL - Below detectable Emit

Aa ,OONS 50

Table: 5.22 (Contd ...)

Total heavy metal concentration in Thane creek during winter(neap tide)

Location Ni Mn Zn Cr Cu Cd Pb

(mg/ L)

Tr2 LT W BDL 0.57 0.06 035 BDL BDL BDL

Tr 2 LT C 0.01 0.35 BDL 0.60 0.02 BDL BDL

Tr 2 LT E 0.12 Q59 0.03 0.50 BDL BDL BDL

Ti 3 LT W 0.04 0.17 0.08 0.36 BDL BDL BDL

Tr 3 LT C BDL 0.16 BDL 050 BDL BDL BDL

Tr 3 LT E BDL 0.55 0.04 0.37 BDL BDL BDL

Tr 4 LT W BDL 0.06 0.02 0.62 BDL BDL BDL

Tr 4 LT C BDL 0.17 0.05 0.42 0.01 BDL BDL

Tir 4 LT E 0.06 0.07 0.19 0.48 BDL BDL BDL

Tr 2 XT W 0.03 0.26 0.17 0.25 0.02 BDL BDL

Tr 2 HT C 0.03 0.08 0.04 0.59 BDL BDL BDL

Tr 2 HT E 0.06 0.68 BDL 0.42 0.01 BDL BDL

Ti 3 HT C 0.14 0.04 0.03 0.47 BDL BDL BDL

Tr 4 HT C BDL 0.01 0.22 0.41 BDL BDL BDL

* - TansectW - west, C - centre, E - eastBDL - Wow detectable limit

AERATEDLAGOOS L51

marginally higher than the drinking water standards for some of the tracemetals. Furtlher, their comparison with the tolerance level of sensitivemarne biota indicates that the dissolved metal concentrations are lowerthan the tolerance values. The comparison, however, could not be madefor Cr, as total soluble Cr was estimated during the survey whereas thetolerance values are in terms of hexavalent Cr. A comparison of metallevels in water column among the various transects do not indicate aappreciable difference. The levels for some metals are, however, higherthan those observed in munidcipal discharges and thus indicate inputsfrom other sources.

Due to the alkaline pH of creek waters, sediments are expected to be majorsink for trace metals and their levels in sediments is a ouperior indicator ofstatus of metal pollution in the creek Accordingly, the sediment samplesin summer and winter were collected at all the four transects Thesampling region was confined to the creek center as the sediments from.the sides are expected to move and accumulate in the central region of thecreek under the influence of natural hydrodynamic processes. The resultsof the trace metal analysis in the sediments are presented in Tables 5.23.

For their interpretation, these values were compared with the naturallyoccurring trace metal levels in Bombay soils and also with the WorldShale. Table 524 presents the ratio of trace metals in Thane creek withrespect to the World Shale and Bombay urban soils. The results indicateconsiderably higher values of Cr, Cu, Pb and Zn in comparison to naturalBombay soil and World Shale levels. The concentrations for Cr and Cu areupto 2 to 6 times higher in the major part of the creek and indicatesignificant industrial pollution The trace metal levels in winter, however,are significantly lower in comparison to summer values. The possiblereasons for these diffeences could be flushing of the enriched sedimentsto the open coastal regions during the monsoon and deposition of freshnatural soil through run-offs.

When compared to the metal levels along the west coast of Bombay, it is-observed that Cr, Cu and Mn levels in mane creek are upto 10 timeshigher In view of low metal concentration in domestic wastewaterdischarged into Thane ceek, these high trace metal levels can not beattributed to municipal discarges and underscore the presence ofsignificant industrial influx into the creek

5.3.7. Nutrients in sediments

For estimations of nutrients in sediments in Thane creek, samples from the

ARED LAGOONS -AR

Tablk : 523

Heavy metals in Thane creek sediments

Sampling station Ni Mn Zn Cr Cu Cd Pb

(mg/ kg)

Summer

Mansect 1 142 1508 189 321 - BDL 45

ransect 2 136 1059 234 434 - BDL 55

Transect3 141 1462 225 461 - BDL 59

Transect 4 153 1093 187 489 - BDL 47

Winter -

Transect 1 --

Transect 2 80 1020 199 116 128 BDL 37

Transect 3 65 911 119 102 98 BDL 22

Transect4 78 889 279 110 197 BDL 41

I = Samples were collected along the main channel of the creek

BDL - Below detectable Lhmit

ACRTDLAOONS 5S3

Table : 524

Ratio of trace metal concentration in Thane creek sediments toBombay urban soil and World Shale backgrounds

Element Bombay Uzban Soil World ShaleBackground Bakground

Witer Summer Wter Summer

max min max max min max min

Ni 0.44 0.58 0.93 105 0.95 125 2.00 2.25

Mn 0.79 1.02 104 1.48 0.94 L22 124 .77

Zn 0.91 331 1.43 1.80 125 4.53 1.96 2.46Cr 1.24 1 3.91 5.96 .13 137 3.56 5.43

cu 0.66 1.91 - - 2.18 630 - -

Pb 051 134 L04 1.37 1.10 Z90 2.25 2.95

ALMED LAGOONS

selected transects were collected during the winter and summer seasons.The sampling was restricted to the central portion of the creek as thesediments from the sides are expected to move and accumulate in thenuddle region of the creek due to tidal currents. These samples wereanalyzed for nutrient parameters comprising total nitrogen andphosphorus, results of which are presented in Tables 5.25.

The total nitrogen concentratiors in Thane creek sediments were observedto be significantly lower during the summer in comparison to the winter.Total rnitrogen levels in Thane areek ranged from 2400 to 3750 mg/kg inwinter compared to 1032 to 1505 mg/kg in summer. Similar seasonaltrends in total ritrogen levels were observed along the west coast ofBombay. The values observed durng summer in the creek are comparableto the concentrations observed along the west coast. Creek sedimentnitrogen levels during the winter were higher than the observed levelsalong the west coast and may be attributed to higher accumulation duringwinter due to lower rates of biological activity and relatively higherconcentration of organic loading in the aeek.

The phosphorus levels exhibit more pronounced variation in the sedimentsamples at different transects in comparison to total nitrogen. Lowestvalue of 150 mg/kg of total phosphorus was observed at the inner mosttransect. At the remaini transects, the levels of total phosphorus variedfrom 750 to 1000 mg/kg during summer and 575 to 900 mg/kg duringwinter These concentrations were comparable to those observed at 1kilometer reference line along the west coast of Bombay.

53.8 Detergents

Wastewater and water

The procedure adopted for estimation of anionic detergents was theMethyl Green method (Moore and Kolbeson, 1956). Detergent analyseswas carried out qt the four transects as mentioned earlier for summer andwinter dunng spring and neap tidal conditions respectively. The resultsare presented in Tables 5.26. The analysis conducted during summerindicate that the concenttion of detergent is higher on the eastern banksof the inner transects (1 and 2) as compared to that of the outer transects (3and 4). This difference in detergent concentration was more pronouncedduring the low tide than high tide. Besides, although, the sewage wasbeing discharged on the western banks, the detergent concentration on theeastern bank was comparable or oacassionally higher to that on westernbank. One can infer from this obserwation that discharges carying

AE LED AGOONS - -5

Table : 5.25

Nutrients in Tlane creek sediments

Sampling station Total kjeldahl nitrogen as N Total phosphorus as P

(mf kg) (mg/ kg

Summer

Transect 1 1032 150

Transect 2 1050 950

Transect 3 1400 1000

Transect 4 1505 750

Winter

Transect 1 _ -

Trasect 2 3750 575

Transect 3 2400 900

Transect 4 2800 650

- - Samples were collected alon& the main channel of the creek

ZAEHTD LAGOONS 5s

Table : 5.26

Detergents in Thane creek water

Neap tide Spring tide

LT HT LT HT

Sampling station W C E W C E W C E W C E

Summer

Tmsect 1 - 034 - 05 0.27 073 - 031- 024 0.03 024

Transect 2 024 0.15 1.07 0.0 0.15 0.23 0.22 031 0.22 0.28 031

Trsect 3 0.15 0.03 0.15 0.04 0. - 0.15 0.19 031 - 0.23 -

Tramect 4 0.15 0.04 004 - 0.01 - 03 0.15 032 - 0.03 -

Wmnter

Transet 1…- - - -

Transect 2 - - BDL BDL BDL - 0.006 BDL BDL BDL BDL BDL

Trasect 3 - BDL - BDL BDL - - - - - BDL -

Traimect 4 BDL - BDL - BDL - - - - - BDL -

Concentrations are in mg/L

W-west, C-centre, E-east

BDL - Below detectable limit

AERAD LAGOONS o

detergents are also reaching the creek from the industrial belt on the east.However, the observed concentration in the creek were within theprescribed water quality standard of 1 mg/L except on one occasion alongthe east bank.

Sediuucwits

The Methyl Green method reported by Moore and Kolbeson, (1956) is forthe analysis of anionic detergent is sewage and wastewater samples. Themethod was suitably modified by incorporating a pretreatment procedure,to analyse for detergents in sediments. The results are presented in Table5.27. The detergent concentrations observed in Thane creek sediment aresignificantly higher (upto 10 times in most of the samples) than valuesobserved along the west coast of Bombay and indicate higher proportion.of industrial discharges into the creek. The winter concentrations are,however, significantly lower than summer and perhaps indicate that mostof the polluted sediments are washed out to sea during the monsoon.

53.9 Wastewater characterization

The wastewater drainage zones in Bombay are divided into seven serviceareas. The wastewater from Bhandup and Ghatkopar service areas directlydischarge along the western bank of Thane crek These dischargesconstitute about 20 per cent of the total municipal wastewater generatedin the city. Estimation of the impact of these discharges on the creek andadjoining coastal ecosystem, evidently, entails their characterization.

Hourly wastewater samples were collected from terminal pumpingstations and characterized for physico-chemical and nutrient parameters(Tables 5.22 and 530). Composite samples were also analysed for tracemetal concentrations. Observations on general parameters indicate thatthe sewage generated in Ghatkopar and Bhandup service areas is mediumto low strength. The total coliform counts in the sewage from 1handupand Ghatkopar areas were observed to range between 1 t 3.x 105 countsper 100 ml.

The results of trace metal analysis in muricipal discharges fromGhatkopar and Bhandup pumping stations ( leading to Bhandup aeratedlagoons) are presented in Table 5.30. The results, inspite of Ghatkoparbeing one of the major industrial area, do not show significantly elevatedmetal concentrations in sewage. The concentrations for Mn, Zn, Cu areonly marginally higher in comparison to other drainage zones. The resultsfurther indicate that the municipal discharges do not pose significant

A tEDAGOONS s5

Table : 5.27

Detergents in Thane creek sediments

Sampling station Concentation

pgl g wet wt)

W C E

Summer

Transect 1 - 3.03

Transect 2 1.78 1.89 1.41

Transect 3 1.23 0.00 3.53

Transect 4 - 1.18 -

Winter

ransect 1 - - -

Transect 2 - 0.4 -

Transect 3 0.1 - -

Transect 4 0.3 _ _

W-west, C-entre, E-east

i-RAW LAGOONS 5

Table : 528

Physico-clemical characteristics of sewage(Bhandup pumping station)

Time pH Conductivity Chlorides Ammoniacal Soluble C O D B O Dnitrogen phosphate

as N asP

hours mhoi cm mg( L mgl L mg/ L mg/ L mg L

08.0 7.4 4030 1380 182 1.9 347 200

09.00 72 3700 1280 16.8 3.0 445 238

10.00 7.1 3540 1180 126 2.6 264 160

100 7.1 3670 1260 105 2.0 292 145

12.00 7.1 4000 1440 8.1 1.8 292 143-

13.00 7.1 4260 1500 7.7 1.6 320 128

14.00 7.1 4450 1600 6.7 1.6 236 153

15.00 7.1 4810 1700 63 1A 236 113

16.00 7.1 3270 1900 63 1.1 222 120

17.00 72 5710 2026 7.0 1.4 320 145

AERAERDLAGON &

Table : 5.29

Physico-chemical characteristics of sewage(Ghatkopar pumping station)

Time pH Conductivity Chlouides Ammoniaca! Soluble C O D B 0 Dnitrogen phosphate

asN asP

hours mhosl cm mg/ L mgl L mgl L mg/ L mg/ L

0730 7.1 683 240 210 3.1 768 283

0M,O 7.4 707 140 21.7 3.1 912 290

0930 72 67C 140 168 3.1 528 270

10.30 7.1 740 130 15A 3.1 704 245

11.30 7.1 778 160 15A 3. 544 210

1230 7.0 1097 1S0 14. 3.0 400 210

13.30 6.8 653 290 12. 2.8 464 200

14.30 7.1 856 150 105 2.9 320 223

1530 7.1 977 200 133 25 384 230

1630 7.0 934 230 14.0 3.1 304 210

1730 7.0 937 200 14.7 3.1 400 200

AAED LAGOONS SA5

Table : 530Heavy metal levels in sewage

(Bhandup and Ghatkopar pumping station)

Zn Cu Ni Mn Cr Cd Pb

(mg/ L)

Summer

Shandup 0.14 0.03 BDL 0.44 0.01 BDL 0.05

0.12 0.03 BDL 0.37 0.06 BDL BDL

Ghatkopar 0.26 0.09 BDL 0.66 0.05 BDL BDL

0.27 0.06 BDL 0.42 0.06 BDL 0.03

Winter

Bhandup 0.1 0.04 0.01 0.40 0.01 0.01 0.13

0.42 0.89 0.08 1.46 0.03 BDL 0.05

Ghatkopar 0.16 0.06 0.03 0.41 0.01 0.01 0.03

0.46 1.14 0.07 1.15 0.07 BDL 0.03

BDL - Below detectable limits

AEIED lADONS 52

hazard of metal pollution of receiving waters as these concentrations arenot only well below the permissible limits for industrial effluents andsewage discharges into marine and coastal areas (Envirorunent(Protection) Act, 1986) but also are fairly close to the permissible limits fordrinking water standards.

Sewage samples from Bhandup and Ghatkopar pumping stations wereanalyzed for detergent content by the Methyl Green ilmethod. Thedetergent contents in sewage on an average were observed to be 1.0 mg/L.for both Bhandup and Ghatkopar. Comparison with the receiving waterquality standards for fresh surface water for Alkyl Benzene Sulfonatecontent of 1.0 mg/L reveals that the detergent contents of the sewagesamples just meets this permissible limit.

5.3.10 Solid wastes characterization

The operation of preliminary treatment facilities at the aerated lagoons,shall result in the production of screenings and grit wastes. Ifimproperly disposed, these wastes may give rise to foul odour, flybreeding and pollute the near by areas. In addition to attracting flies, poorsolid waste disposal practices may also lead to other vermin such asscavenging birds (crows, mynahs), rats, mice and perhaps dogs.

Selection of a proper methodology for disposal of screenings and grit isgoverned by the characteristics of these wastes. The solid wastesgenerated at the existing facilities were analyzed to obtain data on theirorganic and inorg*nic content, moisture, particle size and calorific value,.so as to enable the choice of a suitable management option

Screnzhigs

The detailed analysis of samples of screenings collected from Mulund(terminal pumping station for Bhandup drainage zone) and Worlipumping stations for their physico-chemical characteristics are given inTables A 5.54 and 5.55 (Ref. Marine outfalls Report). Physical analysisindicates that the screenings are not biodegradable and only 15 to 25 percent of the screenings are compostable. Average moisture content of thewaste ranges from 67.8 to 73.7 per cent and C/N ratio varies between 193to 20.1 per cent. The screenings are therefore not suitable for composting.The average calorific value is found to be 690.0 Kcal /kg. The low calorificvalues and high moisture contents of the screenings render themunsuitable for incineration. However, these wastes contain someputrifiable fraction which may decompose and cause odour problems.

AIED LAGOONS 5

Screenings should, therefore, be transported as early as possible aftercollection to disposal site. Observations on heavv metals indicate lowconcentrations and, therefore, the screenings may be disposed off alongwith city refuse.

Grit

Grit consists of the solids which are removed from the grit chambers. Atthe initial stage grit samples were callected from Lovegrove pumpingstation. These samples were analyzed for particle size and basicphysica-chemical characteristics. The results are presented in Tables A 5.56and A 5.57 (Ref. Marine outfalls Report).

A few grit samples collected from Love Grove treatment plant were alsoanalyzed for various particle sizes and heavy metal distribution. Thedetailed results are given in Tables A 5.58 and A 5.59 respectively (Ref.Marine outfalis Report). The data indicate that the organic fraction (losson ignition) decreases with decrease in particle size. Pliosphorous andPotassium were also distributed in a similar way. The C/N ratio,however, varied in reverse order. Heavy metal distribution among thevariable size grit particulates was more or less uniform and does notshow any variation for the metals al alyzed. The overall concentrations ofheavy metals in grit are well below the levels prescribed for their landapplication (WPCF, 1989). On observation the physical and physico-chemical properties of screenings from Lovegrove and Mulund pumpingstations compare well. Though the characterization of Mulund grit has notbeen carried out, it is assumed that grit characteristics at Worli could beused for Mulund service area.

Presently, most of the solid wastes generated in Bombay are beingdisposed at locations identified by the MCGB, which have beenconsidered for disposal for screenings and grit. Present estimate from twopumping stations is not more than 1-2 trips of solid wastes generated perday. As this quantity is negligible in comparison to the 5000 tonnes of cityrefuse generated daily, screenings and grit can be disposed along with itand is not expected to cause any additional impacts.

5.4 Conclusions

Continued wastewater discharges from Bhandup and Ghatkopar servicearea to the inner Thane creek have resulted in significant water qualityimpairment in this region. The observations on creek water qualityindicate that the wastewater discharged into the creek moves back and

AEDLAGOONS 5.

forth with the tidal action and remains trapped within the creek. Due tonegligible exchange with the coastal sea, the pollutant concentrations inthe aeek are entirely governed by the rate of their assimilation within thecreek. In inner regions, the creek is shallow and narrow wlhere combineddisdcarges from Bhandup and Ghatkopar overwhelm the availableassimilative capacity. As a result, about 10 kilometers long stretch alongthe west bank of the creek has very poor water quality with low dissolvedoxygen and high BOD levels. During the ebb tides, in these regionsdissolved oxygen routinely falls below 2 mg/ L and BOD levels rise upto 7mg/L. The observations on bacterial quality in the creek also indicate itspoor status with frequent occurrences of total coliform concentrationsexceeding 104 per 100 ml. The creek sediments also show highconcentration of ammoniacal nitrogen depicting organic pollution due tolarge sewage discharges. Observations on biological indicators presentinferences similar to those evidenced by the physico-chemical parameters.

The analyses, of sediment samples indicate significant accumulation ofheavy metals at the centre of the creek. The concentrations areconsiderably high especially for Cr and Cu thereby, indicating significantindustrial pollution. The levels of trace metals are lower in winter ascompared to summer. The sediments and water samples show highdetergent concentrations during summer.

Due to its remoteness and good vegetation cover, the region does notsuffer from air and noise pollution. Air quality analyses at Bhandup and.Ghatkopar lagoon sites indicate that present air quality in term of SPMNO, faLs within Indian standards for ambient air qualitv at both sites- Theobservations on noise levels are also well within the limits prescriLied forurban residential.

AEEDLAGOONS SAS

Chapter 6NUMERICAL MODEL FOR THANE CREEK

6.1 Preamble

For scientific assessment of a wastewater management scheme, it is desirableto quantify the impacts of effluent discharges on water quality of thereeeiving waters. Tidal currents which dilute, disperse and advect theeffluent, play the most prominent role ingoverning the pollutant levels in thecoastal environment. Simulation of ambient coastal currents in relation to thetidal variations, bathymetry and bed characteristics, therefore, is an integralpart of water quality simulation. The fate of water quality constituents,however, also depends upon the natural biochemical and physical processes.Numerical models which provide necessary framework to simulate thehydrodynamic features along with the simpler assimilative processes in-coastal environment, therefore, have become a popular choice for analysis ofwater quality impacts of coastal water quality management schemes.

As water quality impacts on Tharte creek are the most importantconsiderations for assessing the proposed project, the scope of this chapterhas been confined to detail the numerical model used for water qualitysimulation in the creek The model description indudes bathymetric featuresand tidal variations in the creek, and also details the results of caLibration ofthe numercal model against the observed water quality and hydrodynamicfeatures.

62 Model selection

In a wide range of flow and pollutant transport model studies, the hydraulicbasin can be assumed to be well mixed vertically and the hydrodyuamicmodel can be reduced to a two-dimensional model of the depth integratedtype. For studies where this assumption can be justified, including pollutanttransport studies in non-stratified coastal waters, the depth integrated form-of three-dimensional equation of motion is used.

WiLth the time varying water elevation and velocity fields being obtainedfrom the numerical solution of two dimensional depth integrated equationsof motion, a range of water quality parameter distributions can be solved forby adding the general form of the advective-diffusion equation to thecorresponding hydrodynamic model.

In the present application, the effluents from Bhandup and Ghatkoparaerated lagoons are proposed to be discharged in hane creek. With the tidalaction, the dischrges could advect to the harbour and coastal regions in thesouth arnd the adjacent Bassein creek in the north which are connected

AE_MLOONS 6.1

through Thane creek (Figure 2.1). As the first step towards model selection,therefore, data on creek bathymetry, tidal elevations, tidal currents, andspatial extent of Thane creek and the adjacent coastal regions were collected.The data was then evaluated to decide the extent of modelling domain,model resolution and suitability of use of depth integrated form for thepresent application.

A scaled map of the creek with the salient bathymetric features and locationsof the proposed effluent discharge points is presented in Figure 6.1. Themaximum tidal range in the creek is of the order of 5 meters and theassociated maximum current speeds range between 12 -1.5 meters persecond. It is further observed from Figure 6.1, that the discharge points fromthe proposed aerated lagoons are in the sidearms of the creek. The presentwastewater discharges from Bhandup and Ghatkopar drainage zones alsoreach the creek through the respective sidearms.

From the bathymetric information on the creek, it was observed that even forthe maximum tidal height of 5 meters during the highest spring tides, waterdepth near Bhandup effluent discharge point did not exceed 7 meters.Whereas maximum depth near Ghatkopar effluent discharge point wasapproximately 7 meters near the westward region of main channel and about9 meters in its center These depths are negligible in comparison to the springtide creek width of about 3 kilometers and creek length of approximately 30kilometers between the harbour region towards south and Bassein creektowards north ( Figure 2.1). Based on these observations, it w.as consideredappropriate to assume that soon after their discharge the effluents willachieve vertical homogeneity in the creel

The hydrodynamic and water quality variations under tidal forcing in Thanecreek, were therefore, simulated through a 2-dimensional numerical model.Acronymed DIVAST (Depth Integrated Velocity and Solute Transport), themodel was originally developed by Falconer* and uses fuiite differenceschemes to solve the governing equations for fluid flow and solute transportin2-dimensional form. The model operates by defining the bathymetry of theregion of interest over a uniform rectangular grid which divides the waterbody into cells of uniform area. The tidal forcing at the open boundaries isspecified by defining the water elevations and/or flows obtained throughfield observations at relevant locations. Using the principles of continuity of

* FaIie, RA. (1984) A nwthematical modJ study of the flushing chractristics of a shallow tidal bay. Prc Ihut.Cvi Engrs. Part 2, VdL 77Z, 3111-

Falcwu, R.A. (1986 A water qualty simulation study of natural khbOuw. 1. W_tway, Pot Ct OcmnEngineurizi AscE, 'L ilZ 234-259

AERAD LAGOONS 62

Figure: 6.1

Bathymetric features and wastewater dischargelocation in Thane creek

Depths:

10~~~~~~~~~~~~~~~~~~~~~~1

Tj"S4"~~~~

0. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~.

I!5X' / i . F'e

-ARAUCLAOONS .,.3

mass and conservation of momentum, the water level, flow and soluteconcentration in each cell are computed as they vary throughout the tidalcycie.

WhiLe simulating pollutant concentration in a tidally influenced water body,it is generally necessary to consider a large modeling domain so that thepollutants' concentrations near the open boundaries reduce to thebackground levels. Such considerations for Thane creek would have requiredthat the model covered a large portion of the narrow channel on the northconnecting the Thane and Bassei creeks. Tis would have increased the sizeof the model and necesstated coverage of regions with poorly definedbathymetry. Similarly, it would have been necessary to extend the southwardmodel boundary to include portions of harbour region where restrictions dueto vessel traffic regulations would have made it difficult to obtain the currentobservations.

To circumvent the above difficulty, a modified version of the numericalmodel providing flexibilityof defining solute concentration for tidal inflow atopen boundaries as a function of outgoing solute concentration at the time oftide reversal and background concentration was used. For instance, theincoming solute concentration for the neap tide was considered equal to theoutgoing concentration upto one hour after the tide reversal and was linearlyallowed to achieve the background levels in next one and a half hour period.In view of stronger tidal currents and consequent higher dispersion anddiution of pollutants, the respective time intervals for spring tide werelowered to half an hour and one hour. These values were selected bcased oninsitu observations on water quality variations with tide at the southwardboundary of modelled region of Thane creek.

63 Thane creek model

Bat lymetry

Ihe domain for Thane creek model covered the entire creek including themain creek arms over a 20 kilometer stretch beginning from the Bombay-Thane rail bridge (Figure 62). The southward boundary of the modelextended upto Trombay, about 7 kilometers south of Bombay-Vashi railbridge. The south boundary, thus, was located just north of dredged channelmaintained in the harbour region to facilitate movement of vessels. The bedtopography of the modelled region was obtained from the hydrographiccharts prpared by the concerned departments of Government ofMaharashta in 1990. The charts had a resolution of 25 meters by 100 meters.The depth at sides of 200 meters by 200 meters grid used for model

AWEAD LAGOONS 6

Figure : 6.2

North and south boundaries for Thane creek model

11 sr *7s '1'

bunda,~tm

'IS

°r AL;~~~~~~

10~~~~~~~~~~~~~~~~~~~~~~~~~~1

km

I~~~~~~~~~~~o I h:

I,~~~~~~~~~~7

Bbandupboudar

72S4' 72' sS'

AGOONSAC ,

computations were arrived at by averaging the depths provided inhydrographic charts. It was further observed from creek bathymetry that thecreek bed sloped gradually towards the harbour and had a minor depressionin the southward region near Vashi bridge (Figure 6.1).

Tidal clevations

The tidal variations in water elevation and currents in the creek weresimulated by defining the tidal elevations at the south and north boundarieswhich were the only open boundaries of the model. The elevations wereobtained by deploying recording type tide gauges at the respectiveboundaries for a period of 8 days and covered pre- and post-tidal variationsfor the neap tide of February 6, 1994. A set of limited tidal elevations wasobied at Vashi bridge for model calibratiorL

The tidal conditions used to simulate about 66 hours long simulation at southand north boundaries of the model are presented in Figure 6.3. The southboundary was approximately 7 kilometers south of Ghatkopar dischargenear Trombay, whereas the north boundary was about 6 kilometers north ofBhandup discharge at Kalva bridge. The two boundaries were 20 kilometersapart and the tidal elevations at these boundaries differ significantly inphase, the high and low waters at Trombay preceding those at Kalva bridgeby about 60-90 minutes.

mida: curvehnts

The Thane creek model was tuned to simulate the hydrodynamic conditionsin the creek by comparing the observed and predicted tidal currents at twopositions in the creek. The current observations were made on February 6 atabout 4 kilometers north and 1 kilometer south of Vashi bridge in the maincreek channeL These locations (position 1 and 2 ) represented the inner andouter creek regions, respectively ( Figure 6A). These observations werecarried out by placing the boats at the desired locations and lowering thfecurrent meters into the water over a complete tidal cyde. The observationscommenced at the high tide slack and continued upto subsequent high tide.

The water level on the day of current observation fell by 2.5 meters duringthe ebb tide and rose by 2.58 meters during the subsequent flood tide. Whilesimulating the flood and ebb tides, only those cells where water depthexceeded 30 centimeters were used for computing water elevations and- tidalcurrents. The simulation was carried out for a bed roughness height of 20millimeters.

AU LAGOONS 6

Figure : 6.3TLdal elevations at open boundaries of Thane creek model

ELEVATION BOUNDARIES FOR ThANE MODELVARlATION IN WATER ELEVAIION WlITH NEAP TDE5.0 ----

~~- - D -N l _ -- i- - _ -

40

Qo z0 __.. 1 .T ..V

I~~~I

0.0 ----L ---- I--------0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64

TIME IN HOURS FROM HIGHTIDE SLACK_. SOUTH BOUNDARY ATTROMBAY+ NORTH BOUNDARY AT KALVA BRIDGE

AU ILAGOO4S

Figur : 6.4Locations for current and water quality observations

4' 17" is' 7-3

0 Observation Locat ions

0~~~~~~~~~~~~~~~~~~

19' e1^s -s

AED LAGOONS,

The predicted and observed tidal currents in the inner and outer region ofmodelling domaini for nieap tide variations of February 6, 1994, are presentedin Figures 6.5 and 6.6, respectively. The observations indicated a fairagreement in observed and predicted speed of tidal currents at both thelocations in the creek. The flood currents were observed to be slightlystronger than the ebb currents, perhaps due to higher variation in elevationduring the flood tide on February 6. The maximum currents observed were inthe range of 0.6 meters/second.-A minor phase difference in observed andpredicted currents was observed in the outer region. The variation, however,was not expected to significantly affect simulation of advectionin the creek.

6A Model calibration of water quality parameters

Depth integrated advection-diffusion model for water quality simulationsused the results of hydrodynamic model for simulating creek water qualityin terms of Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD)and ammomiacal-N. The model considered that carbonaceous organic matterand ammoriiacal-N removal was governed by the first order kinetics. Thedifference between the oxygen transfer due to surface reaeration and oxygenuptake due to Sediment Oxygen Demand (SOD); oxidation of carbonaceousorganic matter and ammoniacal-N governed the net dissolved oxygen levelsin the creek. While simulating polluted creek conditions, the modelleddissolved oxygen levels were not allowed to drop below 1 mg/L. A flag wasused to indicate the violation of aerobic kinetics of water qualitytransformation.

For calibration of water quality component of the model, water qualityobservations were carried out at two locations in the creek on February 6,1994. The sampling locations, designated as Location 1 and 2 are depicted inFigure 6.4 with respect to the model boundaries and discharge. locations.Water quality observations were commenced soon after the high tide slackand samples were collected every one and.a half hour until the low tide slack.The model was tuned by varying the model coefficient for BOD removal rate.The coefficients for SOD and ammoniacal-N removal were selected based onthe published values in literature for coastal waters receiving raw municipalwastewaters and were kept at 5 g/m2/day and 0.4 per day, respectively. Thereaeration coefficent was adjusted in the model internally for water depthsand velocities based on Owen's relation.

The results of modi calibration for DO and BOD are presented in Tables 6.1and 62 for locations 1 and 2, respectively. For different times of observations,the tables provide the observed, simulated concentrations of dissolvedoxygen and BOD, and also the distance of nearest position from the samplinglocations where model results matched well with the observations.

ASU;EDLAGOONS .'6

Fipumc: 6.5Hydrodynamic calibration of Thane creek model (inner region)

VARIATION IN TIDAL CURRENTS DURING NEAP TIDEINNER CREEK REGION

0.7 ----- …

0.6- -

im .5.

Iz

0.1-

2.5 35 45 5S5 65 7.5 85 9.5 105 115 12.5 13.5 145TIME IN HOURS AFTER LOW TIDE SLACK

Simulated Profile at Location I * Observed profile at Location 1

Figure :6.6Hydrodynamic calibration of Thane creek model (outer region)

VARIATION IN TIDAL CURRENTS DURING NEAP TIDE

0.7 -- a a-

0.4

2.5 3.S 45 5.5 65 7.5 8.5 93510.5 11IS 12.5 13.S MS.'liME INHOURS AFTER LOW TIE SLACK

-Simulated Profile at Location 2 *observed prorile at Location 21

AERLED LAGOONS 6.11

'1aI,Ic: 6.1

Calibration results for dissolved oxygen

rTme of Observed Simulated . Nearest location where simulated Matchedobservation DO DO value matches observed value simulated

(hours) (mg L) (mg/ UL _alue

Distance from Direction with (mg/ Upoint of repect to point

observation of observation(m)

Inner Thane creek

9.00 3.0 1.5 800 East 3.0

11.00 2.3 2.0 200 East 2.5

12.30 2.5 1.6 200 East 2.6

14.00 1.5 2.7 400 West 2.0

Outer Thane creek

9.00 4.9 5.6 400 West 5.1

11.00 5.2 3.6 1000 South 5.2

12.30 4.5 2.7 80 East 4.5

14.00 2.0 2.0 Nil 2.0

AERAE UWij 6.12

Tabk 62

Calibration results for biochemical oxygen demand

Time of Observed Simulated Nearest location where simulated Matchedobservation DOD BOD value matches observed value simulated

(hours) (mg/ L) (mg/ L) valueDistance from Direction with (mg/ L)

point of respect to pointobservation of observation

(U'

Inner Thane creek

9.00 2.7 1.8 400 West 2.6

1.0-0 2.4 1.6 400 North 23

12.30 1.9 4.7 400 South 2.2

14.00 2.6 4.0 200 East 2.8-

Outer Thane creek

9.00 1.6 1.2 - 12'

11.00 2.9 1.0 400 East 2.7

12.30 32 0.9 600 West 3.5

14.00 5.2 1.2 700 North-West 5.1

* None of the simulated values were above 1.2 mg/L in outer creek region

AEAIED LAGOONS ~~~~~~~~~~~~~~~~~~~6.13

When viewed with Figures 6.7 and 6.8, depicting simulated water qualitydistribution in the creek, these values dearly indicate the degree of precisionachieved by the model in simulating creek water quality for existingwastewater discharges.

A comparison of simulated and predicted water quality at the inner creekregions indicated that simulated results matched the observations within 400meters of the sampling location, except for dissolved oxygen at 9 hours whenmatch was obtained at 800 meters. For the outer region, the model resultswere in good agreement with all the observations within 1000 meters of themonitoring locations. On many occasions, however, a good match wasobtained within 600 meters of the sampling location (Figures 6.7 and 6.8).Considering the extent of modelling domain and advection of pollutantswith tidal currents, calibration results were considered satisfactory for model.application for developing water quality scenarios in the creek.

6.5 Conclusions

In Thane creek, water depths are much smaller in comparison to horizontaldimensions of the creek. The hydrodynaniic and water quality features of thecreek were, therefore, simulated through numerical model usmg depthintegrated form of equation of motions along with the advective-dffusionequation.

The model was calibrated for hydrodynamic and water quality features forneap tide conditions which are found to be critical for creek water quality.Simulated tidal currents and DO and BOD levels at two critical locations inthe creek were compared with those observed over a complete tid.11 Cycle andwere found 'o be in reasonable agreement.

ARAI LAG;OONS

Chapter 7PREDICTION OF IMPACTS

7.1 Preamble

The major activities associated with the construction of aerated lagoons atBhandup and Ghatkopar Rre site clearance, earth work and materialtransfer. The site clearance involves removal of mangroves from parts ofthe sites, filling and leveling operations and transfer of unusable materialfor disposal. The prominent impacts of these activities are rise in ambientnoise levels and impairment of air quality near the construction site.

During the operation phase, being a pollution abatement project, theproposed aerated lagoons are expected to improve the water quality inThane creek. Higher dissolved oxygen level in creek waters and cleansingof the bed sediments through natural biological processes are the primaryimpacts expected after the reduction of wastewater loads into the creek.Based on the extent of improvement in creek water quality, the mostimportant secondary impacts would 'be increased yield of marine biota inthe creek. The most significant associated air quality impact would beelimination of malodorous, conditions common around the polluted creekduring the low tides, at present Jointly, these improvements shallconsiderably enhance the aesthetic value of the region and may open upthe possibility of developing Thane creek as recreational area for watersports at a later date.

Some of the important processes which govern the primary envirozunentalimpacts of construction and operation of aerated lagoons can bemathenuatically modelled. The associated impacts can. therefore. bepredicted with reasonable confidence. Mathematical models tor simulationof these processes along with the method of their calibration andverification have been presented in the previous chapter. ror estimatingthe efficacy of aerated lagoons in restoring the creek ecosystem, aqualitative approach was adopted. Accorditigly, observations on ecologicalparameters were carried out in the areas which had water quality similar tothe futuie projections for Thane creek after implementation of wastewatertreatment scheme.

7.2 Construction phase impacts

72:1 Impacts of mangroves reclamation

Mangwves protect the coastal regions by moderating the strength of tidalcurrents and provide spawning grounds for a number of coastal species.Mangroves, thus play a vital role in maintaining ecological stability of

AERMED LAGOONS 7.1

creeks and coastal regions. Recent satellite imageries indicate that about750 hectares of inter tidal region in upper Thane aeek support rich growthof mangrove forests comprising Avicennia, Salvadora azd Cedops sps., as thedominant species. It is estimated that approximately 40 hectares of thiscover will be lost due to reclamation of land for construction of theproposed three cell aerated. lagoons.

A quantitative estimate of the impacts of loss of about 5 per cent of themangrove cover in the region on creek ecosystem is not possible. Themangroves in this region represent one of the best such surviving areasalong Bombay's coast which once supported them extensively. Anyfurther loss of these areas is evidently undesirable and should beconpensated by replanting equivalent areas. Alternatively, the remainingmangrove areas should be protected against future encroachment andillegal felling so that their growth offsets the loss due to proposed-reclamation.

7.2 Noise impacts

For predicting the increase in noise levels at sensitive locations near theaerated lagoon sites during construction, data on noise characteristics andoperation pattern of construction machine units during differenL stages ofconstruction were collected (Table 7.1). A site survey to measure ambientnoise levels at the lagoon sites was conducted. It was observed that thenearest residential locations are about 1 to 1.5 kilometers away from thesite. A direct imnpact of construction activities at lagoon site on the noiselevels at these locations could not be ascertained as no significantconstruction activity has been in progress for about one year at these sites.

The noise characteristics data of construction machinery and observationsduring their operation indicated that noise levels could be upto 96 dBAnear the generator sets. For noise predictions it was assumed that allmachine units were in simultaneous operation and were randomly locatedwithin a 50m by 50m area at the construction site. The predictions weremade using the model for hemisphercal sound wave propagation. Themodel results in terms of isopleths of sound pressure level in dBA(A-weighted decibels) are presented in Figures 7.1 and 72 for Bhandupand Ghatkopar, respectively.

The nearest residential areas at Bhandup and Ghatkopar are more than 1kilometer away from the aerated lagoon sites. The results of noisemodelling indicate that the noise due to construction is expected to drop to-approximately 40 dBA at the receptor location in these areas and thus

ARAIwLAIoONS 7.2

Table: 7.1

Noise levels generated by different machineries used inconstruction

Machines No. in Noise level inOperation dBA

1. Cement concrete mixer 1 89

2. Crane with damshell

bucket 1 88

3. Generator sets 1* 96

4. Trucks 2 85

ABAII LAGOONS 7.3

Figum: 7.1

Predicted noise levels at Bhandup lagoon site

NO DEVELOPMENT ZONE

AERATEID L 0N

AIRAlE U%CK 7A

Figure: 7.2Predicted noise levels at Ghatkopar lagoon site

AERAlEE UCLOONS AERAM LAGCKM ~~~~~~~~~~~~~~~~~~~~~~7.5

would be fully attenuated to the background levels. Thle constructionactivities associated with the aerated lagoons, therefore, are not expected togive rise to any adverse noise related impacts.

7.22.1 Noise impacts on construction workers

Equivalent sound level averaged over 8 hours, Leq (8 hrs), is used todescribe exposure of noise in work places. The damage risk criteria forhearing, as enforced by OSHA (Occupational Safety and HealthAdministration) and other organizations to reduce hearing loss, stipulatesthat noise levels upto 90 dBA are acceptable for eight hours exposure (Leq(8 hr)) per day. Whereas ACGIH (American Conference of GovernmentIndustrial Hygienists) proposed an Leq (8 hr) limit of 85 dBA. Exposure toimpulses or impact noise should not exceed 140 dBA (Peak acousticpressure). Exposure to 10,000 impulses of 120 dBA are permissible per day.

The Director General of Mines Safety in his circular No.DG(Tech)/18 of1975 has prescibed the noise level in mining occupations (TILV) forworkers, in an 8 hour shift period with unprotected ear as 90 dBA or less.Although there are some noise sources which are likely to exceed the limit,they do not produce sound levels above 90 dBA for more than 2-5 hoursper shift reducing Leq (8 hr) to be well within the limits.

Heavy machinery drivers and personnel working very near to thesemachineries are likely to get exposed to higher levels than the presaibedlimits if the exposure is continuous and should therefore be provided withprotective gear.

72.3 Air quality impacts

The concentration levels of air borne pollutants such as NO,, SO, and SPMare well within the prescribed air quality standards. However, the valuesof SPM levels may go up on commencement of construction activities and'may require mitigatory measures for its control.

7.24 Water quality impacts

The construction of aerated lagoons would not have any major impact onthe creek water quality because the transient discharges, if any, during theconstruction phase will be insigniicant in comparison to the existingpollution load on the creed Similarly as the area covered by the lagoons isless than even 2 per cent of the intertidal zone region of the creek,construction of aerated lagoons would not have an adverse effect such as

AERAMED LAGOONS 76

flooding of regions adjoining the lagoois. Care should, however, be takennot to close any natural drainage channel wlile reclaiming thie land for thelagoons with out providing adequate diversion for run-off.

7.3 Operation phase impacts

7.3.1 Air quality impacts

Findings on creek water quality impacts do not indicate a significantimprovement after the implementation of the proposed single cell aeratedlagoons (section 7.32). Anaerobic conditions in the creek giving rise to.malodorous conditions in the surrounding areas, therefore, will persist.

Also, there is a possibility of significant I-1S emissions from the lagoons inthe event of their malfunctioning, especially that of aerators. The probableair quality impacts for such incidences have been quantified by modellingground level concentrations of 1iS around the lagoon sites. A multi-sourceGaussian plume model for Point, Area and Line sources (PAL) has beenused for air quality simulation. This model is part of the family of airquality models available under the UNAMAP package released by USEnvironmental Protection Agency, U.S.A.

The I17S emissions from aerated lagoon sites have been considered as areasources in this model and the effective height of emiissions at bothBhandup and Ghatkopar are considered to be at ground level. The hourlyground level concentrations as well as 8 liourly averages of I-LSconcentrations have been predicted for a typical winter dav. A lotal of 441receptors separated by 0.5 kx*i distance, in a square grid uf 1) Lm x 1x 0 km,have been considered for this purpose. The simulations laive Leel carriedout by assuming the lagoons as an area source of H.5 emissions at thecenter of the grid. Surface meteorological data recorded at Bombay during1992 have been used for this purpose. The emissions at aerated lagoonshave been evaluated through an empirical.formula reported in literature*.The source detaiLs of Bhandup and Ghatkopar lagoons are given in Table 72.

Air quality simulation results show that H25 impact around the aeratedlagoon will be maximum in the morning hours, in south through westdirectiorns from the lagoon sites during winter. Considerable impact couldbe observed upto 2 kilometers distance from the project sites under stableconditions. The predicted 8 hourly average concentrations of H.S variedbetween 193 ig/m3 at 0.5 kilometers to 33 jig/xr3 at 2.0 kilometers distancearound Ghatkopar site and from 132 g/gl 3 at 0.5 kilometers to 24 Itgrm3 at2.0 kilometers distance at Bhandup site in the south from the lagoons.

Wrww..'tw tirginint k r politim conutrd by Soli J. Arceivalia (19¶M). Tha Mk4raw Hill Nbli&hing CtinppmiU L imitd.

AED ULAGOONS 77

Table: 7.2

H2S Emissions at aerated lagoons ofBombay sewage disposal project

Aerated Design Total Emission Area Source SW corner coordinateslagoon capacity Emission Rate

East North E-W N-S(/ day) (gd day) (gi sed m2 ) (Km) (Km) (Km) (Km)

Bhandup 164.0x106 4.990x105 4.637x10-5 4.880 4.741 0.240 0.519

Ghatkopar 363.x106 1.164x106 1.326x406 4.734 4.905 0.532 0.191

The mnnimum levels which a human being can detect according to somesurveys are in the range of 60-90 p*g/mn. The predicted values thusindicate that malfunctioning of the aeration mechanism in lagoons couldcreate serious odour nuisance near the Bhandup lagoons within about 1.0kilometer radius. For Ghatkopar lagoons, due to their larger capacity, theimpacts could be discernible upto as far as 1.5 kilometers from the lagoonsites.

7.3.2 Water quality impacts

7.3.1 Proposed treatment

Direct municipal discharges into Thane creek have caused widespreaddegmdation of water quality especially in the inner creek region.Approximately 400 mld of municipal v.. Xwater is disharged into inmerThane creek from Bhandup and Ghatkopar service areas. Poor creek waterquality in this region indicates that the pollution load carried by thesedischarges exceeds the assimilative capacity of the inner creek especiallyduring the neap tides. Wastewater treatment as will be iniaiated by theproposed project, therefore, is essential for upgrading the creekenvirorument.

The planned treatment level at Bhandup and Ghatkopar aerated lagoonsalong with the present and prciected flows for the year 2005 are presentedin Table 7.3. The present design capadties of Bhandup and Ghatkoparlagoons are 180 and 385 mld respectively. In view of significantly largerestimated flows (280 mild) in Bhandup service area for the year 2005, it willbe necessary to redesign the Bhandup lagoons for the new flows. Theprojected wastewater flows at Ghatkopar by the year 2005 ( 235 mld afterdiversion of 50 mld for industrial use), however, are considerably less than.the design flows. Ghatkopar lagoons, therefore, would be underloaded inthe year 26005 by about 40 per cent and are expected to achieve effluentBOD of 90 mg/L and 35 mg/L for single and three cell configurations,respectively. These lagoons would not contribute to any significantreduction in ammoniacal nitrogen load in the wastewater. Table 7.3 alsosummarises the present and expected carbonaceous BOD load in the year2005 on the creek with single cell as well as three cell lagoons. It is seenthat single cell lagoons will achieve 45 per cent reduction in the presentcarbonaceous BOD load on the creek and three cell lagoons will reduce itby 80 per cent.

The following sections of the chapter present a comprehensive analysis ofwater quality impacts of discharges from the proposed single and three

A0UAW IArOONS 7.9

Table: 7.3

Present and projected BOD loads in Thane creek(Municipal discharges)

Treatment Service Wastewaterd Wastewated Pollution load

option area effluent flow effluent BOD (Kg BOD/ day)(mid) level (mgl L)

Present flows

No treatment Bhandup 150 225 33,750Ghatkopar 250 225 56,250

Total 90,000

Projected flowsfor the year 2005

Single cell Bhandup 280 100 28,000

lagoons (as Ghatkopar 235* 90 21,150

proposed in firstphase Total 49,150

Three cell Bh.dileduS 280 35 9,800

lagoons Gh.lkipir 235" 35 8,225

Total 18,025

* The expected flowv is 285 nild fr(mi whici 50 mid will be used in neighbouring industries.

cell lagoons for the projected wastewater flows in the year 2005. With aview to developed a long term wastewater management strategy, variousoptions for wastewater treatment and disposal were also examined for theprojected flows for the year 2015. The options considered, however,assume that wastewater discharge locations for future options remainwithin the Bhandup-Ghatkopar stretch of the creek. This analysis, thus,does not examine the possible advantages of transporting wastewater toregions outside the modelled area.

7.3.22 Analysis of alternatives

The proposed level of wastewater treatment effort at Bhandup andGhatkopar was selected with the objective to achieve effluent standards of100 mg/L both for BOD and suspended solids. The effluent standarc!s, as acondition for discharge of treated wastewater into Thane creek, werespecified by Mashashtra Pollution Control Board. Unfortunately,constraints on creek assimilative capacity due to weak tidal flushingduring the neap tides were not taken into account while specifying theeffluent standards. It is apparent from the discussion in section 73.2.1 thatdue to considerable quantum of wastewater flows by the year 2005, onlymarginal improvement in creek water quality is expected by meeting theprescibed effluent standards.

The management altermatives were, terefore, evaluated with respect tothe objective of achieving minimal necessary improvement in Thane creekwater quality to restore its ecological role in sustaining marine life. Amanagement goal to ensure a minimum dissolved oxygen level of 2 mng/Lin the creek was selected. Water quality scenarios for competingmanagement options were developed using a depth integrated'hydrodynamic and water quality model DIVAST, calibrated for Thanecreek through field surveys.

Following section describes the results of such analyses as also theprobable impact on water quality if the present creek disLharges areallowed to be continued.

7.32.3 No action scenano

The municipal wastewater discharges from Bhandup and Ghatkoparservice areas are presently estimated at 400 mld and are expected to rise to520 mld by the year 2005. A further steep rise in wastewater generation inthese service areas is expected due to planned augmentation of water

AERATED lGooNs ~7.11

supply. By 2015, wastewater generation in these areas is expected to reach1000 mld. Due to the natural slopes, the entire wastewater ultimately willdrain into the imner Thane creek giving rise to approximately a two and ahalf fold increase in the pollution load. If no wastewater treatmentfacilities are implemented, creek water quality which already exhibitswidespread impairment dunng the low tides, would further beconsiderably degraded. Under such scenario the entire inner Thane creekregion is expected to be devoid of dissolved oxygen for considerableportions of the tidal cycles.

7.32.4 Augmentation of wastewater management effort

For examining the impact of different wastewater mangement options oncreek water quality, quantitative estimates were developed thmughcomputer simulation. The solute transport model DIVAST which wasearlier calibrated for both neap and spring tide conditions, was used for.water quality predictions. While simulating water quality, the renerationrate coefficient was intnally calculated by OwenYs relation. The BODdecay coefficient was allowed to vary from 0.5 to 0.3 /day and sedimentoxygen demand (SOD) from 4 to 3 g/m 21 day, subject to the degree ofwastewater treatment effort For instance, BOD decay coefficient of 0.5 perday along with SOD of 4 g/m 2 fday was used for single cell aerated lagooneffluents. The values were gradually decreased to 0.3 per day for BODdecay coefficient and 3 g/m21day for SOD as the degree of treatment wasraised to secondary leveL Removal rate for ammoniacal-N was consideredat 0.4/per day for all simulations.

In a tidally influenced water body, water quality is intimately related withthe tidal strength which undergoes a fortnightly cyclic change. Waterquality simulations for a complete neap-spring-neap tidal cycle wereimpractical due to greater computer time requirement. The managementalternatives were, therefore, developed by running the simulation forabout 72 hours for five and a balf tidal cydes centered about the neap tideof February 21, 1994. During this period, the mirimum rise in waterelevation from low to high tide recorded was 0.65 meters which was thesixth lowest for the entire year

The simulations were started at the high water slack period assumingclean water quality conditions in the creek. These conditions were definedby DOD and DO levels of 3 mg/L and 4 mg/L, respectively. Further, as thecreek considerably widens near the Vashi bridge, where the Ghatkopardischarges reach the creek, considerable lateral water quality differencesoccur in this region. For instance, a patch of low dissolved oxygen (less

AERAE IAGOONS 7.12

than 1 mg/L) can occur near the discharge points whereas dissolvedoxygen near the opposite bank could be above 4 mg/L. The results ofwater quality simulations for different nanagement options were,therefofe, interpreted by considering the spatial extent of attainabledissolved oxygen levels for respective options. If a management optionwas found unsuitable due to occurrence of wide spread dissolved oxygendepletion, the mangement effort was raised by increasing degree oftreatment or shifting the discharge location near the creek center.Atinment of dissolved oxygen above 2 mg/L during the entire tidalcyde, was defined as the water quality management objective.

Further, while evaluating the management options, the treatmentefficiencies were so selected as to be compatible with the proposedfacilities. The augmentations in treatment effort, to the extent possible,were considered as phased development to the first phase facilities (singlecell lagoons). The options for treatment effort, however, were defined in.terms of treatment efficiencies rather than treatment flow sheets to allowwider choice of tre!itment options and their combinations.

As the first management alternative, four streams of single cell aeratedlagoons both at Bhandup and Ghatkopar were considered for flows for theyear 2005. The effluent BOD and NH3-N levels under this option weretaken to be 100 mg/L and 15 mg/L for Bhandup and 90 mg/L and 15mg/L for Ghatkopar lagoons. The simulations were carried out forsummer (water temperature 30C) which constitute the critical conditionsfor creek water quality due to higher BOD decay rates and lowerdissolved oxygen saturation levels. The predicted creek dissolved oxygenfor the treatment option are summarised in Table (7.4 [item 1]) and Figures.73 and 7.4.

The simulations were carried out for five and a half tidal cycles and theinterpretations were based on the final tidal cycle which correspondedwith minimum tidal variations between the high and low tides. Thesimulation results indicate widespread depletion of dissolved oxygen ininner creek regions. For instance, at the time of high tide, dissolved oxygenin approximately 50 per cent of the upper creek area north of Vashi bridge,is expected to fall below 2.5 mg/L. The area with dissolved oxygen below2 mg/L at this stage is expected to be about 4.2 kilometers long and 1.3kilometers wide near Ghatkopar creekleL Another low oxygen patchabout one-fourth the size of that expeted r.ear Ghatkopar is likely todevelop near Bhandup discharge location.

AED' WON5OC 7.13

Table: 7.4

Water quality distribution in Thane creek for various management scenarios

Management Management Effort Simulation Effluent characteristics Prbable impacts on creek

Scenarios conditions and disposal scheme water quality

1 Single cell aerated lagoons Summer BOD-100 mg/L, DO Nil, Widespread occurrences of water

both at Bhandup Neap tide NH3 -N-15 mg/L, quality state with DO below 2 mg/L

and Ghatkopar 2005 flows during the entire tidal cycle.

2 Single cell aerated lagoons Summer BOD-100 mg/L, DO Nil, Widespread occurrences of water

both at Bhandup Neap tide NH3 -N-15 mg/L, quality state with DO below 2 mg/L

and Ghatkopar 2005 flows, 50 mid exceeding I km length and 05 indiverted at Ghatkapar during the entire tidal cycle.for industrial use.

3 Three cell aerated lagoons Summer BOD-35 mg/L, DO Nil, Minor occurrences of DO marginally below

both at Uhandup Neap tide NH3 -N-S15 mg/L, 2 mg/L. The affected region not

and Ghatkopar 2005 flows, 50 mid exceeding 2.2 kilometers in length anddiverted at Ghatkopar 0.8 kilometers in width at anyfor Industrial use. time of the tidal cycle.

'a,

Table : 7.4 (Conitd..)

Mana8ement Management Effort Simulation Effluent characteristics Probable impkcts on creek

§ Scenarios conditions and disposal scheme water quality

4 High efficiency secondary Summer Gluatkopar Marginal improvement in DO

treatment at Ghaikopar Neap tide BOD-15 mg/L, (less than 0.5 mg/L)

and three cell aerated DO-2 mg/L as compared to scenario 3.

lagoons at Bhandup NI-H3-N-15 mg/L,Blhandu1pBOD-50 mg/L, DO-Nil,NH3-N 15 mg/L,2005 flows, 50 mIddiverted at Ghatkoparfor Industrial use.

5 Three cell aerated lagoons Summer Ghatkopar & Blhindup Minor occurrences of DO rnarginally below

both at Uhandup Neap tide BOD-35 mg/L, DO Nil, 2 mg/L, near Bhandup and Ghatkopar.

and Ghalkopar NH3 -N-15 mg/L, The affected region not exceeding

2005 flows, 50 mid 2.2 kilometers in length and

Nitrilication followed by diverted at Ghatkopar 0.8 kilometers in width at any

secondary treatment ftur for industrial use. time of the tidal cycle.

discharges near VikhrtliNear Viki:rofi DO always above 25 mg/L

BOD-1 mg/L, near Vikhmli.DO-2 mg/L,NH3-N-15 mg/L,Wastewater flow 520 mid

During the low tide, the low dissolved oxygen region shifts southwardswith the ebb currents and is expected to occupy about 60 per cent of thecreek width, south of Ghatkopar creeklet. The dissolved oxygen levels in aregion of 4 kilometers in length and 1.1 kilometers in width near Vashibridge are expected to be below 2 mg/L. The concurrent BOD levels nearthe discharge point are expected to be 10-12 mg/L with occurrence of BODabove 4 mg/L in large portions of inner creek

Another set of simulations, for single cell lagoons at Bhandup and'Ghatkopar, were carried out by reducing the wastewater flow atGhatkopar by 50 mld, the expected demand for raw sewage for theindustrial use in Ghatkopar service area. The expected water qualityscenario for this management alternative is presented in Figures 7.5 and7.6 and the observations on aeek DO are summarised in Table 7.4(item 2).A comparison of Figures 7.3 and 7.4 with Figures 7.5 and 7.6, zespectively,reveals only a marginal improvement in creek water quality for the

-reduced wastewater flow at Ghatkopar. None of these options achieves theminimal desired water quality for the year 2005 flows. It is evident fromthis analysis that implementation of proposed first phase facilities,although would arrest the growing impairment of creek water quality,would not result in its significant improvement, even up to the year 2005.

As the next management option, treatment facilities comprising fourstreams of three cell aerated lagoons both at Bhandup and Ghatkopar wereconsidered. The water quality scenarios were developed for projectedwastewater flows for the year 2005 after accounting for sewage demand atGhatkopar. The effluent BOD and ammoniacal-N levels for this optionwere assumed to be 35 mg/L and 15 mg/L. Simulation results for 2005flows indicate considerable improvement in creek water qualitv withrespect to single cell aerated lagoons (Table 7.4 (item 3)). The resultsindicate that for this option, during the high tide only small region ofdissolved oxygen below 2 mg/L develops in the creek. The extent of theregion with low oxygen remains below 1.5 kilometers in length and 500meters in width (Figure 7.7 & 7.8). Further only approximately one-fourthof the creek region north of Vashi bridge exhibits DO below 2.5 mg/L. Atlow tide, the low dissolved oxygen region shifts to south anid centers atabout 2 kilometers south of Vashi bridge. The spatial extent of this regionis about 2.2 kilometers in length and 800 meters in width. BOD levelsunder this management option are above 4 mg/L in stretches of 1kilometer and 500 meters along the creek's west bank near Bhandup andGhatkopar creeklets, respectively.

AEIWED LAGOONS 7.17

Further water quality scenarios for 2005 flows were also developed toevaluate the efficacy of enhanced secondary treatment options, such as theactivated sludge process at Ghatkopar. For these simulations the effluentBOD of 15 mg/L and ammoniacal-N of 15 mg/L were assumed.Simulation results indicated a marginal improvement of 0.3 mg/L in creekdissolved oxygen over three cell aerated lagoons option (Table 7.4 (item-4)). Shifting the effluent discharge location to the center of the creek alsodoes not yield any significant improvement in creek DO. It was furtherobserved that for 2005 flows nitrification was necessary to raise creek DOabove 2.5 mg/I; at this location.

When extended to 2015 flows, the simulations indicated that it was notfeasible to discharge effluents beyond the flows projected for the year 2005at Bhandup and Ghatkopar, even after nitrification of effluents. The needfor an additional discharge location when the wastewater flows exceed2005 projections, is thus apparent Simulations were, therefore, performedwith different discharge locations for additional flows. The resultsrevealed that the creek in its inner region near Vildroli could assimilatedischarge of 260 mid after secondary treatment (effluent BOD 15 mg/L) inaddition to the 280 mld and 235 ald to be discharged at Bhandup andGhatkopar, respectively. The projected combined wastewater flows inBhandup and Ghatkopar service areas for 2015, however, exceed the 2005projections by about 520 mld. It will be necessary to provide nitrificationfor these additional flows. Creek water quality conditions for suchwastewater management option are described in Table 7.4 (item 5).

The above analysis indicates that constructing three cell aerated lagoonsfor the proposed design flows is an adequate measure for creek waterquality management upto the year 2005. These discharges will, however,fully exhaust the assimilative capacity of the creek in regions around thedischarge locations presently identified. For future flows, it will thus benecessary to build additional wastewater treatment facilities anddischarge the effluents at new locations in the creek. The analysisindicates, that if one were to discharge within the inner Thane creek, itwould be possible to do so near Vlkhroli. Such an option, however, wouldentail tertiary level treatment of the discharges of Vikhroli and would beadequate only upto the year 2015. Considering the need to plan evenbeyond the year 2015, it would be prudent to investigate options fordischarging the wastewaters in other regions of the creek. Under suchcase, because of assimilative capacityof these waters, it may be adequateto treat the effluents only upto secondary level anid tlhe cost of transportingthe wastewater may be off-set by savings in the cost of its treatment.

AERYED LOONS 720

7.4 Socio-economic impacts

Rehabilitation of displaced populations is generally one of the major socialconcern associated with development projects. The project area forBhandup and Ghcatkopar lagoons, however, is uninhabited and does notinvolve any displacement of people. The project, during the construction,is expected to generate some employment which would have marginalpositive impacL The operation of aerated lagoons does not require a largeworkforce and therefore any large scale residential development in theregion, due to the implementation of the project, is not expected. Theimplementation of the project, would result in beneficial impacts in termsof higher fish yield thereby increasing fishing activities in inner Thanecreek. However, the extent of these impacts will be difficult to quantify.

7.5 Conclusions

The environmental impacts arising due to construction of aerated lagoonsare the possible increase in noise and SPM levels during construction. Thenoise predictions indicate that the inpact cf noise at the nearest residentiallocalities was negligible and the high SPM levels could be controlledthrough mitigatory measures. The visual impairment, if any, due toconstruction of treatment systems amidst green regions can also beeffectively ititigated by developing green-belt around the lagoons.Another important impact of construction of proposed lagoons is the lossof about 40 hectares of mangroves due to land reclamation. It is necessaryto compensate for this loss by replanting equivalent areas in the innercreek region itself and protecting existing mangroves from futureencroachmnenL

The major envirounental impacts of the project will 'ccur during itsoperation and if fully developed to three cell configuration andcommissioned by the year 2005 will be highly beneficial. The water qualitypredictions through rigorous hydrodynaTiic and water quality modelling,indicate that the proposed first phase treatment effort through single cellaerated lagoons would not provide significant improvement in creekwater quality. Such implementation would, however, arrest rising trend ofwater quality impairment.

When augmented to three cells aerated lagoons, the proposed wastewatertreatment would be adequate until wastewater flows exceed the projectedflows for the year 2005. Importantly, the post-project ecological conditionsin inner Thane creek are expected to be similar to those existing in Manooncreek on the west coast of Bombay. Observations on Manord creek have-

AEU= ED . 721

confirmed that the creek sustains a diverse ecosystem and plays aninvaluable role in maintaining the bio-productivity of adjoining coastalecosystem An adequate water quality effort at Bhandup and Ghatkopar,therefore, also has potential of enriching the coastal ecology of Thanecreek.

In order to sustain water quality conditions favourable for supporting ahealthy ecosystem in the creek after 2005, it would be necessary to buildadditional treatment facilities and discharge the effluents at new locations.Within the inner creek region, additional flows upto 260 mld.could bedischarged near Vikhroli after secondary treatment. For effective futurewastewater management, however, it appears necessary to explore thewastewater assimilative capacity of other regions of the creek. Acombination of wastewater treatment and transport enabling effluentdischarges in outer Thane creek, in areas south of Trombay, appearsnecessary for effective future water quality management in the creek.

AsRlm LAGOONS 722

Chapter 8RECOMMENDATIONS FOR

MANAGEMENT PLAN

8.1 Preamble

Bombay Sewage Disposal Project is one of the most ambitious pollutionabatement schemes undertakeninIndia. Under the project, constructionoftwo marine ouLtfalls at Worli and Bandra; and four aerated lagoons at.Bhandup, Ghatkopar, Malad and Versova is envisaged. With theimplementation of the project, considerable improvement in coastal waterquality around Bombay is expected due to the large reduction in pollutionloads in wastewaters presently reaching the near-shore coastal waters.

As the project involves large expenditure for environmental improvement,the most important aspect of environmental impact assessment is todetermine the effectiveness of the project in achieving desiredenvironmental benefits and to suggest modifications, if required. Theprocess should also identify the adverse impacts associated with theconstruction of the project and delineate the mitigatory measures. Theenvironmental impact assessment study of the project, ffierefore, wasaimed at fulfilling these objectives. The findings and recommendations onproject components of (a) marine outfalls at Worli and Bandra and (b)aerated lagoons at Malad and Versova have already been documented inthe two preceding reports. This report, the last in the series of the threereports envisaged on the project, deals with the environmental issuesrelated with the proposed aerated lagoons in Bhandup and Ghatkoparservice areas.

As the wastewater from the terminal pumping stations in Bhandup andGhatkopar service areas drains into Thane creek, creek water qualityscenarios for a number of wastewater treatment and discharge optionswere developed. The results of this effort clearly establish that the currenteffluent standards prescribed by the Maharashtra Pollution Control Boardp 4PCB) for discharging treated wastewater into the creek are not related tothe latter's assimilative capacity. It is observed that due to the largevolume of expected wastewater discharges into the creek by the years 2005through 2015, meeting the prescribed effluent standards will not beadequate to protect the ecological health of the creek.

The recommendations of this study, therefore, are based nm an asse.ssmentof achievable creek water quality if different treatmen t strategies areimplemented and are not constrained by assuming the adoption of astrategy which only complies with the stipulated effluent standards. In due

AERSED LAGOONS .i

course MPCB may consider developing lcation specific dischargestandards for all major discharges into Thanie creek and promulgate thenecessary regulations in a time bound manner to supplement the pollutionabatement effort undertaken by the MCGB. This study and itsrecommendations attempt to provide a robust framework for evolving-such standards.

82 Management options for Thane creek

The findings of the study indicate that notwithstanding the significantassimiLative capacity of Thane creek, approximately 80 per cent reductionin the present carbonaceous BOD load generated in MCGB area will benecessary to achieve the 1inimal conditions (DO more than 2 mg/L)required to sustain a healthy creek ecosystem. For the projectedwastewater flows for the year 2005 and 2015, the requisite pollutionabatement effort implies 84 and 92 per cent reduction in carbonaceousBOD load to the creek, respectively. If options of transporting the effluentsto new creek regions are not considered, an additional reduction ofapproximately 80 per cent of projected nitrogenous BOD load will benecessary by the year 2015.

MCGB has proposed the construction of single cell aerated lagoons atBhandup and Ghatkopar. If designed to treat the projected flows, these areexpected to provide 50 per cent reduction in the estimated pollution load inthe year 2005 from Ghatkopar and Bhandup service areas. Whilst the singlecell lagoon treatment would satisfy the discharge consent standards, themoodel simulations indicate that this treatment effort would not achieve theminimal conditions to sustain a healthy creek ecosysteni in ii ww.r Tluhnccreek. The construction would certainly arrest the onigoig deterioration ofaeek water quality and after implementation, the overall water qualitycondition in the creek in the year 2005 is expected to be Ititter than it is atpresent.

Hiowever, the projected flows at Bhandup for the year 2005 exceed byabout 50 per cent, the capacity for which those lagoons are at presentdesigned. As a result, BOD levels in the effluent from single cell lagoons atBhandup would be higher- tan 100 mg/L, the standard stipulated byMPCB and would thus fall short of the minimum statutory requirement foreffluelnt disharge. It would, therefore, be necessary that the lagoons atBlhandup be designed for the flows which they will be expected to treat by2005.

If, instead of constructing single cell, three cells aerated lagoons to achieve

-AUD LAGOONS 2

effluent BOD of 35 mg/L or below were constructed then the assessmentindicates that when operating at their full capacity, the lagoons would beable to attain acceptable ecological conditions in Thane creek forwastewater flows upto 280 mid at Bhandup and 235 mid at Ghatkopar. If50 mid sewage in Ghatkopar service area is diverted to nearby industriesfor reuse, these limiting design flows are not expected to be exceeded untilthe year 2005. With such treatment of sewage, the dissolved oxygen allalong the creek would rarely fall below 2 mg/L and when it did it wouldonly do so marginally.

The effluent discharges near Ghatkopar and Bhandup, however, wouldfully exhaust the assimiative capacity of the creek at these locations. Theresults indicate that even activated sludge treatment instead of aeratedlagoons at Ghatkopar and Bhandup would not provide a significantimprovement in minimum DO levels in the affected regions of the creek.

While the investigations firmly establish that tlhee cells aerated lagoonswould significantly improve the existing ecological status of the innerThane creek and would provide a reasonable degree of pollution controlupto 2005, advanced treatment facilities would be necessary to cater to thewastewater flows after 2005.

To accommodate the future increases in wastewater flows, it will benecessary to build additional treatment facilities and transport the treatedeffluent for discharge at new locations in the creek. The StLEdies indicatethat in regions near Vikhroli, it will be possible to discharge additionalwastewater flows of about 260 mld after secondary treatment and upto 520mid after advanced biological treatment (nitrification after removal of.carbonaceous matter). Additional treatnent capacity of 520 mld along withthe proposed aerated lagoons at Bhandup and Ghatkopar would thenaccommodate the projected wastewater flows upto 2015. However, if anoption to discharge the effluents in creek regions south of Trombay areconsidered, treatment upto secondary level may be adequate to achievedesired creek water quality.

In order to put the management objective of achievimg miniimum die :lvedoxygen of 2 mg/L in the creek in a correct perspective, simulations wereconducted to determine highest achievable creek dissolved oxygen levelsnear Bhandup and Ghatkopar for the projected flows in the year 2005. Itwas observed that even a highly resource intensive treatment effort,comprising of activated sludge process followed by nitrification facilitiesand targeted to provide effluent BOD of below 15 mg/L and ammoniacal

AIDLAGOONS 3

nitrogen of below 1 mg/L, would not be adequate to raise creek dissolvedoxygen significantly above 25 mg/L, at all times.

Construction of properly designed single cell aerated lagoons at Bhandupand Ghatkopar is thus, the minimum admissible treatment effort necessaryto meet the current effluent discharge standards. Construction of suchwastewater treatment facilities at Bhandup and Ghatkopar would be apositive step towards the objective of overall water quality improvementin Thane creek and is strongly recommended.

For significant improvement in creek water quality, however, it will beessential to augment the aerated lagoons at Bhandup and Ghatkopar to athree cells configuration designed to produce effluents with BOD below 35*mg/L Considering that such augmentation would remain effective onlyupto the year 2005, subject to funds being available, implementation of thisconfiguration could be considered at the present stage. If the three celllagoons are not to be considered immediately then single cell lagoonsshould be so designed that they can be extended to three cell lagoonsyielding an effluent with 35 mg/L BOD.

The recommended long term water quality management option for theTmane creek is, therefore, to build three cell aerated lagoons at Bhandupand Ghatkopar and to develop additional treatment units with facilities todischarge the effluent at new locations within the creek. One of the suitabledischarge locations has been identified near Vikhroli and has potential toreceive about 260 mid of effluents after secondary treatment It wiU benecessary to conduct additional water quality modelling studies to assessassimilative capacity of the creek south of Trombay, as a possible neweffluent discharge area for expected wastewater flows in Bhandup andGhatkopar service areas by the years 2015 and after.

The conclusions of this assessment, however, are limited to the study ofmunicipal wastewater loads from Ghatkopar and Bhandup service areas.While evaluating the management options, it was assumed that the waterquality in the inner Thane creek is not significantly affected by otherdischarges entering the creek, especially from its eastern catchment area.This assumption would be valid only if other wastewater discharges intothe creek also are adequately treated.

For achieving the full water quality benefits of the investments intreatment that MCGB plans to make, it is thus imperative that acomprehensive management plan be developed for the creek, withcomparable treatment levels applied to other discharges. Because thisinvolves multiple jurisdictions, it may be best accomplisewd byGovernment of Maharashtra. Considering the probable enviroiunentalimpairment due to delays, it is desirable that immediate priority be

AUAIED LAGOONS IA

nitrogen of below 1 mg/L, would not be adequate to raise creek dissolvedoxygen significantly above 2.5 mg/L, at all times.

Construction of properly designed single cell aerated lagoons at Bhandupand Ghatkopar is thus, the minimum admissible treatment effort necessaryto meet the current effluent discharge standards. Construction of suchwastewater treatment facilities at Bhandup and Ghatkopar would be apositive step towards the objective of overall water quality imnprovementinL Thane creek aid is strongly recommended.

For significant improvement in creek water quality, however, it will beessential to augment the aerated lagoons at Bhandup and Ghatkopar to athree cels configuration designed to produce efEluents with BOD below 35mg/L. Considering that such augmentation would remain effective onlyupto the year 2005, subject to funds being available, implementation of thisconfiguration could be considered at the present stage. If the three celllagoons ace not to be considered immediately then single cell lagoonsshould be so designed that they can be extended to three cell lagoonsyielding an effluent with 35 mg/L BOD.

The recommended long term water quality management option for theTane creek is, therefor, to build three cell aerated lagoons at Bhandupand Ghatkopar and to develop additional treatment units with facilities todischarge the effluent at new locations within the creek. One of the suitabledischarge locations has been identified near Vduhroli and has potential toreceive about 260 mld of effluents after secondary treatment. It will benecessary to conduct additional water quality modeLiing studies to assessassimilative capacity of the creek south of Trombay, as a possible neweffluent discharge area for expected wastewater flows in Bhandup andGhatkopar service areas by the years 2015 and after.

The condusions of this ament, however, are limited to the study ofmunidpal wastewater loads from Ghatkopar and Bhandup service areas.While evaluating the management options, it was assumed that the waterquality in the inner Thane creek is not significantly affected by otherdischarges entering the ceek, especially from its eastern catchment area.This assumption would be valid only if other wastewater discharges intothe creek also -are adequately treated.

For achieving the full water quality benefits of the investments intreatment that MCGB plans to make, it is tuLs imperative that acomprehensive management plan be developed for the creek, withcomparable treatment levels applied to other discharges. Because thisinvolves multiple jurisdictions, it may be best accomplished byGovernment of Maharas Considedng the probable environmentalimpairment due to delays, it is desirable that immediate pdority be

*ABU LAGOONS aA

assigned to planning and implementation of such a managemiient scheme.

8.3 Mitigation plan

&3.1 Construction phase

Loss of about 5 per cent of the total mangrove cover in the inner Thanecreek due to land redamation for lagoons is the most importantconstruction phase impact of the project. To compensate for theunavoidable loss of mangrove area, MCGB should designate about 200hectares of mangrove area along the creek as protected area and takemeasures against further reclamation or unauthorized cutting.Alternatively, MCGB should undertake fresh planting of nuangrove forestsof area equivalent to the reclaimed area in the inner Thane creek region.

Another potentially negative impact of aerated lagoon construction is arise in the ambient noise and dust levels. This impact can be prevented byadherence to good construction and house keeping practices. Measuressuch as avoidance of unnecessary idling of construction machinery andspillage of fuel and oil and adequate maintenance of constructionmachinery to ensure efficient and trouble fiee operation should beprovided for in the construction contracts.

Analysis of the noise levels at the site and surrounding areas indicate thatthe effect of construction activities during the day, is not felt outside theconstruction site due to the local inoises. At night, however, theconstruction activities can raise the noise levels and the nearbv residentiallocations beyond the night time standards for such areas. It is, therefore,recommended that the noise generating construction activities should berestricted only to day time hours.

Air quality analysis at the sites indicates that observed levels of SPM, NO,and So. are wel within the Indian Standards for ambient air quaflty.

E - However, the SPM levels may, on some occasions, surpass the standards atthe time of site clearing and construction activities. Provision of waterspraying on all haul roads at the costruction site should be made tominimize the dust. Also, green belts should be developed around theboundary of the lagoon sites on the sides facing habitation to safeguardagainst aesthetic impairment An inventory of requisite mitigatorymeasures is provided inTable 8.1. The recommended specifications for thegreen belts are presented in Table 8.2.

A-AIED lAGOONS X-A

Table: 8.1

Mitigation plan for constuction and operationalimpacts of areated lagoons

.

No. Environmental Issues Actions to be taken Responsible entity

A. Construction phase

1. Dust contamination at Construction sites and MCGB/Prospectivesite and on haul roads access roads will be Contractor (PC)

watered twice each day

2. Noise pollution Operation of heavy cons- MCGB/PCtuction machinery causingnoise pollution to berestricted to daytime hours

WelL maintained vehiclesto be used for muck andmaterial transport. Ihevehide speed should belimited to 40 kilometersper hour in the residentialareas.

3. Air pollution Monitoring at site and on MCCBaccess roads for SPM, NOxand S02 twice each week

4. Disposal of excavated In case of semi solid waste MCGBmaterial and provision to be made forconstruction debris dewatering/drying prior

to its use for reclamation

Daily inspection at haul MCGBroad and sites forconstruction debris, itscollection and disposal tolandfill sites

aU

Tablc: 8.1 (Corttd...)

No. Environmental Issues Actions to be taken Responsible entity

5. Traffic and All hauling materials to be PCtransportation covered while being

transported

Routine check of vehicle PCused for transportation andtheir proper maintenanceto mininize vehicularpollution

6. Domestic sewage and Provision of waste disposal PCrubbish facilities like septic tanks at

construction worker'scolony

Provision at site and in PCworker's colony for waste-bins for solid wastecollection

Transportation for PCdumping the solidwaste from worker'scolony to a nearbycollection or landfillwithin the area

7. Public participation Public awareness MCGBprogrammes to beconducted

8. Loss of about 40 Mangrove replantation of MCGBhectares of mangroves equivalent area in innerfor site dearance Thane creek

AEADW AOONS

Table: 8.1 (Contd.)

No. Environmental Issues Actions to be taken Responsible entity

B. Operational phase

9. Effluent monitoring Weekly monitoring of MCGB/NEERImonitoring lagoon effluents quality for

BOD, suspended solids,NH3 -N, Org. -N and DOprior to discharge intoThane creek

Monthly monitoring of MCGB/NEER[metal concentrations inlagoon effluants

10. Environmental Seasonal monitoring in the MCGB/NEERImorWring creek for BOD, DO and

NH1-N levels and biologicalparameters during theneap tides. Theobservations should coverregion of impacts duringpre- and post-projectperiod

U. Maintenance Routine maintenance of allmechanical and electricalequipments like aeratorsand pumps for efficientoperation

12 Solid Waste Disposal Disposal of sceenings and MCGBgrit along with city refuse

Environmentally suitable MCGB/NEERIdisposal of sludge fromdesludging operations oflagoons taing intoaccount concentration ofheavy metals in the sludge

'# 's . '' . ' - ' '.IA*1 ~ ~ A= AYXN

Table: 8.2

Recommended plantation in areas near the proposed aeratedlagoon sites

Site Total Name of the plant Plant to Totallength species plant numberapprox spacing of plants(m) (in) required

Three rows of plants 2000 Pride of India 10 200along the boundary of Cocos nucifera 10 200Bhandup aerated lagoon Pride of India 10 200site

Three rows of plants 1800 Pride of India 10 180along the boundary of Cocos nucifera 10 180Ghatkopar aerated Pride of India 10 180lagoon site

;

AEEA1~~~~~~~~~~~~~~~~~~~ LAGON 1

83.2 Operation phase

If the facilities are limited to single cell lagoons, water quality in the regionof discharge into the creek wiUl remain below the level necessary for ahealthy ecosystem. An adequate mitigatory measure, therefore, would beto construct three cell aerated lagoons at this stage itself or to augment thesingle cell lagoons to three cell configuration as soon as possible. Withrespect to the treatment facilities, care should be taken to extend theeffluent discharge point upto 20 meters beyond the low water line in thecreeklets to avoid formation of sludge mats in the inter-tidal zone. In orderto achieve acceptable environmental conditions in the vicinity of the creekproper functioning of aerators is of prime importance. Adequate back upsystems should be incorporated in design stage itself to ensure theircontinuous and trouble free operation.

&3.3 Environmental monitoring

A systematic water quality monitoring effort within the creek should beinitiated before and after commissioning the aerated lagoons at both thedischarge locations. At the post-commissioning stage, the monitoringshould be aimed at evaluation of water quality projections and validatingthe water quality mdel used in the present study. Such validation will beuseful for future planning.

A regular effluent monitoring programme to establish the performanceparameters for the treatment system should, however, be undertakenimmediately after commissioning the treatment systems and continued.during the entire operation period of the treatment systems. Guidelinesfor such monitoring are provided in Table 8.1.

Creek water quality monitoring along with observations onhydrodynamic parameters should, be initiated by Government ofMaharashtra to develop a comprehensive water quality model for theentire Thane creek, a prerequisite for developing the overall wastewatermanagement plan for the region The exercise should aim at developinglocation specific discharge standards for vanous industrial discharges intothe creek to ensure that the overall pollution load to the creek are withinits assimilative capacity.

A limited monitoring at the creek may also be undertaken to documentthe improvement in the creek ecosystem comparing the pre andpost-project water quality conditions. A summary of the recommendationsfor environmental monitoring are presented in Table 8.1.

AELED LAGOONS a.10

83.4 Public participation

The proposed wastewater management effort along Thane creek involvessignificant investment of public funds. The findings of the study indicatethat evenL more comprehensive treatment efforts will be necessary tosafeguard the creek water quality in the not-too-distant future. It is,therefore, desirable to create public awareness for the project activities tofacilitate their involvement in the decision making. Towards this end,findings of this study should be placed for public discussions amongrepresentatives of fishing communities, general public and local NGOs.The report summary should also be translated in local languages anddistributed among the fishing communities.

A comprehensive awareness program on the need for the project, majortechnical and social issues and the environmental benefits should beundertaken through local media. The coverage should incLude discussionson IV and radio by parnls comprising concerned ctizens and officialsconnected with imPlementation and environmental assessment of theprojecL An outline for environmental awareness programme has alreadybeen suggested in the report on marine outfalls submitted earlier.

83.5 Institutional needs

There is a need for substantial institutional development within theMCGB for effective operation of aerated lagoons and thie additionaltreatment and effluent diversion options which will have to be developedlater. Trairnng programmes for various levels of associated staff of MCGBshould be conducted for efficient operation of the project. On certiinenvironmental aspects such as use of water quality models for effectivewater quality monitoring in the creek, evaluation of long term post-projectenvironmental impacts and wastewater management planning for futuredischarges it may be necessary for MCGB to take recourse to the expertiseavailable with the research Institutes active in these areas.

For effective implementation of the recommended effluents andenvironmental monitoring, it will be necessary to develop adequatefacilities for sampling and analysis. It will be desirable to operate an

r environmental monitoring cell, with adequate training andinstrumentation support for coastal water quality monitoring and analysisrelated to the aerated lagoon project. Govenmment and privatelaboratories with adequate infrastructural facilities and expertise may alsobe identified to assist in these activities.

AALE LAGCOONS '.11