ESAI Colloquium,Dundalk Institute of Technology,

Co. Louth, Ireland

Sustainable Wastewater Management in

Rural Housing Developments

3rd February 2008

Padraic Mulroy, Managing DirectorMulroy Environmental

• Qualifications– BSc. Microbiology, (2:1), 1993 - NUIG;– MSc. (Major: Soil & Water Science &

Minor: Environmental Engineering) - 1996, University of Florida, US.

• Professional Affiliations– MIEI (Institute of Engineers)– IRCA (International Register of Certified Auditors)

• Non-Professional Affiliations– IOWA (Irish On-site Wastewater Association)– IAH (International Association of Hydrogeologists)

BACKGROUND

ACADEMIC 1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

• Capabilities– Wastewater Treatment Plant Design for Single,

Small Community, Commercial & Industrial Development

– Site Suitability Assessment– Due Diligence Site Investigation/Contaminated

Land Risk Assessment– Remediation/Bioremediation of Contaminated

Soil & Water– Waste Licence & Permit Applications– IPPC Licensing– Environmental Impact Assessment– Sludge Management Expertise– Strategic Environmental Assessment– Environmental Monitoring

BACKGROUND

MULROY ENVIRONMENTAL1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

GUIDELINES

Local Authorities

• ‘Sustainable Rural Housing, Guidelines for Planning Authorities’, DOELG, 2005:

Main drivers:

– Ribbon development needed to be curbed;– Development should concentrate around

rural villages;– Clustered approach to development to be

encouraged; and– ‘Wastewater treatment facilities in rural

areas should therefore be located, constructed and maintained to the highest standards to ensure minimal impacts on water quality and particularly groundwater quality.’

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

GUIDELINES

Wastewater Treatment Plant Design & Site Assessment

EPA Manual, Treatment systems for Single Houses, 2000

Draft Code of Practice Wastewater Treatment Systems for Single Houses (PE<10)

EPA Manual, Treatment systems for Small Communities, Business, Leisure Centres and Hotels, 1999

BS5930, Code of Practice for Site Investigations.

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

LEGISLATION

Water Pollution Act(s) 1977 & 1990 Water Framework Directive SI 772 of 2003 Nitrates Directive Phosphorus Regulations Statutory Instrument 258 of

1998 Groundwater Directive as implemented by SI 271 of

1992 Protection of Groundwater Regs. (SI 41 of 1999) Freshwater Fish SI 293 of 1988 Shellfish SI 200 of 1994 where discharge is either

directly or indirectly to a shellfish area. Quality of Salmonid Waters SI 293 of 1988 Bathing Water SI 155 of 1992 and 230 of 1996 where

discharge is either directly or indirectly to a bathing area.

Surface Water Abstraction Regulation SI 294 of 1989 Quality of Surface water intended for abstraction of

drinking waters SI 294 of 1989 Any relevant Water quality management plan

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

LEGISLATION

Memorandum No 1 Technical Committee on Effluent and Water Quality Standards

EPA 1998 Environmental Quality objectives and Environmental Quality Standards

Any other relevant national Environmental Quality standards and objectives

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

INFRASTRUCTURE DEFICIT

• Wastewater Treatment Plants (WWTPs)– Existing Public WWTP may be at

design capacity;– Local Authority do not have

sufficient funds to upgrade or replace existing plant;

– Private developer then advised to identify own solution to treat wastewater from development;

– LAs are looking to Private Developers to ‘make up the deficit’

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

DISCHARGE LICENCE APPLICATION

PROCESS

When is a Discharge Licence Required?

All Industrial or Commercial Development discharging to surface waters or groundwater;

All Residential Development discharging to surface water; and

8 houses or >5m3 of effluent discharging to groundwater.

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Preliminary Investigation/Desk Study– How big is the development (i.e. PE)?– Available footprint for WWTP?– Discharge of treated effluent - surface water or

groundwater?

– Surface Water• Adjacent surface water bodies to site?• Existing discharges to surface water body?• Liaison with Regional Fishery Board

– Groundwater • Existing discharges to groundwater body?• Proximity of adjacent water abstraction wells?• GSI Well Database search

– Review of Discharge Licence Application & Licence Database within Local Authority

– Liaison with Local Authority & Local Area Engineer– Financial outlay – Recoup costs from

development?

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Surface Water – Capacity of surface water body?

• Preliminary assessment during August, September & October indicates >10:1 Dilution – Yes

• Correlated to nearby rated station - 95 %ile flow and Dry Weather Flow

• LA and/or Fisheries Board may require Hydrometric station installation

– Chemical/microbiological composition of the effluent & receiving surface water body

– Biological assessment of receiving water body– Assessment of impacts of the proposed discharge

on the chemical, biological and microbial quality on the surface water having consideration for relevant legislation

– Main problem - Phosphorous Regulations specify a concentration of 0.015mg/l for Q5 River

– Only MBR WWTP capable of consistent low P levels - 0.1mg/L to 0.5mg/L Orthophosphate-P - Cost?

– Cumulative impact of P is a major concern for LAs & Fisheries Boards

WWTP SOLUTION

Size/Assimilative capacity?

• Surface Water Discharge

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

• Surface Water Discharge

WWTP SOLUTION

Hydrometric stations – remote data logging & telemetry systems

• Surface Water Discharge

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

• Surface Water Discharge

WWTP SOLUTION

• Groundwater DLA Requirements– Industrial & commercial - Harmful

substances present in effluent 1st & 2nd Schedule of Protection of Groundwater Regs. (SI 41 of 1999)

– The hydrogeology of the area in which the aquifer is located.

– The risk of deterioration in the quality of the water to the entry of harmful substance

– The risk to human health or water supplies, aquatic ecosystem or interference with the use of water for agriculture, commercial, domestic, fisheries, industrial or recreational purposes.

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Groundwater DLA Requirements – Discharge is to a locally or regionally

important aquifer, an examination of the aquifer in respect of extent, estimated volume of water and estimated rate of recharge required.

– Nature, slope, thickness, particle size distribution, vulnerability, variations with depth and permeability of any overlying soil and subsoil

– Permeability of bedrock– Depth to Groundwater, recharge estimates

and hydraulic gradient– Existing Groundwater Quality

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Groundwater DLA Requirements

Field Work Required– Trialpitting & percolation (T & P) tests

(i.e. Site Suitability Assessment standard)– 2 monitoring wells installed into bedrock

aquifer – upgradient & downgradient of proposed discharge area

– Short duration (2hr) constant discharge Pumping & Recovery Test

– Wells & wastewater treatment systems inventory within 100 meters of proposed treatment plant or percolation area (500m preferable).

– Each borehole sampled on 4 occasion over 1 month duration to calculate mean values

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Groundwater DLA Requirements

– Trialpitting – 3m minimum (5m preferable)1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Groundwater DLA Requirements

– T-Test & P-Test – run concurrently1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Groundwater DLA Requirements

– Drilling – Bedrock aquifer depth

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Groundwater DLA Requirements

– 2 Groundwater Monitoring Wells

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Groundwater DLA Requirements

– Monitoring Well – permanent installation

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

WWTP SOLUTION

• Groundwater DLA Requirements

– Pump Testing – 4 hour duration

WWTP SOLUTION

• Groundwater DLA Requirements

– Pump Testing

• Drawdown Chart

WWTP SOLUTION

• Groundwater DLA Requirements

– Pump Testing

• Recovery Chart

WWTP SOLUTION

• Groundwater DLA Requirements

– Hydraulic Flow Calculations

q = Kb (h1-h2) L

= 1.26m3/day/metre of aquifer width

• q = flow through each metre of aquifer width• K = hydraulic conductivity (i.e. Average of BH101 & BH102 = Xm/day)• h1-h2 = hydraulic head – difference in water level between upgradient and downgradient monitoring wells • L = flowpath distance – distance between upgradient and downgradient monitoring wells • b = aquifer thickness – this is taken as the depth of saturated aquifer

WWTP SOLUTION

• Groundwater DLA Requirements

– Dilution of Effluent

Final Nitrate (as NO3-N) groundwater concentration =

(Effluent Concentration * Volume) + (Average Groundwater Conc. * Volume)(Groundwater Volume + Effluent Volume)

WWTP SOLUTION

• Groundwater DLA Requirements

– What’s acceptable to Local Authority?

• Existing Nitrate levels in groundwater need to be low

• Wastewater treatment plant needs to have proven

track record on nitrate removal

• Cumulative impact on NO3-N levels need to be negligible

• NO3-N levels in effluent need to be significantly lower than groundwater concentrations

CASE STUDY – SITE ‘X’

• 19-House Development• Population equivalent of 76P.E.• Total Daily Dry Weather Flow = 13,680 litres/day.

13,680 DWF = 24 x 3600 = 0.158 l/s

Peak Flow = 2.5 x 0.158 = 0.395 l/s

• Organic Load @ 4.1kg BOD/day; and• Ammonia load @ 0.54kg NH3/day.

CASE STUDY – SITE ‘X’

• Solution

Submerged Membrane Bioreactor (125PE)

Mounded Stratified Sand Polishing Filter

Bedrock/Groundwater

CASE STUDY – SITE ‘X’

CASE STUDY – SITE ‘X’

CASE STUDY – SITE ‘X’

CASE STUDY – SITE ‘X’•Soil Map

TMpRck

CASE STUDY – SITE ‘X’•Bedrock Map

Dark Blue Grey Slate

Green & Grey Slate

CASE STUDY – SITE ‘X’•Aquifer Map

Ll

Pl

CASE STUDY – SITE ‘X’•Vulnerability Map

CASE STUDY – SITE ‘X’

– Groundwater DLA Requirements– Trialpit Log

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

CASE STUDY – SITE ‘X’– Groundwater DLA Requirements– Borehole Log

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

CASE STUDY – SITE ‘X’– Groundwater DLA Requirements

– Borehole Log

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

CASE STUDY – SITE ‘X’

1 Background

2 Legislation/

Guidelines

3 DLA Process

4 Results

5 Source protection measures

6 Conclusions

• 125 PE Membrane Bioreactor– Effluent with low suspended solids– Complete sludge retention, can be operated at

high MLSS and it minimises excess sludge production

– Final effluent quality of 5:5:5 BOD:SS:NH3. – 4-log reduction in viruses (i.e. enterovirus and

coliphage) and a 6-log reduction in bacteria.

– Proven ability to reduce NO3 levels to background levels

– Phosphate removal system can be added (Ferric Sulphate precipitation)

– Tertiary Treatment levels attained!– However, expensive and requires quarterly

maintenance & sludge removal

CASE STUDY – SITE ‘X’

1 Background

2 Legislation/

Guidelines

3 DLA Process

4 Results

5 Source protection measures

6 Conclusions

• Stratified Sand Filter– All indigenous soil removed to bedrock level

(i.e. approximately 3.0 to 3.5m bgl) and replaced with stratified sand filters (i.e. alternative layers of sand and pea gravel)

– Further reduction of orthophosphates but expected to saturate with time

– Evidence of nitrification occurring which will reduce Ammonia levels further

– Certain degree of removal by microbial community of further dissolved organic carbon compounds and subsequently BOD reduction

CASE STUDY – SITE ‘X’SUBMERGED MEMBRANE BIOREACTOR

CASE STUDY – SITE ‘X’ SUBMERGED MEMBRANE BIOREACTOR

CASE STUDY – SITE ‘X’ SUBMERGED MEMBRANE BIOREACTOR

CASE STUDY – SITE ‘X’MOUNDED STRATIFIED SAND FILTER

CASE STUDY – SITE ‘X’MOUNDED STRATIFIED SAND FILTER

CASE STUDY – SITE ‘X’MOUNDED STRATIFIED SAND FILTER

CASE STUDY – SITE ‘X’MOUNDED STRATIFIED SAND FILTER

CONCLUSIONS (I.E. EXPERIENCE TO-DATE)

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

• WFD & Nitrate Directive are being enforced at Local Authority level with regard to the DLA Process:

Background NO3-N levels - levels greater than 25mg/l will be refused

Proposed WWTP capacity to reduce NO3-N levels

• Best Performance Proprietary WWTP is Submerged Membrane Bioreactor

• Best Hydraulic Solution would appear to be a Mounded Stratified Sand Polishing Filter

CONCLUSIONS (I.E. EXPERIENCE TO-DATE)

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions

• Technological & engineering solutions to comply with WFD and Nitrates Directive are available

• Validation of WWTP Construction and on-going monitoring are required to ensure performance

• Management of WWTP issues have arisen:

• Malfunctioning Housing Estate Management Companies/Payment of Annual Maintenance Fees

• Selling of property with planning permission & lack of awareness by buyer of WWTP specification

• Costs incurred by Local Authority if Management Companies fail to manage WWTP correctly – need to be taken in charge

CONCLUSIONS (I.E. EXPERIENCE TO-DATE)

1 Background

2 Guidelines

3 Legislation

4 Infrastructural Deficit

5 Discharge Licence Application Process

6 WWTP Solution

7 Case Study –

Site ‘X’

8 Conclusions