wetlands of karnataka - environmental information...

Wetlands of Karnataka: Bioremediation Options

Ahalya NEnergy and Wetlands Research Group

Centre for Ecological Sciences, Indian Institute of Science, Bangalore – 560 012

WETLANDS• Wetlands are the transitional zone between land and

water, where saturation with water is the dominant factor.

• Inland wetlands - precipitation, river outflow, surface overland flow, ground water discharge, etc.

• Uses - intrinsic ecological and environmental values, fishing, transportation, irrigation, industrial water supply, receiving waters for wastewater effluents.

• moderate temperatures, regulate stream flow, recharge ground water aquifers and moderate droughts,provide habitat to aquatic plants and animals

Wetlands of Karnataka

• Inland wetlands dominate in Karnataka, which account for 93.44% while coastal wetlands account for 6.56%.

• Out of the 682 wetlands, 622 are inland &60 are coastal wetlands.

WETLANDS OF BANGALORE• occupy about 4.8% of the city’s geographical area (640

sq.km)

• decreased from 379 (138 in north and 241 in south) in 1973 to 246 (96-north and 150-south) in 1996 .

• decrease of 35.09% - attributed to urbanisation and industrialisation, residential layouts, commercial establishments, sport complexes, etc.

• 30% of the lakes are used for irrigation. Fishing is carried out in 25% of the lakes , cattle grazing in 35%, agriculture in 21%, mud-lifting in 30%, drinking in 3%, washing in 36% and brick-making in 38%

Temporal Change Analyses of Bangalore City Wetlands

SOURCES OF POLLUTION• Point Sources - municipal and industrial wastewater.• Non-point Sources - urban and agricultural run-off• Major degrading factors - eutrophication, siltation,

construction, introduction of exotic species; acidification from atmospheric sources, acid mine drainage; contamination by toxic metals such as mercury and organic compounds such as poly-chlorinated biphenyls.

• Hydrologic manipulations (e.g. Damming outlets to stabilise water levels)

Consequences of loss of wetlands

• The tanks were reclaimed for various purposes such as residential layouts, commercial establishments, sport complexes, etc.

• For e.g. Darmombudi tank has been converted into the current city bus stand, Millers tank into a residential layout, Sampangi tank into the Kanteerva stadium,etc.

• This has changed the climate of the city and affected its ground water level.

• The loss of wetlands has led to decrease in catchment yield, water storage capacity, wetland area, number of migratory birds, floral and faunal diversity and ground water table.

• Studies reveal the decrease in depth of the ground water table from 35-40 to 250-300 feet in 20 years due to the disappearance of wetlands.

Conservation of wetlands

• An ecosystem approach is needed to address the wetland problems

• The ecosystem approach considers both human water needs within the larger context of the drainage basin and environmental water needs or ecological requirements.

• Increasingly, constructed wetlands are used for the treatment of municipal and industrial wastewater before the treated water is let into lakes and wetlands.

• They offer the most sustainable means for the treatment of wastewater

What are constructed wetlands?

A constructed wetland is "a designed and man-made complex of saturated substrates, emergent and submergent vegetation, animal life, and water that simulates natural wetlands for human use and benefits." (from Constructed Wetlands for Wastewater Treatment: Municipal, Industrial and Agricultural, 1989, D.A. Hammer, ed. Lewis Publishers, Inc. Chelsea, Michigan)

Description of Constructed Wetland

• A plot of land is chosen near the wastewater that is to be purified

• A shallow pond is built and plants found in natural wetlands such as cattails, reeds, and rushes are set out

• The wastewater is then routed through the wetland • Microbial utilization and plant uptake of nutrients

results in cleaner water leaving the constructed wetland than what entered

Heavy Metals in Constructed Wetland• Dissolved metals are removed by the macrophytes, which may

lead to phytotoxic symptoms.

• In the anaerobic areas, such as sediments and in the benthic zone, microbes reduce sulphate (SO4

- -) to hydrogen sulphide (H2S).

• Many dissolved metals, including zinc, lead, copper, and several others react with sulphide to form highly insoluble compounds. Such compounds are retained permanently - in the wetland sediments and they cannot be used as fertiliser or agricultural amendment.

• Upon organic matter decomposition or mineralisation, the metals will become more mobile or available, as the decreasing organic matter cannot tightly bind them any longer.

Solution to overcome the Disadvantages

• Include a sorbent filter system just before the water flows into the constructed wetland to remove the heavy metals from wastewater

Sorption• It includes both adsorption and absorption.• When sorption is mediated by biological materials, its

called biosorption

BIOSORPTION

• The use of biological biological materials to aid in removing hazardous substances

Advantages:• Low cost;• High efficiency;• Minimisation of chemical and /or biological sludge;• No additional nutrient requirement;• Regeneration of biosorbent; and • Possibility of metal recovery.

BIOSORBENTS• Biological materials capable of sequestering heavy

metals• Biosorbents can be bacteria, fungi, algae, yeast etc• Biosorbents can come from

- industrial waste which should be obtained free of charge

- organisms easily available in large amounts in nature- organisms of quick growth that is especially cultivated

for biosorption purposes.

OBJECTIVES• To determine out the adsorption capacity of the four husks namely

Tur dal (Cajanus cajan) husk (TDH); bengal gram husk (BGH), seed coat of Cicer arientinum; coffee (Coffee arabica) husk (CH) and tamarind (Tamarindus indica) pod shells (TH) for the removal of heavy metals from aqueous solutions

• Characterisation of the adsorbents for their carbon, nitrogen and sulphur content

• Characterisation of functional groups on the surface of the adsorbent that contributes to the biosorption of heavy metals and dyes used in the present study through infrared spectroscopy.

• Determination of the agitation/equilibrium time, pH and effect of adsorbent at different initial metal concentrations.

• Calculation of the adsorption capacity and intensity using Langmuir and Freundlich isotherm models.

• Desorption of metals from metal loaded adsorbents to determine the mechanism of adsorption.

MATERIALS AND METHODS

• Biosorbents– Tur dal husk, Channa dal husk, Tamarind pod shells

and coffee husk.• Metals

– Chromium (VI), Iron (III), Mercury (II) and Nickel (II).

Batch Mode Studies– Effect of pH, adsorbent dosage, agitation time,

Desorption studies• Estimation of Carbon, Sulphur and Nitrogen of

the four husks• Infra Red Spectral Analysis

Characterisation of the adsorbent

The analysis of the carbon, hydrogen and nitrogen content of the husk, showed relatively low percentage of nitrogen, revealing the low content of protein in the adsorbents.

0.946.1446.01Tamarind husk

0.636.2145.33Coffee husk

1.136.3540.66Tur dal husk

0.866.3138.57Bengal gram husk

NHCBiosorbent

BIOSORPTION ISOTHERMS• Sorption isotherms are plots between the sorption

uptake (q) and the final equilibrium concentration of the residual sorbate remaining in the solution (Ce).

• The langmuir isotherm represents the equilibrium distribution of metal ions between the aqueous and solid phases.

q = qmax bCeq/ (1+ bCeq)

Ceq equilibrium metal/dye solution concentration (mg/l)q metal/dye adsorbed onto the husk (mg/g)qmax Langmuir constant which represents the maximum sorbate

under the given conditions;b coefficient related to the affinity between the sorbent and sorbate.

Chromium

Nickel

Iron

012345678

0 200 400 600

Ceq

Ceq

/q

0

2

4

6

8

0 200 400 600

Ceq

Ceq

/q0

2

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Ceq

/q

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/q

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/q

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/q

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/q

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/q

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/q

00.5

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/q

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/q

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/q

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0 200 400 600

Ceq

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/q

Mercury

Langmuir adsorption isotherm for metal biosorption by BGH, TDH, CH and TH

FREUNDLICH ISOTHERMS• This model considers a monomolecular layer coverage

of solute by the sorbent.

• It assumes that the sorbent has a heterogeneous surface suggesting that the binding sites are not equivalent and/or independent.

• Freundlich isotherm provides information on the monolayer adsorption capacity and intensity

• For a single component adsorption:qeq = KfCeq

1/n

Where,Kf and n are the Freundlich constants related to adsorption

capacity and adsorption intensity respectively

Chromium

Mercury

Iron

0

1

2

3

4

5

0 2 4 6 8

In Ceq

ln q

0

2

4

6

0 2 4 6 8

ln Ceq

ln q

-2

0

2

4

6

-2 0 2 4 6 8

ln Ceq

ln q

00.5

11.5

22.5

33.5

0 2 4 6 8

ln Ceq

ln q

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3

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5

0 2 4 6

ln Ceq

ln q

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2

4

6

0 2 4 6

ln Ceq

ln q

0

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2

3

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5

0 2 4 6

ln Ce q

ln q

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3

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5

0 2 4 6

ln Ceq

ln q

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3

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5

-4 -2 0 2 4

ln Ceq

ln q

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6

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ln Ceq

ln q

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ln Ceq

ln q

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0 2 4 6

ln Ceq

ln q

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ln Ceq

ln q

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ln Ceq

ln q

0

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4

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0 2 4 6 8

ln Ceq

ln q

-0.5

0

0.5

1

1.5

2

0 2 4 6

ln Ceq

ln q

Nickel

Freundlich adsorption isotherm for metal biosorption by BGH, TDH, CH and TH

ADSORPTION CAPACITY OF CHROMIUM (VI)

q

et al

et al

et al

et al

Adsorbent max Reference

Rhizopus arrhizus 23.88 Prakasham (1999)

Rhizopus nigrificans 99.00 Bai and Abraham (2001)

Chlorella vulgaris 33.80 Cetinkaya (1999)

Scenedesmus obliquus 30.20 Cetinkaya (1999)

Synechocystis sp. 39.00 Cetinkaya (1999)

Cone biomass 201.81 Ucunet al , 2002

Bengal gram husk 91.64 Present work

Tur dal husk 96.05 Present work

Coffee husk 27.73 Present work

Tamarind husk 44.95 Present work

ADSORPTION CAPACITY OF IRON (III)

q

(

Adsorbent max (mg/g) Reference

Industrial biomass

Aspergillus niger grown on

wheat bran)

19.2 Chandrashekar et al , 1998

Streptomyces rimosus 125 Selatnia et al , 2004

Chlorella vulgaris 24.49 Aksu et al , 1997

Schizomeris leibleinii 101.70 Ozer et al , 1999

Zoologea ramifera 65.49 Sag and Kutsal, 1995





ADSORPTION CAPACITY OF MERCURY (II)

q

et al


Fly ash 2.82 Sen and Dey, 1987

Fly ash 11.0 Banerjee , 2004

Fly ash-C 0.63–0.73 Kapoor and Viraraghvan,

2004

Rice husk ash 9.3 Feng et al , 2004





ADSORPTION CAPACITY OF NICKEL (II)

q

Parab

et al


Coir pith 15.72 et al , 2006

Sphagnum moss peat 9.18 Ho et al , 1995

Baker's yeast 11.40 Padmavathy , 2003

Sheep manure waste 7.20 Abu Al-Rub, 2002

Waste tea 18.42 Malkoc and Nuhoglu, 2005




Coffee husk 54 Present work

EFFECT OF AGITATION TIME & ADSORBATE CONCENTRATION ON

ADSORPTION

• The uptake of adsorbate increased with the increase in contact time for all the metals studied and it remained constant after an equilibrium time

• The equilibrium time varied with the type of husk under consideration and it increased with the increase in initial metal concentration.

• At any contact time, increase in initial adsorbateconcentration decreased the percent adsorption and increased the amount of adsorbate uptake (q) per unit weight of the adsorbent.

EFFECT OF AGITATION TIME & ADSORBATE CONCENTRATION ON

ADSORPTION

• The equilibrium time required by the adsorbents used in the present study is less, compared to others reported in literature.

• In process application, this rapid (or instantaneous) biosorption phenomenon is advantageous since the shorter contact time effectively allows for a smaller size of the contact equipment, which in turn directly affects both the capacity and operation cost of the process.

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Chromium Iron

Mercury Nickel

Effect of agitation time on Metal biosorption by BGH, TDH, CH and TH (♦ 10 mg/L ■ 20 mg/L ▲ 50 mg/L ● 100mg/L)

EFFECT OF ADSORBENT DOSAGE ON ADSORPTION

• The biosorption of metal was studied at various biosorbent concentrations ranging from 0.5 to 5 mg/L

• For all the adsorbents studied, adsorbent dosage of 1g –2g/L was sufficient for adsorption of 90% of the initial metal concentration.

Chromium Iron

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BGH (g/L)

% C

r (V

I) ad

sorb

ed

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TDH (g/L)

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r (V

I) ad

sorb

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CH (g/L)

% C

r (V

I) ad

sorb

ed

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TH (g/L)%

Cr (

VI) a

dsor

bed

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BGH (g/L))

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e (II

I) ad

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e (II

I) ad

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CH (g/L)

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e (II

I) ad

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TH (g/L)

% F

e (II

I) ad

sorb

ed

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BGH (g/L)

% H

g (II

) ads

orbe

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TDH (g/L)

% H

g (II

) ads

orbe

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BGH (g/L)

% N

I (II)

ads

orbe

d

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0 1 2 3 4

TDH (g/L)

% N

i (II)

ads

orbe

d

Effect of adsorbent dosage on Metal biosorption by BGH, TDH, CH and TH (♦ 10 mg/L 20 mg/L ▲ 50 mg/L ● 100mg/L)

NickelMercury

0

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C H (g /L )

% H

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) ads

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TH (g /L)

% H

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CH (g/L)

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i (II)

ads

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% N

I (II)

ads

orbe

d

4 6

TH (g /L)

EFFECT OF pHIrrespective of the type of the adsorbent, the optimum

pH for the removal of metals were as follows

Metal Optimum pHChromium 2

Iron 2.5

Mercury 5.5

Nickel 6

Chromium

Nickel

Iron

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pH

% C

r (V

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pH

% C

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p H

% C

r (VI

) ads

orbe

d

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0 2 4 6

pH%

Cr

(VI)

adso

rbed

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pH

% F

e (II

I) ad

sorb

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% F

e (II

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CH (g/L)

% F

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sorb

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pH

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d

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pH

% H

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pH

% H

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pH

% H

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) ads

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pH

% N

I (II)

ads

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d

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0 2 4 6 8

pH

% N

i (II)

ads

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d

0

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pH

% N

i (II)

ads

orbe

d

0

20

40

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0 2 4 6 8

pH

% N

I (II)

ads

orbe

d

Mercury

Effect of pH on metal biosorption by BGH, TDH, CH and TH (♦ 10 mg/L ■ 20 mg/L ▲ 50 mg/L ● 100mg/L)

DESORPTION STUDIES

• Desorption and regeneration studies of the adsorbatesshowed that regeneration and recovery of the adsorbatesis possible.

• Chemisorption/ion exchange was the main mechanism by which the adsorbates (metals and dyes) were attached to the adsorbents.

• Since about 85% of dyes and 70 % of the metals still remained on sorbents, it indicates that most of dyes/metals are able to form strong bonds with the adsorbents.

0

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25

0 5 10 15

pH

% C

r (V

I) de

sorb

ed

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0 5 10 15

pH

% F

e (II

I) de

sorb

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pH

% N

i (II)

des

orbe

d

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100

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pH

% H

g (II

) des

orbe

d

Effect of pH on the desorption of Chromium (VI), Iron (III), Nickel (II) and Mercury (II) (♦ BGH ■ TDH ▲ CH ● TH)

INFRARED SPECTRAL ANALYSIS

• The infrared spectral analysis of the adsorbents showed that Carbon bonded with hydrogen and oxygen atoms played a major role in the adsorption of metals.

• The absorption spectra revealed that –C-O, C-N and C=O bonds were predominant in the surface of the adsorbents and played a major role in the adsorption process.

INFRARED ABSORPTION BANDS AND THEIR CORRESPONDING GROUPS

-C-O, C-N1115.57

-CH893.25

-COO-, -C=O1634.34-CH2918.89

-OH, -NH3437.38

Functional groupFrequency (cm-1)

BGH TDH

CH TH

CONCLUSIONS

• BGH, TDH, TH and CH as agro-industrial wastes have negligible cost and have also proved to be an efficient biosorbent for the removal of metals.

• Furthermore, these adsorbed metals can be easily desorbed and the biomass be incinerated for final disposal.

• These biosorbents are of low cost; its utility will be economical and can be viewed as a part of a feasible waste management strategy.

THANK YOU

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