Wetlands of Karnataka: Bioremediation Options Ahalya N Energy and Wetlands Research Group Centre for Ecological Sciences, Indian Institute of Science, Bangalore – 560 012
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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
4
6
8
10
0 100 200 300 400
Ceq
Ceq
/q
0
5
10
15
20
25
0 200 400 600
Ceq
Ceq
/q
0
1
2
3
4
5
6
0 100 200 300
Ceq
Ceq
/q
0
2
4
6
0 100 200 300 400
Ceq
Ceq
/q
0
1
2
3
4
5
0 100 200 300
Ceq
Ceq
/q
0
5
10
15
20
25
0 200 400 600
Ceq
Ceq
/q
0
0.2
0.4
0.6
0.8
1
0 10 20 30 40
Ceq
Ceq
/q
0
1
2
0 100 200 300
Ceq
Ceq
/q
0
2
0 100 200 300
Ceq
Ceq
/q
0
0.1
0.2
0.3
0.4
0.5
0.6
0 20 40 60 80
Ceq
Ceq
/q
00.5
11.5
22.5
33.5
0 100 200 300
Ceq
Ceq
/q
0
1
2
3
4
5
0 100 200 300 400
Ceq
Ceq
/q
0
1
2
3
4
5
6
0 100 200 300
Ceq
Ceq
/q
0
2
4
6
8
0 200 400 600
Ceq
Ceq
/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
0
1
2
3
4
5
0 2 4 6
ln Ceq
ln q
0
2
4
6
0 2 4 6
ln Ceq
ln q
0
1
2
3
4
5
0 2 4 6
ln Ce q
ln q
0
1
2
3
4
5
0 2 4 6
ln Ceq
ln q
0
1
2
3
4
5
-4 -2 0 2 4
ln Ceq
ln q
0
1
2
3
4
5
6
0 2 4 6
ln Ceq
ln q
0
1
2
3
4
5
6
-2 0 2 4 6
ln Ceq
ln q
0
2
4
6
0 2 4 6
ln Ceq
ln q
0
1
2
3
4
5
0 2 4 6
ln Ceq
ln q
0
1
2
3
4
5
0 2 4 6 8
ln Ceq
ln q
0
2
4
6
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
Bengal gram husk 72.16 Present work
Tur dal husk 66.63 Present work
Tamarind husk 56.55 Present work
Coffee husk 64.80 Present work
ADSORPTION CAPACITY OF MERCURY (II)
q
et al
Adsorbent max (mg/g) Reference
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
Bengal gram husk 51.85 Present work
Tur dal husk 196.32 Present work
Tamarind husk 184.39 Present work
Coffee husk 145.73 Present work
ADSORPTION CAPACITY OF NICKEL (II)
q
Parab
et al
Adsorbent max (mg/g) Reference
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
Bengal gram husk 112.22 Present work
Tur dal husk 96.58 Present work
Tamarind husk 111.11 Present work
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.
0
20
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Time (min)
% C
r (V
I) ad
sorb
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Time (min)
% C
r (V
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sorb
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0 50 100 150
Time (min)%
Cr
(VI)
adso
rbed
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e (II
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) ads
orbe
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Time (min)
% N
I (II)
ads
orbe
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Time (min)
% N
i (II)
ads
orbe
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Time (min)
% N
i (II)
ads
orbe
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0 200 400 600
Time (min)
% N
I (II)
ads
orbe
d
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
0
20
40
60
80
100
0 2 4 6
BGH (g/L)
% C
r (V
I) ad
sorb
ed
0
20
40
60
80
100
0 2 4 6
TDH (g/L)
% C
r (V
I) ad
sorb
ed
0
20
40
60
80
100
0 2 4 6 8
CH (g/L)
% C
r (V
I) ad
sorb
ed
0
20
40
60
80
100
0 5 10
TH (g/L)%
Cr (
VI) a
dsor
bed
0
20
40
60
80
100
0 2 4 6
BGH (g/L))
% F
e (II
I) ad
sorb
ed
0
20
40
60
80
100
0 2 4 6
TDH (g/L)
% F
e (II
I) ad
sorb
ed
0
20
40
60
80
100
0 2 4 6
CH (g/L)
% F
e (II
I) ad
sorb
ed
0
20
40
60
80
100
0 2 4 6 8
TH (g/L)
% F
e (II
I) ad
sorb
ed
0
20
40
60
80
100
0 1 2 3 4
BGH (g/L)
% H
g (II
) ads
orbe
d
0
20
40
60
80
100
0 1 2 3 4
TDH (g/L)
% H
g (II
) ads
orbe
d
0
20
40
60
80
100
0 1 2 3 4
BGH (g/L)
% N
I (II)
ads
orbe
d
0
20
40
60
80
100
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
20
40
60
80
100
0 1 2 3 4
C H (g /L )
% H
g (II
) ads
orbe
d
0
20
40
60
80
100
0 10 20 30 40
TH (g /L)
% H
g (II
) ads
orbe
d
0
20
40
60
80
100
0 1 2 3
CH (g/L)
% N
i (II)
ads
orbe
d
0
20
40
60
80
100
0 2
% 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
0
20
40
60
80
100
0 2 4 6 8
pH
% C
r (V
I) ad
sorb
ed
0
20
40
60
80
100
0 2 4 6
pH
% C
r (V
I) ad
sorb
ed
0
20
40
60
80
100
0 2 4 6 8
p H
% C
r (VI
) ads
orbe
d
0
20
40
60
80
100
0 2 4 6
pH%
Cr
(VI)
adso
rbed
0
20
40
60
80
100
0 1 2 3
pH
% F
e (II
I) ad
sorb
ed
0
20
40
60
80
100
0 1 2 3 4
pH (g/L)
% F
e (II
I) ad
sorb
ed
0
20
40
60
80
100
0 1 2 3 4
CH (g/L)
% F
e (II
I) ad
sorb
ed
0
20
40
60
80
100
0 1 2 3 4
pH
% F
e (II
I) ad
sorb
ed
0
20
40
60
80
100
0 2 4 6 8
pH
% H
g (II
) ads
orbe
d
0
20
40
60
80
100
0 2 4 6 8
pH
% H
g (II
) ads
orbe
d
0
20
40
60
80
100
0 5 10
pH
% H
g (II
) ads
orbe
d
0
20
40
60
80
100
0 2 4 6 8
pH
% H
g (II
) ads
orbe
d
0
20
40
60
80
100
0 2 4 6 8
pH
% N
I (II)
ads
orbe
d
0
20
40
60
80
100
0 2 4 6 8
pH
% N
i (II)
ads
orbe
d
0
20
40
60
80
100
0 2 4 6 8
pH
% N
i (II)
ads
orbe
d
0
20
40
60
80
100
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
5
10
15
20
25
0 5 10 15
pH
% C
r (V
I) de
sorb
ed
0
20
40
60
80
100
0 5 10 15
pH
% F
e (II
I) de
sorb
ed
0
20
40
60
80
100
0 1 2 3 4 5
pH
% N
i (II)
des
orbe
d
0
20
40
60
80
100
0 1 2 3 4 5
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.
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