Wetlands of Karnataka: Bioremediation Options

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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

• 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

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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.

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WETLANDS OF BANGALORE

• occupy about 4.8 of the citys 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

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Temporal Change Analyses of Bangalore City
Wetlands
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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)

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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.

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• 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.

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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

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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)

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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

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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.

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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

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Sorption

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

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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.

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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.

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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.

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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

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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.
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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.

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Chromium
Iron
Nickel
Mercury
Langmuir adsorption isotherm for metal
biosorption by BGH, TDH, CH and TH
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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 KfCeq1/n
• Where,
• Kf and n are the Freundlich constants related to
  adsorption capacity and adsorption intensity
  respectively

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Chromium
Iron
Nickel
Mercury
Freundlich adsorption isotherm for metal
biosorption by BGH, TDH, CH and TH
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ADSORPTION CAPACITY OF CHROMIUM (VI)
q
et al
et al
et al
et al
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ADSORPTION CAPACITY OF IRON (III)
q
(
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ADSORPTION CAPACITY OF MERCURY (II)
q
et al
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ADSORPTION CAPACITY OF NICKEL (II)
q
Parab
et al
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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
  adsorbate concentration decreased the percent
  adsorption and increased the amount of adsorbate
  uptake (q) per unit weight of the adsorbent.

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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
Nickel
Mercury
Effect of agitation time on Metal biosorption by
BGH, TDH, CH and TH (? 10 mg/L 20 mg/L ? 50
mg/L ? 100mg/L)
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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.

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Chromium
Iron
Nickel
Mercury
Effect of adsorbent dosage on Metal biosorption
by BGH, TDH, CH and TH (? 10 mg/L 20 mg/L ? 50
mg/L ? 100mg/L)
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EFFECT OF pH

• Irrespective of the type of the adsorbent, the
  optimum pH for the removal of metals were as
  follows

Metal Optimum pH
Chromium 2
Iron 2.5
Mercury 5.5
Nickel 6
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Chromium
Iron
Nickel
Mercury
Effect of pH on metal biosorption by BGH, TDH, CH
and TH (? 10 mg/L 20 mg/L ? 50 mg/L ? 100mg/L)
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DESORPTION STUDIES

• Desorption and regeneration studies of the
  adsorbates showed that regeneration and recovery
  of the adsorbates is 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.

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Effect of pH on the desorption of Chromium (VI),
Iron (III), Nickel (II) and Mercury (II) (? BGH
TDH ? CH ? TH)
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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 CO bonds were predominant in the surface of
  the adsorbents and played a major role in the
  adsorption process.

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INFRARED ABSORPTION BANDS AND THEIR
CORRESPONDING GROUPS
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BGH
TDH
TH
CH
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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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THANK YOU