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  • Tamilnadu has 60% tanneries of India69,000 tons of Cr annually waste is produced in 1600 tanneries (Iyer and Mitrokis, 2006)Tannery waste has contaminated 55,000 ha of agricultural land.
  • Ketan seminar ppt

    1. 1. HEAVY METALOCCURRENCE INGROUNDWATER ININDIA ANDEVALUATION OFREMOVALTECHNOLOGIESByWadodkar Ketan Kishor KetkiPhD. Student (CESE)124180004Under Guidance ofProfessor Sanjeev ChaudhariPh.D Seminar onCenter for Environmental Science and EngineeringIIT Bombay
    2. 2. CONTENTIntroduction Chromium Health Hazard Source of Cr contaminationChromium Chemistry in aqueous systemChromium problem in IndiaRemedial Measure/Chromium Removal Insitu ExsituCase Study (Remedial Measures in Indian Context)6/16/2013 PHD SEMINAR 2
    3. 3. INTRODUCTIONChromium It is 21st most abundant element in the earth’s crust. Shiny, silvery, hard and brittle represented by 52Cr24(abundant isotope), falls in VI B group in periodic table and is ubiquitousin nature.Shows various oxidation states from -4 to + 6.Generally in environment it is present in: Cr(0) which occurs in metallic or native chromium Cr(III) or Cr(+3)which occurs in chromic compounds Cr(VI) or Cr (+6) which occurs in chromate anddichromate compounds.6/16/2013 PHD SEMINAR 3
    4. 4. Cr (III)-TrivalentChromiumMore stable and abundant form of CrLess mobile and less mobile in waterLess toxic (even reported as important for C6H12O6 metabolism)Cr (III) typically found in cation formOccurs as insoluble chromium oxide (Cr2O3), chromium hydroxide[Cr(OH)3], soluble Chromium hydroxide cations: CrOH2+ andCr(OH)2+ depending on pH.Cr (VI)-HexavalentChromiumHigh mobility in waterHighly soluble in waterReduced to Cr(III) in presence of Electron donorCr (VI) is known to be 100−1000 times more toxic than the Cr(III)(Gauglhofer and Bianchi, 1991).Cr (VI) typically found in anion formOccurs as: Chromate (CrO4-) and Dichromate form [Cr2O72-],depending on pH.6/16/2013 PHD SEMINAR 4
    5. 5. HEALTH HAZARDS OFCHROMIUM:Cr(VI) is strong oxidant, hence is very harmful evenat small dose.Cr(VI) compounds are corrosive/caustic may causeburn on skin, chronic exposure leads to deeplypenetrating ulcers if untreated.Long term and high exposure of Cr(VI) affects: function of lungs and blood system gastrointestinal bleeding, hepatic and renal damage and potential death. weakened immune system kidney and liver damage Tissue necrosis skin sensitizationCr(VI) compounds are mutagenic and may causechromosomal aberrations and sister chromatidexchanges in humans (Result of Cr(VI) to Cr(III)reduction).6/16/2013 PHD SEMINAR 5Standards for Chromium inwater:• USEPA : Total Cr < 0.1mg/L in drinking water• BIS: Cr (VI) < 0.05mg/L for Cr(VI).• WHO: Cr(VI) < 0.05mg/L and total Cr < 2mg/L.
    6. 6. In China 155 workers consumingwater with 20 mg/L of Cr(VI) caused oral ulcer, diarrhoea, vomiting,abdominal pain and indigestion) and theaffected blood (leucocytosis and immatureneutrophils).In another study (EVM, 2003),Long term exposure of Cr: resulted in weight loss, anaemia,haemolysis, liver dysfunction (elevatedaminotransferases and total bilirubin) andrenal failure.Is not carcinogenic when ingestedthrough water, as Cr(VI) will bereduced to Cr(III) which isessential nutrient. Though mightprove carcinogenic if inhaled(ATSDR, 2000).In plants, high levels of Cr supplycan inhibit seed germination and6/16/2013 PHD SEMINAR
    7. 7. ChromiumOccurrenceinenvironment 1% volcanic emission30% by biologicalcyclesExtraction from soil byplants (15%)Weathering of rocks(15%)70% man madesource:Ore and metalproduction (3%)Metal use (60%)Coal burning and othercombustion (7%)SOURCE: MERIAN(1984)6/16/2013 PHD SEMINAR 7
    8. 8. Fig 1.1: Fate of Chromium in environment (Source:USEPA, 2000)6/16/2013 PHD SEMINAR 8
    9. 9. PRESENCE OF CHROMIUM ININDIAN CONTEXTSukinda valley (Odisha): Is declared as 4th worlds highestpolluted site declared by studyconducted by Blacksmith Institute.(Source; Open cast mining is followed leavingwaste around 7.6 million tonnes ofreject minerals. 97% of total proven chromite of Indiafound in the Sukinda Valley, over anarea appx. 200 sq. km. Approximately 70% of the surfacewater and 60% of the drinking watercontains Cr(VI) at more than double ofnational standards.6/16/2013 PHD SEMINAR 9(Source;
    10. 10. Cr(VI) content in certain parts ofOdisha: 550-1500 mg/l in well water 25-100 mg/l in irrigationreservoirs 4000 mg/l in the soil making itunfit for domestic usages. (Iyerand Mastorakis, 2006)26,00,000 est. people are in threatof danger.Orissa Voluntary HealthAssociation (OVHA) (Source: 84.75% of mine workers deaths, and86.42% of nearby villagers deaths wererelated to Cr induced diseases.6/16/2013 PHD SEMINAR 10(Source;
    11. 11.  About 2,500 tanneries in India,approximately 80% of them use chrometanning process. A single tannery can cause GW pollutionaround 7-8 km radius. (Ansari et al.,1999)Ranipet/Vellore (Tamilnadu) The conc. of total Cr in these wells variesbetween 3.1 to 246 mg/L whereas theconc. of Cr(VI) varies between 2.1 to 214mg/L. Bore well water sample at 2 km fromclosed tannery at Walajpet had Total Cr >than 950 μg/L (typically Total Cr in India4–7 μg/L) (Rao et al., 2011).Chromepet, Chennai: Cr (VI) concentration between 0.01 mg/Lto 0.99 mg/L. (Brindha et al., 2010).6/16/2013 PHD SEMINAR 11• Potentially affectedPeople: 34,82,000
    12. 12. Kanpur Kanpur has about 350 industrial leather tanneries,which discharges there waste directly to GW or RiverGanga (Singh et al., 2005). Noraiakheda, Kanpur has developed right on top of aplume of Cr VI emitted by toxic sludge from an oldchemical plant that had supported the tanneries. A report of CPCB on GW quality of Kanpur revealedCr VI levels of 6.2 mg/L Every month >2000 million ton of sludge is dumpedon the open ground. the CGWB recorded 0.01–16.30mg/l of Cr(VI) in Kanpur’s industrial belt. (source: PHD SEMINAR 12
    13. 13. Bangalore, Karnataka: Study has found a staggering 17.75mg/l of Cr(VI) in bore wells in Peenya(Shankar et al., 2009). Out of 30 samples tested in study byShankar et al., 2009) 53% were foundnon-potable due to excess of Cr.Pune, Maharashtra: Due to Mantarwadi Landfill site, havehigh level of Cr in near by area around5-8 mg/L.6/16/2013 PHD SEMINAR 13Source: The Hindu, Wednesday, Mar 30,2011 Vadodara, Gujarat: Around 77000 tons of Cr waste dumped by Hema Dyechem ltd (souce:Blacksmith Institute, 2012). GPCB has sued the industry for Rs. 17crores. Between 1999 to 2001, 9 Hema Chemicals workers died due to chromiumtoxicity. Cr related morbidity associated with biochemical abnormality was noted inabout 25% of the high-risk group of workers.
    14. 14. CR CHEMISTRY IN AQUEOUSSYSTEMSolubilitys• Cr (VI) soluble in water• Cr (III) relatively insoluble in water (Ksp ~10-30) usually occurs as particulate matter[Cr(OH)3] in neutral to alkaline pH.The solubility of Cr (III) is significantly enhanced when theconcentration of organic compounds in wastewater is 10 fold orhigher than that of Cr (III) (Yang and Fan, 1990).Biotic and abiotic oxidation – reduction reactions regulates thedistribution between Cr (VI) and Cr (III) in aqueous systems.The redox transformation of Cr (III) to Cr (VI) or vice versa canonly take place in the presence of another redox couple, likeH2O/O2 (aq), Mn(II)/Mn(IV), Fe (II)/Fe(III), S2-/SO42- (Richard andBourg, 1991).6/16/2013 PHD SEMINAR 14
    15. 15. (Source: Palmer and Wittbrodt, 1991)6/16/2013 PHD SEMINAR 15
    16. 16. Source: McNeill et al.,20126/16/2013 PHD SEMINAR 16(Source: Dzombak and Morel 1990)
    17. 17. CHROMIUM REDUCTION6/16/2013 PHD SEMINAR 17Description Occurs in the presence of Typical LocationReduction of Cr (VI) to Cr (III):Fast (minutes tohours)CrO42- + 3 Fe 2+ + 8 H+ → Cr3+ + 3 Fe3+ + 4H2O2 CrO42- + 3 Sn2+ + 16 H+ → 2 Cr3+ + 3 Sn4- + 8H2O2 CrO42- + 3 SO32- + 10 H+ → 2 Cr3+ + 3 SO42-+ 5 H2OLower DO GW,water treatment,and distributionsystemSlower (days toyears)Absence of DO, Sulphides and bacteria2 CrO42- + 3 S2- + 16 H+ → 2 Cr 3+ + 3 S0 + 8H2OGroundwater, ironmains/dead endsConversion of soluble Cr (III) to particulate CrFast (seconds tohours)Water pH > 5Fe or Al oxidesPossible when Cr(III) is > 1 µg/LAddition ofCoagulant
    18. 18. CHROMIUM OXIDATION6/16/2013 PHD SEMINAR 18Description Occurs in the presence of Typical locationCr (III) oxidation to Cr (VI)Fast(minutes tohours)MnO2 solids2 Cr3+ + 3 MnO2 + 2 H2O → 2 CrO42- + 3 Mn2++ 4 H+Chlorine, H2O2, KMnO42 Cr3+ + 3 HOCl + 5 H2O → 2 CrO42- + 3 Cl-+ 13 H+2 Cr3+ + 3 H2O2 + 2 H2O → 2 CrO42- + 10 H+5 Cr3+ + 3 MnO4 + 2 H2O → 2 CrO42- + 3 Mn2++ 4 H+Oxygenatedhigh pH GW,water treatmentand distributionsystemSlower(hours todays)Chloramine2 Cr3+ + 3 NH2Cl + 8 H2O → 2 CrO42- + 3 Cl-+ 13H+DistributionsystemSlowest(days toDissolved Oxygen4 Cr3+ + 3 O2 + 10 H2O → 4 CrO42- + 20 H+GW, distributionsystem
    19. 19. REMEDIAL MEASURE/CHROMIUM REMOVALInsitu: Geochemical Fixation Permeable ReactiveBarriers (PRB) Reactive Zones Soil Flushing/ ChromiumExtraction Electro kinetics Natural Attenuation Phytoremediation Vitrification Solidification/stabilization BiotransformationExsitu: Coagulation/Flocculation Lime Softening Ion exchange Adsorption Membrane Filtration Soil Washing andSeparation Technologies Electro-coagulation Reduction-Precipitation6/16/2013 PHD SEMINAR 19
    20. 20. IN-SITU TREATMENT6/16/2013 PHD SEMINAR 20Geochemical Fixation: Concept: extracting contaminated groundwater and treating it above ground, followed byreinjection of the treated groundwater with reductant into the aquifer. In general, sulphur compounds such as sulphide and sulphite reduce Cr(VI). For sulphidesto reduce Cr(VI), Fe(II)must be present to act as a catalyst.Permeable Reactive Barriers (PRB): Reactive barriers of permeable nature are installed as permanent, semi-permanent, orreplaceable units across the flow path of a contaminant plume, which act as treatmentwalls.Reactive Zones: Are subsurface zones where migrating contaminants are intercepted and permanentlyimmobilized or degraded into harmless end products. These zones are established in-situ by injecting reagents and solutions in predeterminedlocations within the contaminated groundwater plume, and allowing them to “react” with thecontaminants. (USEPA 2000). These reactions can happen in different pathways, eitherabiotic or biotic or both.Soil Flushing/Chromium Extraction: Chromium is leached out from the soils by flushing with water or aqueous solutionNatural Attenuation: Natural attenuation includes a variety of physical, chemical, or biological processes that,under favourable conditions, act without human intervention to reduce the mass, toxicity,mobility, volume or concentration of contaminants in groundwater.
    21. 21. Electro-kinetics: GW remediation by using electric current via electro-osmosis, electro-migration andelectrophoresis is called electro-kinetic remediation. Non-ionic species will be transported along with the electro osmosis-induced water flow. Removing chromium as Cr (VI) is much efficient than as Cr (III) (Reddy andChinthamreddy, 1999)Vitrification: Arrays of electrodes are placed into soil and electric current is sent till metals metls andseals in glassy mixture. The remaining solidified block of glassy soil makes the soil not suitable for growing crops.Phytoremediation: Remediation of contaminated soil and ground water by plants, which can take up,accumulate, and/or degrade inorganic and organic constituents, is called phyto-remediation.Solidification/stabilization: Solidification refers to treatment that solidifies Cr into an immobile mixture with an additive,such as cement. Stabilization, also known as fixation, refers to the formation of an insoluble Cr compound.Biotransformation: Bacterias can reduce Cr (VI) to Cr (III). Groundwater bio-transformation can be done intwo ways: (i) natural attenuation/Bio-stimulation, and (ii) bio-augmentation. Bacterias causing reduction of Cr(VI) Aero monas, Escherichia, Pseudomonas, and6/16/2013 PHD SEMINAR 21
    22. 22. Coagulation/Floculation: Alum and Ferrous sulphate cannot remove Cr(VI) as theyas extremely soluble. (Sorg, 1979). Hydroxide precipitation requires 1st conversion of Cr(VI) toCr(III). (Besselievre, 1969).Lime Softening: Effective Cr(III) removal but poor Cr(VI) removal. high pH softening processes hinders Cr(VI) reduction. Cr(OH)3 formed might be re-dissolved to form aq Cr(III),hence possibility of oxidation of Cr(III) is possible inpresence of oxidants. (Clifford and Chau 1987). For 1 kg of Cr removed 32 kg of sludge is generated(Reddithota et al., 2007).6/16/2013 PHD SEMINAR 22EX-SITU TREATMENT
    23. 23. Ion exhchange: Dissolved Cr(VI) ions bind to the resin and displace the previouslybound ions (usually Cl– or OH– ions). naturally occurring inorganic zeolite or a synthetic weak base or strongbase anion exchanger resin. Competition by other anions (namely SO42–, nitrate (NO3–), and Cl–) isnot a problem in most applications, since Cr has a higher affinity for allpolymeric anion exchangers. Regeneration is typically accomplished using NaOH and alkaline brine.Cr(VI) in the regeneration effluent is either disposed of in concentratedform or is recovered for reuse.Soil Washing and Separation Technologies: Soil washing is used to chemically or physically separate Cr-contaminated soil from other soils prior to disposal. Chemical treatment typically involves the addition of an acid, oxidant,surfactant, or a chelating agent to the soil slurry to increase the amountof Cr in the aqueous phase. Leachability of Cr(VI) increases with the pH of the washing solution. The leachate has to be again treated hence soil washing is not majorlyfollowed.6/16/2013 PHD SEMINAR 23
    24. 24. ADSORPTIONIt is surface phenomenon.It involves accumulating on a surface in contact withcontaminant.Two categories: A) Physical adsorption and Chemisorption.Physical adsorption: Not site specific Electrostatic attraction between a charged surface and an ionic species. So,Cr(VI) can be potentially be removed by attraction to +vely charged surface.Chemisorption: Site specific reaction that exchanges electrons ligand exchange-chelation: hydroxyl ion group is involved, when multiple ligandsare involved with a single ion it is called chelation surface reduction-precipitation: Cr(VI) enters into oxidation-reduction reactionwith a reduced metal (ex. Fe) and is reduced to Cr(III), which forms precipitateand deposits on surface of adsorbent.6/16/2013 PHD SEMINAR 24
    25. 25. CrO42- is rapidly reduced by Fe0 to Cr3+ and precipitation of Cr(OH)3 orCrxFe1-x(OH)3. CrO42- + Fe0 +4H2O ↔ Cr3+ + Fe3+ + 8OH-All detectable Cr on Fe0 surface was Cr(III), as ionic radii of Cr(III)(0.63 Å) and Fe(III) (0.64 Å) are same, so they fit readily to formcrystalline structure of Fe(III)-Cr(III) hydroxide solid or (oxy)hydroxidesolid. (Buerge and Hug, 1997) (1-x) Fe3+ + xCr3+ + 3H2O ↔ (CrxFe1-x)(OH-)3(s) + 3H+ (1-x) Fe3+ + xCr3+ + 2H2O ↔ CrxFe1-xOOH-(s) + 3H+6/16/2013 PHD SEMINAR 25Fig: Adsorption (Source: Brandhuber et al.,
    26. 26. MEMBRANE FILTRATIONMembrane has –ve surface charge, hence Cr(VI) and otheranions are repelled by membrane surface.As ionic strength of water increases, Cr(VI) removal decreases.pH increase, increases the membrane surface de-protonation andhence increases rejection rate.For Cr(VI) removal by microfiltration or Nano filtration,pretreatment is done to complex Cr(VI) to larger molecule.Hexadecylpyridine chloride is used as pre-treatment agent givinga 98% Cr(VI) removal (Bohdziewicz, 2000).Acid or antiscalants are added in pretreatment to avoid formationof inorganic precipitates such as CaCO3, CaSO4 etc.6/16/2013 PHD SEMINAR 26
    27. 27. 6/16/2013 PHD SEMINAR 27Fig: Flow sheet of membrane filtration (Source: Brandhuber etal., 2004)
    28. 28. ELECTRO-COAGULATIONElectrocoagulation is a process of creating metallic hydroxid flocsby electrodissolution of soluble anodes made of aluminum or iron.CrO42-+ 3Fe2+ + 4H2O + 4OH- → 3Fe(OH)3 + Cr(OH)3Fe3+ and Cr3+ ions combine with the generated OH- ions andprecipitate as insoluble hydroxides.Fe3+ ions undergo hydration and give, depending on pH, cationicspecies such as Fe(OH)2+, Fe(OH)22+ in acidic conditions.Fe(OH)3 in neutral conditions and anionic species such asFe(OH)4-, Fe(OH)63- in alkaline conditions which result formationof gelatinous Fe(OH)3 effecting the coagulation and co-precipitation from the solution by adsorption.EC is pH dependent, removal of Cr increases with increase in pHfrom 2-8.The removal rate increases with increase in current density.Khosla et al. (1991)6/16/2013 PHD SEMINAR 28
    29. 29. CASE STUDY: BIOREMEDIATIONOF HEXAVALENTCHROMIUMCONTAMINATED SOILAND AQUIFERSSite: TamilNadu ChromateChemicals Limited, Ranipet,Vellore District , Tamilnadu. Chromium waste Disposal area: 5acres (2 hectares) 2 x105 Tones ofwaste)In-situ bioremediation ofCr(VI) contaminated aquifer ina 5 m × 5 m area of aquifer inthe vicinity of TamilnaduChromates and ChemicalsLimited (TCCL), Ranipet, byinjection well - reactive zonetechnology6/16/2013 PHD SEMINAR 29
    31. 31. RESULTS:SOIL REMEDIATIONFig: Variation of Cr(VI) concentration with respect to time in solidwaste remediation (Mass of untreated sludge added at various timeis mentioned inside the graph)6/16/2013 PHD SEMINAR 31
    32. 32. AQUIFERREMEDIATIONBIOREMEDIATION USINGMOLASSES (JAGGERY)AS THE CARBONSOURCEFig: Variation of Cr (VI)concentration with respect to time inwells 1 and 2 (molasses as carbonsource)6/16/2013 PHD SEMINAR 32Fig: Water samples fromvarious wells before and afterremediation
    33. 33. Fig: Variation of Cr (VI)concentration withrespect to time in wells7, 8, 9 and 10(molasses as carbonsource)6/16/2013 PHD SEMINAR 33Fig: Variation of Cr (VI)concentration withrespect to time in wells 11– 14 (molasses as carbonsource)
    34. 34. BIOREMEDIATIONUSINGSUGARASTHECARBONSOURCERemediation of Cr(VI) aquifers were also carried out using sugar as thecarbon source.For this study the initial biomass concentration was reduced to 1/10th of thatused in the previous case.Carbon source concentration also was reduced to 1/4th and feeding intervalwas increased to 7- 10 days.The fate and transport of chromium (both Cr(VI) and Cr(III)), sugar and itsderivatives, and microbes during the study period was monitored.6/16/2013 PHD SEMINAR 34
    36. 36. ANALYSIS OFHEAVYMETALSINAQUIFERConclusion:In this field level study, we have demonstrated conclusively thatbioremediation is an Effective and Environmentally friendly technology for the remediation of hexavalent chromiumcontaminated soils and aquifers.6/16/2013 PHD SEMINAR 36
    37. 37. SUMMARYThe literatures indicates that, Kanpur (UP), Ranipet and Chromepet(TN), Bangalore (KA) and Sukinda, Jajpur (OR) are severely affectedby Cr pollution.Out of two forms of Cr, Cr (VI) is toxic in nature.The reduction of Cr (VI) to Cr (III) can be a phenomenon of removalwhich is accomplished in many processes stated in this report.The oxidation of Cr (III) to Cr (VI) in DO is rare and Cr (III) to Cr (VI)can be possible in presence of MnO2.Zero Valent Iron (ZVI, Fe0) can be used for reduction and removal ofCr (VI).The process of reduction takes place even during adsorption of Cr(VI).Complex of Cr-Fe is formed which easily precipitates.Sulphides also reduce Cr (VI) in presence of Fe catalyst to increasereaction rates.6/16/2013 PHD SEMINAR 37
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