Ketan seminar ppt

HEAVY METAL
OCCURRENCE IN
GROUNDWATER IN
INDIA AND
EVALUATION OF
REMOVAL
TECHNOLOGIES
By
Wadodkar Ketan Kishor Ketki
PhD. Student (CESE)
124180004
Under Guidance of
Professor Sanjeev Chaudhari
Ph.D Seminar on
Center for Environmental Science and Engineering
IIT Bombay

CONTENT
Introduction
 Chromium
 Health Hazard
 Source of Cr contamination
Chromium Chemistry in aqueous system
Chromium problem in India
Remedial Measure/Chromium Removal
 Insitu
 Exsitu
Case Study (Remedial Measures in Indian Context)
6/16/2013 PHD SEMINAR 2

INTRODUCTION
Chromium
 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 ubiquitous
in 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 and
dichromate compounds.

Cr (III)-
Trivalent
Chromiu
m
More stable and abundant form of Cr
Less mobile and less mobile in water
Less toxic (even reported as important for C6H12O6 metabolism)
Cr (III) typically found in cation form
Occurs as insoluble chromium oxide (Cr2O3), chromium hydroxide
[Cr(OH)3], soluble Chromium hydroxide cations: CrOH2+ and
Cr(OH)2
+ depending on pH.
Cr (VI)-
Hexaval
ent
Chromiu
m
High mobility in water
Highly soluble in water
Reduced to Cr(III) in presence of Electron donor
Cr (VI) is known to be 100−1000 times more toxic than the Cr(III)
(Gauglhofer and Bianchi, 1991).
Cr (VI) typically found in anion form
Occurs as: Chromate (CrO4
-) and Dichromate form [Cr2O7
2-],
depending on pH.

HEALTH HAZARDS OF
CHROMIUM:
Cr(VI) is strong oxidant, hence is very harmful even
at small dose.
Cr(VI) compounds are corrosive/caustic may cause
burn on skin, chronic exposure leads to deeply
penetrating 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 sensitization
Cr(VI) compounds are mutagenic and may cause
chromosomal aberrations and sister chromatid
exchanges in humans (Result of Cr(VI) to Cr(III)
reduction).
Standards for Chromium in
water:
• USEPA : Total Cr < 0.1
mg/L in drinking water
• BIS: Cr (VI) < 0.05
mg/L for Cr(VI).
• WHO: Cr(VI) < 0.05
mg/L and total Cr < 2
mg/L.

In China 155 workers consuming
water with 20 mg/L of Cr(VI)
 caused oral ulcer, diarrhoea, vomiting,
abdominal pain and indigestion) and the
affected blood (leucocytosis and immature
neutrophils).
In another study (EVM, 2003),
Long term exposure of Cr:
 resulted in weight loss, anaemia,
haemolysis, liver dysfunction (elevated
aminotransferases and total bilirubin) and
renal failure.
Is not carcinogenic when ingested
through water, as Cr(VI) will be
reduced to Cr(III) which is
essential nutrient. Though might
prove carcinogenic if inhaled
(ATSDR, 2000).
In plants, high levels of Cr supply
can inhibit seed germination and
Source:
www.blacksmithinstitute.org

ChromiumOccurrencein
environment 1% volcanic emission
30% by biological
cycles
Extraction from soil by
plants (15%)
Weathering of rocks
(15%)
70% man made
source:
Ore and metal
production (3%)
Metal use (60%)
Coal burning and other
combustion (7%)
SOURCE: MERIAN
(1984)6/16/2013 PHD SEMINAR 7

Fig 1.1: Fate of Chromium in environment (Source:
USEPA, 2000)

PRESENCE OF CHROMIUM IN
INDIAN CONTEXT
Sukinda valley (Odisha):
 Is declared as 4th worlds highest
polluted site declared by study
conducted by Blacksmith Institute.
(Source;
http://www.blacksmithinstitute.org/)
 Open cast mining is followed leaving
waste around 7.6 million tonnes of
reject minerals.
 97% of total proven chromite of India
found in the Sukinda Valley, over an
area appx. 200 sq. km.
 Approximately 70% of the surface
water and 60% of the drinking water
contains Cr(VI) at more than double of
national standards.
(Source;
http://www.blacksmithinstitute.org
/)

Cr(VI) content in certain parts of
Odisha:
 550-1500 mg/l in well water
 25-100 mg/l in irrigation
reservoirs
 4000 mg/l in the soil making it
unfit for domestic usages. (Iyer
and Mastorakis, 2006)
26,00,000 est. people are in threat
of danger.
Orissa Voluntary Health
Association (OVHA) (Source:
http://www.pacsindia.org/grants/cs
o-partners/orissa/ovha):
 84.75% of mine worker's deaths, and
86.42% of nearby villager's deaths were
related to Cr induced diseases.
(Source;
http://www.blacksmithinstitute.org
/)

 About 2,500 tanneries in India,
approximately 80% of them use chrome
tanning process.
 A single tannery can cause GW pollution
around 7-8 km radius. (Ansari et al.,
1999)
Ranipet/Vellore (Tamilnadu)
 The conc. of total Cr in these wells varies
between 3.1 to 246 mg/L whereas the
conc. of Cr(VI) varies between 2.1 to 214
mg/L.
 Bore well water sample at 2 km from
closed tannery at Walajpet had Total Cr >
than 950 μg/L (typically Total Cr in India
4–7 μg/L) (Rao et al., 2011).
Chromepet, Chennai:
 Cr (VI) concentration between 0.01 mg/L
to 0.99 mg/L. (Brindha et al., 2010).
• Potentially affected
People: 34,82,000

Kanpur
 Kanpur has about 350 industrial leather tanneries,
which discharges there waste directly to GW or River
Ganga (Singh et al., 2005).
 Noraiakheda, Kanpur has developed right on top of a
plume of Cr VI emitted by toxic sludge from an old
chemical plant that had supported the tanneries.
 A report of CPCB on GW quality of Kanpur revealed
Cr VI levels of 6.2 mg/L
 Every month >2000 million ton of sludge is dumped
on the open ground. the CGWB recorded 0.01–16.30
mg/l of Cr(VI) in Kanpur’s industrial belt. (source:
http://post.jagran.com/Drinking-water-with-
carcinogenic-chromium-fatal-to-industrial-inhabitants-
in-UP-1323347306)

Bangalore, Karnataka:
 Study has found a staggering 17.75
mg/l of Cr(VI) in bore wells in Peenya
(Shankar et al., 2009).
 Out of 30 samples tested in study by
Shankar et al., 2009) 53% were found
non-potable due to excess of Cr.
Pune, Maharashtra:
 Due to Mantarwadi Landfill site, have
high level of Cr in near by area around
5-8 mg/L.
Source: 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 chromium
toxicity.
 Cr related morbidity associated with biochemical abnormality was noted in
about 25% of the high-risk group of workers.

CR CHEMISTRY IN AQUEOUS
SYSTEM
Solubility's
• 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 the
concentration of organic compounds in wastewater is 10 fold or
higher than that of Cr (III) (Yang and Fan, 1990).
Biotic and abiotic oxidation – reduction reactions regulates the
distribution between Cr (VI) and Cr (III) in aqueous systems.
The redox transformation of Cr (III) to Cr (VI) or vice versa can
only take place in the presence of another redox couple, like
H2O/O2 (aq), Mn(II)/Mn(IV), Fe (II)/Fe(III), S2-/SO4
2- (Richard and
Bourg, 1991).

(Source: Palmer and Wittbrodt, 1991)6/16/2013 PHD SEMINAR 15

Source: McNeill et al.,2012
(Source: Dzombak and Morel 1990)

CHROMIUM REDUCTION
Description Occurs in the presence of Typical Location
Reduction of Cr (VI) to Cr (III):
Fast (minutes to
hours)
CrO4
2- + 3 Fe 2+ + 8 H+ → Cr3+ + 3 Fe3+ + 4H2O
2 CrO4
2- + 3 Sn2+ + 16 H+ → 2 Cr3+ + 3 Sn4- + 8
H2O
2 CrO4
2- + 3 SO3
2- + 10 H+ → 2 Cr3+ + 3 SO4
2-
+ 5 H2O
Lower DO GW,
water treatment,
and distribution
system
Slower (days to
years)
Absence of DO, Sulphides and bacteria
2 CrO4
2- + 3 S2- + 16 H+ → 2 Cr 3+ + 3 S0 + 8
H2O
Groundwater, iron
mains/dead ends
Conversion of soluble Cr (III) to particulate Cr
Fast (seconds to
hours)
Water pH > 5
Fe or Al oxides
Possible when Cr
(III) is > 1 µg/L
Addition of
Coagulant

CHROMIUM OXIDATION
Description Occurs in the presence of Typical location
Cr (III) oxidation to Cr (VI)
Fast
(minutes to
hours)
MnO2 solids
2 Cr3+ + 3 MnO2 + 2 H2O → 2 CrO4
2- + 3 Mn2++ 4 H+
Chlorine, H2O2, KMnO4
2 Cr3+ + 3 HOCl + 5 H2O → 2 CrO4
2- + 3 Cl-+ 13 H+
2 Cr3+ + 3 H2O2 + 2 H2O → 2 CrO4
2- + 10 H+
5 Cr3+ + 3 MnO4 + 2 H2O → 2 CrO4
2- + 3 Mn2++ 4 H+
Oxygenated
high pH GW,
water treatment
and distribution
system
Slower
(hours to
days)
Chloramine
2 Cr3+ + 3 NH2Cl + 8 H2O → 2 CrO4
2- + 3 Cl-+ 13
H+
Distribution
system
Slowest
(days to
Dissolved Oxygen
4 Cr3+ + 3 O2 + 10 H2O → 4 CrO4
2- + 20 H+
GW, distribution
system

REMEDIAL MEASURE/
CHROMIUM REMOVAL
Insitu:
 Geochemical Fixation
 Permeable Reactive
Barriers (PRB)
 Reactive Zones
 Soil Flushing/ Chromium
Extraction
 Electro kinetics
 Natural Attenuation
 Phytoremediation
 Vitrification
 Solidification/stabilization
 Biotransformation
Exsitu:
 Coagulation/Flocculation
 Lime Softening
 Ion exchange
 Adsorption
 Membrane Filtration
 Soil Washing and
Separation Technologies
 Electro-coagulation
 Reduction-Precipitation

IN-SITU TREATMENT
Geochemical Fixation:
 Concept: extracting contaminated groundwater and treating it above ground, followed by
reinjection of the treated groundwater with reductant into the aquifer.
 In general, sulphur compounds such as sulphide and sulphite reduce Cr(VI). For sulphides
to 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, or
replaceable units across the flow path of a contaminant plume, which act as treatment
walls.
Reactive Zones:
 Are subsurface zones where migrating contaminants are intercepted and permanently
immobilized or degraded into harmless end products.
 These zones are established in-situ by injecting reagents and solutions in predetermined
locations within the contaminated groundwater plume, and allowing them to “react” with the
contaminants. (USEPA 2000). These reactions can happen in different pathways, either
abiotic or biotic or both.
Soil Flushing/Chromium Extraction:
 Chromium is leached out from the soils by flushing with water or aqueous solution
Natural 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.

Electro-kinetics:
 GW remediation by using electric current via electro-osmosis, electro-migration and
electrophoresis 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 and
Chinthamreddy, 1999)
Vitrification:
 Arrays of electrodes are placed into soil and electric current is sent till metals metls and
seals 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:
 Bacteria's can reduce Cr (VI) to Cr (III). Groundwater bio-transformation can be done in
two ways: (i) natural attenuation/Bio-stimulation, and (ii) bio-augmentation.
 Bacteria's causing reduction of Cr(VI) Aero monas, Escherichia, Pseudomonas, and6/16/2013 PHD SEMINAR 21

Coagulation/Floculation:
 Alum and Ferrous sulphate cannot remove Cr(VI) as they
as extremely soluble. (Sorg, 1979).
 Hydroxide precipitation requires 1st conversion of Cr(VI) to
Cr(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 in
presence of oxidants. (Clifford and Chau 1987).
 For 1 kg of Cr removed 32 kg of sludge is generated
(Reddithota et al., 2007).
EX-SITU TREATMENT

Ion exhchange:
 Dissolved Cr(VI) ions bind to the resin and displace the previously
bound ions (usually Cl– or OH– ions).
 naturally occurring inorganic zeolite or a synthetic weak base or strong
base anion exchanger resin.
 Competition by other anions (namely SO4
2–, nitrate (NO3–), and Cl–) is
not a problem in most applications, since Cr has a higher affinity for all
polymeric anion exchangers.
 Regeneration is typically accomplished using NaOH and alkaline brine.
Cr(VI) in the regeneration effluent is either disposed of in concentrated
form 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 amount
of 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 majorly
followed.

ADSORPTION
It is surface phenomenon.
It involves accumulating on a surface in contact with
contaminant.
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 ligands
are involved with a single ion it is called chelation
 surface reduction-precipitation: Cr(VI) enters into oxidation-reduction reaction
with a reduced metal (ex. Fe) and is reduced to Cr(III), which forms precipitate
and deposits on surface of adsorbent.

CrO4
2- is rapidly reduced by Fe0 to Cr3+ and precipitation of Cr(OH)3 or
CrxFe1-x(OH)3.
 CrO4
2- + 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 form
crystalline structure of Fe(III)-Cr(III) hydroxide solid or (oxy)hydroxide
solid. (Buerge and Hug, 1997)
 (1-x) Fe3+ + xCr3+ + 3H2O ↔ (CrxFe1-x)(OH-)3(s) + 3H+
 (1-x) Fe3+ + xCr3+ + 2H2O ↔ CrxFe1-xOOH-
(s) + 3H+
Fig: Adsorption (Source: Brandhuber et al.,

MEMBRANE FILTRATION
Membrane has –ve surface charge, hence Cr(VI) and other
anions are repelled by membrane surface.
As ionic strength of water increases, Cr(VI) removal decreases.
pH increase, increases the membrane surface de-protonation and
hence 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 giving
a 98% Cr(VI) removal (Bohdziewicz, 2000).
Acid or antiscalants are added in pretreatment to avoid formation
of inorganic precipitates such as CaCO3, CaSO4 etc.

Fig: Flow sheet of membrane filtration (Source: Brandhuber et
al., 2004)

ELECTRO-COAGULATION
Electrocoagulation is a process of creating metallic hydroxid flocs
by electrodissolution of soluble anodes made of aluminum or iron.
CrO4
2-+ 3Fe2+ + 4H2O + 4OH- → 3Fe(OH)3 + Cr(OH)3
Fe3+ and Cr3+ ions combine with the generated OH- ions and
precipitate as insoluble hydroxides.
Fe3+ ions undergo hydration and give, depending on pH, cationic
species such as Fe(OH)2+, Fe(OH)2
2+ in acidic conditions.
Fe(OH)3 in neutral conditions and anionic species such as
Fe(OH)4
-, Fe(OH)6
3- in alkaline conditions which result formation
of 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 pH
from 2-8.
The removal rate increases with increase in current density.
Khosla et al. (1991)

CASE STUDY: BIOREMEDIATION
OF HEXAVALENT
CHROMIUMCONTAMINATED SOIL
AND AQUIFERS
Site: TamilNadu Chromate
Chemicals Limited, Ranipet,
Vellore District , Tamilnadu.
 Chromium waste Disposal area: 5
acres (2 hectares) 2 x105 Tones of
waste)
In-situ bioremediation of
Cr(VI) contaminated aquifer in
a 5 m × 5 m area of aquifer in
the vicinity of Tamilnadu
Chromates and Chemicals
Limited (TCCL), Ranipet, by
injection well - reactive zone
technology

WELL LOCATIONS IN THE
EXPERIMENTAL PLOT

RESULTS:
SOIL REMEDIATION
Fig: Variation of Cr(VI) concentration with respect to time in solid
waste remediation (Mass of untreated sludge added at various time
is mentioned inside the graph)

AQUIFER
REMEDIATION
BIOREMEDIATION USING
MOLASSES (JAGGERY)
AS THE CARBON
SOURCE
Fig: Variation of Cr (VI)
concentration with respect to time in
wells 1 and 2 (molasses as carbon
source)6/16/2013 PHD SEMINAR 32
Fig: Water samples from
various wells before and after
remediation

concentration with
respect to time in wells
7, 8, 9 and 10
(molasses as carbon
source)
concentration with
respect to time in wells 11
– 14 (molasses as carbon
source)

BIOREMEDIATIONUSING
SUGARASTHECARBON
SOURCE
Remediation of Cr(VI) aquifers were also carried out using sugar as the
carbon source.
For this study the initial biomass concentration was reduced to 1/10th of that
used in the previous case.
Carbon source concentration also was reduced to 1/4th and feeding interval
was increased to 7- 10 days.
The fate and transport of chromium (both Cr(VI) and Cr(III)), sugar and its
derivatives, and microbes during the study period was monitored.

HEXAVALENT CHROMIUM
CONCENTRATION DURING THE
STUDY PERIOD

ANALYSI
S OF
HEAVY
METALS
IN
AQUIFER
Conclusion:
In this field level study, we have demonstrated conclusively that
bioremediation is an
 Effective and
 Environmentally friendly technology for the remediation of hexavalent chromium
contaminated soils and aquifers.

SUMMARY
The literatures indicates that, Kanpur (UP), Ranipet and Chromepet
(TN), Bangalore (KA) and Sukinda, Jajpur (OR) are severely affected
by 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 removal
which 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 of
Cr (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 increase
reaction rates.

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