TITLE:
A process for treatment of contaminated water.
FIELD OF THE INVENTION:
This invention relates to a process for treatment of contaminated water.
BACKGROUND OF THE INVENTION:
Chromite Mines in Orissa having 97% of India's chromite ore deposits and the
mine's untreated wastewater is discharged in the river. The river is the only water
source for the residents and treatment facilities are extremely limited. The
untreated waste water contains high amount of Chromium. Chromium exists in
two forms - hexavalent chromium (CrVI) and trivalent Chromium (CrIII) of which
Cr(VI) is highly poisonous, toxic and carcinogenic.
The acute toxicity of Cr(VI) is due to its strong oxidation properties. Chromium is
toxic to both plants(in high concentrations) and animals. Chromium toxicity
affects the plant growth and metabolism, leading to stunted growth, reduced crop
yield, delayed germination, senescence, premature leaf fall, enzymatic changes
and reduced biosynthesis. The chromium contaminated mine water and soil
become nutrient deficient and

exhibit stress impacts on plant and microbes. And for humans, after it reaches
the blood stream, it damages kidney, liver, blood cells through oxidation reaction.
the damage results into hemolysis, renal and liver failure. Cr(VI) is highly
genotoxic.
Cr(VI) concentration in the mine waste water exceeds the permissible level
.WHO recommended maximum allowable concentration of Cr(VI) in drinking
water is - 0.05 mg/L , irrigation water - 0.008 mg/L , and fresh water system -
0.001 mg/L. LD50 for Cr(VI) ranges from 50-150 mg/kg.
Phytoremediation is a plant based bioremediation technique that uses green
plants that mitigate the environmental problem without the need to excavate the
contaminant material and dispose of it elsewhere.
Water hyacinth (Eichhornia crassipes) native from the Amazon basin is one of
the fastest growing weeds in ponds; its duplication rate is around 7 days. It is a
free-floating perennial aquatic plant (or hydrophyte) with broad, thick, glossy,
ovate leaves and a very developed root system. Water

hyacinth is a hyper-accumulator of heavy metals with effective rhizofiltration and
phytoextraction ability of attenuating the toxicity of Cr (VI)
from mine waste water. The weed attenuates the Cr(VI) concentration through
bioaccumulation in its roots and shoots.
The Fungal biomass effectively adsorbs the Cr(VI) from the mine waste water
and is reported to convert Cr(VI) to a nontoxic Cr(III) form.
In this study, its seen that the treatment of the Cr(VI) laden wastewater with the
integrated use of water hyacinth (Phytoremediation) and Fungal Biomass
(Bioremediation) have resulted in a significant decrease in the concentration of
Cr(VI) from the mine waste water.
In the conventional process:
Mines effluent wastewater containing Cr(VI) is passed through settling chamber
to remove suspended solids.
Then the above wastewater is dosed with ferrous sulfate in acidic conditions(pH
below 4) to convert Cr(VI) into non-toxic and sparingly soluble Cr(III).

Finally passing through gravel filter after lime precipitaion the water is filtered out
to get discharge quality water stream.
CrO4 2-+3Fe2++4H2O→Cr3++3Fe3++8OH-
OBJECTS OF THE INVENTION:
An object of the present invention is to propose a process for treatment of water
contaminated with hexavalent chromium.
Another object of the present invention is to propose a eco-friendly technique for
detoxification of hexavalent chromium below permissible limit.
Still another object of the present invention is to propose a economic process for
treatment of water contaminated with hexavalent chromium.
Further object of the present invention is to propose a process for treatment of water
contaminated with hexavalent chromium which is self adapting and requires minimal
manual intervention.
Still further object of the present invention is to propose a process for treatment of water
to reduce hexavalent chromium and also TSS and BOD.

BRIEF DESCRIPTION OF THE INVENTION:
According to this invention there is provided a process for treatment of water
contaminated with hexavalent chromium comprising including the contaminated water
into the primary settling tank (1) to remove the floating and other suspended impurities,
treating the waste water in the bio-phyto tank(2) to convert hexavalent chromium into
nontoxic trivalent chromium, subjecting the treated water to the step of settling in
secondary settling tank (4) for about 2 hours, discharging the treated water.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 – Shows the conventional water treatment process.
Figure 2 – Shows the Flowchart of Myco-Phyto treatment process.
Figure 3 – Shows the percent distribution of chromium in plant
DETAILED DESCRIPTION OF THE INVENTION:
The water is pumped from the quarries and the tailings pond to the myco-phyto
wastewater processing plant.
The MycProd tank or Myco Production Tank, fungus Aspergillus niger (MTCC-
281) is cultured in Media (Sucrose 30.000, Sodium nitrate 3.000,

Dipotassium phosphate 1.000, Magnesium sulphate 0.500, Potassium chloride
0.500, Ferrous sulphate 0.010, Final pH ( at 25°C) 7.3±0.2) at 35oC in in-house
designed air lift bioreactors. The biomass is then harvested on sieve and strained
of residual moisture. The biomass obtained is then transferred to bio-treatment
tank at 10% v/v ratio. The biomass treats water and converts hexavalent chrome
to trivalent chrome. The biomass after treatment is regenerated in bio-
regeneration tank using 10-15% NaOH. After 12-16 hrs the water is passed to
next tank for Phyto-treatment. Here the residual hexa chrome and tri-chrome is
filtered out of water by Eichhornia crassipes (Mart) Solms and stored in roots,
shoots and leaves after reducing it to trivalent chromium. The extensive root
systems of plants habituated by microbial biofilm also support the process of
reduction of hexavalent chromium and maintaining a reducing environment for
detoxification of toxic chrome in water. The suspended solids are precipitated out
due to settling and arresting of water velocity due to the roots which act as
horizontal trickling bed filter.
A process for treatment of Cr(VI) laden wastewater and liquid effluents involving
simultaneous detoxification and accumulation of heavy metals by a combined system
consisting of an aquatic plant and fungal species is disclosed.

A process for removal of hexavalent chromium occurring due to natural and
anthropogenic causes from wastewater from Chromite mines
The wastewater is first settled to remove out any floating and suspended solids in
Primary Settling Tank (1) for about 2 hours. The pH of the wastewater is about 7-7.5
Wastewater is then brought into the next chamber where in bio and phyto treatment
occur simultaneously to remove hexavalent chromium out of water and accumulated
into the aquatic macrophyte after conversion to non-toxic trivalent chromium. The pH of
the wastewater in combined treatment step is about 4.5-5. This is due to the organic
acids produced by fungus Aspergillus niger (MTCC-281).
The fungus Aspergillus niger (MTCC-281) was cultured at 35oC for 5-7days in media
containing Sucrose 30gm/L, Sodium nitrate 3gm/L, Dipotassium phosphate 1gm/L,
Magnesium sulphate 0.5gm/L, Potassium chloride 0.5gm/L, Ferrous sulphate 0.01gm/L,
Final pH ( at 25°C) 7.3±0.2. This culture is added to the Bio-Phyto treatment tank at 10-
20% v/v concentration. Addition of this fungal culture to the bio-phyto treatment tank
changes the pH from 7.5 to below 6.
The plants are of Eichhornia crassipes (Mari) Solms species and are adapted to mines
conditions for 20-30 days. The plants grow very rapidly and cover the surface of the
tank within 15 days after inoculation. The depth of the water is maintained at 30cm from

the bottom of the tank. The wet biomass of plants should be at least 18kg/m2. The
extensive root systems of plants habituated by microbial biofilm support the process of
reduction and removal of hexavalent chromium and maintaining a reducing environment
for detoxification of toxic chrome in water. The suspended solids are precipitated out
due to settling and arresting of water velocity due to the roots which act as horizontal
trickling bed filter.
The water after treatment in myco-phyto tank is settled in secondary settling tank for
another 2 hours and the overflow is discharged.
The sludge generated in all the three tanks is mixed together and composted for a
month to use as organic fertilizer for plantations in the mines region.
The process is eco-friendly technique for detoxification of hexavalent chromium below
permissible limit for water discharge from chromite mines.
There is no chemical contaminants residual in the discharged water as almost no
chemicals are used in this technique.

The process is very economic as no mechanized parts and almost negligible energy is
needed.
The system is self-adapting and requires minimal manual intervention.
Also reduces TSS and BOD along with Cr(VI)

WE CLAIM:
1. A process for treatment of water contaminated with hexavalent chromium comprising
including the contaminated water into the primary settling tank (1) to remove the floating
and other suspended impurities, treating the waste water in the bio-phyto tank(2) to
convert hexavalent chromium into nontoxic trivalent chromium, subjecting the treated
water to the step of settling in secondary settling tank (4) for about 2 hours, discharging
the treated water.
2. The process as claimed in claim 1, wherein the PH of the waste water is 7 to 7.5.
3. The process as claimed in claim 1, PH of waste water after conversion of non-toxic
trivalent chromium is 4.5 to 5.
4. The process as claimed in claim 1, wherein bio-phyto treatment comprises cultured
fungus Aspergillus niger and the plant used in Eichhornia crassipes (Mari) solms
species.
5. The process as claimed in claim 4, wherein the said Aspergillus niger is cultured at
35oC for 5-7days in media containing Sucrose 30gm/L, Sodium nitrate 3gm/L,
Dipotassium phosphate 1gm/L, Magnesium sulphate 0.5gm/L, Potassium chloride
0.5gm/L, Ferrous sulphate 0.01gm/L, Final pH ( at 25°C) 7.3±0.2. for maintaining an
environment for detoxification.

6. The process as claimed in claim 4, wherein the said Eichhornia crassipes are grown to
form wet biomass of at least 18 Kg/m2 and their extensive root system helps in
reduction and removal of hexavalent chromium.

7. The process as claimed in claim 1 wherein the sludge generated in all the 3 tanks is
mixed together and composted(anaerobically) for a month to use as organic fertilizer for
plantation in the mines region.