FIELD OF THE INVENTION:
The present invention relates to a system for chemo-bioreactor for treatment of inorganic
wastewater involving precipitation of undesired metals and sulfides from dissolved sulfate.
In particular, the chemo-bioreactor system of the present invention and its method of
treatment is adapted to treat heavy concentration of metals in water as well as high
concentration of Sulfate. More importantly, the chemo-bioreactor of the present: invention
can treat the waste water to make it free of metals and sulfate in a single system/reactor
column, unlike the conventional treatment requiring each of biological/bacterial and
chemical means in separate columns and/or reactors following different independent
process steps. The chemo-bioreactor of the present invention is further adapted for
providing adequate environment so as to supply growth substrate, attachment site, required
proper pH and Alkalinity, anaerobic conditions and the like, favorable for sulfate reducing
bacterial (SRB) growth as well as chemical treatment of the water. Thus the present
invention is directed to advantageous simultaneous passive (biological) as well as active
(chemical) treatment process of the wastewater in a single reactor. The chemo-bioreactor
system of the present invention is advantageously adapted to run continuously for up to 2
years without downtime or requiring any major maintenance and also capable of treating
running waste water requiring such treatment for separation of heavy metals as well as
sulfate. The system and the method of water treatment would favour its use /application in
domestic as well as community drinking water treatment project with high efficiency and is
thus having inherent wide commercial prospects.
BACKGROUND ART:
Treatment of inorganic waste water by the precipitation process is quite commonly applied
process in existing knowledge relating to wastewater treatment, effluent treatment of some

industrial waste water and similar other purposes. The existing systems and methods for
treating waste water, the same suffers from the limitations with respect to inefficiency of
the metal removal which drops drastically within a short period of time and sulfide
precipitation is almost non existent and thus making the existing method inefficient since
the reactor column becomes ineffective within a short period of time.
While the bioreactors and chemical precipitation methods are widely used in conventional
methods for water treatment, the treatment of metals and the sulfate are carried out in
separate columns and reactors, following different process steps for separation of each from
the wastewater.
Some attempts have been made to improve the efficiency of the treatment of waste water
rich in metals and sulfate, such as in Acid Mine Drainage Polypropylene hollow fibre
membrane bioreactor (Rakesh and Henry, 2003), Fluidized bed reactor (Kaksonen 2004), up
flow anaerobic bioreactor (Elliott, Ragusa & Catcheside, 1998), Compost Bio-reactor
(Johnson and Hall berg 2005) wherein said treatment reported to have been used, but none
could achieve efficiency and enhanced performance as of the combined passive and active
treatment of waste water of the present invention.
US 4,354,937 discloses a process for precipitating heavy metals from wastewater
containing sulfate ions by treatment of the water with sulfate reducing bacteria. Said
bacteria will reduce the sulfate ions to hydrogen sulfide which in its turn will precipitate the
metal ions in the form of metal sulfides. According to the invention the bacteria are cultured
in one or more culturing vessels in the presence of a nutritive solution and a portion of the
wastewater, and the resulting aqueous solution containing hydrogen sulfide produced by the
bacteria is introduced into a precipitation vessel together with the remaining major portion
of the wastewater.

US 4,522,723 is directed to a process for reducing the concentration of water soluble ionic
heavy metal species and sulfate ions in aqueous waste solutions containing the same. The
process comprises passing said waste solution through a treatment zone containing a
porous matrix on which are retained populations of at least one bacteria of the genera
Desulfovibrio and Desulfotomaculum. The passing of said aqueous solution through said
treatment zone is carried out at predetermined rates of flow, and contact between said
solution and said bacteria is conducted under anaerobic conditions and at predetermined pH
and temperature levels. The process provides for the conversion of the water soluble sulfate
ions to hydrogen sulfide and reaction between said hydrogen sulfide and water soluble ionic
heavy metal species to water insoluble heavy metal species which are substantially retained
on the porous matrix and which are recoverable therefrom.
US 4,664,804 concerns a process for the removal of heavy metals from wastewater prior to
being fed to a wastewater treatment installation, with anaerobic sludge to cause the
anaerobic sludge to absorb heavy metals in the wastewater. Thus, the heavy metals
depleted wastewaters can then be treated in a conventional treatment plant and thereafter,
the resultant sludge can be directly employed for agricultural purposes without requiring
further treatment to remove heavy metals therein. To effect the process a preferred reactor
is made up of two parts, a cylindrical mixing tank and a superposed funnel-shaped
sedimentation zone
US 4,810,385 is on a device suitable for seeding bacterial cultures to waste flowing through
or which has accumulated in a collection system which comprises a porous outer covering
member which forms an enclosed package with a source of bacterial cultures contained
within said package, said cultures suitable for seeding a collection system as a waste stream
flows through the porous covering member of said enclosed package causing the bacteria to
be released into said waste stream.

US 4,839,052 relates to a process for the treatment of water containing dissolved calcium
ions and dissolved sulphate ions. The water is passed at a pH of 5-8,5 through an anaerobic
biological sulphate removal stage wherein microorganisms utilize sulphate ions in the water
to produce hydrogen sulphide. The water from the sulphate removal stage is then passed
through a hydrogen sulphide removal stage where hydrogen sulphide is removed therefrom.
Water form the hydrogen sulphide removal stage is passed through an aerobic biological
treatment stage wherein microorganisms cause at least partial biodegradation of any
organic material remaining in the water and wherein calcium carbonate is precipitated. The
invention also provides a biological water treatment installation which comprises an
enclosed reservoir means which provides an anaerobic stage and which feeds into a
hydrogen sulphide removal stage, which feeds into a reservoir means having oxygenating
means therein for oxygenating water therein and providing an aerobic stage.
US 5,968,359 involves a method of cleaning up heavy metal-laden waters and soils,
conditions are established in the soils and waters to be treated so that the microorganism
present there will form hydrogen sulfide, and optionally apathogenic facultative anaerobes
that are tolerant of heavy metals are added to produce hydrogen sulfide, and the hydrogen
sulfide formed by microbiological action is allowed to react with the heavy metals to form
metal sulfides.
US 5,976,372 is related to a method of treating a biomass comprising liquid manure from
animal husbandry containing heavy metals, the method comprising the steps of subjecting
the biomass to an anaerobic microbial degradation to form a biogas containing i.e. hydrogen
sulphide gas, conveying at least a part of the biogas through at least a part of the
microbially degraded biomass to precipitate the heavy metals as metal sulphides and
separating the resulting mixture in a precipitate and a supernatant.

US 6,325,923 describes a bioreactor for reacting an aqueous heavy metal and sulfate
containing mine drainage solution with sulfate reducing bacteria to produce heavy metal
sulfides and reduce the sulfuric acid content of the solution. The reactor is an elongated,
horizontal trough defining an inlet section and a reaction section. An inlet manifold adjacent
the inlet section distributes aqueous mine drainage solution into the inlet section for flow
through the inlet section and reaction section. A sulfate reducing bacteria and bacteria
nutrient composition in the inlet section provides sulfate reducing bacteria that: with the
sulfuric acid and heavy metals in the solution to form solid metal sulfides. The sulfate
reducing bacteria and bacteria nutrient composition is retained in the cells of a honeycomb
structure formed of cellular honeycomb panels mounted in the reactor inlet section. The
honeycomb panels extend upwardly in the inlet section at an acute angle with respect to the
horizontal. The cells defined in each panel are thereby offset with respect to the honeycomb
cells in each adjacent panel in order to define a tortuous path for the flow of the aqueous
solution.
It would be clearly apparent from the above that although bioreactors and chemical
precipitation methods are widely used in conventional water treatment, but these basically
involved separate and different treatment such as biological or bacterial treatment in
bioreactor column and chemical treatment in another column/chemical reactor. Thus the
conventional systems suffered from limitations and disadvantages relating to complexity in
operation involving a number of independent process steps, extra space for plant
installation and additional cost of equipments and auxiliaries, additional operating personnel
and relatively low operational efficiency in terms of treatment capability and output, since
the reactor column becomes ineffective within a short period of time.
There has ,therefore, been a persistent need for developing a system for treatment of
wastewater, which would be adapted to treat wastewater more efficiently and also operate

ceaselessly over longer period in a simple and cost effective manner. The need for a
combined system was felt to resolve limitations of the prior art process for the treatment of
water rich in heavy metals and dissolved sulfates. There remains a need for a simple
device/reactor adapted to facilitate fast and convenient elimination of the high
concentration of metals as well as the high concentration of sulfate from waste water using
a combination of biological and chemical treatment processes.
OBJECTS OF THE INVENTION:
It is thus the basic object of the present invention to provide a chemo-bio reactor/ system
comprising means for both biological/bacterial treatment as well as chemical treatment in a
singe column for treatment of wastewater efficiently for longer operational life.
Another object of the present invention is directed to achieve a process in said chemo-
bioreactor system of the invention as a combination of the passive (biological) and the
active (chemical) treatment processes, carried out in said single column.
A further object of the present invention is directed to achieve said waste water treatment
system in the form of chemo-bioreactor to provide adequate environment for Sulfate
Reduction Bacterial (SRB) growth as well as chemical treatment of water rich in metals and
dissolved sulfate.
A still further object of the present invention directed to chemo-bioreactor for treatment of
wastewater in a combination method wherein a single column comprising a number of
precipitation vessels is used.

A still further object of the present invention directed to the chemo-bioreactor for waste
water treatment wherein the system performing the combined biological and chemical
process in one single column is adapted to run continuously for about 2 years without any
major maintenance and can be used for running water needing such treatment.
A still further object of the present invention directed to the single column chemo-bioreactor
for wastewater treatment wherein the same system is performing the combined biological
and chemical process to remove metals/sulfate as precipitation is adapted to be used for
domestic application as well as the community drinking water projects with higher
efficiency.
SUMMARY OF THE INVENTION:
Thus according to the basic aspect of the present invention there is provided a chemo-bio
reactor/system for metal and sulfate removal from waste water comprising a main reactor
having :
an organic host of sulfate reducing bacteria ;
a growth substrate adapted to provide nutrient and attachment sites to the microbes
of said sulfate reducing bacteria
means to control the pH for the said sulfate reducing bacteria growth, provided such
that the water to be treated containing the sulfate is treated by the reducing bacteria
to produce H2S which in turn reacts with the metal to precipitate as metal sulfide to
thereby achieve microbial sulfate reduction and chemical precipitation in the same
main reactor.

In particular, the chemo-bioreactor system of the invention comprises said main
reactor bed having limestone, a growth substrate and gravels from bottom to top and
means for regulated carbon dosing. More particularly, the main reactor of the invention
comprises lime, lime stone, Soda Ash, NaOH, KOH, alum ,bone dust or combinations
thereof, alongwith spent mushroom compost ,Leaf liter, coconut grounded dust, saw
dust, used tea leaf, coconut fiber, sludge and red mud.
According to a preferred aspect of the invention the chemo-bioreactor system
comprises:
a plurality of settling tanks operatively connected to the main reactor such as to
supply the water to be treated enters the main reactor at the top and passes through
the reactor bed to the bottom and finally the post treatment the water is passed to
further settling tank.
In accordance with yet another aspect of the invention the chemo-bioreactor system
comprises of first three settling tanks operatively connected to feed the water for
treatment at the top of the main reactor and two settling tanks ahead of the main
reactor to settle the treated waste water.
According to a preferred embodiment the said settling tanks and said main reactor
comprises cylindrical tanks obtained of acrylic sheets to favour entry of light to facilitate
the growth of photosynthetic microorganism and provide extra nutrient to the sulfate
reducing bacteria as well as help in bio-film formation.
Importantly, in the reactor of the invention, the said limestone is provided to increase
the pH for metals precipitation and for the sulfate reduction by bacterial growth.

Advantageously, also the chemo-bioreactor system comprises sample ports throughout
the length adapted to facilitate taking samples from time to time.
According to an aspect of the invention, in the chemo-bioreactor system all the tanks
open at the top and are connected through three channels except the main reactor
channel which is connected with the adjacent tank through one operative channel /flow
path, said channel /flow paths being provided with flow controllers.
According to yet another aspect the chemo-bioreactor system of the invention is
provided such that the main reactor comprises a ratio of height and diameter in the
range of 2: 1 to 15:1.
According to another aspect of the invention there is provided a process for treatment of
inorganic waste water by precipitation using the chemo-bioreactor comprising:
passing the water to be treated from the settling tanks into the main reactor at the
top and allowing the passage of water therethrough the main reactor wherein the
sulfate reducing bacteria produces H2S which in turn reacts with the metal to
precipitate as metal sulfide, said sulfides being deposited at the growth substrate
and limestone bed; and
finally allowing the thus treated water to pass from the main reactor to further
settling tanks ahead of said main reactor.
In accordance with a preferred aspect in the above process of the invention the same
includes step of controlled carbon dosing for desired maintenance of growth substrate
and wherein the pH for the sulfate reducing bacteria is controlled such as to maintain
low solubility of the metal hydroxide and metal sulfide and favour effective treatment of
the waste water.

Advantageously, the process provides for controlled rise in the pH to influence the
sulfide precipitation.
The process of the invention involving the chemo-bioreactor of the invention would
enable carrying out static or a continuous process for removal of metals and sulfate from
waste water or in other bio-chemical technology.
The details of the invention, its objects and advantages are explained hereunder in greater
detail in relation to non-limiting exemplary illustrations as per the following accompanying
figures:
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1: is the schematic illustration of the main Bioreactor column along with the sampling
unit with ports and settling tanks receiving water from bottom exit of reactor column, as
integral part of the chemo-bioreactor system as composite unit for biological as well as
chemical treatment of wastewater, according to the present invention.
Figure 2: is the illustration of the arrangement of mixing and settling tanks connected
through three channels in between the successive tanks in series, through which the inlet
water flows in to the main reactor column.
Figure 3: is the schematic illustration of the main reactor column of the Chemo-bioreactor
system according to the present invention, having means for controlled accurate measured
Carbon dosing at site at right time in said reactor column, for desired growth of
photosynthetic SRB in substrate for enhanced sulfate reduction and ensuring longer
continuous operation.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The Chemo-bioreactor according to the present invention has a set of 6 tanks substantially
cylindrical in section vertical reactor column made of non-reactive transparent poly acrylic
sheet, at the bottom of which the lime bed is prepared and placed, comprising lime, lime
stone, NaOH, KOH, alum, bone dust etc. in selective proportion and as combination of two
or more such substances. The reactor vessels in chemo-bioreactor are hollow cylindrical
vessels having a length to diameter ratio ranging from 2:1 to 15:1 based on volume flow
and treatment requirements. The main reactor is preferably having said ratio of 5:1.
Reference is first invited to accompanying Figure 1 that illustrates the main reactor column
of the chemo-bioreactor system comprising separate columns and settling tanks totaling 6
numbers of such vessels in a set, as already described, for bacterial/biological treatment of
dissolve sulfate and also chemical treatment for separating the metals and sulfide by
precipitation. In a typical up flow bioreactor column as shown in Figure 1, the reactor
column made up of transparent polyacrylic sheet or similar other non reactive material and
is having typical dimensions such as diameter of about 30 cm and a total column height of
about 150 cm. The biodegradable environment for sulfate reduction by bacteria is provided
preferably disposing introducing compost substrate etc through an injection system
releasing towards the bottom of column above the lime layer comprising lime, lime stone,
KOH, alum etc in desired combination and said sulfate reduction is favored by presence of
dissolved organic carbon dosing at controlled rate and desired frequency.
It contains a bacterial growth substrate on the bottom bed, comprising any or more in
combination of Spent mushroom compost, leaf liter, coconut grounded dust, saw dust, used
tea leaf, coconut fibre, sludge, red mud etc. and the bed is bound by gravels from bottom to

top. The name Chemo-bioreactor is derived from the fact that 'chemo' is because of the
limestone bed will increase the pH for Sulfate Reducing Bacteria (SRB) growth and 'bio'
because the growth substrate which is supposed to provide nutrient and attachment site to
microbes. The main reactor also contains three sample ports at selective heights of column
to collect samples from time to time.
Water to be treated comes through first three mixing and settling tanks to the main reactor
and is removed through an exit point at the bottom surface of the reactor column and
passed on to the next two tanks acting as settling tank. All tanks are connected through
three flexible tube connections except that the main reactor is connected to the immediate
next one flexible connecting tube. All intermediate channels are provided with flow
controller valves. Accompanying Figure 2, is the illustration of an embodiment of the
mixing and settling tanks connected in series through three communicating flexible
connections at preferred spacing, for the incoming water before entering the main reactor
tank for being treated biologically and chemically in the main reactor column.
It is clear from the illustrative embodiments of the chemo-bioreactor system of the
invention having all the tanks being open only at top. The water coming through the
channels/tubes and enters the main reactor at top, passes through the reactor and the
sulfate reducing bacteria (SRBs) that grows at the bottom at growth substrate produces
Hydrogen sulfide. This H2S reacts with the metals present in chemically untreated water and
to be precipitated as metal sulfides. The sulfides are deposited at the growth substrate and
limestone bed. Because of the body of the main reactor being made of transparent acrylic
sheet, light can enter into the chemo-bioreactor and facilitates the growth of photosynthetic
microorganisms. This again provide extra nutrient to SRBs as well as help in bio film
formation.

Thus the chemo-bioreactor of the present invention achieves the use of chemical
precipitation and microbial sulfate reduction together in a combined process such that
higher efficiency and economy of long-term operation of the reactor for treating various
inorganic wastewater is favorably established, as compared to the conventional similar
processing of water in separate reactors and columns.
The chemo-bioreactor is developed on the theory of low solubility of metal hydroxide and
metal sulfide at a controlled pH. Generally metal sulfides have low solubility than metal
hydroxide.
Reference is now invited to accompanying Figure 3 that illustrates an embodiment of the
main reactor column of the chemo-bioreactor system of the present invention as already
described in the preceding paragraphs, along with suitably disposed favored carbon dosing
system in combination, for replenishment of nutrient for the bacterial growth in the
substrate favoring higher efficiency of reactor and faster sulfate reduction. As already
described the chemo-bioreactor of the present invention has been configured to treat heavy
concentration of metals in water as well as high concentration of sulfate wherein the
dissolved carbon dosing helps to replenish the depletion of reducing environment by
controlled carbon dosing at the actual place of use in the reactor column at controlled rate
and frequency.
As already described the chemo-bioreactor of the present invention essentially involves
said reactor bed including spent mushroom compost, leaf liter, coconut grounded dust ,
saw dust, used tea leaf, coconut fibre, sludge, red mud etc. The object is to provide
adequate environment for sulfate reducing bacterial (SRB) growth as well as chemical
treatment of the various source of inorganic waste water.Thus a bioreactor and a chemical
reactor are combined together to serve same purpose of water treatment more efficiently

than the two of them working separately. Thus the equipment and process of the present
invention by way of the arrangement of chemo-bioreactor save cost, reduce space
requirement and frequent repair/ maintenance or servicing. The chemo-bioreactor can be
modular in design and can be retrofitted into any water pipeline to find out better quality
treated water.
The treatment of water involving the chemi- bio reactor of the invention was carried out
under different variable parameters and test results were recorded and analyzed to assess
the efficiency of the device in terms of treatment capacity and purification of inorganic
waste water rich in metals and dissolved sulfates. Such tests were carried out under two
broad categories : (a) Static Column Experiment and (b) Continuous Flow Experiment.
(a) In static experiment six samples are taken. An initial sample (0 hour) showing the
actual wastewater solution. The samples are taken after 66 hr, 132 hr, 180 hr, 300 hr,
396 hr from starting of the experiment. Various parameters values are recorded for
these samples and the comparative study of the static experiments are presented in
the following Table 1.


Analysis of observed data in Table 1:
In static experiment, sulfate to an extent of about 77.27% is achieved. Decrease of D.O. from
6mg/L to 0.1mg/L and acidity from 73 meq/L to 65 meq/L and an increase of conductivity from
3.9 mS/cm to 4.3 mS/cm, salinity from 2.4 ppt to 2.7 ppt, total dissolved solid from 1.94 ppt to
2.17 ppt also resulted. Reduction of Cu from 317ppm to 210 ppm and Al from 264 ppm to 1.4
ppm has also been shown. Where as C.O.D., O.R.P. and Fe values fluctuate continuously
through the experiment and remain more or less the same as of the initial sample value.
As the time passes, the pH rises and acidity decreases. It so happens because of the Alkalinity
generated by the limestone and the spent mushroom compost in combination. The slow rise in
pH value is likely due to slow dispersion of the water from the bottom to up in the static
experiment. The rise of pH also influences the sulfide precipitation, which is the main reason of
high sulfate reduction.
(b) In the Continuous Flow Experiment, as a transition phase from the steady state/static
condition to the continuous flow condition goes on inside the chemo-bioreactor for over
hours together or for days, a predetermined settling time was allowed in the chemo-
bioreactor. Few samples were taken initially. In the first week, a selective set of a few
samples were taken from first tank (at time 0), main reactor or fourth tank(144 hrs), fifth
or first effluent tank(0 hrs i.e. effluent of static experiment was released) and from sixth or
final effluent tank(120 hrs) Only Mg is increased in continuous flow experiments. The
parameter values corresponding to the above sample observations are presented in the
accompanying Table 2, comprising readings from initial stage of continuous experiment.


Analysis of observed data in Table 2:
The observed results as presented in the table 2 above, clearly shows marked reduction of the
metals by way of metal sulfide precipitations in various tanks from the inorganic waste water
rich in metals and dissolved sulfate being treated by the chemo-bioreactor process under
continuous flow condition.
Further sampling and analysis has been carried out taking selective sampling from the
Fourth(D) Tank and Sixth(F) Tank, at predetermined time intervals from the initial starting of

flow condition. It may be noted that here five different sets of observation of parameter values
were taken at 96 hrs(Dl,Fl); 192 hrs(D2, F2); 288 hrs(D3, F3); 384 hrs(D4, F4); and 480
hrs(D5, F5). The comparative results of the observed values for the different parameters
considered in the continuous flow experiments are presented in the accompanying Table 3.

The observed results in general shows a desired significant reduction of metals and sulfate in
waste water being treated and also other parameters both in D as well as F tank, sampled and
recorded at selective time intervals. Also it is noted that the levels of contents is much less in F
tank as compared D tank, F tank being at further down stream in said continuous flow condition
and is exposed to longer reaction time of biological and chemical treatment.

t is thus possible by way of this invention to achieve for the first time the treatment of the
vaste water rich in metals and dissolved sulfates, in combined equipment ,the chemo-
ioreactor which would serve to increase the efficiency of treatment of water by way of
eliminating the metals and sulfides by way of precipitation, while treating the water both
jiologically/passive as well as chemically/active in the same chemo-bioreactor column, and
allowing precipitation of solids more efficiently. Thus the chemo-bioreactor system of the
present invention is effective and less costly and is a much faster process for treating waste
water and is capable of being applied with advantage for both domestic and the community
water supply projects on commercial scale.

WE CLAIM:
1. A chemo-bio reactor/system for metal and sulfate removal from waste water
comprising a main reactor column having :
a sulfate reducing bacteria source ;
a growth substrate adapted to provide nutrient and attachment sites to the microbes
of said sulfate reducing bacteria
means to control the pH for the said sulfate reducing bacteria growth, provided such
that the water to be treated containing the sulfate is treated by the reducing bacteria
to produce H2S which in turn reacts with the metal to precipitate as metal sulfide to
thereby achieve microbial sulfate reduction and chemical precipitation in the same
main reactor column.
2. A chemo-bioreactor system as claimed in claim 1 comprising said main reactor bed
having limestone, a growth substrate and gravels from bottom to top and means for
regulated carbon dosing.
3. A chemo-bioreactor system as claimed in anyonme of claims 1 or 2 wherein the main
reactor comprises lime, lime stone, NaOH, KOH, alum ,bone dust or combinations
thereof, along with spent mushroom compost ,Leaf liter, coconut grounded dust, saw
dust used tea leaf, coconut fiber, coir mat, sludge and red mud.
4. A chemo-bioreactor system as claimed in anyone of claims 1 or 2 comprising :
a plurality of settling tanks operatively connected to the main reactor such as to
supply the water to be treated enters the main reactor at the top and passes through
the reactor bed to the bottom and finally the post treatment the water is passed to
further settling tank.

5. A chemo-bioreactor system as claimed in claim 4 comprising first three settling tanks
operatively connected to feed the water for treatment at the top of the main
reactor and tow settling tanks ahead of the main reactor to settle the treated waste
water.
6. A chemo-bioreactor system as claimed in anyone of claims 1 to 5 wherein said
settling tanks and said main reactor comprises cylindrical tanks obtained of acrylic
sheets to favour entry of light to facilitate the growth of photosynthetic
microorganism and provide extra nutrient to the sulfate reducing bacteria as well as
help in bio-film formation.
7. A chemo-bioreactor system as claimed in anyone of claims 1 to 6 wherein said
limestone is provided to increase the pH for the sulfate reduction bacteria growth.
8. A chemo-bioreactor system as claimed in anyone of claims 1 to 7 wherein said main
reactor comprises sample ports throughout the length adapted to facilitate taking
samples from time to time.
9. A chemo-bioreactor system as claimed in anyone of claims 1 to 8 wherein all the
tanks open at the top and are connected through three channels except the main
reactor channel which is connected with the adjacent tank through one operative
channel /flow path, each said channel /flow paths being provided with flow
controllers.
10. A chemo-bioreactor system as claimed in anyone of claims 1 to 9 wherein the main
reactor comprises a ratio of height and diameter in the range of 2: 1 to 15:1.
11. A process for treatment of inorganic waste water by precipitation using the chemo-
bioreactor as claimed in anyone of claims 1 to 10 comprising:

passing the water to be treated from the settling tanks into the main reactor at the
top and allowing the passage of water therethrough the main reactor wherein the
sulfate reducing bacteria produces H2S which in turn reacts with the metal to
precipitate as metal sulfide, said sulfides being deposited at the growth substrate
and limestone bed; and
finally allowing the thus treated water to pass from the main reactor to further
settling tanks ahead of said main reactor.
12. A process as claimed in claim 11 comprising controlled carbon dosing for desired
maintenance of growth substrate and wherein the pH for the sulfate reducing
bacteria is controlled such as to maintain low solubility of the metal hydroxide and
metal sulfide and favour effective treatment of the waste water.
13. A process as claimed in anyone of claims 11 or 12 wherein the rise in the pH
influences the sulfide precipitation.
14. A process as claimed in anyone of claims 11 to 13 comprising a static or a
continuous process for removal of metals and sulfate from waste water or in other
bio-chemical technology.
15. A chemo-bio reactor /system for metal and sulfate removal from waste water and a
process for treatment of waste water using the same substantially as
hereindescribed and illustrated with reference to the accompanying figures.

A system for chemo-bioreactor for treatment of inorganic wastewater involving precipitation
of undesired metals and sulfides from dissolved sulfate. In particular, the chemo-bioreactor
system and its method of treatment is adapted to treat heavy concentration of metals and
Sulfate in water. Importantly, the chemo-bioreactor of the invention treat wastewater to
make it free from metals and sulfate in a single system/reactor column, by both
biological/bacterial and chemical means. The system provide for supply growth substrate,
attachment site, required proper pH and Alkalinity, anaerobic conditions and the like,
favorable for sulfate reducing bacterial (SRB) growth as well as chemical treatment of the
water. Thus simultaneous passive (biological) as well as active (chemical) treatment process
is achieved. The system is adapted to run continuously for up to 2 years without major
maintenance and treating running wastewater for separation of heavy metals/sulfate. The
system and the method of water treatment would favour its use /application in domestic as
well as community drinking water treatment project with high efficiency.