FIELD OF THE INVENTION
The present invention relates to a system and method for treatment of coke oven
effluent/waste water. More particularly, the present invention is directed to a system
and electrochemical process for pre treatment of coke oven plant effluent before
biological treatment to enhance the effectiveness of biological treatment process. The
electrochemical pre treatment process according to the present invention favors
removing recalcitrant toxic constituents including long chain organic and
organometallic compounds from waste water by coagulation and sedimentation.
Importantly, floes formed by the process are similar to chemical floe, except that this
floe tends to be much larger, contains less bound water, is acid-resistant and more
stable, and therefore, can be separated faster by filtration.
BACKGROUND ART
In recent years, environmental concerns have led to extensive research regarding the
removal of harmful organic compounds from industrial waste streams. In this context,
thermochemical processes such as wet air oxidation and catalytic wet air oxidation, and
advanced oxidation processes (AOPs) such as UV irradiation, ozonation, Fenton and
photo-Fenton oxidation and electrochemical oxidation are promising alternatives to
conventional treatments.
Physico-Chemical methods have been the principal method used to prevent water
pollution and remove specific pollutants across industries. These methods employ
either unit operations or unit processes to remove specific pollutants. However it is
very expensive in the long run, and additionally there are secondary pollution problems
associated with it.
Since removal of micro constituents through physico-chemical treatment is an
expensive proposition, biological treatment is adopted for treatment of high volume
effluent containing organic compounds. However, presence of recalcitrant toxic
constituents often affect the performance of biological treatment process.
Existing physico-chemical treatment processes generally target reduction in suspended
solids concentration before biological treatment. However, most of the recalcitrant

toxic constituents remain either in dissolved ionic level or very low size range of
suspension which cannot be removed by traditional processes of suspended solids
removal. These refractory components are basically long chain organic and
organometallic compounds. Conventional treatment processes were found ineffective
for the purpose. Since from practical experience and literature survey it was clear that
lack of proper pre-treatment leads to relatively ineffective biological treatment of
effluent in steel plant, need for an efficient and effective pre-treatment process was
felt.
There has been therefore a persistent need in the related field to developing a method
and apparatus for pre treatment of the coke oven effluent to remove all kind of
pollutants, suspended as well as dissolved low size particles, including refractory
components comprising long chain organic and organometallic compounds, before
biological treatment. The process of the present invention eliminates the limitations of
the prior art of waste water treatment process by providing an electrochemical pre-
treatment process and equipment involving a selectively configured batch reactor with
selective anode material.
In order to enhance effectiveness of biodegradation, an electrochemical pretreatment
process is thus proposed which would reduce the toxicity level, along with associated
recalcitrance of the wastewater through reduction in concentration of normative
constituents or reduction in size of the compounds for easier biodegradation. In the EC
process, the coagulant is generated in situ by electrolytic oxidation of an appropriate
anode material. In this process, charged ionic species - metals or otherwise - are
removed from wastewater by allowing it to react with an ion having opposite charge, or
with floe of metallic hydroxides generated within the effluent.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to providing a system for
electrochemical pre treatment of coke oven effluent/wastewater and a process to
reduce unwanted toxicity level of said wastewater before biological treatment to
enhance effectiveness of biodegradation for treatment of high volume effluent
containing organic compounds generated from coke making process in steel plant.

A further object of the present invention is directed to a system and method for
electrochemical pre treatment process before biological treatment of waste water
generated from coke making process to completely eliminate the dissolved as well as
suspended pollutants involving batch reactor having selective anode material.
A still further object of the present invention is directed to a system and method for
electrochemical pre treatment process before biological treatment of waste water
generated from coke making process for elimination of most of the recalcitrant toxic
constituents either in dissolved ionic level or very low size range of suspension/colloidal
level including refractory components of long chain organic and organometallic
compounds, which cannot be removed by traditional processes of suspended solids
removal.
A still further object of the present invention is directed to a system and method for
electrochemical pre treatment process before biological treatment of waste water
generated from coke making process wherein coagulant can be generated in situ by
electrolytic oxidation of an appropriate anode material.
A still further object of the present invention is directed to a system and method for
electrochemical pre treatment process before biological treatment of waste water
generated from coke making process wherein ion from sacrificial anode is released in
presence of specific ions.
A still further object of the present invention is directed to a system and method for
electrochemical pre treatment process before biological treatment of waste water
generated from coke making process wherein coagulation, floe formation and
separation is achieved by removing charged ionic species - metals or otherwise - from
wastewater by allowing it to react with an ion having opposite charge, or with floe of
metallic hydroxides generated within the effluent.
A still further object of the present invention is directed to a system and method for
electrochemical pre treatment process before biological treatment of waste water
generated from coke making process wherein micro-processor based multi parameter
controller is performed for process optimization with PC interface to achieve desired
quality of treated water.

A still further object of the present invention is directed to a system and method for
electrochemical pre treatment process before biological treatment of waste water
generated from coke making process wherein removal of pollutants including dissolved
and colloidal particles are achieved by electrolysis of effluent samples reflected by
decrease in peak current, decrease in absorbance and also decrease in TDS, decrease
in COD and change in pH.
A still further object of the present invention is directed to a system and method for
electrochemical pre treatment process before biological treatment of waste water
generated from coke making process wherein higher percentage removal can be
attributed to the greater average solution contact time with the required working
electrode surface area.
A still further object of the present invention is directed to a system and method for
electrochemical pre treatment process before biological treatment of waste water
generated from coke making process wherein high decolourization is generally related
to considerable lowering of toxicity.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a system for
electrochemical treatment of coke oven effluent/wastewater, comprising
A reactor of desired volumetric capacity;
An anode comprising of sacrificing anode material and a cathode in said reactor;
a DC source to supply required electric potential for electrolysis of wastewater sample;
an Electro-coagulation cell comprising said anode and cathode alongwith preferably a
vibrator fitted in a cylindrical container with holes;

a microprocessor based controller interfaced with PC adapted to control the process
variables for optimum electrochemical process for desired removal of toxic pollutant
from said effluent.
Another aspect of the present invention is directed to said system wherein said reactor
is a cylindrical container made of Perspex of desired capacity preferably with 10 liters
capacity.
A further aspect of the present invention is directed to said system wherein said anode
materials(sacrificing) comprises aluminium sheet having a thickness of 2.5 to 3.5 mm
preferably of 3mm thickness, shape selected preferably rectangular size 7cm to 4 cm.
preferably about 25 sq.cm and a plate with similar geometric dimensions as a cathode.
Also in said system , said electrodes are separated by a small gap of the order of 1 mm
to 2 mm, preferably 1.5 mm.
A still further aspect of the present invention is directed to an electrochemical
pretreatment process for coke oven effluent before biological treatment using the
system as described above comprises the steps of carrying out the process involving
combination of coagulation and oxidation and wherein for the purposes of coagulation
the release of ions is controlled based on the target effluent treatment requirement.
Yet another aspect of the present invention is directed to said electrochemical
pretreatment process for coke oven effluent comprise:
providing effluent to be treated in a reactor which is circulated between the electrodes
obtained selectively of aluminium and selectively spaced apart in the range of 1 mm to
2 mm preferably about 1.5 mm;
supplying a selective voltage in the range of 8 to 12V between the electrodes for
electrolysis;
maintaining current density depending on charge loading;
ascertaining the optimal parameter values using micro-processor based multiparameter
controller unit with PC interface and software;

allowing required retention time for the said effluent to be treated in reactor for
desired electrochemical pre-treatment process for eliminating all pollutants including
the dissolved and colloidal toxic pollutants by coagulation/floc formation followed by
filtration, to achieve turbidity, COD, pH etc of treated wastewater at desired level.
A further aspect of the present invention is directed to said electrochemical
pretreatment process for coke oven effluent, wherein optimum values of process
variables comprise
effluent charge of 7.5 litres per batch;
Initial Conductivity: 400-450 uS;
pH : 7.8-8.2;
Temp : Ambient;
electrode gap of 1 to 2mm, preferably 1.5mm;
applied voltage between electrodes of 8 to 12 V, preferably 9V;
retention time of 25 to 30 minutes, preferably 30 minutes;
presence of external agent 5 gm NaCI for volume of effluent;
According to a further aspect of the present invention directed to said electrochemical
pretreatment process for coke oven effluent wherein fluid is introduced into said
reactor chamber, the treatment module is removed, cleaned and re-inserted, floe is
removed from top and treated clearer water is removed from lower portion of the
chamber to render the process sustainable.
A still further aspect of the present invention is directed to said electrochemical
pretreatment process for coke oven effluent, wherein driving force for treatment is the
electrical potential applied from a DC power source to said specially designed reactor
chamber.
According to a further aspect of the present invention is directed to an electrochemical
pretreatment process for coke oven effluent, comprising greater average solution
contact time with the working electrode surface area enables higher percentage
removal.
The objects and advantages of the present invention is described in greater details with
reference to the accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: is the photograph of the test setup showing the wastewater in the batch
reactor before the electrochemical treatment.
Figure 2: is the photograph of the test setup showing floe formation during the waste
water pre treatment(electrochemical) and clarity of water after treatment.
Figure 3: is the photograph of test setup showing the arrangement of the batch reactor
and the microprocessor based multi parameter controller for optimizing process
parameters.
Figure 4: is the schematic block diagram of the micro processor based multi parameter
controller with PC interface involving required software to implement control.
Figure 5: is the graph plot of resident time vs effect on turbidity(NTU) of treated waste
water.
Figure 6: is the graphical plot showing effect of the initial pH of waste water on % COD
removal.
Figure 7:is the graphical plot of effect of applied voltage on COD removal.
Figure 8: shows graphically the variation in pH with treatment time.
Figure 9: shows graphically the variation of treatment time with current density.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention relates to an electrochemical pre treatment process to enhance
effectiveness of subsequent biological treatment of waste water generated from coke
making process and apparatus to carry out such process involving batch reactor having
selective sacrificing anode, wherein removal of pollutants including dissolved and
suspended/colloidal particles including refractory components of long chain organic and
organometallic compounds are achieved by electrolysis of effluent samples.
In the electrochemical treatment process charged particles in colloidal suspension are
neutralized by mutual collision with counter ions and are agglomerated, followed by
sedimentation. The coagulant is added in the form of suitable chemical substances.
Coagulation is a phenomenon in which the charged particles in colloidal suspension are

neutralized by mutual collision with counter ions and are agglomerated, followed by
sedimentation. It is generally accepted that coagulation is brought about primarily by
the reduction of the net surface charge to a point where the colloidal particles,
previously stabilized by electrostatic repulsion, can approach closely enough for van
der waal's forces to hold them together and allow aggregation. The reduction of the
surface charge is a consequence of the decrease of the repulsive potential of the
electrical double layer by the presence of an electrolyte having opposite charge.
Coagulant can be generated in situ by electrolytic oxidation of an appropriate anode
material. In this process, charged ionic species - metals or otherwise - are removed
from wastewater by allowing it to react with an ion having opposite charge.
In the electrochemical process for pre-treating coke oven effluent according to the
present invention, the driving force for treatment is the electrical potential applied from
a DC power source to a specially designed reactor chamber and wherein coagulation
and oxidation is combined and unlike conventional coagulant requiring fixed dosage,
ions are released based on target treatment requirement.
Reference is first invited to the accompanying Figure 1 that illustrates the
experimental setup showing the wastewater in the batch reactor before the
electrochemical treatment.
Electrochemical effluent treatment was performed in a specially fabricated lab scale
experimental setup. Batch reactor with a capacity of 10 litres using aluminium plate of
3 mm thickness as anode material of recetangular size and shape and a plate with
similar geometric dimensions were used as a cathode. Ten litres of effluent was
circulated between the electrodes separated by a gap of 1.5 mm, while specific optimal
voltage of 8-9 V DC was supplied between the electrodes.
The apparatus includes a primary reactor chamber that houses removable anodes and
cathodes kept as a single unit. This unit is having cylindrical container made of Perspex
with capacity for sample of approximately 10 litres. The unit is provided with DC
vibrator/stirrer for mixing. Electro-coagulation cell and vibrator is fitted in a cylindrical
container with holes. The cell contains Anode material (Sacrificial) for release of ions as
per requirement of treatment of effluent.
Multi-variable experiments have been conducted in presence as well as absence of
external agents. During the electrolysis the samples were drawn at regular intervals
and parameters like turbidity, COD, pH etc, were determined.

A process has been developed where under optimal process conditions (Variables)
significant reduction of turbidity and COD has been achieved which is discussed in
results section : a combination of stirring and vibration has been resorted to for mixing
with minimal shear and to ascertain the optimal parameter values, micro-processor
based multiparameter controller unit with PC interface and software is utilized.
In the present electrochemical pre treatment process for treating coke oven effluent,
the driving force for treatment is the electrical potential applied from a DC power
source to said specially designed reactor chamber. In the said process, coagulation and
oxidation is combined and unlike conventional coagulant requiring fixed dosage, ions
are released from sacrificial anode based on target treatment requirement. In the pre-
treatment process before biological treatment, removal of turbidity leads to removal of
biological recalcitrance. All process parameter for pre-treatment of effluent has been
identified, established and optimized.
In the above process, fluid can be introduced into said rector chamber, the treatment
module can be removed, cleaned and re-inserted, floe is removed from top and treated
clean water is removed from lower portion of the chamber to render the process
sustainable.
According to an embodiment of the process of the invention, the optimal process
conditions used are as follows:
• Applied Voltage : 8-9V DC
• Retention time : 25 -30 min
• pH : 7.8-8.2
• Initial Conductivity: 400-450 uS
• Temp : Ambient
• Anode, cathode : Aluminium sheet
• External Agent : 5 gm NaCL ( for volume of effluent)
Accompanying, Figure 1 shows Wastewater sample in experimental reactor unit before
treatment; Figure 2 shows wastewater in experimental unit floe formation during
treatment(electrochemical) and clarity of water after treatment; Figure 3 shows an
overview of experimental setup; Figure 4 shows schematic line/block diagram of
process monitoring and control system involving micro-processor based
multiparameter controller with PC interface and software.

The observed result of the electrochemical pre treatment process applied on coke oven
wastewater sample following the above process steps, are as follows:
(i) turbidity is remarkably reduced through electrochemical techniques as illustrated
in accompanying Fig 5 .
(ii) Moderately good reduction is achieved in case of COD as observed in accompanying
Fig 6.
(iii) Electrochemical experiments have shown pH dependent and temperature
independent behaviour as illustrated in accompanying Fig 7 & Fig 8.
(iv) After electrolysis all the effluent samples showed decrease in peak current and
decrease in absorbance and also decrease in TDS, decrease in COD and change in pH
as illustrated in accompanying Fig 9.
(v) All the effluent samples after electrolysis leading to decolourisation presented
increase in pH.
(vi) The higher percentage removal can be attributed to the greater average solution
contact time with the working electrode surface area.
(vii) High decolourization is generally related to considerable lowering of toxicity. The
selected effluents intense colour could successfully be electrolysed for 90-95 percent
colour removal (almost zero absorbance level), 60 percent COD removal and 60
percent TDS removal in lab scale batch system in presence of electrolyte.
(viii) In the electrochemical method, ion from sacrificial anode is released in presence
of specific ions;
(ix) Floes formed by the process are similar to chemical floe, except that this floe
tends to be much larger, contains less bound water, is acid-resistant and more
stable, and therefore, can be separated faster by filtration. EC produces effluent
with less total dissolved solids (TDS) content as compared with chemical
treatments.
It is thus possible by way of the present invention to providing an apparatus and
process to carryout pre treatment of toxic effluent of coke oven plant to remove all
pollutants including the recalcitrant toxic components in dissolved or colloidal phase in
order to enhance the effectiveness of subsequent biological treatment process so that
the clean water can be safely recycled/disposed off.

We Claim:
1. A system for electrochemical treatment of coke oven effluent/wastewater,
comprising
A reactor of desired volumetric capacity;
An anode comprising of sacrificing anode material and a cathode in said reactor;
a DC source to supply required electric potential for electrolysis of wastewater sample;
an Electro-coagulation cell comprising said anode and cathode alongwith preferably a
vibrator fitted in a cylindrical container with holes;
a microprocessor based controller interfaced with PC adapted to control the process
variables for optimum electrochemical process for desired removal of toxic pollutant
from said effluent.
2. A system as claimed in claim 1 wherein said reactor is a cylindrical container made
of Perspex of desired capacity preferably with 10 liters capacity.
3. A system as claimed in anyone of claims 1 or 2 wherein said anode
materials(sacrificing) comprises aluminium sheet having a thickness of 2.5 to 3.5 mm
preferably of 3mm thickness, shape selected from rectangular preferably and size 20
sq cm to 30 sq cm preferably about 25 sq cm and a plate with similar geometric
dimensions as a cathode.
4. A system as claimed in anyone of claims 1 to 3 wherein electrodes are separated by
a small gap of the order of 1 to 2 mm, preferably 1.5 mm.
5. An electrochemical pretreatment process for coke oven effluent before biological
treatment using the system as claimed in anyone of claims 1 to 4 comprising the steps
of carrying out the process involving combination of coagulation and oxidation and
wherein for the purposes of coagulation the release of ions is controlled based on the
target effluent treatment requirement.

6. An electrochemical pretreatment process for coke oven effluent as claimed in claim
5 comprising :
providing effluent to be treated in a reactor which is circulated between the electrodes
obtained selectively of aluminium and selectively spaced apart in the range of 1 to 2
mm preferably about 1.5 mm;
supplying a selective voltage in the range of 8V to 12V between the electrodes for
electrolysis;
maintaining current density depending on charge loading;
ascertaining the optimal parameter values using micro-processor based multiparameter
controller unit with PC interface and software;
allowing required retention time for the said effluent to be treated in reactor for
desired electrochemical treatment process for eliminating all pollutants including the
dissolved and colloidal toxic pollutants by coagulation/floc formation followed by
filtration, to achieve turbidity, COD, pH etc of treated wastewater at desired level.
7. An electrochemical pretreatment process for coke oven effluent as claimed in claim
6, wherein optimum values of process variables comprising
effluent charge of 7.5 litres per batch;
Initial Conductivity: 400-450 uS;
pH : 7.8-8.2;
Temp : Ambient;
electrode gap of 1 to 2 mm, preferably 1.5mm;
applied voltage between electrodes of 8 to 12V, preferably 9V;
retention time of 25 to 30 minutes, preferably 30 minutes;
presence of external agent 5 gm NaCI for volume of effluent;
8. An electrochemical pretreatment process for coke oven effluent as claimed in
anyone of claims 5 to 7 , wherein fluid is introduced into said reactor chamber, the
treatment module is removed, cleaned and re-inserted, floe is removed from top and
treated clearer water is removed from lower portion of the chamber to render the
process sustainable.

9. An electrochemical pretreatment process for coke oven effluent as claimed in
anyone of claims 5 to 8, wherein driving force for treatment is the electrical potential
applied from a DC power source to said specially designed reactor chamber.
10. An electrochemical pretreatment process for coke oven effluent as claimed in
anyone of claims 5 to 9, comprising greater average solution contact time with the
working electrode surface area enables higher percentage removal.

ABSTRACT

A system and a method for treatment of coke oven effluent/waste water are disclosed.
More particularly, the present invention is directed to a system involving reactor with
special electrodes with selective spacing and provided with stirrer and vibrator for
carrying out electrochemical process for pre treatment of coke oven plant effluent
before biological treatment involving combination of coagulation and oxidation and
wherein for the purposes of coagulation the release of ions is controlled based on the
target effluent treatment requirement, to enhance the effectiveness of biological
treatment process. The electrochemical pretreatment process according to the present
invention favors removing recalcitrant toxic constituents including long chain organic
and organometallic compounds from waste water by coagulation and sedimentation.
Importantly, flocs formed by the process are similar to chemical floc, except that this
floc tends to be much larger, contains less bound water, is acid-resistant and more
stable, and therefore, can be separated faster by filtration.