CA1156966A - Electro-chemical treatment of lquid effluent - Google Patents
Electro-chemical treatment of lquid effluentInfo
- Publication number
- CA1156966A CA1156966A CA000245193A CA245193A CA1156966A CA 1156966 A CA1156966 A CA 1156966A CA 000245193 A CA000245193 A CA 000245193A CA 245193 A CA245193 A CA 245193A CA 1156966 A CA1156966 A CA 1156966A
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- CA
- Canada
- Prior art keywords
- anode
- waste water
- water
- cathode
- stream
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/46104—Devices therefor; Their operating or servicing
- C02F1/46109—Electrodes
- C02F1/46114—Electrodes in particulate form or with conductive and/or non conductive particles between them
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Water Treatment By Electricity Or Magnetism (AREA)
- Paper (AREA)
- Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The invention provides a process of treating a stream of waste water of a type such as that emanating from pulp and paper manufacturing processes. The inventive process includes the steps of causing the waste water to flow mainly over and through an anode as well as over a cathode. The anode comprises fibres retained by a diaphragm and an electrical potential difference is created between the electrodes for anodic action on the waste water.
The invention provides a process of treating a stream of waste water of a type such as that emanating from pulp and paper manufacturing processes. The inventive process includes the steps of causing the waste water to flow mainly over and through an anode as well as over a cathode. The anode comprises fibres retained by a diaphragm and an electrical potential difference is created between the electrodes for anodic action on the waste water.
Description
6~
This invention relates to a process and appara-tus particularly for use in treating a s-tream of waste wa-ter of the type resulting from pulp and paper manufacturing processes -to reduce the oxygen demand of the waste water and to improve the colouration of this water so that the treated wa-ter will be more environmentally acceptable.
Waste water from pulp and paper processes includes many organic substances which are too numerous and too complex to treat individually. Quantitative tests have been devised for comparing one such waste water with another waste water, and also for comparing waste water before treatment with the resulting water after treatment. One such test produces a value known as the Chemical Oxygen Demand (C.O.D.) and is a measure of the quantity of oxidizable components present in the waste water. Because the carbon and hydrogen in organic matter are oxidized by chemical oxidants, the oxygen concerned is a measure only of the chemically oxidizable compounds.
?.0 Another test produces a value known as the Biochemical Oxygen Demand (B.O.D.). This value is an expression of the quantity,of dissolved oxygen required during stabilization of the decomposable organic matter by aerobic biochemical action. Because C.O.D. does not diEferentiate stable from uns-table organic matter, C.O.D~
will not correlate with B.O.D.
Other tests include colour -tests and ~oxicity tests. A typical colour test involves measuring the degree of dilution which must be used to cause waste ,`i~
~ 2 -~s~
water to have a similar light transmission property to that of a s-tandard liquid.
A commonly used toxicity test is done using fish which are placed in a given volume of waste water to determine how many fish survive after a given period of time in the waste water.
Tests such as those mentioned are described in aetail in publications such as ~'Standard Methods for the Examination of Water and Waste Water" published jointly by The American Public Health ~ssociation, The American Water Working Association and The Wa~er Pollution Control Federation.
;
A typical waste water having a high organic content is that from pulp and paper manufacturing processes. Such ~ waste water includes many polluting materials which are ; derived either from the wood used as a raw material, or from materials introduced during the pulp and paper manu-facturing process.
The wood based mate~ials include tree bark, wood debris~ lignins and their decomposition products, and the other materials include starches, resins, gums and proteins.
The complexity o~ the problem o~ improving the quality o~ waste water associated with pulp and paper processes is illustrated by reviewing some o-E the ma-terials which have been identified in such waste water. For instance, toxicity is believed to be due to resin acids, monochloro and dichloro dihydro abiet;c acids, trichloro and tetrachloro guaiacol, 9, 10-dichloro, and 9, 10-epoxy-stearic acid.
~5696~i In addition, unsaturated fatty acids such as palmitoleie, oleic, linoleic and linolenic sometimes contribute to toxicity in waste water~ Other toxic subs-tances sometimes present are diterpene alcohols, principally pimarol and isopimerol and corresponding aldehydes as well as the resin acids, abietic, dehydro abietic, isopimaric, palustric and pimaric.
The colour of the waste water from pulp and paper manufacturing processes is usually due mainly to lignin alone or to lignin in combination wi-th the decomposition products of lignin. Some of the chromophorie substances such as the dihydroxystilbenes, the quinonemethides and the stilbenequinones also eontribute to colouration. All of these substances may be oxidized to form colourless degradation products. Although the various standards of the water regulating organizations are less stringent in relation to eolour than they are in relation to toxieity, a clean-looking waste water is obviously desirable.
Various processes for treating waste water from ~ pulp and paper manufacturing processes have been used, but biochemieal and physico-chemical processes are most comrnon. O~ these; the biochemical methods are used rnost frequen~ly.
Although biochemical methods provide satisfactory decreases in B.O.D. levels, -they provide uncertain detoxification results, no reduction in colour and only small decreases in C.O.D. values. Moreover, biochemical systems are less effective in winter temperatures, require large lagoon areas, and require at least several days to effect any significant improvement in the quality of the waste water. Because of this, a number of physico-chemical treatments have been investigated such as lime treatment, alum coagulation, activated carbon absorption, absorption with X.A.D. resins, ion-exc;hange, ozonation, reverse osmosis and flocculation.
Generally, the physico-chemical processes provide a satisfactory reduction of colour, C.O.D. levels and to a limited extent toxicity, but a satisfactory decrease in B.O.D. levels is not generall~ achleved. Also, these methods tend to be too expensive to be cor~mercially viable.
Attempts have also been made to use electro-chemical methods involving consumable electrodes of a ;~ material which goes into solution and induces flocculation in the waste water.
The present invention is directed to the problem of providing a process and an apparatus which will be useful in treating waste water of a type such as that emanating pulp and paper manufacturing processes to make the B.O.D., C.O.Dc, toxicity, and colour values more acceptable and to thereby,prod~ce a resulting water which is more environmentally acceptable.
In one of its aspects the invention provides an eleckrochemical process for treatin~ a stream of was-te watex as it emanates from pulp and paper manufacturin~
plants. rrhe waste water has unacceptable biochqmical and chemical oxygen dernands, an unacceptable -toxicity level, and an unacceptable colouration. The process comprises the steps of flowing the waste water through an electro-. ~ . .
6Gi chemical reactor which has a fibrous anode and a cathode. The fibrous anode has a high surface area to volume ratio and a relatively large oxygen overpotential. Electrolytic continuity is provided between the anode and the cathode and the anode is at a generally constant electrical potential different from that of the cathode.
As a result at least some of the compounds present in the stream are electrochemically oxidized at the anode and gases are produced at the anode. These gases produce turbulence and movement in the hydrodynamic boundary layers so that these layers are broken down to further increase the mass transfer rates at the anode. The quality of the waste water is thereby improved for the purpose of discharging the waste water stream into natural water sources.
; The invention will be better understood with reference to the following description and drawing (Fig. 1) which is a diagrammatic sectional side view of a preferred embodiment of apparatus according to the invention.
As seen in Fig. 1, a reactor 10 is provided having a housing 12, inlet 14 and outlet 1~. The reactor includes an anode 18 of carbon fibres retained in a bed by a diaphragm 20 made from a nylon mesh, a plate-like cathode %2 is provided adjacent the nylon mesh, and the anode and cathode are coupled to an electrical supply 23 to provide an electrical potential di~erence between the ele~trodes.
The reactor housing 12 includes a trough 24 adjacent the inlet 14 to absorb the flow energy of the waste water so that there is a gentle flow over the work-.
~ r ,.
~5t;g66 ing electrode. Similarly, a trough 26 is provided adjacent the outlet 16 to collect the resulting treated water thereby ensuring a more uniform flow over the anode prior to discharge through outlet 16. f The flow of water through the reactor will beessentially over and through -the anode 18. Some of the water flowing above the anode will contact the cathode 22 and will be affected by the process less than water which passes continuously over and through the anode. It is therefore desirabIe in this design of reactor,to arrange for a maximum flow ,to take place over and through the anode ' 'rather than over the cathode.
The diaphragm 20 should have a mesh which is as large as possible without permitting the carbon fibres 'of the anode to touch the cathode.
Because of the large overpotential of oxygen at the carbon fibre anode, it is possible to electro-oxidize and thus break up a large proportion of the organic compounds before the production of oxygen becomes predominant. Also if the waste water con~ains sufficient sodium chloride, chlorine and hypochlorite will be formed at the anode, a,nd these substances further oxidize and break up the polluting substances in the waste water~ This effect can be enhanced where necessary by the addition of sodium chloride, calcium chloride, po-tassium chloride or brine, to the waste water~ Also, oxygen is produced at the anode and this further oxidizes the pollu~ing substances.
It has been found that the reactor can be used to treat waste watér of the type emanating from pulp .,.
~S6966 and paper manufacturing processes using a very short residence time in the order of minutes. This is because of the high mass transfer rates which are achieved to some extent because of the production of gases (for example chlorine and oxygen at the anode~. These gases create turbulence or movement in the hydrodynamic boundary layers resulting in breakdown of the layers.
The carbon fibre anode is preferably of relatively long carbon fibres in a bed, although shorter lengths can be used. Such short lengths will require a diaphragm having a close mesh to prevent these fibres from passing through the diaphragm. Typical carbon fibres are sold under the Trade Mark GRAFIL by Courtaulds Limited of England. A carbon fibre anode was used in the following examples.
EXAMPLE I
Waste water from a pulp and paper mill was col-lected and found to have 9,000 colour units and a C.O.D.
of 1,800 mg/litre.
The waste water was passed through a reactor consisting of a carbon fi~re.anode, a nylon diaphragr with 10 micron mesh size, and a steel cathode. About 99 percent of the solution passed through and over the anode and only about 1 percent passed over the cathode.
A reactor voltage of 3.5V was used with a current of 1 amp, which leads to an electrochemical poténtial o~
1.7V being set up between the carbon fibre anode and a saturated calomel electrode (which was used as a reference electradé to measure the electrode/solution potential).
~S6~G
After a single pass through the reactor the colour units dropped by 60 percent to become 4,000 colour units and the C.O.D. level dropped to 1,000 mg/litre.
EXAMPLE I I
Example I was repeated except that the waste water was passed through the reactor five times. It was found that the colour was lowered to 1,500 colour units.
In some instances it may be preferable to change the form of the reactor while continuing to cause a major portion of the flow to pass through and over the anocle.
Such changes are within the scope of the invention.
A modiflcation to the process is to pass the waste water through a reactor such as that described and then to pass the resulting water through a second reactor after first mixing some sodium chloride (or any other suitable chloride) into the resulting water. The treated water leaving the second reactor has an enhanced quality not found by using a single pass through a reactor after adding a chloride. , , ' ' ., ~
6~i EXAMPLE III
-The same waste water as that used in Example I
was used. Howe~er, some sodium chloride was added to the solution such that the solution had 2 percent sodium chloride. A reactor voltage of 3.5V could now support a current of 2.5 amps owing to the decrease in solution resistance. Here a single pass leads to a colour reduction from 9,000 units to 1,000 units. This is a 90 percent reduction, while C.O.D. dropped from 1,800 mg/litre to 500 mg/litre, a drop of 72 percent.
EXAMPLE IV
A different pulp and paper mill waste water was taken which had initial colour of 12,500 units, a C.O.D.
level of 2,125 mg/litre and a B.O.D. of 690 mg/litre.
The waste water toxicity was also determined. At 60 percent concentration, the initial toxicity resulted in 100 percent mortality of fish in 22 hours.
A first pass of the waste water was made at 1 amp and 3.5V and the colour decreased to 6,000 units. Then some sodium chloride was added to produce a 2 percent solu-tion and multiple passes were made at 3.5V and 2.5 amps.
The colour was found to have decreased from 12,500 units to 1,000 units, a reduction of 92 percent. The C.O.D.
dropped from 2,125 mg/litre to 1,336 mg/litre, a decreas~
of 48 percent. The B~O.D. dropped from 690 mg/litre to 365 mg/litre, a decrease of 48 percent and toxicity on a 60 pexcent concentration decreased from 100 percent mortal-ity in 22 hours to 0 percent mortality after 96 hours.
G~
' ~56~616 S [~PPLEMENTARY D I SCLOSURE
In some instances it may be preferable to change the form of the reactor while con-tinuing to cause a major portion of the flow to pass through and over the anode. Such changes are within the scope of the invention and an example of such a modification is shown in Fig. 2 which is a diagrammatic sectional side view. In this embodiment an anode 28 is contained in a housin~
30 and separated from a chamber 32 containing a ' metal cathode 34 by a diaphragm 36. In this instance the diaphragm is of NAFION which is a proprietary product of Dupont of Canada Limited. The electrodes are connected to an electrical power supply 38 and respective inlets 40, 42 and outlets 44, 46 are providea for the anode and cathode.
The Fig. 2 arrangement ensures complete separation of waste water from the cathode 34 so that all of the waste water passing between inlet 40 and outlet 44 must pass through housing 30 filled with anode 28. Electro-lytic continuity is provided by circulating water ;~which is preferably alkaline) through chamber 32. As a result, while the waste water is treated at the anode 28, hydrogen is formed as a by-product and is collected downstream of outlet ~6.
Although specific diaphragms have been described with reference to the illustrated embodiments it is within the scope o~ the invention to change these diaphragms for other equivalent diaphragms. Many diaphragms are available and it is expected skillin the art to select a suitable alternative where desired.
., ~ .
This invention relates to a process and appara-tus particularly for use in treating a s-tream of waste wa-ter of the type resulting from pulp and paper manufacturing processes -to reduce the oxygen demand of the waste water and to improve the colouration of this water so that the treated wa-ter will be more environmentally acceptable.
Waste water from pulp and paper processes includes many organic substances which are too numerous and too complex to treat individually. Quantitative tests have been devised for comparing one such waste water with another waste water, and also for comparing waste water before treatment with the resulting water after treatment. One such test produces a value known as the Chemical Oxygen Demand (C.O.D.) and is a measure of the quantity of oxidizable components present in the waste water. Because the carbon and hydrogen in organic matter are oxidized by chemical oxidants, the oxygen concerned is a measure only of the chemically oxidizable compounds.
?.0 Another test produces a value known as the Biochemical Oxygen Demand (B.O.D.). This value is an expression of the quantity,of dissolved oxygen required during stabilization of the decomposable organic matter by aerobic biochemical action. Because C.O.D. does not diEferentiate stable from uns-table organic matter, C.O.D~
will not correlate with B.O.D.
Other tests include colour -tests and ~oxicity tests. A typical colour test involves measuring the degree of dilution which must be used to cause waste ,`i~
~ 2 -~s~
water to have a similar light transmission property to that of a s-tandard liquid.
A commonly used toxicity test is done using fish which are placed in a given volume of waste water to determine how many fish survive after a given period of time in the waste water.
Tests such as those mentioned are described in aetail in publications such as ~'Standard Methods for the Examination of Water and Waste Water" published jointly by The American Public Health ~ssociation, The American Water Working Association and The Wa~er Pollution Control Federation.
;
A typical waste water having a high organic content is that from pulp and paper manufacturing processes. Such ~ waste water includes many polluting materials which are ; derived either from the wood used as a raw material, or from materials introduced during the pulp and paper manu-facturing process.
The wood based mate~ials include tree bark, wood debris~ lignins and their decomposition products, and the other materials include starches, resins, gums and proteins.
The complexity o~ the problem o~ improving the quality o~ waste water associated with pulp and paper processes is illustrated by reviewing some o-E the ma-terials which have been identified in such waste water. For instance, toxicity is believed to be due to resin acids, monochloro and dichloro dihydro abiet;c acids, trichloro and tetrachloro guaiacol, 9, 10-dichloro, and 9, 10-epoxy-stearic acid.
~5696~i In addition, unsaturated fatty acids such as palmitoleie, oleic, linoleic and linolenic sometimes contribute to toxicity in waste water~ Other toxic subs-tances sometimes present are diterpene alcohols, principally pimarol and isopimerol and corresponding aldehydes as well as the resin acids, abietic, dehydro abietic, isopimaric, palustric and pimaric.
The colour of the waste water from pulp and paper manufacturing processes is usually due mainly to lignin alone or to lignin in combination wi-th the decomposition products of lignin. Some of the chromophorie substances such as the dihydroxystilbenes, the quinonemethides and the stilbenequinones also eontribute to colouration. All of these substances may be oxidized to form colourless degradation products. Although the various standards of the water regulating organizations are less stringent in relation to eolour than they are in relation to toxieity, a clean-looking waste water is obviously desirable.
Various processes for treating waste water from ~ pulp and paper manufacturing processes have been used, but biochemieal and physico-chemical processes are most comrnon. O~ these; the biochemical methods are used rnost frequen~ly.
Although biochemical methods provide satisfactory decreases in B.O.D. levels, -they provide uncertain detoxification results, no reduction in colour and only small decreases in C.O.D. values. Moreover, biochemical systems are less effective in winter temperatures, require large lagoon areas, and require at least several days to effect any significant improvement in the quality of the waste water. Because of this, a number of physico-chemical treatments have been investigated such as lime treatment, alum coagulation, activated carbon absorption, absorption with X.A.D. resins, ion-exc;hange, ozonation, reverse osmosis and flocculation.
Generally, the physico-chemical processes provide a satisfactory reduction of colour, C.O.D. levels and to a limited extent toxicity, but a satisfactory decrease in B.O.D. levels is not generall~ achleved. Also, these methods tend to be too expensive to be cor~mercially viable.
Attempts have also been made to use electro-chemical methods involving consumable electrodes of a ;~ material which goes into solution and induces flocculation in the waste water.
The present invention is directed to the problem of providing a process and an apparatus which will be useful in treating waste water of a type such as that emanating pulp and paper manufacturing processes to make the B.O.D., C.O.Dc, toxicity, and colour values more acceptable and to thereby,prod~ce a resulting water which is more environmentally acceptable.
In one of its aspects the invention provides an eleckrochemical process for treatin~ a stream of was-te watex as it emanates from pulp and paper manufacturin~
plants. rrhe waste water has unacceptable biochqmical and chemical oxygen dernands, an unacceptable -toxicity level, and an unacceptable colouration. The process comprises the steps of flowing the waste water through an electro-. ~ . .
6Gi chemical reactor which has a fibrous anode and a cathode. The fibrous anode has a high surface area to volume ratio and a relatively large oxygen overpotential. Electrolytic continuity is provided between the anode and the cathode and the anode is at a generally constant electrical potential different from that of the cathode.
As a result at least some of the compounds present in the stream are electrochemically oxidized at the anode and gases are produced at the anode. These gases produce turbulence and movement in the hydrodynamic boundary layers so that these layers are broken down to further increase the mass transfer rates at the anode. The quality of the waste water is thereby improved for the purpose of discharging the waste water stream into natural water sources.
; The invention will be better understood with reference to the following description and drawing (Fig. 1) which is a diagrammatic sectional side view of a preferred embodiment of apparatus according to the invention.
As seen in Fig. 1, a reactor 10 is provided having a housing 12, inlet 14 and outlet 1~. The reactor includes an anode 18 of carbon fibres retained in a bed by a diaphragm 20 made from a nylon mesh, a plate-like cathode %2 is provided adjacent the nylon mesh, and the anode and cathode are coupled to an electrical supply 23 to provide an electrical potential di~erence between the ele~trodes.
The reactor housing 12 includes a trough 24 adjacent the inlet 14 to absorb the flow energy of the waste water so that there is a gentle flow over the work-.
~ r ,.
~5t;g66 ing electrode. Similarly, a trough 26 is provided adjacent the outlet 16 to collect the resulting treated water thereby ensuring a more uniform flow over the anode prior to discharge through outlet 16. f The flow of water through the reactor will beessentially over and through -the anode 18. Some of the water flowing above the anode will contact the cathode 22 and will be affected by the process less than water which passes continuously over and through the anode. It is therefore desirabIe in this design of reactor,to arrange for a maximum flow ,to take place over and through the anode ' 'rather than over the cathode.
The diaphragm 20 should have a mesh which is as large as possible without permitting the carbon fibres 'of the anode to touch the cathode.
Because of the large overpotential of oxygen at the carbon fibre anode, it is possible to electro-oxidize and thus break up a large proportion of the organic compounds before the production of oxygen becomes predominant. Also if the waste water con~ains sufficient sodium chloride, chlorine and hypochlorite will be formed at the anode, a,nd these substances further oxidize and break up the polluting substances in the waste water~ This effect can be enhanced where necessary by the addition of sodium chloride, calcium chloride, po-tassium chloride or brine, to the waste water~ Also, oxygen is produced at the anode and this further oxidizes the pollu~ing substances.
It has been found that the reactor can be used to treat waste watér of the type emanating from pulp .,.
~S6966 and paper manufacturing processes using a very short residence time in the order of minutes. This is because of the high mass transfer rates which are achieved to some extent because of the production of gases (for example chlorine and oxygen at the anode~. These gases create turbulence or movement in the hydrodynamic boundary layers resulting in breakdown of the layers.
The carbon fibre anode is preferably of relatively long carbon fibres in a bed, although shorter lengths can be used. Such short lengths will require a diaphragm having a close mesh to prevent these fibres from passing through the diaphragm. Typical carbon fibres are sold under the Trade Mark GRAFIL by Courtaulds Limited of England. A carbon fibre anode was used in the following examples.
EXAMPLE I
Waste water from a pulp and paper mill was col-lected and found to have 9,000 colour units and a C.O.D.
of 1,800 mg/litre.
The waste water was passed through a reactor consisting of a carbon fi~re.anode, a nylon diaphragr with 10 micron mesh size, and a steel cathode. About 99 percent of the solution passed through and over the anode and only about 1 percent passed over the cathode.
A reactor voltage of 3.5V was used with a current of 1 amp, which leads to an electrochemical poténtial o~
1.7V being set up between the carbon fibre anode and a saturated calomel electrode (which was used as a reference electradé to measure the electrode/solution potential).
~S6~G
After a single pass through the reactor the colour units dropped by 60 percent to become 4,000 colour units and the C.O.D. level dropped to 1,000 mg/litre.
EXAMPLE I I
Example I was repeated except that the waste water was passed through the reactor five times. It was found that the colour was lowered to 1,500 colour units.
In some instances it may be preferable to change the form of the reactor while continuing to cause a major portion of the flow to pass through and over the anocle.
Such changes are within the scope of the invention.
A modiflcation to the process is to pass the waste water through a reactor such as that described and then to pass the resulting water through a second reactor after first mixing some sodium chloride (or any other suitable chloride) into the resulting water. The treated water leaving the second reactor has an enhanced quality not found by using a single pass through a reactor after adding a chloride. , , ' ' ., ~
6~i EXAMPLE III
-The same waste water as that used in Example I
was used. Howe~er, some sodium chloride was added to the solution such that the solution had 2 percent sodium chloride. A reactor voltage of 3.5V could now support a current of 2.5 amps owing to the decrease in solution resistance. Here a single pass leads to a colour reduction from 9,000 units to 1,000 units. This is a 90 percent reduction, while C.O.D. dropped from 1,800 mg/litre to 500 mg/litre, a drop of 72 percent.
EXAMPLE IV
A different pulp and paper mill waste water was taken which had initial colour of 12,500 units, a C.O.D.
level of 2,125 mg/litre and a B.O.D. of 690 mg/litre.
The waste water toxicity was also determined. At 60 percent concentration, the initial toxicity resulted in 100 percent mortality of fish in 22 hours.
A first pass of the waste water was made at 1 amp and 3.5V and the colour decreased to 6,000 units. Then some sodium chloride was added to produce a 2 percent solu-tion and multiple passes were made at 3.5V and 2.5 amps.
The colour was found to have decreased from 12,500 units to 1,000 units, a reduction of 92 percent. The C.O.D.
dropped from 2,125 mg/litre to 1,336 mg/litre, a decreas~
of 48 percent. The B~O.D. dropped from 690 mg/litre to 365 mg/litre, a decrease of 48 percent and toxicity on a 60 pexcent concentration decreased from 100 percent mortal-ity in 22 hours to 0 percent mortality after 96 hours.
G~
' ~56~616 S [~PPLEMENTARY D I SCLOSURE
In some instances it may be preferable to change the form of the reactor while con-tinuing to cause a major portion of the flow to pass through and over the anode. Such changes are within the scope of the invention and an example of such a modification is shown in Fig. 2 which is a diagrammatic sectional side view. In this embodiment an anode 28 is contained in a housin~
30 and separated from a chamber 32 containing a ' metal cathode 34 by a diaphragm 36. In this instance the diaphragm is of NAFION which is a proprietary product of Dupont of Canada Limited. The electrodes are connected to an electrical power supply 38 and respective inlets 40, 42 and outlets 44, 46 are providea for the anode and cathode.
The Fig. 2 arrangement ensures complete separation of waste water from the cathode 34 so that all of the waste water passing between inlet 40 and outlet 44 must pass through housing 30 filled with anode 28. Electro-lytic continuity is provided by circulating water ;~which is preferably alkaline) through chamber 32. As a result, while the waste water is treated at the anode 28, hydrogen is formed as a by-product and is collected downstream of outlet ~6.
Although specific diaphragms have been described with reference to the illustrated embodiments it is within the scope o~ the invention to change these diaphragms for other equivalent diaphragms. Many diaphragms are available and it is expected skillin the art to select a suitable alternative where desired.
., ~ .
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electrochemical process for treating a stream of waste water as it emanates from pulp and paper manufacturing plants, the waste water having unacceptable biochemical and chemical oxygen demands, an unacceptable toxicity level, and an unacceptable colouration, the process comprising the steps:
flowing the waste water through an electro-chemical reactor having a fibrous anode with a high surface area to volume ratio and a relatively large oxygen over potential so that the waste water flows over and through the fibrous anode, and a cathode;
providing electrolytic continuity between the anode and the cathode; and contemporaneously maintaining the anode at a generally constant electrical potential different from that of the cathode so that at least some of the organic compounds present in the stream are being electrochemically oxidized at the anode while gases are also being produced at the anode, these gases creating turbulence and movement in the hydrodynamic boundary layers whereby the layers are broken down to further increase the mass transfer rates at the anode so that the quality of the waste water is improved for the purpose of discharging the waste water stream into natural water sources.
flowing the waste water through an electro-chemical reactor having a fibrous anode with a high surface area to volume ratio and a relatively large oxygen over potential so that the waste water flows over and through the fibrous anode, and a cathode;
providing electrolytic continuity between the anode and the cathode; and contemporaneously maintaining the anode at a generally constant electrical potential different from that of the cathode so that at least some of the organic compounds present in the stream are being electrochemically oxidized at the anode while gases are also being produced at the anode, these gases creating turbulence and movement in the hydrodynamic boundary layers whereby the layers are broken down to further increase the mass transfer rates at the anode so that the quality of the waste water is improved for the purpose of discharging the waste water stream into natural water sources.
2. An electrochemical process for treating a stream of waste water as it emanates from pulp and paper manufacturing plants, the waste water having unacceptable biochemical and chemical oxygen demands, an unacceptable toxicity level, and an unacceptable colouration, the process comprising the steps:
flowing the waste water through an electro-chemical reactor having an anode of carbon fibres with a high surface area to volume ratio and a relatively large oxygen overpotential so that the waste water flows over and through the fibrous anode, and a cathode;
providing electrolytic continuity between the anode and the cathode; and contemporaneously maintaining the anode at a generally constant electrical potential different from that of the cathode so that at least some of the organic compounds present in the stream are being electrochemically oxidized at the anode while gases are also being produced at the anode, these gases creating turbulence and movement in the hydrodynamic boundary layers whereby the layers are broken down to further increase the mass transfer rates at the anode so that the quality of waste water is improved for the purpose of discharging the waste water stream into natural water sources.
flowing the waste water through an electro-chemical reactor having an anode of carbon fibres with a high surface area to volume ratio and a relatively large oxygen overpotential so that the waste water flows over and through the fibrous anode, and a cathode;
providing electrolytic continuity between the anode and the cathode; and contemporaneously maintaining the anode at a generally constant electrical potential different from that of the cathode so that at least some of the organic compounds present in the stream are being electrochemically oxidized at the anode while gases are also being produced at the anode, these gases creating turbulence and movement in the hydrodynamic boundary layers whereby the layers are broken down to further increase the mass transfer rates at the anode so that the quality of waste water is improved for the purpose of discharging the waste water stream into natural water sources.
3. A process as claimed in claims 1 or 2 in which the waste water has a significant chloride content resulting in the formation of chlorine and hypochlorite.
4. A process as claimed in claims 1 or 2 and further comprising a preliminary step of adding a chloride to the waste water to cause the formation of chlorine.
5. A process as claimed in claims 1 or 2 in which the waste water is made to flow over and through the anode several times before being discharged as treated water.
6. A process as claimed in claims 1 or 2 and further comprising the steps of adding a chloride to the water resulting from the process claimed in claims 1 or 2 to thereby create a new water, and subjecting the new water to the process claimed in claims 1 or 2 to further improve the quality of the water.
7. A process as claimed in claims 1 or 2 and further comprising the steps of adding sodium chloride to the water resulting from the process claimed in claims 1 or 2 to thereby create a new water, and subjecting the new water to the process claimed in claims 1 or 2 to further improve the quality of the water.
CLAIM SUPPORTED BY SUPPLEMENTARY DISCLOSURE
CLAIM SUPPORTED BY SUPPLEMENTARY DISCLOSURE
8. A process as claimed in claims 1 or 2 and further comprising the step of collecting hydrogen gas from the water after the water leaves the electrochemical reactor, the hydrogen being present in the water as a by-product of the process.
9. An electrochemical reactor for use in treating a stream of waste water emanating from pulp and paper manufacturing processes to provide a resulting water which is environmentally more acceptable, the apparatus comprising: a housing defining at least one flow path for the waste water; a fibrous anode having a high surface area to volume ratio and a relatively large oxygen over-potential, the anode being contained in the housing and positioned for flow of waste water over and through the fibrous anode; a cathode contained in the housing and spaced from the anode; and means adapted to guide the waste water through the anode to provide for maintaining electrolytic continuity between the anode and the cathode, the guide means including a substantially impermeable diaphragm restraining the fibres to prevent movement towards the anode, and means adapted to cause an electrical potential difference between the anode and the cathode.
Priority Applications (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000245193A CA1156966A (en) | 1976-02-06 | 1976-02-06 | Electro-chemical treatment of lquid effluent |
| GB4736/77A GB1570122A (en) | 1976-02-06 | 1977-02-04 | Eletro-chemical treatment of liquid effluent |
| SE7701252A SE442987B (en) | 1976-02-06 | 1977-02-04 | SET FOR ELECTROOXIDATION OF ORGANIC MATERIAL |
| FR7703322A FR2340279A1 (en) | 1976-02-06 | 1977-02-07 | RESIDUAL WATER TREATMENT METHOD AND APPARATUS |
| JP52012370A JPS6034439B2 (en) | 1976-02-06 | 1977-02-07 | Industrial wastewater treatment method and equipment |
| DE19772705007 DE2705007A1 (en) | 1976-02-06 | 1977-02-07 | ELECTROCHEMICAL PROCESS FOR WASTE WATER |
| NO770393A NO770393L (en) | 1976-02-06 | 1977-02-07 | ELECTRO-CHEMICAL TREATMENT OF LIQUID SEWER LIQUID. |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000245193A CA1156966A (en) | 1976-02-06 | 1976-02-06 | Electro-chemical treatment of lquid effluent |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1156966A true CA1156966A (en) | 1983-11-15 |
Family
ID=4105173
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000245193A Expired CA1156966A (en) | 1976-02-06 | 1976-02-06 | Electro-chemical treatment of lquid effluent |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS6034439B2 (en) |
| CA (1) | CA1156966A (en) |
| DE (1) | DE2705007A1 (en) |
| FR (1) | FR2340279A1 (en) |
| GB (1) | GB1570122A (en) |
| NO (1) | NO770393L (en) |
| SE (1) | SE442987B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS55500639A (en) * | 1978-09-12 | 1980-09-11 | ||
| FR2470093A1 (en) * | 1979-11-26 | 1981-05-29 | Anvar | Electrochemical disinfection of water - by anodic oxidn. of bromide using porous anode |
| NL8006412A (en) * | 1980-11-25 | 1982-06-16 | Tno | METHOD FOR DETOXIFYING CHEMICAL WASTES. |
| DE3245474A1 (en) * | 1982-12-08 | 1984-06-14 | Vladimir Petrovič Šustov | Process for regenerating an iron chloride/copper chloride etching solution |
| CN106517427A (en) * | 2016-10-21 | 2017-03-22 | 河海大学 | Wastewater treatment device and method |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR704257A (en) * | 1930-10-02 | 1931-05-16 | Method and apparatus for the purification and sterilization of water | |
| JPS5128938B1 (en) * | 1970-11-26 | 1976-08-23 | ||
| US3730864A (en) * | 1971-04-14 | 1973-05-01 | Hooker Chemical Corp | Decreasing the phenolic content of liquids by an electrochemical technique |
| JPS4870362A (en) * | 1971-12-27 | 1973-09-22 | ||
| FR2316196A1 (en) * | 1975-06-30 | 1977-01-28 | Sorapec | Electrochemical purification of industrial effluent - esp. from paper mills, by continuous anodic oxidation of organic pollutants |
-
1976
- 1976-02-06 CA CA000245193A patent/CA1156966A/en not_active Expired
-
1977
- 1977-02-04 SE SE7701252A patent/SE442987B/en not_active IP Right Cessation
- 1977-02-04 GB GB4736/77A patent/GB1570122A/en not_active Expired
- 1977-02-07 DE DE19772705007 patent/DE2705007A1/en not_active Ceased
- 1977-02-07 JP JP52012370A patent/JPS6034439B2/en not_active Expired
- 1977-02-07 FR FR7703322A patent/FR2340279A1/en active Granted
- 1977-02-07 NO NO770393A patent/NO770393L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6034439B2 (en) | 1985-08-08 |
| DE2705007A1 (en) | 1977-08-18 |
| FR2340279A1 (en) | 1977-09-02 |
| SE7701252L (en) | 1977-08-07 |
| FR2340279B1 (en) | 1983-08-26 |
| GB1570122A (en) | 1980-06-25 |
| NO770393L (en) | 1977-08-09 |
| JPS52103850A (en) | 1977-08-31 |
| SE442987B (en) | 1986-02-10 |
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