CA1069856A - Waste water treatment using microbubbles - Google Patents
Waste water treatment using microbubblesInfo
- Publication number
- CA1069856A CA1069856A CA209,897A CA209897A CA1069856A CA 1069856 A CA1069856 A CA 1069856A CA 209897 A CA209897 A CA 209897A CA 1069856 A CA1069856 A CA 1069856A
- Authority
- CA
- Canada
- Prior art keywords
- waste water
- tank
- flow path
- current density
- current
- 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
Links
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
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
-
- 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
- C02F1/465—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electroflotation
-
- 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
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2201/00—Apparatus for treatment of water, waste water or sewage
- C02F2201/46—Apparatus for electrochemical processes
- C02F2201/461—Electrolysis apparatus
- C02F2201/46105—Details relating to the electrolytic devices
- C02F2201/4612—Controlling or monitoring
- C02F2201/46125—Electrical variables
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Water Treatment By Electricity Or Magnetism (AREA)
Abstract
WASTE WATER TREATMENT
Abstract of the Disclosure:
Waste water containing suspended particles such as mineral oil, fats, proteins, fibers, and biodegradable ma-terials, etc., is clarified by passing said water over a plurality of electrode banks whereby gradient current density zones and gradient energy zones are used to create micro-bubbles which float the particles to the surface where they may be skimmed off.
Abstract of the Disclosure:
Waste water containing suspended particles such as mineral oil, fats, proteins, fibers, and biodegradable ma-terials, etc., is clarified by passing said water over a plurality of electrode banks whereby gradient current density zones and gradient energy zones are used to create micro-bubbles which float the particles to the surface where they may be skimmed off.
Description
~;9~S!~
This invention is concerned wi~h a method for treatment o:~ was-te waters and othex e~fluen-ts containing emulsified amounts o~ o~ls; fats, greases and othe~ oily materials which may or ma~ not contain proteins~ biodegrad-able matarials and other polar substancesO The process is especially use~ul in connection with edible oil operations or with packinghouse operations7 but can also be used to advantage in the treatment o~ ef~uents containing min-eral oils from industrial plantsg Accordingly, ~e inven-tion relates to the removal o a phase by ~lotation from a liquid containing the phaseO
There are, in various fields of industry, ef~luents from the operating processes, usually aqueous w~ich contain a separable phaseO In the paper industry, for example, the e~fluent ~rom the manufacturing process contains cellulose, fibers and sometimes mineral ~illers such as kaolinO In the meat indus~ry, the waste from the abatt~rg contain animal fats, proteins and other organic materialsO In the ; 20 manufacture of iron products so as in rolling mills, e~flu-ent waters contain oil and particles of ironO In the petro-: leum industry, numerous products having densities lower than that of water are separable only with difieulty using or-dinary methods such as decantation or centri~ugationO Some industrial processes contain phases which are hydrophobic such as the latex or plastics industries~ Clearly, many of the rivers and streams of the world are contaminated with all sor~s o~ insolubl~ and susp~nded organic and in-~` organic materlalsO
Generally speaking, ~ree ~at and oil, i~eO, not emulsi~ied ~at and oil~ present no serbus problems in re~
gard to separation ~rom water as they generally float to ~` 1o~69 ~ 5 ~
the sur~ace and can be ~kimmed oE:E0 ~mulsifl~d ~ats, on the other hand, stay in solution, causlng severe pollutisn problemsO In this connection, it has been the usual prac~
tice in the past ~o run the waste water rom a p~ckinghouse to a settling tank or basin having baffles wherein the water would set or an hour or so and the free fat would rise to the top and be skimmed offO The emulsiied ~at would o~ course remain in the water and would accompan~ it ~o the ~ sewersO Various means~ such as aeration and complex appar-atus have been employed in attempts to de-emulsi~y the was~e wa~ersO Usually, however, unless ~he emulsi~ied oil ; was very valuable~ no effort was made -to recover it from the water that was eventually passed to the sewers and hence to ~he streams and rivers O
In processes where water is reused, the oil ean be removed rom the system by coagulation with aluminum sulfa~e and alkali, foLlowed by il~ration. The oil is caught in the ~loc and filtered out of the systemO However, periodlc backwashes of the ilter with hot caustic soda are required~ I~ should ~e noted, however, that the processes used to comple~ely remove the oil from the water are clearly uneconomical for use in cleaning up waste water from pack~
-: : .
inghouses, petroleum industry waste and edible oil opera- -:
tionsO
In order to resolve the problem o~ separating a - ~uspended phase from waste water, various industrial proc- ;
esses have used the technique o~ 10tation by introducing bubbles of gas into the liquid which attach themselves to the particles of ~he separable pha~e, which may be ei~her solid or liquid, imparting an apparent density to the par-ticles which causes them to be lifted out of the liquid which contains t~em and which transports them to the surface . ~ , , .
~06~1~ilS~i from wilence they can be removed. The flotation processes and apparatuses heretofore known possess a major difflculty in that bubbles of gas produce substantial turbulence in the volume of the liquid immediately above the pOillt in which the bubbles are released, this turbulence acting to carry impurities into the clarified liquid. As there was no possibillty of increasing the number of bubbles to any substantial extent, e.g., to produce froth, the liquid effluent was difficult to clarify and the purification was onerous.
Accordîngly, it is one object of this invention to quickly and effeciently remove foreign, dissolved and/or supended materials from waste water.
It is another Gbject of this invention to remove suspended particles from waste water ~ithout producing stream turbulence throughout the clarifica-tion zone.
This invention relates to a process for coagulating, agglomerating, and floating suspended and dissolved material in a waste water comprising flowing a waste water containing suspended and dissolved material through a flow path along an electrode grid within a tank, supplying an electric current gradient along said electrode grid, said electric current gradually diminishing in density along said flow path, the greatest density being at the influent end of the flow path, contacting said flowing waste water with said elec-trode grid and said gradually diminishing gradient of average current densities, forming microbubbles by electrolytically decomposing the waste water, and creating high water turbulence within the waste water only at the influent end, said high water turbulence being created and maintained within the grid itself and thereabove by the microbubbles formed by said influent end grea~est current density.
In general, this invention is concerned with the treatment of water systems containing suspended or dissolved particles by subjecting the water to a plurality of gradient current density zones. Each current zone contains an electrode bank comprising a grid or electrode pairs having an important relationship to the amount of impurities in the water, Ideally, the average .
~ 3 _ L0~ 6 current density at the bottom oE the tank îs dlm~nlshed ~s the water passes through a treating tank. 'l~is is accompl~shed by varying the voltage, the amperage, the distance ketween electrodes or the arrangement oF the electrodes as will be brought out more in detail as the speci$ication proceeds.
It should be mentioned at this timc that t~o types of current densities are discussed in this specification, There is a current densit~ produced at the electrodes wh~ch is real and there is one $ound a~ the tank bo~tom ~hich ~s imaginar~ but calculatable. There is an unlimited '~
~ .. .
','"'.'.
''; ~:
-~ .
, .
- ~ - 3a -' ' ' . , :
~;9851f~
number o~ ways ~o produce a gradient o~ current densities a~ ~he tank bottomO For example, i~ the amperage a~ thQ
electrode remains constant, the average currant density per square foot o~ tank bottom will diminish if the elec~rode pairs are placed far~her apart or the distance ~e~ween anode and cathode is increasedO
Most waste watersg especially from mea~ treating operations or edible oil plants have one common denomina-tor, iOeO, the presence of suspended, charged~ solid parti~
cles which will not settle even if allowed to stand or months on endO It is generally recognized that in the usual situations more than 90% of the suspanded solids are nega-tively charged~ I~ order to precipi~ate these particles, the charge mus~ be brought to zeroO At zero charge~ the particles will precipitate and form a ~loc, some o which may arise and some of whic~ may fallO It is possibLe ~o coagulate some particles in industrial waste water by simp-ly chan~ing the p~ of the solutionO
In addition, positively charged particles, iOeO~
metal ions are usually added ~o wast~ waterO These posi-~ e ~s~ e,~;
`~~ tively charged particles attarh~o the ~ega~ive particles already in the waste water and bring about an over-all zero charge in the solu~ion with resultant coalescence of the particles, Ferric chloride, ferric sulfate, aluminum salts such as alum all of which ~orm their respective in-sol~ble metal hydroxidPs in the solution are posit~vel~
charged particles useful in this invention to treat industri-al waste waterO
A further improvement ~n producing ~loC9 to rise to the surace comprises the additi.on of synthetic poly-mers to the water, such polymers usually being of t.he poly-aerylamide typeO These ~echnical pol~mer flocculants of ~)698Sf~
water-soluble polymers range from moderate molecular weights of 7 million to the highest practical limit and include weak~
medium and strong charge densities.
In treating waste water from a plant, about 100-1000 ppm, usually about 300-400 ppm of alum or other multivalent metal salt will ~e placed in the influent pipe usually about 2a feet ahead of the tank. Very gentle mixing is desired and extreme agitation is avoided. After a few minutes of mixing a small amount, about 0.1 to about 5 ppm of a polyelectrolyte is added to the system. The waste water is allowed to flow over a plurality of electrodes ~ ;~
creating a current density gradient at the tank bottom.
The current density zones are created by the use of a plur-ality of electrode banks lying near the bottom of the tank floor. The current densities used are related to the amount of solid, foreign material in the waters above the grid. -The higher the concentration of foreign materials present the higher must be the effective current density employed.
Further, average current density per unit of tank bottom at the influent end is substantially greater (about 2-100 times, preferable more than 10 times greater) than that at the effluent end. The gradient from one end of the tank to the other may be step-wise or gradual.
In this invention, it is preferred to have the electrode banks extend over substantially the entire surface of a treating tank at or near the bottom of the tank.
The current density that is referred to in this invention is expressed in amps per square foot o~ tank bottom covered by the electrode bank, even though the anode and cathode 3a structures may be made of mesh wire, open grid (70% open area) or spaced wire or electrode pairs. Good results have been obtained in us:ing sheets of hexagonal patterned stretch ' . . .
: ~ .
~o~s~
metal for cathodes with rod-shaped anodes sanclwiched in between. However, one may use any sort of open area ~e-sign.
The invention stipulates that optimum results are obtained if two or more ranges of current density values are used in a single waste treating tank. The invention also encompasses the use of a gradient of energy input ~rom one end of the tank to the other. Energy input is the product of current times voltage, i.e., watts, and like current density, the average energy input per unit area of tank bottom at the influent end should be substan-tially greater than that at the effluent end. When the voltage is constant, wattage is directly proportional to the amperage.
Generally, a waste water treating tank will vary in size depending upon the amount of water being treated.
In order to treat 600 U.S. gallons per minute of industrial waste water, for example, the following dimensions would be considered realistic: length 40 feet; width 15 feet;
and depth 4 1/2 feet.
Since there is a critical relationship between optimum current density of the anode-cathode grid or elec-trode pairs and the amount of impurities in the water, it follows that ideally the current density in the electrode banks should be diminished as the water passes through the treating tank. Ideally, the invention can best be applied by dividing a treating tank into four banks sections. However, it is specifically pointed out that three sections, five sections, or additional sections may be employed. In a four zone clarification tank the current density in the second section is a fraction of that in the first section such as approximately half that in the first section.
- 106~8S~i Subsequent current ~ensi-ties between successive zones are diminished usually by a factor o~ abou~ one-half. For example, if the current density in the ~irst section (closest to the in-fluent end) lies between about 3 to 20 amps per square foot of tank bottom over that section; the second section would have a current density of about 2.5 to 10 amps per square foot.
The third section will have about 1.25 to 5 amps per square foot; while the last section will have about 1/2 to 2 1/2 amps per square foot.
When using anode-cathode grids, the present in-vention defines the optimum space in between the anode and cathode to be somewhere between .25 inches and 2 inches. ~ ~
It is possible ~o operate an anode-cathode grid beyond the ~ ~ -
This invention is concerned wi~h a method for treatment o:~ was-te waters and othex e~fluen-ts containing emulsified amounts o~ o~ls; fats, greases and othe~ oily materials which may or ma~ not contain proteins~ biodegrad-able matarials and other polar substancesO The process is especially use~ul in connection with edible oil operations or with packinghouse operations7 but can also be used to advantage in the treatment o~ ef~uents containing min-eral oils from industrial plantsg Accordingly, ~e inven-tion relates to the removal o a phase by ~lotation from a liquid containing the phaseO
There are, in various fields of industry, ef~luents from the operating processes, usually aqueous w~ich contain a separable phaseO In the paper industry, for example, the e~fluent ~rom the manufacturing process contains cellulose, fibers and sometimes mineral ~illers such as kaolinO In the meat indus~ry, the waste from the abatt~rg contain animal fats, proteins and other organic materialsO In the ; 20 manufacture of iron products so as in rolling mills, e~flu-ent waters contain oil and particles of ironO In the petro-: leum industry, numerous products having densities lower than that of water are separable only with difieulty using or-dinary methods such as decantation or centri~ugationO Some industrial processes contain phases which are hydrophobic such as the latex or plastics industries~ Clearly, many of the rivers and streams of the world are contaminated with all sor~s o~ insolubl~ and susp~nded organic and in-~` organic materlalsO
Generally speaking, ~ree ~at and oil, i~eO, not emulsi~ied ~at and oil~ present no serbus problems in re~
gard to separation ~rom water as they generally float to ~` 1o~69 ~ 5 ~
the sur~ace and can be ~kimmed oE:E0 ~mulsifl~d ~ats, on the other hand, stay in solution, causlng severe pollutisn problemsO In this connection, it has been the usual prac~
tice in the past ~o run the waste water rom a p~ckinghouse to a settling tank or basin having baffles wherein the water would set or an hour or so and the free fat would rise to the top and be skimmed offO The emulsiied ~at would o~ course remain in the water and would accompan~ it ~o the ~ sewersO Various means~ such as aeration and complex appar-atus have been employed in attempts to de-emulsi~y the was~e wa~ersO Usually, however, unless ~he emulsi~ied oil ; was very valuable~ no effort was made -to recover it from the water that was eventually passed to the sewers and hence to ~he streams and rivers O
In processes where water is reused, the oil ean be removed rom the system by coagulation with aluminum sulfa~e and alkali, foLlowed by il~ration. The oil is caught in the ~loc and filtered out of the systemO However, periodlc backwashes of the ilter with hot caustic soda are required~ I~ should ~e noted, however, that the processes used to comple~ely remove the oil from the water are clearly uneconomical for use in cleaning up waste water from pack~
-: : .
inghouses, petroleum industry waste and edible oil opera- -:
tionsO
In order to resolve the problem o~ separating a - ~uspended phase from waste water, various industrial proc- ;
esses have used the technique o~ 10tation by introducing bubbles of gas into the liquid which attach themselves to the particles of ~he separable pha~e, which may be ei~her solid or liquid, imparting an apparent density to the par-ticles which causes them to be lifted out of the liquid which contains t~em and which transports them to the surface . ~ , , .
~06~1~ilS~i from wilence they can be removed. The flotation processes and apparatuses heretofore known possess a major difflculty in that bubbles of gas produce substantial turbulence in the volume of the liquid immediately above the pOillt in which the bubbles are released, this turbulence acting to carry impurities into the clarified liquid. As there was no possibillty of increasing the number of bubbles to any substantial extent, e.g., to produce froth, the liquid effluent was difficult to clarify and the purification was onerous.
Accordîngly, it is one object of this invention to quickly and effeciently remove foreign, dissolved and/or supended materials from waste water.
It is another Gbject of this invention to remove suspended particles from waste water ~ithout producing stream turbulence throughout the clarifica-tion zone.
This invention relates to a process for coagulating, agglomerating, and floating suspended and dissolved material in a waste water comprising flowing a waste water containing suspended and dissolved material through a flow path along an electrode grid within a tank, supplying an electric current gradient along said electrode grid, said electric current gradually diminishing in density along said flow path, the greatest density being at the influent end of the flow path, contacting said flowing waste water with said elec-trode grid and said gradually diminishing gradient of average current densities, forming microbubbles by electrolytically decomposing the waste water, and creating high water turbulence within the waste water only at the influent end, said high water turbulence being created and maintained within the grid itself and thereabove by the microbubbles formed by said influent end grea~est current density.
In general, this invention is concerned with the treatment of water systems containing suspended or dissolved particles by subjecting the water to a plurality of gradient current density zones. Each current zone contains an electrode bank comprising a grid or electrode pairs having an important relationship to the amount of impurities in the water, Ideally, the average .
~ 3 _ L0~ 6 current density at the bottom oE the tank îs dlm~nlshed ~s the water passes through a treating tank. 'l~is is accompl~shed by varying the voltage, the amperage, the distance ketween electrodes or the arrangement oF the electrodes as will be brought out more in detail as the speci$ication proceeds.
It should be mentioned at this timc that t~o types of current densities are discussed in this specification, There is a current densit~ produced at the electrodes wh~ch is real and there is one $ound a~ the tank bo~tom ~hich ~s imaginar~ but calculatable. There is an unlimited '~
~ .. .
','"'.'.
''; ~:
-~ .
, .
- ~ - 3a -' ' ' . , :
~;9851f~
number o~ ways ~o produce a gradient o~ current densities a~ ~he tank bottomO For example, i~ the amperage a~ thQ
electrode remains constant, the average currant density per square foot o~ tank bottom will diminish if the elec~rode pairs are placed far~her apart or the distance ~e~ween anode and cathode is increasedO
Most waste watersg especially from mea~ treating operations or edible oil plants have one common denomina-tor, iOeO, the presence of suspended, charged~ solid parti~
cles which will not settle even if allowed to stand or months on endO It is generally recognized that in the usual situations more than 90% of the suspanded solids are nega-tively charged~ I~ order to precipi~ate these particles, the charge mus~ be brought to zeroO At zero charge~ the particles will precipitate and form a ~loc, some o which may arise and some of whic~ may fallO It is possibLe ~o coagulate some particles in industrial waste water by simp-ly chan~ing the p~ of the solutionO
In addition, positively charged particles, iOeO~
metal ions are usually added ~o wast~ waterO These posi-~ e ~s~ e,~;
`~~ tively charged particles attarh~o the ~ega~ive particles already in the waste water and bring about an over-all zero charge in the solu~ion with resultant coalescence of the particles, Ferric chloride, ferric sulfate, aluminum salts such as alum all of which ~orm their respective in-sol~ble metal hydroxidPs in the solution are posit~vel~
charged particles useful in this invention to treat industri-al waste waterO
A further improvement ~n producing ~loC9 to rise to the surace comprises the additi.on of synthetic poly-mers to the water, such polymers usually being of t.he poly-aerylamide typeO These ~echnical pol~mer flocculants of ~)698Sf~
water-soluble polymers range from moderate molecular weights of 7 million to the highest practical limit and include weak~
medium and strong charge densities.
In treating waste water from a plant, about 100-1000 ppm, usually about 300-400 ppm of alum or other multivalent metal salt will ~e placed in the influent pipe usually about 2a feet ahead of the tank. Very gentle mixing is desired and extreme agitation is avoided. After a few minutes of mixing a small amount, about 0.1 to about 5 ppm of a polyelectrolyte is added to the system. The waste water is allowed to flow over a plurality of electrodes ~ ;~
creating a current density gradient at the tank bottom.
The current density zones are created by the use of a plur-ality of electrode banks lying near the bottom of the tank floor. The current densities used are related to the amount of solid, foreign material in the waters above the grid. -The higher the concentration of foreign materials present the higher must be the effective current density employed.
Further, average current density per unit of tank bottom at the influent end is substantially greater (about 2-100 times, preferable more than 10 times greater) than that at the effluent end. The gradient from one end of the tank to the other may be step-wise or gradual.
In this invention, it is preferred to have the electrode banks extend over substantially the entire surface of a treating tank at or near the bottom of the tank.
The current density that is referred to in this invention is expressed in amps per square foot o~ tank bottom covered by the electrode bank, even though the anode and cathode 3a structures may be made of mesh wire, open grid (70% open area) or spaced wire or electrode pairs. Good results have been obtained in us:ing sheets of hexagonal patterned stretch ' . . .
: ~ .
~o~s~
metal for cathodes with rod-shaped anodes sanclwiched in between. However, one may use any sort of open area ~e-sign.
The invention stipulates that optimum results are obtained if two or more ranges of current density values are used in a single waste treating tank. The invention also encompasses the use of a gradient of energy input ~rom one end of the tank to the other. Energy input is the product of current times voltage, i.e., watts, and like current density, the average energy input per unit area of tank bottom at the influent end should be substan-tially greater than that at the effluent end. When the voltage is constant, wattage is directly proportional to the amperage.
Generally, a waste water treating tank will vary in size depending upon the amount of water being treated.
In order to treat 600 U.S. gallons per minute of industrial waste water, for example, the following dimensions would be considered realistic: length 40 feet; width 15 feet;
and depth 4 1/2 feet.
Since there is a critical relationship between optimum current density of the anode-cathode grid or elec-trode pairs and the amount of impurities in the water, it follows that ideally the current density in the electrode banks should be diminished as the water passes through the treating tank. Ideally, the invention can best be applied by dividing a treating tank into four banks sections. However, it is specifically pointed out that three sections, five sections, or additional sections may be employed. In a four zone clarification tank the current density in the second section is a fraction of that in the first section such as approximately half that in the first section.
- 106~8S~i Subsequent current ~ensi-ties between successive zones are diminished usually by a factor o~ abou~ one-half. For example, if the current density in the ~irst section (closest to the in-fluent end) lies between about 3 to 20 amps per square foot of tank bottom over that section; the second section would have a current density of about 2.5 to 10 amps per square foot.
The third section will have about 1.25 to 5 amps per square foot; while the last section will have about 1/2 to 2 1/2 amps per square foot.
When using anode-cathode grids, the present in-vention defines the optimum space in between the anode and cathode to be somewhere between .25 inches and 2 inches. ~ ~
It is possible ~o operate an anode-cathode grid beyond the ~ ~ -
2 inch spacing ~ut the power consumed becomes even larger with larger distances. It is pointed out that it is very important that the anode-cathode grid be as far away from the skimming surface as possible. If the spacing is much greater than 8 inches from the bottom of the tank, some ~; of the desired neutralization and coagulation is irretrievably lost.
In a specific embodiment of this invention, a ! ., flotation tank of 16 to 20 feet long, approximately 5 to 6 feet high and 7 feet wide was utilized. Both the inlet and exit conduits are about 5 feet from the bottom of the tank.
The tank was divided into four electrochemical or current density sections employing four banks of cells covering essentially the entire bottom of the tank and placed as close to the bottom of the tank as possible. All four cells are operated in parallel with one rectifier.
` 30 The first bank or anode-cathode grid (nearest the influent end) coMprised two cathodes and one set of cylindri-cal or rod-shaped anodes spaced e~ual distances between the .
~ ' ., ~. .
~L0~85~i cathodes. The cathodes were stretche~ mild steel, rec-tangular plates (grids~ and between 1/16 and 1/4 inch thick-ness with about 66 to 70% openings. Each opening was a~out .6 inches x 1.7 inches. Eleven ferrosilicon anode rods, 5 feet 4 inches in length and 1 l/2 inches in diameter, were sandwiched between the cathodes. The bottom cathode was rested 4 inches from the tank bottom and it, along with the top cathode, ~as separated from the anodes by non-conducting material. All anodes were on one plane, but offset from each other about 6 inches. They were lying trans-verse to the flow of water and were about 5 inches apart ~ -as measured from their center line. The cathode grids were movable to the extent of 2 inches at l inch inter-vals, but generally were placed about 2 to 2 l/2 inches from the center line of the anodes.
' The second bank is similar to the first except that nine ferrosilicon anodes (6 inches apart) were used in the space so that the center line of the cathodes was between about 3 to 3 l/2 inches. The third bank consisted 20 oE 5 ferrosilicon anodes in one plane spaced 10 inches apart and also transverse the flow of the water. These anodes '~ were placed about 3 to 4 inches above one cathode grill which was also about 4 inches from the tank bottom. The -~ ourth bank consisted of four ferrosilicon anodes spaced 12 inches apart, all on one plane, about 4 to 5 inches above one cathode. This cell, at the effluent end, was placed at about a 45 angle with one end of the grid about 4 inches from the bottom of the tank and the top edge ap-~ proaching the sux~ace o~ the water. The top o the ~lota-30 tion t,ank contalns skim bars to remove the flocculated particles from the top o~ the tank while clear water was discharged below the skimming means, but at a level of ~o~ 8 about 5 eet from the tank bottom.
Rectified AC current of about 10 volts and hig~
amperage was utilizedO In the first bank7 the upper and lower current limits wer~ about 60-150 amps. The current carrying limits of the second bank were about 50-100 ampsO
The third bank employed about 15-40 amps while the las~ bank used 10-20 ampsO A more meaningful language is that the influent section, covering an area of approximately 1/4 of the tank bottom, had a current density o~ between about 10 5-10 a~ps per square ~oot o~ tank bot~omO Section 2~ also covering about 1/4 of the tank bottom, carried a curren~
density in the range of 2-5 amps per square foot of tank bottomO Section 3 had current densities in the range of 1/2 to 1 amp per square foot while the e~fluen~ section had current densities in the range of 1/10 to 5/10 amps per square footO When the eurrent was turned on, electrolysis . of the water took place producing micro~ubbles oE o~ygen - and hydrogen in appreciable amounts which carried the particles to the surfaceO The tank was enclosed in a housing or cham~er and the hydrogen vented to the atmos-phereO About 6 cu~ic feet per hour of hydrogen was ven~ed Energy input can also be delivered through electrode pairs, i.e~, an anode and cathode rod ~ere the distance (sur~ace to sur~ace) between electrodes in each electrode pair is no less than about o25 inches nor usually greater than 4 inchesO Very good results are obtained at 1 inch distances~ To ~btain the energy gradient, these electrode pairs are spaced at larger dis~ances as the waste water passes through the treatment tank thus producln~ a gradual -~` gradlentO
In a typical tank 20 feet long and 8 fee~ wide .
a series of electrode pairs 1 inch apart between anode and cathode can be used. Distance between the first electrode pair and the second electrode pair is 4 inches, that be-tween the second electrode pair and the third electrode pair is 8 inches, between the third electrode pair and the fourth electrode pair is 12 inches, and so on with dis-tances between consecutive electrode pairs always in--creasing about 4 inches. This kind of energy distribution is gradual rather than step-down. Thus energy input in the treatment tank is made up of small packages (electrode pairs) and the current densities of these pairs are varied to provide the desired energy gradient. usually, the enersy input at the influent section of the tank, based on area of tank bottom should lie between about 40 and ` 120 watts (preferable 50-100 watts) while at the efflu-end portion of the tank energy input will range from about 4 to 12 watts (preferable 5-10 watts) per square foot when 10 volts is used.
In a specific example, a tank 25 feet long, 6 feet deep and 8 feet wide was divided into 4 sections. Each section was 8 feet by 4 feet leaving 9 feet at the influ~
`~ ent end to be used as the floc chamber and for baffles.
The first section (nearest the influent end) had 9 rod-shaped Duriron* electrodes 2 3/8 inches in diameterand 7 feet long spaced equally over 4 feet and transverse to the flow of water.
The second section employed 7 electrodes, section 3 had 5 electrodes while section 4 used 4 electrodes. The electrodes in these sections were equally spaced apart and were alternately anodes and cathodes connected in parallel. Currenk drawn in each of the 4 sections was approximately 150 amperes, 75 amperes, 40 amperes and 20 amperes. Ten volts was employed and common to all *Trade mark for a high silicon iron alloy .
1069~5~;
4 sections. Waste water, high in protein and fats from a meat packing plant was treated. Properties of entering and leaving water from the tank was as follows: ~
Influent Waste Water Efflue~t Water ~-.
1. Hexane extractables 5,230 ppm 30 ppm 2. Suspended solids 4,300 ppm 100 ppm
In a specific embodiment of this invention, a ! ., flotation tank of 16 to 20 feet long, approximately 5 to 6 feet high and 7 feet wide was utilized. Both the inlet and exit conduits are about 5 feet from the bottom of the tank.
The tank was divided into four electrochemical or current density sections employing four banks of cells covering essentially the entire bottom of the tank and placed as close to the bottom of the tank as possible. All four cells are operated in parallel with one rectifier.
` 30 The first bank or anode-cathode grid (nearest the influent end) coMprised two cathodes and one set of cylindri-cal or rod-shaped anodes spaced e~ual distances between the .
~ ' ., ~. .
~L0~85~i cathodes. The cathodes were stretche~ mild steel, rec-tangular plates (grids~ and between 1/16 and 1/4 inch thick-ness with about 66 to 70% openings. Each opening was a~out .6 inches x 1.7 inches. Eleven ferrosilicon anode rods, 5 feet 4 inches in length and 1 l/2 inches in diameter, were sandwiched between the cathodes. The bottom cathode was rested 4 inches from the tank bottom and it, along with the top cathode, ~as separated from the anodes by non-conducting material. All anodes were on one plane, but offset from each other about 6 inches. They were lying trans-verse to the flow of water and were about 5 inches apart ~ -as measured from their center line. The cathode grids were movable to the extent of 2 inches at l inch inter-vals, but generally were placed about 2 to 2 l/2 inches from the center line of the anodes.
' The second bank is similar to the first except that nine ferrosilicon anodes (6 inches apart) were used in the space so that the center line of the cathodes was between about 3 to 3 l/2 inches. The third bank consisted 20 oE 5 ferrosilicon anodes in one plane spaced 10 inches apart and also transverse the flow of the water. These anodes '~ were placed about 3 to 4 inches above one cathode grill which was also about 4 inches from the tank bottom. The -~ ourth bank consisted of four ferrosilicon anodes spaced 12 inches apart, all on one plane, about 4 to 5 inches above one cathode. This cell, at the effluent end, was placed at about a 45 angle with one end of the grid about 4 inches from the bottom of the tank and the top edge ap-~ proaching the sux~ace o~ the water. The top o the ~lota-30 tion t,ank contalns skim bars to remove the flocculated particles from the top o~ the tank while clear water was discharged below the skimming means, but at a level of ~o~ 8 about 5 eet from the tank bottom.
Rectified AC current of about 10 volts and hig~
amperage was utilizedO In the first bank7 the upper and lower current limits wer~ about 60-150 amps. The current carrying limits of the second bank were about 50-100 ampsO
The third bank employed about 15-40 amps while the las~ bank used 10-20 ampsO A more meaningful language is that the influent section, covering an area of approximately 1/4 of the tank bottom, had a current density o~ between about 10 5-10 a~ps per square ~oot o~ tank bot~omO Section 2~ also covering about 1/4 of the tank bottom, carried a curren~
density in the range of 2-5 amps per square foot of tank bottomO Section 3 had current densities in the range of 1/2 to 1 amp per square foot while the e~fluen~ section had current densities in the range of 1/10 to 5/10 amps per square footO When the eurrent was turned on, electrolysis . of the water took place producing micro~ubbles oE o~ygen - and hydrogen in appreciable amounts which carried the particles to the surfaceO The tank was enclosed in a housing or cham~er and the hydrogen vented to the atmos-phereO About 6 cu~ic feet per hour of hydrogen was ven~ed Energy input can also be delivered through electrode pairs, i.e~, an anode and cathode rod ~ere the distance (sur~ace to sur~ace) between electrodes in each electrode pair is no less than about o25 inches nor usually greater than 4 inchesO Very good results are obtained at 1 inch distances~ To ~btain the energy gradient, these electrode pairs are spaced at larger dis~ances as the waste water passes through the treatment tank thus producln~ a gradual -~` gradlentO
In a typical tank 20 feet long and 8 fee~ wide .
a series of electrode pairs 1 inch apart between anode and cathode can be used. Distance between the first electrode pair and the second electrode pair is 4 inches, that be-tween the second electrode pair and the third electrode pair is 8 inches, between the third electrode pair and the fourth electrode pair is 12 inches, and so on with dis-tances between consecutive electrode pairs always in--creasing about 4 inches. This kind of energy distribution is gradual rather than step-down. Thus energy input in the treatment tank is made up of small packages (electrode pairs) and the current densities of these pairs are varied to provide the desired energy gradient. usually, the enersy input at the influent section of the tank, based on area of tank bottom should lie between about 40 and ` 120 watts (preferable 50-100 watts) while at the efflu-end portion of the tank energy input will range from about 4 to 12 watts (preferable 5-10 watts) per square foot when 10 volts is used.
In a specific example, a tank 25 feet long, 6 feet deep and 8 feet wide was divided into 4 sections. Each section was 8 feet by 4 feet leaving 9 feet at the influ~
`~ ent end to be used as the floc chamber and for baffles.
The first section (nearest the influent end) had 9 rod-shaped Duriron* electrodes 2 3/8 inches in diameterand 7 feet long spaced equally over 4 feet and transverse to the flow of water.
The second section employed 7 electrodes, section 3 had 5 electrodes while section 4 used 4 electrodes. The electrodes in these sections were equally spaced apart and were alternately anodes and cathodes connected in parallel. Currenk drawn in each of the 4 sections was approximately 150 amperes, 75 amperes, 40 amperes and 20 amperes. Ten volts was employed and common to all *Trade mark for a high silicon iron alloy .
1069~5~;
4 sections. Waste water, high in protein and fats from a meat packing plant was treated. Properties of entering and leaving water from the tank was as follows: ~
Influent Waste Water Efflue~t Water ~-.
1. Hexane extractables 5,230 ppm 30 ppm 2. Suspended solids 4,300 ppm 100 ppm
3. pH 7 - 12 6.5 - 7.5 Energy input in each_section is:
Section 1 - 48 watts/square foot of tank bottom Section 2 - 24 watts/ " " " " "
Section 3 12 watts/ " " " " "
Section 4 - 6 watts/ " " " " "
Generally speaking, the higher the current density the ` smaller is the diameter of the microbubbles formed at the cath-odes and anodes. It is desired to have small bubbles~ and, accordingly, it is preferred that the size of the bubbles will ` vary between 10 microns and about 250 microns with the bulk ; ranging about 100 microns when a cathodic current density of 12 amperes per foot squared is used. The bubbles, having a density ;~
lighter than water, tend to rise and carry the floc to the surface where it is skimmed off.
The higher concentration of colloidal particles require stronger current densities and, accordingly, as the number of the colloidal particles diminishes, the amount of current xequired will fall off. This is why large cur-rent densities are used in the influent end as compared to lower current densities at the effluent end. The electro-flocculation process takes ~ull advantage of a cloud of charged "microbubbles" formed on both the anodes and cathodes. These bubbles are uniformly distributed throughout the tank and therefore provide uniform lift in raising the relatively charge-free floc to the sur~ace. While the bubbles are ' ~69~
uniEormly distributed ~hroughou~ the body of wa~er~ current distribution throug~out the tank is not uni~ormO
There is a pH lowering effect that takes place at the anodes which often breaks the ~at-wa~er emulsionO Af~er the emulsion is broken, the fat will rise ~o the sur~aceO
Coalescence of the fine particles is also aided by the addi tion of char~ed positive particles, ~eO, iron, alumlnum, cal-cium ions along with an anionic polymerO Par~icle pre-cipi~ation, floc formation, par~icle ~:Lotation, impressed 10 current and electrolysis are dynamic systemsO In the pro-cess of this invention, the influen~ section is mainly used to neutralize the negative charge oE foreign particles and to lift the ~locs in the presence of high water turbulenceO
In the next section of the tank, a second electrochemical cell is used to coalesce remaining loose Eloc under inter-mediate ~urbulence~ In Section 3, loose residual ~loc is floated to the surface under low turbulence~ Section 4 is ~` used to forcP unmanageable floc to rise and remain at the surfaceO Unmanageable floc is reerred to as floc with - .
considerable electrostatic chargeO This ~loc cannot be readily raised and held on the first 3 sections because the turbulence is too higho Very low turbulence ls present in section 40 Obviously many modifications and variations of the invention as hereinbe~ore set forth may be made without departing from the spirit and scope ~hereo~, and, thereore, only such limitations should be imposed as are indicated : in the appended claims~
:`
- 12 _
Section 1 - 48 watts/square foot of tank bottom Section 2 - 24 watts/ " " " " "
Section 3 12 watts/ " " " " "
Section 4 - 6 watts/ " " " " "
Generally speaking, the higher the current density the ` smaller is the diameter of the microbubbles formed at the cath-odes and anodes. It is desired to have small bubbles~ and, accordingly, it is preferred that the size of the bubbles will ` vary between 10 microns and about 250 microns with the bulk ; ranging about 100 microns when a cathodic current density of 12 amperes per foot squared is used. The bubbles, having a density ;~
lighter than water, tend to rise and carry the floc to the surface where it is skimmed off.
The higher concentration of colloidal particles require stronger current densities and, accordingly, as the number of the colloidal particles diminishes, the amount of current xequired will fall off. This is why large cur-rent densities are used in the influent end as compared to lower current densities at the effluent end. The electro-flocculation process takes ~ull advantage of a cloud of charged "microbubbles" formed on both the anodes and cathodes. These bubbles are uniformly distributed throughout the tank and therefore provide uniform lift in raising the relatively charge-free floc to the sur~ace. While the bubbles are ' ~69~
uniEormly distributed ~hroughou~ the body of wa~er~ current distribution throug~out the tank is not uni~ormO
There is a pH lowering effect that takes place at the anodes which often breaks the ~at-wa~er emulsionO Af~er the emulsion is broken, the fat will rise ~o the sur~aceO
Coalescence of the fine particles is also aided by the addi tion of char~ed positive particles, ~eO, iron, alumlnum, cal-cium ions along with an anionic polymerO Par~icle pre-cipi~ation, floc formation, par~icle ~:Lotation, impressed 10 current and electrolysis are dynamic systemsO In the pro-cess of this invention, the influen~ section is mainly used to neutralize the negative charge oE foreign particles and to lift the ~locs in the presence of high water turbulenceO
In the next section of the tank, a second electrochemical cell is used to coalesce remaining loose Eloc under inter-mediate ~urbulence~ In Section 3, loose residual ~loc is floated to the surface under low turbulence~ Section 4 is ~` used to forcP unmanageable floc to rise and remain at the surfaceO Unmanageable floc is reerred to as floc with - .
considerable electrostatic chargeO This ~loc cannot be readily raised and held on the first 3 sections because the turbulence is too higho Very low turbulence ls present in section 40 Obviously many modifications and variations of the invention as hereinbe~ore set forth may be made without departing from the spirit and scope ~hereo~, and, thereore, only such limitations should be imposed as are indicated : in the appended claims~
:`
- 12 _
Claims (17)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for coagulating, agglomerating, and floating suspended and dissolved material in a waste water comprising flowing a waste water containing suspended and dissolved material through a flow path along an electrode grid within a tank, supplying an electric current gradient along said electrode grid, said electric current gradually diminishing in density along said flow path, the greatest density being at the influent end of the flow path, contacting said flowing waste water with said electrode grid, said gradually diminishing gradient of average current densities forming microbubbles by electrolytically decomposing the waste water, while creating high water turbulence within the waste water only at the influent end, said high water turbulence being created and maintained within the grid itself and thereabove by the microbubbles formed by said influent end greatest current density.
2. The process of claim 1 wherein the average current density at the influent end of the flow path is about 3-20 amps per square foot of tank bottom.
3. The process of claim 1 wherein the influent section of the flow path receives about 40 to 120 watts per square foot of corresponding tank bottom and effluent portion of the flow path receives about 4 to about 12 watts per square foot of corresponding tank bottom.
4. The process of claim 1 wherein the electrode grid consists of a plurality of electrode pairs positioned at intervals that gradually increase along said flow path.
5. The process of claim 1 wherein the current density at the effluent end of the flow path is about 0.4 to 1.2 amps per square foot of tank bottom.
6. The process of claim 1, wherein the waste water is from a meat treating operation and contains emulsified charged particles of fat and oil.
7. The process of claim 1, wherein a multivalent metal ion is added to the waste water prior to introduction into the tank to aid in flocculation.
8. The process of claim 1, wherein a polyacrylamide flocculating agent is added to the solution after addition of a multivalent metal ion and prior to introduction into the tank to aid in making solids rise to the surface of the waste water.
9. The process of claim 1 wherein said current density at the influent end of the flow path is about 4-12 amps per square foot of tank bottom.
10. A process for separating suspended and dissolved material from waste water which comprises passing a waste water containing suspended and dissolved material through a receptacle having an inlet end and an outlet end and having a plurality of electrode banks of cells near the bottom of the receptacle, impressing the waste water with an electrical current that is passed through the electrode banks, said current being sufficient to produce a different current density along each bank, said current desnity being greatest at the bank located closest to the inlet end, producing microbubbles by electrolytically decomposing said waste water whereby the waste water is subjected to a plurality of current densities decreasing in value as the water passes from the inlet end to the outlet end, while creating high water turbulence within the waste water only at the inlet end, said high water turbulence being created and maintained within the electrode bank closest to the inlet end and thereabove by the microbubbles produced by said greatest current density at the inlet end bank.
11. The process of claim 10 wherein the current density of each succeeding bank is approximately one-half of that of the previous bank.
12. The process of claim 10 wherein a multivalent metal ion is added to the waste water prior to introduction into the receptacle to aid in flocculation.
13. The process of claim 10 wherein a flocculating agent is added to the solution after addition of a multivalent metal ion and prior to introduction into the receptacle to aid in making solids rise to the surface.
14. The process of claim 13 wherein the flocculating agent is a copolymer of from 90% to 50% by weight of acrylamide or methacrylamide and from 10%
to 50% by weight acrylic or methacrylic acid or water-soluble salt thereof.
to 50% by weight acrylic or methacrylic acid or water-soluble salt thereof.
15. The process of claim 10 wherein 3-20 amps per square foot of receptacle bottom are employed at the inlet end.
16. The process of claim 10, wherein the waste water is from a meat treating operation and contains emulsified charged particles of fat and oil.
17. The process of claim 10, wherein said current density at the inlet end is about 5-10 amps per square foot of receptacle bottom.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US43873774A | 1974-02-01 | 1974-02-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1069856A true CA1069856A (en) | 1980-01-15 |
Family
ID=23741814
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA209,897A Expired CA1069856A (en) | 1974-02-01 | 1974-09-24 | Waste water treatment using microbubbles |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5411611B2 (en) |
| CA (1) | CA1069856A (en) |
| DE (1) | DE2500455C3 (en) |
| FR (1) | FR2259793B1 (en) |
| GB (1) | GB1484974A (en) |
| SE (1) | SE7501116L (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2644744C3 (en) * | 1976-10-04 | 1982-08-19 | Hydromation Filter Co., Livonia, Mich. | Method and device for cleaning a conductive cooling liquid containing contaminating particles |
| JPS58127445U (en) * | 1982-02-23 | 1983-08-29 | アルパイン株式会社 | Tape guide for magnetic head |
| DE4230765A1 (en) * | 1992-09-15 | 1994-03-17 | Hugo Kunz | Recycling used oily emulsions, esp machine tool lubricants - by filtering emulsion, treating with flotation agent, electrolysing and removing floating oil and particles |
| FI95234C (en) * | 1992-11-17 | 1996-08-13 | Vladimir Erosovits Nenno | Method and apparatus for purifying aqueous solutions or the like |
| DE19680818D2 (en) * | 1995-09-25 | 1999-06-17 | Nat Engineering Research Cente | Method and device for the treatment of water contaminated with microorganisms and / or pollutants |
| MY157287A (en) * | 2005-09-09 | 2016-05-31 | World Max Alliance Ltd | Method and apparatus for separation and recovery of fruit, nut or vegetable oils from water, liquids or wastewater |
| RU2507158C2 (en) * | 2011-12-20 | 2014-02-20 | Общество с ограниченной ответственностью "Кристаллические Материалы Групп" | Method of bottom water continuous treatment |
| CN114105320B (en) * | 2021-12-16 | 2022-10-04 | 大连理工大学 | Method for inhibiting electrode surface scaling by utilizing nano/micro-bubble induced scaling substance liquid-phase nucleation |
-
1974
- 1974-09-24 CA CA209,897A patent/CA1069856A/en not_active Expired
- 1974-12-24 JP JP753021A patent/JPS5411611B2/ja not_active Expired
-
1975
- 1975-01-08 DE DE2500455A patent/DE2500455C3/en not_active Expired
- 1975-01-13 GB GB1377/75A patent/GB1484974A/en not_active Expired
- 1975-01-24 FR FR757502222A patent/FR2259793B1/fr not_active Expired
- 1975-01-31 SE SE7501116A patent/SE7501116L/xx unknown
Also Published As
| Publication number | Publication date |
|---|---|
| DE2500455A1 (en) | 1975-08-07 |
| FR2259793A1 (en) | 1975-08-29 |
| SE7501116L (en) | 1975-08-04 |
| JPS5411611B2 (en) | 1979-05-16 |
| GB1484974A (en) | 1977-09-08 |
| FR2259793B1 (en) | 1979-02-09 |
| DE2500455C3 (en) | 1978-10-12 |
| JPS50109167A (en) | 1975-08-28 |
| DE2500455B2 (en) | 1978-02-09 |
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