CA1303259C - System and method for treating pulp and paper mill waste water - Google Patents

System and method for treating pulp and paper mill waste water

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Publication number
CA1303259C
CA1303259C CA 525230 CA525230A CA1303259C CA 1303259 C CA1303259 C CA 1303259C CA 525230 CA525230 CA 525230 CA 525230 A CA525230 A CA 525230A CA 1303259 C CA1303259 C CA 1303259C
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Canada
Prior art keywords
waste water
tank
mixing
paper mill
matter
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 - Lifetime
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CA 525230
Other languages
French (fr)
Inventor
Charles Ackel
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Stone Container Corp
Original Assignee
Stone Container Corp
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Publication date
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Publication of CA1303259C publication Critical patent/CA1303259C/en
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Classifications

    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00Multistage treatment of water, waste water or sewage
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00Biological treatment of water, waste water, or sewage
    • C02F3/02Aerobic processes
    • C02F3/12Activated sludge processes
    • C02F3/1205Particular type of activated sludge processes
    • C02F3/1215Combinations of activated sludge treatment with precipitation, flocculation, coagulation and separation of phosphates
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/24Treatment of water, waste water, or sewage by flotation
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/52Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/26Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof
    • C02F2103/28Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof from the paper or cellulose industry
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00Biological treatment of water, waste water, or sewage
    • C02F3/02Aerobic processes
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02WCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00Technologies for wastewater treatment
    • Y02W10/10Biological treatment of water, waste water, or sewage
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S210/00Liquid purification or separation
    • Y10S210/928Paper mill waste, e.g. white water, black liquor treated

Abstract

SYSTEM AND METHOD FOP TREATING
PULP AND PAPER MILL WASTE WATER

Abstract of the Disclosure A system and method for converting pulp and paper mill waste water into a decolored neutral pH effluent and a solid suitable for use as fuel in a furnace. The treatment system is used following primary and secondary treatment of pulp and paper mill waste waters typically found in the in-dustry. After secondary biological treatment, the waste waters are pumped to a coagulation tank where the waste water is brought in contact with a polyamine coagulant which coagu-lates lignins, degraded sugars, and other compounds which typically discolor this water. The coagulation particles are increased in size by addition of an acrylamide polymer in a floculation tank to improve the hydrophllic characteristics of the coagulant. The waste water is then mixed a dissolved air and water solution under pressure. Upon dissolution of the dissolved air at atmospheric pressure the air is absorbed by the floculated matter in the aeration tank and the flocu-lated matter is caused to migrate towards the area of less pressure, i.e. the surface of the tank. The floculated matter accumulates on the surface of the floculating tank and can be skimmed from the top, dried and ultimately burned in a furnace.

Description

~303259 The r moval of colored constituents has previously been done to papermaking waste water in order to recycle the colored constituents back to the papermaking processes.
This treatment, referred to as a "pretreatment", as disclosed in applicant's U. S. Patent 4,724,045, issued February 9, 19~3, Charles S. Ackel, can only be used in treatment of certain concentrated streams of waste water from the pulp mill processes which have and undergone primary and secondary waste water treatment.
Consequently, the "pretreatment" processes cannot be used to produce a neutral pH waste water having a low enough concentration of colored bodies to allow release directly to the open environment.
Accordingly, it is an object of an aspect of the present invention to provide a system for treatment of the entire pulp and paper mill waste water effluent which converts this waste water to a liquid containing a low concentration of colored bodies at a near neutral p~, and a solid suitable for burning in a furnace or rec~cle to the papermaking process.
It is an object of an aspect of the present invention to provide a system and a method for decoloring waste water, removing insoluble BOD, phosphates and hydrogen sulfide.
It is an object of an aspect of the present invention to provide a system and a method for removing colored bodies from the the waste water in a manner that said colored bodies are removed as a solid suitable for burning in a furnace.
It is an object of an aspect of the invention to recover part of the originally added coagulant from the treated waste water, thus enabling reuse of the coagulum and reductions in overall cost of waste water treatment.

~l3~3~59 The foregoing and other objects, features, and advantages af this invention will be apparent from the following description and illustrations of the preferred embodiment ot this invention.
Summary of tke Invention The present invention provides both a system and a method for converting waste water produced in papermaking processes with or without pretreatment, such as disclosed in aforementioned U. S. Patent No. 4,724,045, to a decolored, near neutral pH, liquid effluent and a solid suitable for burning in a furnace. The system comprises a series of tanks which can hold the waste water and mix the waste water or bring it in contact with various agents with an in-line continuous process.
The waste water treated initially from the pulp and paper mill is treated conventionally by primary clarification and secondary biological treatment. The biologically treated waste water then continues to a coagulation tank which communicates with a source of coagulant which allows the coagulant to contact the waste water in the coagulation tank. A coagulated precipitate is therein formed with the colored bodies which then travels with the waste water to a floculation tank which further communicates with a source of acrylamide polymer.
The acrylamide polymer is contacted with the waste water containing the coagulant, causing the coagulant to in-crease in size and to form a floculated matter which has a larger more hydrophilic particle.
The floculation tank communicates with a dissolved air mixing tank such that the waste water containing the floculated matter can Elow into the mixing tank where it is mixed with water containing dissolved air. The mixing at ~3~325~3 -the mixing tank causes the floculated matter to adsorb to the air in solution. The aeration mixing tank also has a pressure gradient such that the floculated matter which adsorbed the air bubbles will migrate toward the surface of the mixing tank where the atmospheric pressure is the lowest pressure available to the floculated matter.
Floculated matter accumulates at the surface of the mixing tank and may be removed by a simple skimming operation, further treated and, ultimately, burned as a source of energy.
Dissolved air will not separate colloidal particles from suspension because these particles are too small to attach to air bubbles. The coagulum formed from the particles and the polyamine or alum also is too small. The function of the acrylamide polymer floculent is to enlarge these particles to a size where air attachment will occur.
The method of the invention comprises biologically treating the waste water, adding a coagulating agent, such as polyamine, to the waste water to coagulate the colored materials, adding a floculating agent to increase the size of the coagulated particles, and mixing the floculated materials with pressurized aerated water, such that the air is adsorbed by the materials, and the floculating materials will migrate to and accumulate near the surface of the waste water for removal.

~.. ~

~L31[~325~

4a Various aspects of the invention is as follows:

A system to prepare pulp and paper mill waste water for discharge to the open environment, the waste water having undergone initial primary clarification and biological treatment, the system comprising:

a. first means for mixing waste water with polyamine to coagulate color body particles;

b. second means for mixing the waste water containing the coagulated colored body particles with polyacrylamide to flocculate the colored body particles thereby increasing their size, the second means in communication with the first means; and, c. third means for mixing the waste water containing the flocculated colored body particles with aerated water to produce absorption of air kubbles by the colored body particles, the third means in communication with the second means;

whereby the flocculated colored body particles accumulate at the sur~ace of the waste water in the third means.

A method of treating colored pulp mill waste water for discharge to the open environment at near neutral pH, the method comprising the steps of:

first, primary clarification and biological treatment;

second, adding a coagulating agent to the waste water from the clarification and biological treatment to coagulate color materials without substantial independent reduction of pH;

~3~3259 4b third, adding a flocculating agent to the waste water containing the coagulated materials to increase the size of the coagulated materials to form a flocculated matter;

fourth, mixing the flocculated matter with pressurized aerated water to produce air bubbles adsorbed by the materials, wherein the flocculated matter migrates to near the surface;

fifth, separation of the flocculated matter from the waste water.

A method of converting colored paper mill waste water after initial primary clarification and biological treatment to a decolored, neutral pH liquid effluent and --a solid suitable for burning for fuel, the method comprising the steps of:

coagulating the materials in the waste water by addition of polyamine to produce a coagulant precipitated without substantial independent pH
reduction;

increasing the size of the coagulant precipitate by adding an acrylamide polymer to the waste water to form a flocculated matter;

accumulating the flocculent in the waste water by mixing the waste water with aerated water so the flocculent will absorb air and migrate toward the surface of the waste water; and removing the accumulated f locculent from the : surface of the waste water.

: ~ .
~' ' ~3032S9 4c Brief Description of the Drawinq A better understanding of the invention may be had from a consideration of the following detailed description taken in con~unction with the following drawings, in which:

, .

FIG. 1 is a flow diagram showing the preferred method of the invention;
FI~. ~ is a schematic showing the preferred arrange-ment of component structural parts of the system of the in-vention.

Detailed Description of the Invention The system and method of the present invention is understood by reference to the diagrams described above.
Referring to FIG. 1, the general arrangement of the method steps is depicted by the numeral 10. Pulping in the pulp mill and paper making processes 12 produce waste water con-taining colored bodies ~lignins, degraded sugars). A pretreat-ment is known generally in the prior art and is a distinct process from that which is the subiect of the present in-vention. However, the continued recycling of the discharge from the papermaking processes ultimately produces a waste water having dilute colored contaminants which may not be adequately treated by known processes such that they may be recycled to the papermaking processes. That is, while the discharge from the papermaking may be recycled, eventually some discharge is to~o contaminated to recycle and must be purged.
The waste water leaving the papermaking processes 12 travels through normal, known-in-the-art conduits to a gravity sedimentation primary clarifier 14, where large sediments are removed from the waste stream, and then on to be biologically treated 16 to remove BOD. Such biological treatment and the methods of biological treatment are well known in the art, as revealed in Scott, RoH~, "Sophisticated Treatment at Baikal ~303~S9 Pulp Mill in U.S.S.R.", Pulp and Paper, Volume 48, No. 4, April, 1974, pp. 82-86; Amberg HoR~ et al., "The Status of Water Pollution Control in th~ Soviet Union~, TAPPI, Volume 58, No. 11, November, 1975, pp. 59-67; and Amberg H.R. et al., "The Status of Water Pollution Control in the Soviet Unionn, "TAPPIn, Volume 58, No. 12, December, 1975, pp. 75-77.
Following biological treatment, the waste water con-tinues on through conventional industrial conduit means to a coagulation tank where it is mixed with coagulants 18. The coagulant, preferably polyamine~ is added to the waste water contained in the coagulation tank whereupon it acts to coagulate the lignins and degraded sugars which color the waste water.
It is noted that the pH has not been adjusted in the waste water, except, possibly, slightly during biological treatment or with addition of the coagulant. The addition of the poly-amine causes a coagulated precipitate to form in the coagu-lation tank. However, this precipitant is not eas~ly removed from suspension as it i~ a very shear sensitive and settles slowly. While polyamine is the preferred coagulating agent, other hydrophilic precipitan~s may be used as coagulants, explained in detail in U.S. Patent No. 3,740~363 to Fuller.
A~ter coagula~ion:18, the waste stream cantinues ~o where floculant is added 20. Normally this is accomplished by a tank which holds the waste water until such time as the precipitant is large enough to adsorb air bubbles, as is ex-plained below.
Floculation is preferably accomplished by contacting the waste stream in a tank with a source of acrylamide polymer. The acrylamide polymer increases the size of the 130~2S9 coag~lated precipitate~ also without the necessity of acidi-fying the waste water~ However, the presence of the large precipitate in the floculant tank is much easier to remov~
from the water due to the improved hydrophilic character-istics. It was found through intense and long study that treatment for liquid~solid separation could not be effected in the presence of an intense turbulance or mechanical shear of ~he formed precipitate.
An important feature of the present invention is the particle size of the floculated matter. It must be ade-quately large to adsorb air bubbles, as are used to remove the precipitate from the waste water. This is accomplished by use of a cationic coagulant to create an initial, positi-vely charged particle in colloidal suspension. An even larger partiole is thereafter created by addition, in a later method step, of an anionic floculant, which attracts the positively charges particles ormed by addition of the coagulant.
The flocul~lnt tank 20 is in communication through conventional industrial conduits by gravity flow with an aeration mixirlg tank ~2. The aeration mixing 22 also is in communication with a source of pressurized air in solution.
The aeration mixing t~nk 22 provides an area of low pressure undulating mixing of the was~e water containing the fioculated matter with a pressurized dissolved air solution.
The ~dissolved air solution" is a saturated or near saturated solution of air and water which is maintained at 65 psi prior to release in the aeration mixing tank. The dis-solved air solution may be prepared utilizing waters pre-viously treated by this system. The ratio of dissolved air solution to waste water solution is less than 1:3.

~303~9 The mixing of the dissolved air solution in an area of low pressure results in the evolution of small air bubbles which 'adsorb to the floculated matter causlng tne floculated matter to float, or migrate, to an area of reduced ambient pressure. The aeration mixing tank is open at the top al-lowing the floculated matter to migrate towards the top of the separation tank 24 which is open to the atmosphere, the lowest pressure available in the system~ The floculated matter thereby accumulates at the surface of the separation tank 24 and may be skimmed off, or removed in any other way known in the art and, ultimately, burned for fuel in a Rraft recovery furnace. The liquid effluent 26 leaving the aeration mixing tank has very low concentration of color bodies, re-duced BOD, TDS, ~2S, PO4 contratrations and a pH essentially unchanged by the process, and is suitable for discharge into the op~n environment.
The present invention allows for the sludge to b'e removed Nithout the need to alter the pH of the water to be discnarged. This eliminates any steps required in adjusting t~e acidity or alkalinity of the waste water before ultimate dischar~e. Alternatively the sludge can be treated for re-covery of the coagulalnt 28. In the case of the polyami~e coagulant, acid and additional acrylamide polymer are added to the sludge. This secondary sludge is dewatered; the super-nate contains the'recoverable polyamine which could be used in the coagulation tank 18 to reduce the amount of resh poly-amine required.
The dewatered secondary sludge can be mixed with the black liquor as explained in ~he following text. The sludge removed from the treatment pIant is a useable, fuel caliber ~3~32~;~

sludge, as the sludge is derived from the pulp and paper process, and resembles the organic constituents of materials known in the industry as "black liquor n . It is convenient and economically attractive to mix the sludge with the black liquor 30 prior to the evaporative and combustion process typical in the industry, on recovery of the black liquor. In this manner the sludge is of use which is in contrast to similar treatment which results in additional expense.
Further, the treatment described is cheaper and more effective than those previously known to remove, lignins and degraded sugars~
In summary, the method of the present invention com-prises a tertiary treatment of waste waters which have been initially biologically treated. The colored materials are then coagulated by addition of a coagulant, preferably poly-amine, to produce a coagulated precipitant. The coagulated precipitant is then increased in size by addition of an acryla-mide polymer to the waste water to form a floculated matter.
The floculated matter in the waste water is then mixed with pressurized air in solution, causing the floculated matter to adsorb air bubbles and to float to an area of reduced pressure in a pressure gradien,t~ .The accumulated floculated matter, can then be removed by skimming or any other method known in the art.
The present invention contemplates a preferred em~odi-ment as shown in ~IG. 2. Waste water 40 which has been pre-viously treated, described above, is introduced to a sump 42.
A lift pump 44 conveys the waste water to the coagulation tank 46 while coagulant is dispensed from the coagulant storage tank 48 to the suction drawn by the pump 44. The - lo ~3~3259 coagulant waste water mixture ~s in the tank 46 for a time sufficient for coagulation of the colored bodies to be achieved. This time will vary from 1 to 10 minutes depending upon the particular coagulant used. For example, with the use of Nalco cationic polyamine (No. 8105) coagulation is achieved within one minute with an optimum dose of polymer, In the case of alum, using optimum dose, coagula~ion should be achieved within two minutes.
The waste stream containing the coagulant flows through a conduit to a floculation tank S0. A floculating agent, preferably an anionic acrylamide polymer, of molecular weight in excess of twenty million (Chemlink, Inc. anionic acrylamide polymer No. 8P40~ is added to the waste stream between the coagulation tank 46 and the aeration mixing tank 52. Preferably, i.e. with use of polyacrylamide, floculation is accomplished in a tank, as shown at 50, but alternatively the flocuati~n agent could be added to a waste stream directly without use of a tank structure, depending on the choice of polyacrylamide.
The acrylamide polymer is mixed in a polymer mixing tank 54 and stored in dispensible concentrations in polymer storage tank 56 from w~here:it is pumped, by pumps 58, to con-tact with the waste stream containing the coagulated precipi-tate.
Aeration mixing tank 52 receives both the waste stream from the floculation tank 50 and water saturated with dis-solved air from the air solution tank 60. The aerated water is preferably stored at least 65 psi, and i5 introduced to the aeration mixing tank at 65 psi or above. As previously discussed, the air released from the aerated water, exposed to atmospheric pressure in the aeration mixing tank 52 is adsorbed on the floculated matter which thereafter float to the sùrface of the liquid in the separation tank 62. rne liquid is removed from the bottom of the separation tank 62 for release to the environment at 64, or for return to the air solution tank 60 af~er addition of air (at 66).
The accumulated floculated matter removed from the separation tank 62, preferably by a skimmer (now shown), is held in a sludge storage tank 68. This collected floculated matter is returned to the paper making processes, as pre-viously discussed, or is treated for recovery of coaqulants (as shown in FIG. 1).
The separation tank 62 preferably has surface area of 0.55 square fee times gallons per minute of fluid flow from the floculation tank. The aeration mixing tank 52 preferably has surface area of one-tenth the surface area of the separa-tion tank 62 and height at least two feet below the surface of the liquid level of the separation tankO The separation tank and mixing tank should be arranged to maximize the dis-tance between the edge of the mixing tank and the liquid dis-charge from the Geparation tank. If circular tanks are used for the separation a~d mixing tanks 52 and 62, the mixing tank should be centered within the separation tank, while for rectangular (including square) tanks, the mixing tank 52 is located away from the discharge side of the separation tank.
The particular types of tanks, conduits, pumps and other equipment needed to practice this invention are known in the art. Similarly, the material which these tanks, con-duits, pumps and other equipment contemplated by the present invention also is known in the art.

~303~9 From the above description it will be apparent that there is thus provided a system and a method having the ad-vantages described above as desirable, but wnlcn oDviously is suscepti~le to modification and its form, method, operation, detailed construction and arrangement without departing from the principals involved or sacrificing any of its advantages.
It is to be understood, accordingly, that the in-vention is not limited to the specific features shown, but that the means, method and construction herein disclosed com-prise a preferred form of several modes of putting the in-vention into effect, and the invention is, therefore, claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims. The breadth of the invention shall be measured by these claims.

~3~3259 Background of the Invention The invention pertains to treatment of pulp and mill waste water. In particular, the invention relates to treat-ment of the total waste water effluent from a pulp and paper mill for removal of colored consti~uents, such as lignins and degraded sugars, producing a neutral range pH effluent and a solid suitable for burning.
In the past, waste waters coming from the papermaking processes were decolored by treatment with chemicals to adjust their pH to between 2 and 5 before contacting them with an organic phase containing an amine insoluble in water. A water insoluble organophilic amine complex was formed containing the compounds of the organic matter and colored products in the waste water which thereupon were removed. See, for example, U.S. Patent No. 3,412,018 issued to Mon~ie on Movember 19, 1968. Similarly, ~OS. Patent No. 4,089,780 to 5varz et al.
~May 16, 1978) removed color from paper mill waste waters by treatment with a cationic water soluble polyamine having an average molecular weight of at least 300 at a p~ of 2 to 5, followed by precipation with a water soluble anionic or nonionic organic polymer. Fuller,:U.S. Patent No~ 3,740,363, removed colored bodies in a pre-treatment stage by coagulation with alum in an acid solution and sedimentation of the coagulant in a gravity sedimentation clarifier. All of these past pro-cesses, while removing the color from waste water, left a highly acidic liquid which would damage the environment or require significant buffering, in order to be made suitable for release to the environ~ent.

Claims (15)

1. A system to prepare pulp and paper mill waste water for discharge to the open environment, the waste water having undergone initial primary clarification and biological treatment, the system comprising:
a. first means for mixing waste water with polyamine to coagulate color body particles;
b. second means for mixing the waste water containing the coagulated colored body particles with polyacrylamide to flocculate the colored body particles thereby increasing their size, the second means in communication with the first means; and, c. third means for mixing the waste water containing the flocculated colored body particles with aerated water to produce absorption of air bubbles by the colored body particles, the third means in communication with the second means;
whereby the flocculated colored body particles accumulate at the surface of the waste water in the third means.
2. The system of Claim 1 wherein the first, second and third means are tanks connected by conduits.
3. The system of Claim 1 wherein the third means comprises an aeration mixing tank capable of mixing the waste water and aerated water, and a separation tank containing the mixing tank, the separation tank capable of holding liquid with a surface above the mixing tank and open to atmospheric pressure.
4. The system of Claim 3 wherein the separation tank is open at its top and has surface area about ten times the surface area of the top of the mixing tank.
5. A method of treating colored pulp mill waste water for discharge to the open environment at near neutral pH, the method comprising the steps of:
first, primary clarification and biological treatment;
second, adding a coagulating agent to the waste water from the clarification and biological treatment to coagulate color materials without substantial independent reduction of pH;
third, adding a flocculating agent to the waste water containing the coagulated materials to increase the size of the coagulated materials to form a flocculated matter;
fourth, mixing the flocculated matter with pressurized aerated water to produce air bubbles adsorbed by the materials, wherein the flocculated matter migrates to near the surface;
fifth, separation of the flocculated matter from the waste water.
6. The method of treating pulp and paper mill waste water of Claim 5, wherein the flocculated matter is removed from the surface of the waste water.
7. The method of treating pulp and paper mill waste water of Claim 5, wherein the coagulating agent is a polyamine.
8. The method of treating pulp and paper mill waste water of Claim 5, wherein the flocculating agent is in acrylamide polymer.
9. The method of treating pulp and paper mill waste water of Claim 5, wherein the step of mixing the flocculated matter with water saturated with air is conducted in the bottom of the tank, the tank being open to atmospheric pressure.
10. The method of treating pulp and paper mill waste water of Claim 9, wherein the flocculated matter migrates to the surface of the tank and is removed by skimming.
11. The method of treating pulp and paper mill waste water of Claim 10, wherein the steps are run on the waste water in a continuous process.
12. A method of converting colored paper mill waste water after initial primary clarification and biological treatment to a decolored, neutral pH liquid effluent and a solid suitable for burning for fuel, the method comprising the steps of:
coagulating the materials in the waste water by addition of polyamine to produce a coagulant precipitated without substantial independent pH
reduction;
increasing the size of the coagulant precipitate by adding an acrylamide polymer to the waste water to form a flocculated matter;
accumulating the flocculent in the waste water by mixing the waste water with aerated water so the flocculent will absorb air and migrate toward the surface of the waste water; and removing the accumulated flocculent from the surface of the waste water.
13. The method of Claim 6 wherein the coagulating agent is polyamine.
14. The method of Claim 13, further comprising the steps of:
recovering the polyamine coagulating agent by mixing the flocculated matter with strong mineral acid and acrylamide polymer, dewatering the mixture to produce a supernate which contains polyamine coagulant in a form which may be reused as a coagulating agent.
15. The method of Claim 14, further comprising the step of:
burning the residue from the dewatered mixture as fuel.
CA 525230 1986-02-10 1986-12-12 System and method for treating pulp and paper mill waste water Expired - Lifetime CA1303259C (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US827,947 1986-02-10
US06/827,947 US4738750A (en) 1986-02-10 1986-02-10 System and method for treating pulp and paper mill waste water

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CA1303259C true CA1303259C (en) 1992-06-09

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US (1) US4738750A (en)
AU (1) AU588424B2 (en)
CA (1) CA1303259C (en)
FR (1) FR2594111B1 (en)
GB (1) GB2186275B (en)
PT (1) PT84256B (en)

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US4738750A (en) 1988-04-19
PT84256A (en) 1987-03-01
FR2594111A1 (en) 1987-08-14
GB8625765D0 (en) 1986-12-03
FR2594111B1 (en) 1990-11-30
PT84256B (en) 1989-09-14
GB2186275B (en) 1990-11-14
GB2186275A (en) 1987-08-12
AU6861387A (en) 1987-08-13

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