CA1159165A - Method for treatment of waste water from pulp bleaching plants - Google Patents
Method for treatment of waste water from pulp bleaching plantsInfo
- Publication number
- CA1159165A CA1159165A CA000345541A CA345541A CA1159165A CA 1159165 A CA1159165 A CA 1159165A CA 000345541 A CA000345541 A CA 000345541A CA 345541 A CA345541 A CA 345541A CA 1159165 A CA1159165 A CA 1159165A
- Authority
- CA
- Canada
- Prior art keywords
- waste water
- ozone
- amount
- pulp
- treatment
- 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
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C11/00—Regeneration of pulp liquors or effluent waste waters
- D21C11/0021—Introduction of various effluents, e.g. waste waters, into the pulping, recovery and regeneration cycle (closed-cycle)
- D21C11/0028—Effluents derived from the washing or bleaching plants
Landscapes
- Paper (AREA)
Abstract
ABSTRACT
Waste water from pulp bleaching comprising chlorinated phenol, guaiacol and/or abietic acid derivatives is treated with ozone. By treatment with small amount of ozone, e.g. corresponding to 2 kg ozone/ton pulp, the amount of these chlorinated derivatives can be consider-ably reduced. Reduction degrees of at least 80 % have e.g. been obtained at treatment of waste water from the alkali step of the bleaching process.
Waste water from pulp bleaching comprising chlorinated phenol, guaiacol and/or abietic acid derivatives is treated with ozone. By treatment with small amount of ozone, e.g. corresponding to 2 kg ozone/ton pulp, the amount of these chlorinated derivatives can be consider-ably reduced. Reduction degrees of at least 80 % have e.g. been obtained at treatment of waste water from the alkali step of the bleaching process.
Description
~ ~59 ~ ~
This invention relates to ozone treatment of waste water from pulp blcaching plants.
In most pulp producing countries the cellulose industry has been the branch of industry discharging the largest quantities of organic substance to the water-courses. ~lowever, in a plurali-ty of countries, among others Sweden, these discharges have recently been con-siderably reduced thanks to external and internal mea-sures.
In spite of this the waste water discharged from the pulp mills to the watercourses still contains substances not desired from an environmental point of view. The waste water from the bleaching plants of thc pulp mills is particularly a problem.
In the bleaching process the lignine residues re-maining after cooking the pulp are removed and in this way a chemical pulp of a high whiteness can be obtained. Bleach-ing is carried out with chlorine compounds, such as chlor-ine, chlorine dioxide and hypochlorite, which convert the 3~5 .
Iig~ e int(- an al~clli soluble form. The chlorination is carrie(l out in several steps with intermediate alkali treat-mellt. ~ usual bleaciling se~q-lence for sulfate pulp comprises the following steps: Chlorin.ltion; alkali treatment; hypo-chlorite treatment; chlorine dioxide treatmen~; alkali treat-ment: alld chlorine dioxide treatment.
~ -lowever, it has been found that specific compounds are formed at the bleaching, ancl especially at bleaching of sulfate pulp, which compounds show a high acute toxicity to fish, cause mutations of microorganisms and can be concent-rated in living organisms. These compounds which leave the bleaching plants together with the waste water and are not broken down at conventional biological treatment, e.g. with activated sludge or in aerated dams, substantially consist of chlorinated phenol, guaiacol and abietic acid derivat-ives.
Several different attempts have been made to remove or to reduce substantially the amount of these compounds in waste water, but no economical and reliable method has been developed before. Consequently these compounds are a problem when treating waste water from pulp mills, partic-ularly waste water from sulfate pulp bleaching plants.
Ozone oxidation of waste water from bleaching plants has previously been tested by different researchers, mainly in order to bleach the waste water through the oxidation, above all the water from the alkali step, which accounts for 70-80 ~ of the total coloured discharge from a sulfate I ~ 591~5 mill comprising a bleacl~ g plant. The reqllirecl arnount o~ o~one to achieve e.g. 90 ~ bleaching of the alkaline W.lste is ~-6 kg/-ton pull). I)ue to the high ozone consump-tion and the higll cost o~ tre.ltment associated with this the metho(l has not been usecl in practice.
Tllerefore otller methocls for treatment o-f waste water from bleaching p]ants have been tested ancl it has been found that the problem with bleaching can be solved in a technically satisfactory way, e.g. by ultrafiltration.
However, the prol)lem with the chlorinated derivatives is not solved in this way, as the amounts thereof are only reduced to a slight degree by ultrafiltration.
According to the invention it has now surprisingly been found that the problem with these chlorinated deri-vatives can be eliminated by ozone treatment of the waste water from the bleaching plant and the amounts of these toxic, mutagenic and bioaccumulable compounds can be re-duced to a large extent in spite of the fact that the amounts of ozone necessary for this are considerably less than the amounts required for bleaching the waste water.
By the ozone oxidation the halogenated derivativ-es are split to small units not having the infavourable proper-ties of the halogenatecl derivatives.
This ozone treatment is preferably carried out in combination with previously known technology for treat-ment of waste water from bleaching plants, such as bio-logical purification, adsorption and ultrafiltration, '3 1 ~ ~
which, nowever, do not materially reduce the amount of the halogenated derivatives.
Consequently the invention relates -to a method for treatment of waste water from pulp bleaching, which water contains chlorinated phenol, guaiacol and/or abietic acid derivatives, where in the waste water is treated with ozone.
According to the invention the required ozone amounts vary, i.a. depending on the desired degree of reduction of the compounds, the amounts of chlorinated derivatives in the treated waste water and from which step or steps of the bleaching process the treated waste water originates. Generally speaking, a satisfactory degree of reduction can be obtained with an ozone amount of 1-2 kg/ton pulp, at treatment of waste water from the chlorine step o~ the bleaching process, with an ozone amount of 0.5-2 kg/ton pulp, and preferably 1-2 kg/ton pulp, at treatment of waste water from the alkali step of the bleaching process and with an ozone amount of 1.5-2, and preferably, 2 kg/ton pulp at treatment of waste water combined from the chlorine step and alkali step of the bleaching process.
Usually the concentrations of chlorophenols and chloro-guaiacolsin the chlorine step waste water are considerably below the concentrations in the waste water of the alkali step and therefore it should practically only be necessary to treat the latter water. Of course this is especially advant.lgeolls as thc usecl amount of ozone can be kept as low as ().5-2 kg/ton pulp in this way.
Thc invelltion is explained in the following more in dctail wit?l rcferellce to the enclosed draw;ng in which Fig. 1 shows a block diagram illustrating the method of the invention in principle.
In Fig. I a compressor l is shown, in which air is compressed to a pressure of 0.1-0.2 ~IPa. The main portion of the water content of the compressed air is removed by condensation in a condenser 2 and final drying takes place with a drying agent in a drier 3. The dry gas is led to an ozone generator 4 of a type available on the market, in which ozone is created from the oxygen of the air, when the air is led through an electric arc generated by two electrodes. The ozone content of the air amounts to 1.5-4 ?o and the gas mixture is led to a reactor 5 where it is brought into contact with the waste water from the bleach-ing plant. The gas leaving the reactor may contain small amounts of ozone, which can be dangerous to health and cause corrosion damage. Therefore the gas is passed through a unit 6, where possible remaining ozonc is decomposed catalytically. The plant operates preferably continuously but of course a discontinuous operation is also possible.
One can also use oxygen gas instead of air in the product-ion of ozone.
Exa~ . Waste water from a sulfate pulp bleaching plant, which contained chlorinated phenol and guaiacol ~ ~9:~6~
clcrivat;ves W.lS trc.ltccl ~ith ozone, waste water from he chlorinc stcl) arld th( alkali step ol- the bleaching process l)cirlg treatccl srl)ar;ltc?y with 2.0 kg ozone/ton pulp, rcspcctively. ~moullts or chlorinatecl derivati~es contained in the waste WatC'I` beLolc and after treatment with ozone and reduction clegrecs obtainecl apyear from the following table. The contcnts have been measured by means of gas chrornatography but othcr conventional measuring methods, such as IR-analysis can also be used.
1 159:~G~
h Lr~ Lr) L~ ~r) ~ r~ O
~ L~
`D jfl _ ~
~LI oo ~ ~ ~ o ~ o .~ ~O ,_ t~
,. h ~ O O O o t~ ~ P~ V V V V
S l ~ ~ O ~ l l l n o ~ o o ~ ~ o I
~ ~ X V V
~ ~^ ~ ~ I cr, 4~ ~ ~
h . ~
~ a~^ ~ ~ ~ o ~ x h `O O O
~`J V V L~
a~ ~ ~ 0~o ~ ~ 0~o o a)~ 3 ~ ~
.,-1 u, ~: ~ O a) ~ ~ o 5~ ~ ~ ~ ~
. ~ ~ h a ) t~ O ~ Ll~ ~d O
h ~ ~ ~ h Ll>
_ O ~ ~ h O O ,~ h O O
a~ ~ ~ h S~ ~ U t~ .~ U
,D O " a~o a~O ~ aO~ a)o ~
~ ~ n~ h 2~ ~1 . a~ ~ a ) ~ , E- O _ ~ ~ ~ ~ '5 ~`3 ~15~ S
It is a~)E).llcnt fronl tho table thLt a treatment of the wLste watcr O~ tllc alk.lli step Wit]1 an ozone amount corres-poncling to ' kg/ton pulp recluccs the amount of chlorophenols ancl chloroguaiac-ols by at least 80 S and that in a corres-ponding OZOIlC (IOSagC to ~astc ~atcr from the chlorine step the amount of cl-llolopllcllols is recl-lcecl by more than 80 ~
and the amount of chloroguaiacols by more than 50 ~0.
The invention has substantially been described above ~vith reference to waste watcr from sulfate pulp bleaching plants. Ilowever, it is obvious that the invention can also be utilized at treatment of waste water from sulfite pulp bleaching plants.
This invention relates to ozone treatment of waste water from pulp blcaching plants.
In most pulp producing countries the cellulose industry has been the branch of industry discharging the largest quantities of organic substance to the water-courses. ~lowever, in a plurali-ty of countries, among others Sweden, these discharges have recently been con-siderably reduced thanks to external and internal mea-sures.
In spite of this the waste water discharged from the pulp mills to the watercourses still contains substances not desired from an environmental point of view. The waste water from the bleaching plants of thc pulp mills is particularly a problem.
In the bleaching process the lignine residues re-maining after cooking the pulp are removed and in this way a chemical pulp of a high whiteness can be obtained. Bleach-ing is carried out with chlorine compounds, such as chlor-ine, chlorine dioxide and hypochlorite, which convert the 3~5 .
Iig~ e int(- an al~clli soluble form. The chlorination is carrie(l out in several steps with intermediate alkali treat-mellt. ~ usual bleaciling se~q-lence for sulfate pulp comprises the following steps: Chlorin.ltion; alkali treatment; hypo-chlorite treatment; chlorine dioxide treatmen~; alkali treat-ment: alld chlorine dioxide treatment.
~ -lowever, it has been found that specific compounds are formed at the bleaching, ancl especially at bleaching of sulfate pulp, which compounds show a high acute toxicity to fish, cause mutations of microorganisms and can be concent-rated in living organisms. These compounds which leave the bleaching plants together with the waste water and are not broken down at conventional biological treatment, e.g. with activated sludge or in aerated dams, substantially consist of chlorinated phenol, guaiacol and abietic acid derivat-ives.
Several different attempts have been made to remove or to reduce substantially the amount of these compounds in waste water, but no economical and reliable method has been developed before. Consequently these compounds are a problem when treating waste water from pulp mills, partic-ularly waste water from sulfate pulp bleaching plants.
Ozone oxidation of waste water from bleaching plants has previously been tested by different researchers, mainly in order to bleach the waste water through the oxidation, above all the water from the alkali step, which accounts for 70-80 ~ of the total coloured discharge from a sulfate I ~ 591~5 mill comprising a bleacl~ g plant. The reqllirecl arnount o~ o~one to achieve e.g. 90 ~ bleaching of the alkaline W.lste is ~-6 kg/-ton pull). I)ue to the high ozone consump-tion and the higll cost o~ tre.ltment associated with this the metho(l has not been usecl in practice.
Tllerefore otller methocls for treatment o-f waste water from bleaching p]ants have been tested ancl it has been found that the problem with bleaching can be solved in a technically satisfactory way, e.g. by ultrafiltration.
However, the prol)lem with the chlorinated derivatives is not solved in this way, as the amounts thereof are only reduced to a slight degree by ultrafiltration.
According to the invention it has now surprisingly been found that the problem with these chlorinated deri-vatives can be eliminated by ozone treatment of the waste water from the bleaching plant and the amounts of these toxic, mutagenic and bioaccumulable compounds can be re-duced to a large extent in spite of the fact that the amounts of ozone necessary for this are considerably less than the amounts required for bleaching the waste water.
By the ozone oxidation the halogenated derivativ-es are split to small units not having the infavourable proper-ties of the halogenatecl derivatives.
This ozone treatment is preferably carried out in combination with previously known technology for treat-ment of waste water from bleaching plants, such as bio-logical purification, adsorption and ultrafiltration, '3 1 ~ ~
which, nowever, do not materially reduce the amount of the halogenated derivatives.
Consequently the invention relates -to a method for treatment of waste water from pulp bleaching, which water contains chlorinated phenol, guaiacol and/or abietic acid derivatives, where in the waste water is treated with ozone.
According to the invention the required ozone amounts vary, i.a. depending on the desired degree of reduction of the compounds, the amounts of chlorinated derivatives in the treated waste water and from which step or steps of the bleaching process the treated waste water originates. Generally speaking, a satisfactory degree of reduction can be obtained with an ozone amount of 1-2 kg/ton pulp, at treatment of waste water from the chlorine step o~ the bleaching process, with an ozone amount of 0.5-2 kg/ton pulp, and preferably 1-2 kg/ton pulp, at treatment of waste water from the alkali step of the bleaching process and with an ozone amount of 1.5-2, and preferably, 2 kg/ton pulp at treatment of waste water combined from the chlorine step and alkali step of the bleaching process.
Usually the concentrations of chlorophenols and chloro-guaiacolsin the chlorine step waste water are considerably below the concentrations in the waste water of the alkali step and therefore it should practically only be necessary to treat the latter water. Of course this is especially advant.lgeolls as thc usecl amount of ozone can be kept as low as ().5-2 kg/ton pulp in this way.
Thc invelltion is explained in the following more in dctail wit?l rcferellce to the enclosed draw;ng in which Fig. 1 shows a block diagram illustrating the method of the invention in principle.
In Fig. I a compressor l is shown, in which air is compressed to a pressure of 0.1-0.2 ~IPa. The main portion of the water content of the compressed air is removed by condensation in a condenser 2 and final drying takes place with a drying agent in a drier 3. The dry gas is led to an ozone generator 4 of a type available on the market, in which ozone is created from the oxygen of the air, when the air is led through an electric arc generated by two electrodes. The ozone content of the air amounts to 1.5-4 ?o and the gas mixture is led to a reactor 5 where it is brought into contact with the waste water from the bleach-ing plant. The gas leaving the reactor may contain small amounts of ozone, which can be dangerous to health and cause corrosion damage. Therefore the gas is passed through a unit 6, where possible remaining ozonc is decomposed catalytically. The plant operates preferably continuously but of course a discontinuous operation is also possible.
One can also use oxygen gas instead of air in the product-ion of ozone.
Exa~ . Waste water from a sulfate pulp bleaching plant, which contained chlorinated phenol and guaiacol ~ ~9:~6~
clcrivat;ves W.lS trc.ltccl ~ith ozone, waste water from he chlorinc stcl) arld th( alkali step ol- the bleaching process l)cirlg treatccl srl)ar;ltc?y with 2.0 kg ozone/ton pulp, rcspcctively. ~moullts or chlorinatecl derivati~es contained in the waste WatC'I` beLolc and after treatment with ozone and reduction clegrecs obtainecl apyear from the following table. The contcnts have been measured by means of gas chrornatography but othcr conventional measuring methods, such as IR-analysis can also be used.
1 159:~G~
h Lr~ Lr) L~ ~r) ~ r~ O
~ L~
`D jfl _ ~
~LI oo ~ ~ ~ o ~ o .~ ~O ,_ t~
,. h ~ O O O o t~ ~ P~ V V V V
S l ~ ~ O ~ l l l n o ~ o o ~ ~ o I
~ ~ X V V
~ ~^ ~ ~ I cr, 4~ ~ ~
h . ~
~ a~^ ~ ~ ~ o ~ x h `O O O
~`J V V L~
a~ ~ ~ 0~o ~ ~ 0~o o a)~ 3 ~ ~
.,-1 u, ~: ~ O a) ~ ~ o 5~ ~ ~ ~ ~
. ~ ~ h a ) t~ O ~ Ll~ ~d O
h ~ ~ ~ h Ll>
_ O ~ ~ h O O ,~ h O O
a~ ~ ~ h S~ ~ U t~ .~ U
,D O " a~o a~O ~ aO~ a)o ~
~ ~ n~ h 2~ ~1 . a~ ~ a ) ~ , E- O _ ~ ~ ~ ~ '5 ~`3 ~15~ S
It is a~)E).llcnt fronl tho table thLt a treatment of the wLste watcr O~ tllc alk.lli step Wit]1 an ozone amount corres-poncling to ' kg/ton pulp recluccs the amount of chlorophenols ancl chloroguaiac-ols by at least 80 S and that in a corres-ponding OZOIlC (IOSagC to ~astc ~atcr from the chlorine step the amount of cl-llolopllcllols is recl-lcecl by more than 80 ~
and the amount of chloroguaiacols by more than 50 ~0.
The invention has substantially been described above ~vith reference to waste watcr from sulfate pulp bleaching plants. Ilowever, it is obvious that the invention can also be utilized at treatment of waste water from sulfite pulp bleaching plants.
Claims (8)
1. A method for treatment of waste water from pulp bleaching, said waste water comprising at least one substance selected from the group of chlorinated phenol, guaiacol and abietic acid derivatives, wherein the waste water is treated with ozone in an amount up to 2 kg ozone per ton pulp to reduce its content of chlorinated phenol, guaiacol and/or abietic acid derivatives.
2. The method of Claim 1, wherein the waste water originated from the chlorine step of the bleaching process.
3. The method of Claim 1, wherein the waste water originates from the alkali step of the bleaching process.
4. The method of Claim 1, wherein the waste water consists of a mixture of waste water from the chlorine step of the bleaching process and waste water from the alkali step of the bleaching process.
5. The method of Claim 2, wherein such an amount of ozone is used that the amount of phenol derivatives is reduced by at least 80% and that the amount of guaiacol derivatives is reduced by at least 50%.
6. The method of Claim 3 or 4, wherein such an amount of ozone is used that the amount of phenol and guaiacol derivatives is reduced by at least 80%.
7. The method of Claim 1, wherein the waste water from the chlorine step of the bleaching process is treated with an amount of ozone corresponding to 1-2 kg/ton pulp, the waste water from the alkali step of the bleaching process is treated with an ozone amount corresponding to 0.5-2 kg/ton pulp and the waste water consisting of a mixture of waste water from the chlorine step and alkali step of the bleaching process is treated with an ozone amount corresponding to 1.5-2 kg/to pulp.
8. The method of Claim 1, wherein an ozone amount corresponding to 2 kg/ton pulp is used.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7901248-0 | 1979-02-13 | ||
| SE7901248A SE7901248L (en) | 1979-02-13 | 1979-02-13 | SET FOR TREATMENT OF WASTE WATER FROM PILLOWS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1159165A true CA1159165A (en) | 1983-12-20 |
Family
ID=20337278
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000345541A Expired CA1159165A (en) | 1979-02-13 | 1980-02-12 | Method for treatment of waste water from pulp bleaching plants |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1159165A (en) |
| SE (1) | SE7901248L (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0564443A1 (en) * | 1992-03-15 | 1993-10-06 | Kamyr, Inc. | Treatment of bleach plant filtrates |
| US6106667A (en) * | 1992-02-21 | 2000-08-22 | Ahlstrom Machinery Inc. | Treatment of recycled bleach plant filtrates |
-
1979
- 1979-02-13 SE SE7901248A patent/SE7901248L/en not_active Application Discontinuation
-
1980
- 1980-02-12 CA CA000345541A patent/CA1159165A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6106667A (en) * | 1992-02-21 | 2000-08-22 | Ahlstrom Machinery Inc. | Treatment of recycled bleach plant filtrates |
| EP0564443A1 (en) * | 1992-03-15 | 1993-10-06 | Kamyr, Inc. | Treatment of bleach plant filtrates |
Also Published As
| Publication number | Publication date |
|---|---|
| SE7901248L (en) | 1980-08-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |