Claims
- 1. In a paper-making process a method for treating paper mill waste water to remove the suspended material therein so that the clarified waste water may be reused in the paper-making process, comprising the steps of:
- (a) adding a sufficient amount of sulfuric acid to reduce the pH of the waste water to less than 4.0,
- (b) mixing thoroughly, then,
- (c) adding a sufficient amount of calcium hydroxide to rapidly drive the pH of the acidified waste water to above 10 and cause coagulation of the solid matter in said waste water,
- (d) separating the coagulated solid material from the waste water to clarify it, and
- (e) treating the clarified waste water to return the pH to approximately neutral.
- 2. The method of claim 1 wherein said sulfuric acid is added as a concentrated liquid and thoroughly mixed with said waste water and said calcium hydroxide is added as a dry slaked lime and thoroughly mixed with said acidified waste water.
- 3. The method of claim 2 wherein the acidified waste water is allowed to age for a period of time sufficient to permit a reaction to take place which renders insoluble some of the dissolved emulsified solids in said waste water.
- 4. The method of claim 3 wherein said sulfuric acid is added to a neutral pH waste water at the rate of 320 parts/million, said dry slaked lime is added at the rate of 250 parts/million, and said aging step is conducted at at least room temperature for over five minutes.
- 5. The method of claim 2 wherein said coagulated solid material is separated from said waste water by filtration.
- 6. The method of claim 5 wherein said solid material removed by filtration is further dewatered and, then, burned as a source of fuel for said paper making process.
- 7. The method of claim 5 wherein said solid material removed by filtration is used as a pulp source in the paper-making process.
- 8. The method of claim 7 wherein said paper making process is a boxboard producing process and said solid material removed by filtration is used as a pulp source for the filler section of the boxboard.
- 9. The method of claim 5 wherein said solid material is used as a landfill.
- 10. In a paper making process utilizing large quantities of water for stock preparation and the like, a method of providing the major part of water needed in such process by treatment and recycling of waste water therefrom comprising the steps of
- (a) continuously collecting waste water from the several steps of the paper-making process;
- (b) passing the collected waste water through a first treatment stage and adding thereat sufficient sulfuric acid to reduce the pH of the mixture to at least 4.0;
- (c) mixing thoroughly,
- (d) then passing the acidified waste water through a second treatment stage and adding thereat sufficient calcium hydroxide to raise the pH of the mixture quickly to at least 10 causing coagulation of solids in the mixture;
- (e) removing the coagulated solids from the mixture to clarify the waste water;
- (f) restoring the pH of the clarified waste water approximately to neutral; and
- (g) recycling the neutralized, clarified waste water into the paper-making process as the major source of water for that process.
CROSS REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part of application Ser. No. 612,567, filed Sept. 11, 1975 now abandoned.
US Referenced Citations (8)
Non-Patent Literature Citations (1)
Entry |
"Screening of Effluents," Fuller, Tappi, vol. 56, No. 6, Jun. 1973, pp. 104-106. |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
612567 |
Sep 1975 |
|