초록 ▼

Processes, methods and systems are provided herein for lowering the concentration of phosphorus in wastewater. The process includes adding a suitable amount of an aluminum-based coagulant/flocculent, for example, an aluminum-silicate coagulant/flocculent product to the wastewater while maintaining t

Processes, methods and systems are provided herein for lowering the concentration of phosphorus in wastewater. The process includes adding a suitable amount of an aluminum-based coagulant/flocculent, for example, an aluminum-silicate coagulant/flocculent product to the wastewater while maintaining the pH of the wastewater at between about 4.5 and about 6.65. This step provides an eventual effluent stream of precipitated aluminum-based, phosphorus-containing flocs dispersed in the wastewater. The next step involves physically removing, as by filtering, the precipitated aluminum-based, phosphorus-containing flocs which is dispersed in the wastewater. These steps are able to provide a wastewater effluent containing less than about 0.03 mg total phosphorus per liter of wastewater. The disclosure also teaches novel methods and systems for carrying out the novel process.

대표청구항 ▼

The invention claimed is: 1. A process for lowering the concentration of total phosphorus in wastewater discharged from a settling chamber to a level below about 0.03 milligrams per liter comprising: a) treating the wastewater by adding to said wastewater a suitable amount of aluminum-based coagula

The invention claimed is: 1. A process for lowering the concentration of total phosphorus in wastewater discharged from a settling chamber to a level below about 0.03 milligrams per liter comprising: a) treating the wastewater by adding to said wastewater a suitable amount of aluminum-based coagulant/flocculent for precipitation of phosphorus in said wastewater, the wastewater having a pH of about 4.5 to 6.4 during such treatment, to provide an eventual effluent stream of wastewater with precipitated aluminum-based, phosphorus-containing flocs dispersed in said wastewater; and b) filtering said precipitated aluminum-based, phosphorus-containing flocs from said eventual effluent stream of wastewater to lower the concentration of total phosphorus in the effluent stream of treated wastewater to a level below about 0.03 milligrams per liter. 2. A process for lowering the concentration of total phosphorus in wastewater to a level below about 0.03 milligrams per liter comprising: a) treating the wastewater by adding to said wastewater a suitable amount of aluminum-based coagulant/flocculent for precipitation of the phosphorus in said wastewater to provide a stream of wastewater with precipitated aluminum-based, phosphorus-containing flocs dispersed in said wastewater; and b) a step of physically removing a necessary amount of said precipitated flocs from said stream of wastewater to lower the concentration of total phosphorus in a treated effluent stream wastewater to a level below about 0.03 milligrams per liter, and wherein the suitable amount of aluminum-based coagulant/flocculent is divided into: c) a first amount of aluminum-based coagulant/flocculent, and; d) a second amount of aluminum-based coagulant/flocculent, and wherein the step of adding the suitable amount of aluminum-based coagulant/flocculent includes: e) the preliminary step of adding, in a preliminary treatment zone, the first amount of aluminum-based coagulant/flocculent to said wastewater while the pH of the wastewater is maintained above 6.65 to produce precipitated aluminum-based, phosphorus-containing flocs, f) transferring the wastewater from the preliminary treatment zone to a settling zone wherein at least a portion of the said flocs is allowed to settle from the wastewater while the wastewater is in the settling zone, g) separating the wastewater from the settled flocs, h) a further step adding the second amount of aluminum-based coagulant/flocculent to said separated wastewater while the pH of the wastewater is maintained at or below 6.4 to produce further precipitated flocs, and wherein the step of physically removing precipitated flocs from the wastewater includes the step of filtering precipitated flocs from said wastewater sufficiently to lower the concentration of total phosphorus in the effluent stream of treated wastewater to said level of below about 0.03 milligrams per liter. 3. The process as claimed in claim 2, wherein the pH of the wastewater during the further step of adding the second amount of aluminum-based coagulant/flocculent is maintained at or between 4.5 and 6.4. 4. The process as claimed in claim 3, wherein the pH of the wastewater, when the first amount of aluminum-based coagulant/flocculent is added, is maintained at about 6.8 to about 7.6. 5. The process as claimed in claim 4, wherein, as part of a further step, the wastewater from the settling zone is passed to an in-line mixing zone, and wherein said second amount of aluminum-based coagulant/flocculent product is added to the wastewater in or upstream of the in-line mixing zone. 6. The process as claimed in claim 5, wherein: the pH of the wastewater in the preliminary treatment zone is maintained at about 7.0; and wherein said first amount of aluminum-based coagulant/flocculent comprises about 75% by weight of said suitable amount of said aluminum-based coagulant/flocculent; and wherein the aluminum-based coagulant/flocculent is polyaluminum silicate sulphate; and wherein said suitable amount of aluminum-based coagulant/flocculent is from about 15 to about 50 milligrams as Al2O3 per liter of said wastewater; and wherein the physical removal of a substantial portion of said precipitated flocs from said effluent stream of wastewater is effected through the use of continuous self-cleaning sand filters. 7. The process as claimed in claim 4, wherein the pH of the wastewater in the preliminary treatment zone is maintained at about 6.8 to about 7.6 through the addition of a base to the wastewater. 8. The process as claimed in claim 1 of treating the wastewater at said pH of about 4.5 to 6.4, or the process as claimed in claim 2, 3, 4, 5 or 7 wherein the step by which the pH of the wastewater is maintained at or below 6.4, is effected through the addition of a suitable amount of an acid. 9. The process as claimed in claim 8 wherein the acid is selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, citric acid. 10. The process as claimed in claim 8, wherein the aluminum-based coagulant/flocculent is selected from the group consisting of polyaluminum silicate sulphate, polyaluminum silicate chloride, polyaluminum hydroxychlorosulphate, aluminum sulphate, and polyaluminum chloride. 11. The process as claimed in claim 10, wherein the aluminum-based coagulant/flocculent is polyaluminum silicate sulphate. 12. The process as claimed in claim 1 of treating the wastewater at said pH of about 4.5 to 6.4, or the process as claimed in claim 2, 3, 4, 5 or 7, wherein the step by which the pH of the wastewater is maintained at or below 6.4, is effected through the addition of a suitable amount of an aluminum-based coagulant/flocculent. 13. The process as claimed in claim 12, wherein the aluminium-based coagulant/flocculent is selected from the group consisting of polyaluminium silicate sulphate, polyaluminium silicate chloride, polyaluminium hydroxychlorosulphate, aluminium sulphate, and polyaluminium chloride. 14. The process as claimed in claim 13, wherein the aluminium-based coagulant/flocculent is polyaluminium silicate sulphate. 15. The process as claimed in claim 12 wherein the treating of the wastewater at a pH of 4.5 to 6.4 or the step by which the pH of the wastewater is maintained at or below 6.4, is effected through the addition of a suitable amount of an acid in addition to an aluminium-based coagulant/flocculent. 16. The process as claimed in claim 15, wherein the aluminium-based coagulant/flocculent is selected from the group consisting of polyaluminium silicate sulphate, polyaluminium silicate chloride, polyaluminium hydroxychlorosulphate, aluminium sulphate, and polyaluminium chloride. 17. The process as claimed in claim 16, wherein the aluminium-based coagulant/flocculent is polyaluminium silicate sulphate. 18. The process as claimed in claim 16 wherein the acid is selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and citric acid. 19. The process as claimed in claim 15 wherein the acid is selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and citric acid. 20. The process as claimed in claim 2 or 3, wherein said first amount of aluminium-based coagulant/flocculent comprises about 70% to about 80% by weight of said suitable amount of said aluminium-based coagulant/flocculent. 21. The process as claimed in claim 1, 2, 3, 4, 5, or 7 wherein the aluminium-based coagulant/flocculent is selected from the group consisting of polyaluminium silicate sulphate, polyaluminium silicate chloride, polyaluminium hydroxychlorosulphate, aluminium sulphate, and polyaluminium chloride. 22. The process as claimed in claim 21, wherein the aluminium-based coagulant/flocculent is polyaluminium silicate sulphate. 23. The process as claimed in claim 1, 2, or 3 wherein said suitable amount of aluminium-based coagulant/flocculent is from about 15 to about 50 milligrams as Al2O3 per liter of said wastewater. 24. The process as claimed in claim 1, 2, 3, 4, 5, or 7 wherein the filtering of said precipitated flocs from said stream of wastewater is effected through the use of a filter chosen from the list consisting of sand filters, multimedia filters, ultrafiltration membranes and microfiltration membranes. 25. The process as claimed in claim 2, 3, 4, 5, or 7 wherein the preliminary step of adding, in the preliminary treatment zone, the first amount of aluminium-based coagulant/flocculent to said wastewater is effected in a biological reactor. 26. The process of claim 25 wherein said biological reactor is a rotating biological contactor. 27. The process of claim 25 wherein the aluminium-based coagulant/flocculent is polyaluminium silicate sulphate.