| abstract |
PCT No. PCT/FI94/00376 Sec. 371 Date May 31, 1996 Sec. 102(e) Date May 31, 1996 PCT Filed Aug. 26, 1994 PCT Pub. No. WO95/06004 PCT Pub. Date Mar. 2, 1995Waste water sludge which contains phosphorous, heavy metals and at least one metal originating from a waste water treatment coagulant, is treated in order to recover the phosphorous and the at least one metal, and to discharge the heavy metals. The at least one metal includes iron. The treatment method includes the steps of acidifying the sludge to dissolve metals contained therein; subjecting the acidified sludge to liquid-liquid extraction to thereby provide an aqueous phase or raffinate, and recovering at least a portion of the at least one metal; treating the raffinate, during a first precipitation stage, with an effective amount of chemicals to provide a precipitate including heavy metals, and a solution having a decreased content of heavy metals; discharging the precipitate including heavy metals; treating the solution having a decreased content of heavy metals, in a second precipitation stage, with an effective amount of chemicals to provide a precipitate including phosphorous; and recovering phosphorous from the precipitate including phosphorous. |