PROCESS FOR RECOVERING INORGANIC COAGULANTS FROM WATER OR WASTE WATER TREATMENT SLUDGES

摘要

The invention is concerned with the recovery of inorganic coagulants used in water or waste water treatment processes from the coagulant-containing sludges produced in such processes. The method consists of the following steps: 1) treatment of the sludge with acidic or alkaline material as appropriate in order to dissolve the coagulant; 2) adjustment of liquor pH to 2 - 3, if necessary; 3) addition of polyelectrolyte and optionally a solid adsorbent to the liquor to cause precipitation of some impurities; 4) separation of the liquor containing dissolved coagulant from the residue; 5) contact of the supernatant from step 4 with a positively charged and/or hydrophobic solid adsorbent to remove soluble organic materials. The process described has the dual benefit of reducing the volume of sludge for disposal, and reducing the amount of fresh coagulant needed and hence saving on coagulant costs.