Finding means of recovering ALUM (Coagulant) from the waste sludge to be reused as a coagulant.

Abstract

Alum is used in the coagulation of raw water in almost all water treatment plants worldwide. Thousands of tons of alum are used annually in water treatment plants across the country costing millions of dollars. This scientific research report deals with the recovery of more alum available at the coagulation sludge. The recovery process involved the following steps; concentration of the sludge from 5% to 20% solids, acidification with sulfuric acid or alkalization with sodium hydroxide depending on the recovery methodology to be used. Then the supernatant liquid was separated (screened), decolourized with charcoal, filtrated, concentrated by evaporation to get thick solution and finally crystalized to obtain pure crystals of alum. The effects of operating variables on the efficiency of recovered alum were also studied. The recovered alum was tested in coagultion runs using a jar test. The results obtained were very promising and showed that alum present in sludge can be recovered and reused for multiple times.