Optimization of alum recovery from water treatment sludge‐case study: Samannoud water treatment plant, Egypt

Abstract Alum recovery from water treatment sludge is a promising technique applied for reducing the virgin coagulant demand and the sludge volume and safe disposal of the sludge. The aim of the current study is to optimize alum recovery process from alum sludge in Samannoud water treatment plant, Egypt by acidification technique using sulphuric acid and evaluate the effect of total solids (TS) content in the sludge on alum recovery process. Results showed that the optimal mixing time for alum recovery was 60 min for clariflocculator sludge, whereas 15 min for thickener sludge. Optimum pH value was 1.50 for alum recovery from different sludge types. At optimum conditions, acidification experiments showed that alum recovery percent and sludge volume reduction for clariflocculator sludge were 83 and 91.2%, respectively, versus 35.9 and 45%, respectively, for thickener sludge. Besides, alum recovery and sludge reduction decreased with the increase in TS content in the sludge.