Stabilization of Sewage Sludge by a Combined Chemical and Mechanical Method

A large quantity of dewatered sewage sludge and other waste materials are produced each year in Singapore. The disposal of these waste materials has become a problem. On the other hand, a large amount of fill materials are required for land reclamation. A study to use the sewage sludge and other waste materials for land reclamation was carried out. Portland cement was used as a binder to stabilize the sludge. Another waste material, copper slag, was used as filler. The study shows that the stabilization effect of cement can be greatly enhanced if the cement mixed sludge can be consolidated by mechanical means. Therefore, it is cost-effective to adopt a combined chemical and mechanical method to treat the sludge. Leaching tests were also conducted to show that heavy metals were largely retained in the residual fraction, rendering the stabilized sludge to be more resistant in leaching.