Effect of wastewater composition and cell residence time on phosphorus removal in activated sludge

particularly nitrogen and phosphorus, has received considerable attention in the past several years. Methods of removing phosphorus depend principally on chemi cal precipitation through the use of lime, alum, and ferrous or ferric sulfate. Chem ical precipitation, although very effective and reliable, has several disadvantages. Increased equipment and chemical costs, together with sludge disposal costs and as sociated problems, are factors that must be considered seriously. Removal of phos phorus by biological means is a method of removal that may help alleviate high costs. In the past several years a considerable amount of research has been devoted to