Analysis of the effect of using divalent and trivalent iron compounds on sludge dewatering performance in thickening units

Abstract Sludge is one of the by-products wastewater treatment plants (WWTPs). To assist biological processes, part produced sludge returned to process and excess removed from plant whereby it undergoes thickening dewatering. Numerous studies have been conducted investigate effect different coagulants on dewatering sludge, but using divalent iron for this purpose has not investigated so far. In research, trivalent compounds (ferrous sulfate ferric chloride) first module Bojnourd WWTP (Iran) investigated. regard, first, doses each coagulant optimize characteristics was then pH change by adding lime The results showed that addition optimal FeSO4 (0.6 0.4 g/l) (0.664 1.5866 reduced capillary suction time 30.6 32.7%, respectively, while reducing moisture content cake 26 30.6%.