[Sludge dewaterability with combined conditioning using Fenton's reagent and CPAM].

The moisture of sludge significantly influenced its dewaterability and the disposal cost. Cationic polyacrylamide (CPAM) and Fenton's reagent were investigated for sludge dewatering with separate and combined conditioning. Several parameters were used to evaluate the dewatering performance and to analyze the conditioning mechanism, such as cake moisture, soluble COD, protein and polysaccharide contents in supernatant and sludge particle size. The results indicated that favorable dewaterability was achieved when the sludge was conditioned at higher CPAM degrees, and sludge dewatering ability was further improved at acidic conditions. In Fenton reaction, higher H2O2 dosages enhanced the dewatering performance of sludge. Combined conditioning using Fenton's reagent and CPAM led to considerable improved sludge dewaterability. At the optimized dosages of FeSO4 (2 g x L(-1)) and H2O2 (6 g x L(-1)), the sludge moisture declined to 76.7% from 85.5% (raw sludge), while a moisture as low as 74.8% was obtained by combined conditioning using CPAM (3 kg x t(-1)). Sludge particle size went down and the specific surface area grew bigger after Fenton reaction. As a result of disintegration of extracellular polymeric substances (EPS), the adsorbed and intrinsic water were released from microorganisms and sludge flocs. CPAM addition remarkably promoted the coagulating and flocculating of dispersed flocs. Sludge particle size changed from 35.16 microm to 50.50 microm, and the specific surface area declined from 0.39 m2 x g(-1) to 0.20 m2 x g(-1). The combined conditioning using Fenton's reagent and CPAM was proved to be more effective in improving sludge dewaterability, compared with the separate conditioning.