Study On High Performance Dewatering Technology And Anaerobic Digestion Of Sewage Sludge

As the quantity of sludge increases fast in China,the high performance dewatering of sludge is becoming a hot issue.The sludge form Beiyuan WWTP was hard to dewater because of high VSS.Several kinds of chemicals and project were selected respectively for sludge conditioning.Thermal hydrolysis pretreatment combined with anaerobic digestion were taken for a better dewaterbility of sludge.The results indicated that:?1?Taking FeCl₃,chitosan,anionic polyacrylamides,nonionic polyacrylamides,cationic polyacrylamides as sludge conditioner,sludge resistance?SRF?,capillary suction time?CST?were obtained,and their correlations were investigated by fitting analysis.Results showed under the same conditioning,CST and SRF have linear relationship?R2>0.95?,so CST could be used to indicate the best dosage of conditioner;With different electrical property,CPAM works best among PAM;The recommended dosage of CPAM was 0.2%⁰.8%,chitosan was 2%¹0%,FeCl₃ was 15%²5%.The CST or SRF of sludge could be minimum with these dosage.?2?Taking CPAM?FeCl₃?Ca?OH?₂ and coal fines as conditioner before plate-frame pressure filtration at WWTP to get dewatered sludge cake.The water content of sludge cake could reach 42.3%⁴5.7%,of which,bound water reduced to 10.21%,and the combustion heat of sludge cake could reach 6464 k J/Kg⁶870 k J/kg.The solid content and the combustion heat of sludge cake could reach physical and chemical indicators for incineration alone.Taking thermal hydrolysis pretreatment of sludge at 60 ??70 ??80 ? for 5 min?15 min?30 min?60 min?120 min,then to anaerobic digestion at 35 ??55 ?,with the SRT 20 d and 30 d.Results showed that after thermal hydrolysis treatment,SCOD?VFAs contents and CST of sludge increased.Thermal hydrolysis treatment worked best at 70 ? and 30 min;The contents of protein,polysaccharide,and protein / polysaccharide in slime EPS respectively have linear relationship with CST of sludge?R?0.95?;SRT and temperature both had influence on rate of biogas production and CST of digestion sludge.Temperature of anaerobic digestion proved to have the most important influence.Thermal hydrolysis pretreatment has little influence under thermophilic digestion,but it improved rate of biogas production under mesophilic anaerobic digestion.Both thermal hydrolysis pretreatment and anaerobic digestion increased CST of sludge.The CST of thermal hydrolysis pretreatment sludge was lower than the thermal hydrolysis pretreatment sludge after anaerobic digestion.