Effect of sludge type on sludge alkaline fermentation

There are mainly three types of sludge in the wastewater treatment plant,i.e.,waste activated sludge(WAS),primary sludge(PS) and mixed sludge(MS),for which their composition is different,leading to different products of fermentation.So,in this paper their anaerobic fermentation characteristics was investigated under the condition of 35℃,pH= 10 and the same concentration of VSS(volatile suspend solids).The results showed that there was a sludge order for both the soluble chemical oxygen demand(SCOD)and total volatile fatty acids(TVFA)produced:WASMSPS.The optimal fermentation time for all type of sludge was 8 d,and producing TVFA 529,359,162 mg COD·(g VSS)-1 respectively for WAS,MS and PS.For any type of sludge,acetic acid is the dominant fermentation product in the six short chain volatile fatty acids.The hydrolysis and acidification of sludge were enhanced when mixing waste activated with primary sludge.The ammonia and phosphorus released by fermentation were WASMSPS,MSWASPS.