The Study On The Effect Of Thermal-Alkaline Pretreatment On Two-Phase Anaerobic Digestion Of High Solid Content Sludge

With the improvement of treatment rate of urban sewage, the sludge produced bymunicipal sewage treatment plants need to be disposed scientifically and reasonably,otherwise the environment will be polluted secondly. According to the requirement ofmaking sludge harmless and stable, be reduced and recycled, the study of the anaerobicdigestion process for the high solid content sludge is one of the focus at domestic andinternational.Based on national high technology research development plan (National ‘863’project)-“The Research and Demonstration of Temperature Staging and Biology PhasingAnaerobic Digestion of Sewage Sludge” project, this paper is mainly concerned with theeffect of thermal-alkaline pretreatment on two-phase anaerobic digestion of high solidcontent sludge. Firstly a series of batch experiments were carried out to explore theparameters of thermal-alkaline pretreatment; then sludge was hydrolyzed and acidized bybatch experiments, which was pretreated by thermal-alkaline pretreatment; lastly theparameters were used in two-phase anaerobic digestion reactors. The main conclusions areas follows:The contents of SCOD and VFAs in sludge of TS=8%show that the best parametersare pH=11,30min,80℃in batch experiments of thermal-alkaline pretreatment, and in thiscase, both of SCOD and VFAs are the highest; According to the hydrolysis by NaOHthermal-alkaline pretreatment, KOH thermal-alkaline pretreatment and no pretreatment,the thermal-alkaline pretreatment is good to hydrolysis of the sludge and KOHthermal-alkaline pretreatment is better than NaOH thermal-alkaline pretreatment.To verify the effect of the thermal-alkaline pretreatment, a series of batchexperiments of hydrolysis and acidification were carried out in5days. Both of the trendsof SCOD and VFAs are increasing，and maximum of these contents are peaked in the endof reaction. The order of the content of SCOD and VFAs is KOH thermal-alkalinepretreatment>NaOH thermal-alkaline pretreatment>no pretreatment, the conclusions arethat thermal-alkaline pretreatment can contribute to the hydrolysis and acidification of thesludge and the advantage of KOH thermal-alkaline pretreatment is obvious. The effects of anaerobic digestion of the sludge after different thermal-alkalinepretreatments are compared in this study; the pretreatments are KOH pretreatment, NaOHpretreatment and no pretreatment. The result shows that the hydrolysis and acidification ofthe sludge after thermal-alkaline pretreatment is better than no pretreatment in acidogenicreactors, but there is no difference between KOH pretreatment and NaOH pretreatment.The order of methane production in every methanogenic phase reactor is KOHpretreatment>NaOH pretreatment>blank, this phenomenon indicates that thermal-alkalinepretreatment can promote the anaerobic digestion of the sludge.