| Huge amounts of excess sludge has become a problem of municipal sewage plant.Since the cost of treating excess sludge has grown up with the increasing amounts ofexcess sludge and regulations has limited the moisture of sewage sludge before finaltreatment, it is becoming more and more important to dewater sewage sludge.Gennally, sludge conditioning is needed to improve sludge dewaterability beforemechanical dewatering. Often, flocculating agent is used to condition sludge beforemechanical dewatering. However, sludge cake moisture can be only decreased to80%while using this method, which could hardly meet the requirements of envirenment,economic and regulations. For decades, advanced oxidation processes (AOPs)utilizing free radicals as a primary oxidant, have been given growing attention to forsludge dewatering, in view of short treatment time and high dewatering efficiency.The potential benefits of combining microwave with sodium persulfate tocondition sludge and its mechanisms were investigated in this study. Capillary suctiontime (CST) and sludge cake moisture were used to evaluate sludge dewaterability.The effect of several significant factors on sludge dewaterability, includingmicrowave irradation time, microwave power, initial pH value and sodium persulfatedosage, were investigated and analyzed respectively. The results showed that sludgedewaterability was better improved combining microwave with sodium persulfatethan microwave conditioning or sodium persulfate conditioning alone. The optimalconditions to give preferable dewaterability characteristics were found to bemicrowave irradation time210s, microwave power800W, initial pH3.0-6.0andpersulfate0.8mmol/g (dry solids). After conditioning, sludge showed a bettersettleability compared with before.Extracellular polymeric substances (EPS) content, Zeta potential, microscopicimage of the flocs and FTIR were measured before and after conditioning in order togive possible conditioning mechanism of the team work on the sewage sludge. |
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