Research On Sewage Sludge Reduction Technology By Microwave Induced Process

The conventional activated sludge process is the most widely used biological treatmentprocess for both domestic and industrial wastewater. However, one of its drawbacks is highsludge production. At home and abroad, the studies on sludge treatment and disposal showedthat the existing technologies in environmental and economic aspects are flawed. Sludgereduction technology has a significant place in wastewater biochemical treatment field. As avery fast sludge hydrolysis method, microwave pretreatment has attracted increasingattention.Effects of microwave induced treatment on characteristics of sewage sludge wereinvestigated in this paper. The effects of different operation, such as microwave power,irradiation time, types and dosages of microwave absorbing material were mainly investigatedto optimize the treatment condition. The concentration of SCOD, TN, TP, NH₄⁺-N, proteinand sugar in sludge solution after microwave induced treatment were compared with thesimple microwave treatment. SBR process which continuous experiment in lab scale wascarried out to investigate the effect of sludge reduction by microwave induced. Effect ofmicrowave induced pretreatment on the effluent quality of SBR and the activity of sludgehave been analyzed.The results indicated that microwave induced oxidation treatment increased the lysis ofexcess sludge. By using activated carbon as catalyst, under the optimal operation of800Wmicrowave irradiation power,60s microwave irradiation time and the activated carbondosage of0.3g per gram SS, the sludge dissolving ratio increased to28.9%. Theconcentration of SCOD, soluble protein, total soluble sugar, TP and TN increased to2772mg/L,160.5mg/L,125.2mg/L,29.3mg/L and64.2mg/L which were respectively about3.3times,0.8times,0.5times,1.4times and1.5times as compared with the simple microwavetreatment. Part of organic nitrogen was mineralized by oxidants to NH₄⁺-N from7.9mg/L to14.2mg/L. The oxidants were produced by microwave induced activated carbon. The sludgedissolving ration was increased10.8%compared with the simple microwave treatment with irradiation power of800W, the irradiation time of50s and the dosage of activated carbonfibers0.16g per gram SS. The apparent yield coefficient of microwave induced treatmentreactor decreased with increasing fraction of the treated sludge. It decreased by24.3%,43.3%and62.2%respectively by daily treating5%,10%and15%of the reactor sludge. The effluentSCOD concentration slightly increased with increasing fraction of the treated sludge, but thebiological treatment performance was maintained and the removal rate of SCOD reached tomore than85%. The removal rates of effluent TP decreased by14.8%、27.4%、37.5%compared with the control system. Between the two system the removal rates of NH₄⁺-N andthe degradation rate constants of NH₄⁺-N had respectively little difference. Nitrificationcapabilities was scarcely altered by microwave induced treatment. Between the two systemthe OUR were almost the same, the activity of sludge was still well, the OUR was between12.6and15.2mgO2/（gVSS·h） which belong the normal range.