Study On Property Changes Of The Sludge Dewatered By Electroosmosis

As a new sludge dewatering technology, electroosmotic dewatering has beenpaid attention and widely applied. The process of electroosmotic dewatering changedthe properties of the sludge. Choice on the way of further treatment of sludge afterelectroosmotic dewatering was affected by these property changes. So it wasnecessary to study on these changes. Following works were done based on the wastedsludge from Jizhuangzi wastewater plant in Tianjin.Biological activity and physicochemical property of the sludge were studied. Themoisture content of original sludge was declined to70%under three voltage gradientResearch was done on the property changes of the sludge of differentdistrict——anode district sludge, cathode district sludge and mixed sludge. Resultsshowed: pH of mixed sludge changed very little. SCOD of sludge lixivium wasimproved. Heavy metal was removed out of mixed sludge by electroosmoticdewatering. The highest removal rate of Zn was16.62%, the highest removal rate ofNi was20.19%, the highest removal rate of Pb was26.07%, the highest removal rateof Cu was11.28%. Removal rate of heavy metal of the sludge in anode district andcathode district was different. Biological activity of the sludge in anode districtdecreased by70%-80%, however biological activity of the sludge in cathode districtincreased by20%-50%.Study on sludge used for acid production by anaerobic fermentation afterelectroosmotic dewatering was done. Experiments of different dosing proportionshowed that more VFAs were produced when the dosing proportion of the quality ofdry matter was4:1. Contrast experiments showed that increment concentration ofVFAs reached its maximum——784.21mg/L,701.32mg/L and860.58mg/L at48hwith mixed sludge and sludge of node district and cathode district dosed intoseparated reactors. However increment concentration of VFAs reached itsmaximum——430.11mg/L at36h with original sludge dosed.Biological drying experiments showed that: the start-up speed of sludge afterelectroosmotic dewatering was faster, and the highest temperature was higher by5-20℃than the air dried sludge. In this experiment a better biological drying effect was reached with continuous air-flow and inoculant at the ratio of3:1as the only additive.Biological drying experiment with additional energy showed that additional energycould effectively improve the biological drying effect.Study on the property of filtrate produced by electroosmotic dewatering ofsludge was done. B/C of the filtrate was0.219, which showed that filtrate was hard tobe biodegraded. The output of the filtrate gradually reduced along with thedehydration process, and so was pH of the filtrate, however pH of the filtrate was stillhigher than10. Concentration of TCOD and SCOD of the filtrate firstly increased andthen decreased along with the dehydration process. Concentration of total nitrogenand ammonia nitrogen reduced along with the dehydration process, and about half ofthe total nitrogen existed as ammonia nitrogen.