Enhanced Dewaterability Of Waste Activated Sludge By Fe(?)-activated Peroxymonosulfate Oxidation

Activated sludge processes and its derived processes are important technologies for wastewater treatment,but these biological processes generate large amounts of waste activated sludge.If not disposed properly,large amount of sludge can pose a great threat to human beings and environment.The treatment and disposal of excess sludge generated by a conventional activated sludge treatment plant usually accounts for 50-60%of the total operating expense.Sludge dewatering is a promising approach in reducing sludge volume and cost of sludge transport and ultimate disposal.Sewage sludge has the characteristics of high organic matter content and strong hydrophily.Thus,how to improve sludge dewatering performance and dewatering efficiency becomes a challenge in wastewater and sludge treatments.Sludge conditioning can improve sludge dewaterability before mechanical dewatering.Currently,flocculating agent is most used to condition sludge before mechanical dewatering.However,water content of dewatered sludge cake can be only decreased to 80%using this method,which could hardly meet the requirements of environment and regulations.For decades,advanced oxidation processes(AOPs)have been given growing attention on sludge dewatering,in view of high dewatering efficiency and short treatment time.AOPs based peroxymonosulfate(PMS)was applied to sludge dewatering.The effect of Fe(?)-activated peroxymonosulfate(Fe(?)-PMS)oxidation on the waste activated sludge(WAS)dewatering and its mechanisms were investigated in this study.The capillary suction time(CST),specific resistance to filterability(SRF)of sludge and water content(Wc)of dewatered sludge cake were chosen as the main parameters to evaluate the sludge dewaterability.The effect of several significant factors on sludge dewaterability,including initial pH value,molar ratio of Fe2+/HSO5- and PMS dosage,were investigated and analyzed respectively.Experimental results showed that Fe(?)-PMS effectively disintegrated sludge and improved sludge dewaterability.High CST and SRF reduction(90%and 97%)and low Wc(64%)was achieved at the optimal conditions of PMS(HSO5-)0.9 mmol/gVSS,Fe(?)0.81 mmol/gVSS,and pH 6.8.Scanning electron microscope(SEM),Protein and Polysaccharide content in Extracellular polymeric substances(EPS)and three-dimensional excitation-emission matrix(3D-EEM)fluorescence spectroscopy before and after Fe(?)-PMS oxidation were determined to explain the enhanced dewatering mechanism.The release of EPS-bound water induced by the destruction of EPS was the primary reason for the improvement of sludge dewaterability during Fe(?)-PMS oxidation.