Effect Of Anoxic Acidification Combined With Zero Valent Iron (ZVI) And Hydrogen Peroxide Conditioning On Municipal Sludge Deep Dewatering Performance And Its Rheological Properties Study

Municipal sludge dewatering is generally difficult,because of its extracellular polymeric substances（EPS）.EPS is highly hydrophilic,leading to difficult for sludge dewatering and reducation of sludge volume and stability.At present,removing hydrophilic organics by oxidant oxidation and reconstrucing the structure of sludge flocs is an effective way to improve sludge dewatering performance.Fenton and Fenton-like conditioning technology have achieved considerable results in achieving deep sludge dewatering.There is still room for these technologies to further improve the efficiency of sludge dewatering and the utilization of agents.This research had developed an economical and effective oxidation treatment technology to achieve sludge deep dewatering.In this paper,the sludge samples were collected from the secondary sedimentation tank of a municipal sewage treatment plant in Lijiao,Guangzhou,China.Short-term anoxic mesophilic acidification pretreatment combined with zero valent iron and hydrogen peroxide（ZVI-H₂O₂）was used to deal with municipal sludge to obtain the optimal conditions.The effect of sludge organic compounds on sludge dehydration performance was investigated.At the same time,the relationship among sludge rheological characteristics,surface structure and dewatering performance were discussed.The mechanism of anoxic mesophilic acidification pretreatment combined with ZVI-H₂O₂ technology was analyzed.On the basis of the optimum conditions,the conditioned sludge was filtered under high pressure with a new type high-pressure filter equipment.The deep dewatering performance of the sludge was studied to provide data support for engineering application.The effect of anoxic mesophilic acidification combined with ZVI-H₂O₂ on sludge dewatering performance was studied in this study.The sludge dewaterability was evaluated by specific resistance of sludge（SRF）.SRF was reduced by 93.6%compared with the raw sludge,when conditions are as follows:35?C temperature,270 mg/g dry solid（DS）of ZVI,a pH of 2.5,35?C temperature,4 hours of anoxic process time,and 30 mg/g DS of H₂O₂,15 min Fenton-like reaction time.The results of rheological properties analysis confirmed that the surface structure of the sludge had a great influence on its rheological properties.The souble EPS（SB-EPS）was related to the rheological properties of sludge（R=-0.879,p<0.05）.The viscosity of the sludge treated by combined treatment was reduced by 85.87%.The results showed that the sludge with low viscosity and high shearing ability was conductive to deep dewatering.Mechanism investigation tests showed that anoxic acidification accelerated the hydrolysis of sludge flocs,release of ferrous ion and the structure change on EPS.ZVI-H₂O₂oxidation treatment cause decomposition of EPS,reduction of protein,and production of humic acid and fulvic acid.These change of organic matter and structure of EPS led to the bonund water release,zeta potential and particle size change in the sludge,and finally improving the dehydration performance of the sludge.In general,the combination treatment can achieve the process of sludge hydrolysis,oxidation and flocculation,thus improving the performance of sludge dewatering.The the anoxic mesophilic acidification combined with ZVI-H₂O₂ conditioning and high-pressure pressure filtration technology showed that combined conditioning technology can effectively improve the properties mechanical filter-pressing,dewatering performance,the filter pressing time and the final moisture content of sludge cake.The final moisture content of sludge cake was reduced to 44.2%after 50 minutes of press filtration at 6 MPa pressure.In the case of no increase in cost,the filtration speed was significantly increased.The cost of anoxic mesophilic acidification combined with ZVI-H₂O₂ conditioning and high-pressure filtration was 72.0 USD$/ton DS,which was 10.3%lower than that of traditional Fenton treatment.The technology can effectively achieve deep dewatering of sludge,and the final moisture content of sludge met the requirements of current standards.Therefore,the combination technology had a good application prospect.