Performance And Mechanism Of Sulfate Radical Oxidation Conditioning-Horizontal Electro Dewatering Of Activated Sludge

Activated sludge process is the most widely used in urban treatment plants,which would product a large amount of activated sludge.The sludge transported externally,landfilled or dumped simply has become serious problems.In order to improve the sludge dewaterability,the combination,operating parameter and performance of magnetic fieldielectric fieldimicrowave-oxidation conditioning were studied.The performance and mechanism of oxidation conditioning-horizontal electric field system were studied.The content and conversion of bound water and free water were determined by differential scanning calorimetry,Moreover,excitation-emission matrix(EEM)fluorescence spectroscopy and high-perfornance size exclusion chromatography(HPSEC)were employed to identify the typical organic components in the AS matrix.The results were as followed:In the study,the results showed that the zero-valent iron(ZVI)dosage was 0.35 g/g DS,the persuifate(PS)dosage was 0.15 g/g DS and the conditioning time was 30 min for the best dewaterability.After oxidation conditioning,floe breakage and cell debris were observed,and such effects indicated that the ZVI/PS oxidation could disintegrate the EPS and flocs and disrupt microbial cells.As for the magnetic field/electric field/microwave-oxidation conditioning,no obvious effects in magnetic or electric field occurred.However,in the microwave-oxidation condition,the optimal temperature of sludge for dewatering was 56?,the dosages were 0.31 g/g DS ZVI and 0.13g/g DS PS,reducing to 90%of the original optimal dosage for the best sludge dewaterability.Both the zeta potential and conductivity of the sludge were increased.The results showed that the microwave enhanced the ZVI/PS transfer process,and improved the sludge dewaterability,and the capillary suction time finally decreased to 59.14%.Oxidation conditioning-horizontal electro dewatering process(ZVI/PS-HED)included oxidation conditioning and electric dewatering.The optimum dewatering conditions for ZVI/PS-HED with the final water content of 83.67%were 40 V and 120 min.The corresponding removal ratios of free water and bound water were 96.4%and 79.7%,respectively.At ZVI/PS stage,SO4-· oxidation led to the transformation of some bound water into free water,and the Fe3+ produced through Fe2+oxidation performed coagulation among the broken AS flocs and was beneficial to the high momentum of the electroosmotic flow at subsequent HED stage.The results of extracellular polymer(EPS)showed that the protein and polysaccharide were more easily degraded by ZVI/PS conditioning,and slime had a greater sensitivity to the action from outside.