An on-site investigation was conducted to characterize dissolved organic matter(DOM)in the anaerobic digestion(AD)filtrate that was generated from a typical sludge thermal hydrolysis process(THP).The results show that the concentrations of ammonia nitrogen and COD in the filtrate were as high as 2034(±465)and 4128(±276)mg/L,respectively,and the DOM concentration in the filtrate was mainly macromolecular refractory organic matter,and DOM＞1000Da accounted for 80.6％.The existing"biological pretreatment+two-stage AO-MBR"filtrate treatment process could generally achieve a high-efficiency denitrification(TN removal rate of 94.9％and partial COD removal of 69.9％).Nitrogen removal relied mainly on biological pretreatment units(removal by 79.9％),while DOM removal on membrane filtration of the MBR process(removal by 184.7％).The membrane filtration intercepted DOM was in the order of high molecular polymer＞humic acid substances＞low molecular organic acids and neutral substances.The effluent DOM was mainly composed of humic acid and fulvic acid substances with a high degree of humification.Existing water washing,acid-and alkali washing had certain cleaning effects on organic pollution of membranes,but the types of DOM in the cleaning solution were significantly different.
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