Advanced treatment of effluent from municipal WWTP with different metal salt coagulants: Contaminants treatability and floe properties

摘要

Chemical coagulation with three representative inorganic coagulants was used for the advanced treatment of secondary effluent from WWTP to enhance total phosphorus (TP) and organic removal. The effect of chemical coagulation on organic contaminants was investigated with combined fluorescence excitation-emission matrix (EEM) spectroscopy and High-performance size-exclusion chromatography (HPSEC). The results showed that different coagulation features and benefits were exhibited by FeCl3, A12(SO4)3 and polyaluminum chloride (PAC1). PAC1 had better performance in chemical oxygen demand (COD) removal, while FeCl3 and A12(SO4)3 were more efficient in removing TP. The optimal coagulant in this study was FeCl3. The floe obtained from FeCl3 coagulation was larger, easier to settle and break than that of A12(SO4)3 and PAC1. Coagulation mainly removed orthophosphate and the major phosphorus fraction of coagulated effluent was organic phosphorus. The macromolecule orgailies (molecular weight (MW) >10 kDa) were completely removed regardless of their chemical nature, while inorganic coagulants showed different effects on removal efficiency of organic matters with a MW less than 10 kDa. Besides, 71.24% of the total dissolved organic carbon (DOC) was tryptophan-Iike proteins and soluble microbial byproduct-like materials which could easily be removed by coagulation.