Removal performance of dissolved organic matter from municipal secondary effluent by different advanced treatment processes and preventing the formation of disinfection by-products

Various advanced treatment processes including ultrafiltration (UF), ozonation, enhanced coagulation, and biological aerated filter (BAF) have been applied to reduce dissolved organic matter (DOM) from the secondary effluent of municipal wastewater treatment plants (MWTPs). In this study, DOM were characterized and the relationship between DOM characteristics and disinfection by-products (DBPs) generation was investigated systematically. Results showed that BAF and ozonation processes could significantly affect DOM characteristics in the treated effluents and the following DBP generation. UF and enhanced coagulation reduced the production of DBPs by removing large molecular hydrophobic organics. The removal of low molecule DOM by BAF resulted in a 67.6% reduction in trihalomethanes (THMs) production. Ozonation could oxidize large hydrophobic DOM into small hydrophilic molecules containing aldehyde and ketone groups, leading to 54% increase of halogenated aldehydes (HALs) and halogenated ketones (HKs). Humic acid (HA) was the main organic type in DOM and important precursor for THMs and dichloroacetonitrile (DCAN) formation. The generation of trichloromethane (TCM) showed a significant positive correlation (R-2 = 0.987) with the specific ultraviolet absorbance at 254 nm (SUVA). Large molecule hydrophobic DOM devoted the most to the formation of carbonaceous disinfection by-products and NH4+-N content was an important factor affecting the generation of nitrogenous disinfection by-products. These results are important for the optimization of advanced treatment process in MWTPs, and controlling DBPs should consider the removal of low MW hydrophobic DOM and the reduction of SUVA.