The fates of aromatic protein and soluble microbial products-like organics, as the precursors of dichloroacetonitrile and dichloroacetamide, in drinking water advanced treatment process

Dichloroacetonitrile (DCAN) and dichloroacetamide (DCAcAm) are two typical nitrogenous disinfection byproducts (N-DBPs) with strong cytotoxicity and genotoxicity. In this study, The removals of precursors of DCAN and DCAcAm were investigated when the biological activated carbon filter (BACF) was used as advanced treatment process. The results showed that the removal efficiency of DCAN formation potential (FP) was about 13% higher than DCAcAm FP in summer, while in winter there was no observed difference. The results of fluorescence excitation-emission matrix (EEM) spectra indicated that the concentrations of aromatic protein and amino acids-like organics were related to the variations of DCAN FP and DCAcAm FP. The yields of DCAN and DCAcAm were therefore further investigated during the chlorination of extracted proteins and 20 commercial amino acids. The removal efficiencies of proteins and amino acids by BACF were also measured. The results indicated that the removals of proteins and amino acids led to 24% decrease of DCAN FP and 15% decrease of DCAcAm FP in summer. Based on high-throughput sequencing analysis, the microbial community composition in the BACF had a higher diversity and equitability in summer than that in winter. Proteobacteria and Firmicutes were dominant species, having a biodegradation ability for proteins and amino acids, accounting for the variations of DCAN FP and DCAcAm FP in different seasons.