Formation of disinfection by-products during chlorination of organic matter from phoenix tree leaves and Chlorella vulgaris

Abstract

To better understand the precursor of disinfection by-products (DBPs) and provide useful information for water utilities to manage the drinking water, a study of DBP formation was conducted through chlorination of leaf organic matter (OM) from phoenix tree and algal OM from Chlorella vulgaris. DBPs investigated include trichloromethane (TCM), trichloroacetic acid (TCAA), dichloroacetic acid (DCAA), chloroacetic acid (CAA), dichloroacetonitrile (DCAN) and trichloroacetonitrile (TCNM). Results show that the specific yields (μg/mg C) of C-DBPs (TCM, CAA, DCAA and TCAA) from leaf OM were higher but the specific yields of N-DBPs (DCAN and TCNM) were lower than those from algal OM. Correlation analysis revealed that C-DBPs yields (μg/L) were significantly (p < 0.01) interrelated with each other (r = 0.937-0.996), and for each C-DBP, the hydrophobic OM contributed more to their formation (61-90% of total yields) as compared with hydrophilic OM. In spite of these characteristics, an in-depth examination was conducted revealing that the hydrophobicity and aromaticity of C-DBPs precursors were in the order of TCAA > DCAA & TCM > CAA. DCAN precursors were highly variable: they were dominated by hydrophobic OM (leaf OM: 86%) or hydrophilic OM (algal OM: 61%). Hydrophilic OM was the most important precursor for TCNM (76-79% of total yields), followed by hydrophobic neutral and base substances (29-45% of total yields), but the hydrophobic acids exhibited an inhibition role in TCNM formation.