Relationship between THMs/NDMA formation potential and molecular weight of organic compounds for source and treated water in Shanghai, China

Abstract

Molecular weight (MW) distributions in source and treated water in Shanghai, China were investigated to understand the relationship between trihalomethanes formation potential/N-nitrosodimethylamine formation potential (THMFP/NDMAFP) and dissolved organic carbon (DOC) for different MW ranges (<1K, 1–10K, 10–30K, >30KDa). The result of MW distributions in source water indicated a relationship between THMFP/NDMAFP and DOC such that DOC for <1K and 1–30KDa DOC were linearly related to THMFP and NDMAFP, respectively. In treated water, >30KDa THMFP was totally removed whereas <1KDa THMFP showed linear relationships with R2=0.88 and 0.83 after sand and granular activated carbon (GAC) filtration, respectively. DOC content for 1–10KDa tended to form NDMA according to the results for treated water between DOC and NDMAFP (R2=0.94 and 0.93 for sand and GAC filtration, respectively). The results may provide researchers with targeted treatment strategies to destroy, remove, or reduce the occurrence of THMs and NDMA precursors. The findings presented in this study will be of great value in future work for selecting suitable drinking water treatment processes to minimize the formation of disinfection by-products using chlorine or chloramine disinfection.