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Photochemical and Bacterial Transformations of Disinfection By‐Product Precursors in Water
Author(s) -
Chow Alex T.,
Díaz Francisco J.,
Wong KinHang,
O'Geen Anthony T.,
Dahlgren Randy A.,
Wong PoKeung
Publication year - 2013
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2013.01.0022
Subject(s) - dissolved organic carbon , trihalomethane , chemistry , biogeochemical cycle , environmental chemistry , chlorine , organic matter , water treatment , reactivity (psychology) , environmental engineering , organic chemistry , environmental science , medicine , alternative medicine , pathology
In situ grab sampling from source waters and water extraction from source materials are common methods for determining disinfection by‐product (DBP) formation potential (FP) of water samples or reactivity of dissolved organic matter (DOM) in forming DBPs during chlorination. However, DOM, as the main DBP precursor, collected using these techniques may not represent the DOM reacting with disinfectants due to biogeochemical alterations during water conveyance to drinking water treatment facilities. In this study, we exposed leachates from fresh litter and associated decomposed duff to natural sunlight or Escherichia coli K‐12 for 14 d and evaluated the changes, if any, on the propensity to form trihalomethane (THM), haloacetonitrile (HAN), and chloral hydrate (CHD) during chlorination. Sunlight treatment did not significantly change dissolved organic carbon (DOC) concentration but caused a 24 to 43% decrease in the specific ultraviolet absorbance (SUVA) at 254 nm, indicating that UV‐active chromophores were transformed or degraded. There were significant increases ( P < 0.05) in specific HAN formation potential (HAN‐FP) and specific CHD formation potential (CHD‐FP) (i.e., HAN and CHD formation potentials per unit carbon), but no change in specific THM formation potential (THM‐FP) after sunlight exposure. In contrast, bacterial treatment did not show any significant effect on SUVA, specific chlorine demand, or any specific DBP‐FPs, although bacterial colony counts suggested DOM in leachates was utilized for bacterial growth. Results of this study confirmed that the reactivity of DOM in forming DBPs could be different after biogeochemical processes compared with its source materials. For this study, photochemical reactions had a greater effect on DBP‐FPs than did microbial degradation.