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Transformation of Bisphenol A in Water Distribution Systems, A Pilot-scale Study
Citation:
Li, C., Z. Wang, J. Yang, J. Liu, X. Mao, AND Y. Zhang. Transformation of Bisphenol A in Water Distribution Systems, A Pilot-scale Study. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, 125:86-93, (2015).
Impact/Purpose:
Communication of research results in drinking water distribution system to the scientific community
Description:
Halogenations of bisphenol A (BPA) in a pilot-scale water distribution system (WDS) of cement-lined ductile cast iron pipe were investigated under the condition: pH 7.3±0.3, water flow velocity of 1.0 m/s, and 25 °C ± 1 °C in water temperature. The testing water was chlorinated for a free chlorine concentration at 0.7 mg/L using sodium hypochlorite and was spiked with bisphenol A (BPA) for an initial concentration 100µg/L. Halogeated compounds in BPA experiments were identified by EI/GC/MS and GC. Some BPA congeners, including 2-chlorobisphenol A (MCBPA), dichlorobisphenol A (D2-CBPA), 2,2´,6-trichlorobisphenol A (T3CBPA), 2,2´,6,6´-tetrachlorobisphenol A (T4CBPA) , 2-bormobisphenol A (MBBPA), and bromochlorobisphenol A (MBMCBPA) were found in the earlier 60 min. This result in brominated bisphenol formation is different from those of previous studies, possibly because of bromide ion and bromate in water. Further halogenation yielded other reaction intermediates, including 2,4,6-trichlorophenol (T3CP), C9H10Cl2O2, bromodichlorophenol, and dibromochlorophenol. After halogenation for 120 min, most of the above-mentioned reaction intermediates disappeared and were replaced by trihalomethanes (THMs). Based on these experimental findings, the halogenation process of BPA oxidation in a WDS may include three stages: (1) halogenation on the aromatic ring; (2) chlorine or bromine substitution followed by cleavage of the α-C bond on the isopropyl moiety with positive partial charge and β´-C bond on the benzene moiety with a negative partial; and (3) THMs and minor HAA formation from phenolic intermediates through benzene ring opening with chlorine and bromine substitution of the hydrogen on the carbon atoms. The proposed oxidation mechanisms for entire transformation from BPA to THM/HAA in the WDS may help understand the BPA fate and transport in drinking water, thus its risk profiles and controls in the real-world applications.
