The Transformation Of Bisphenol A In Water Distribution Svstem

In order to study the migration and transformation rule of BPA in water distribution systems, degradation of BPA under different conditions including different pipes materials, hydraulic conditions and water quality was studied in the pilot-scale water distribution systems(WDS). BPA was detected by HPLC Fluorescence with excitation wavelength225nm and emission wavelength is310nm. The experiment results show that the degradation of BPA in WDS is effected by not only NaClO but also wall of pipes and chemical compounds in bulk water. The increase of the concentration of free chlorine, pH values, the concentration of bromide ions, flow velocity and temperature is beneficial to degradation of BPA. In addition, pipe material is another important factor for the degradation of BPA. The degradation rates of BPA follow the order:stainless steel pipe> polyethelene pipe (PE)> ductile iron pipe. The experimental results were shown that the contribution rates of wall of pipes and chemical compounds of bulk water to the degradation of BPA are10%and30%, respectively (including the10%of intermediate products and the20%of final chlorinated compounds).The transformation process of bisphenol A (BPA) in water distribution systems (WDS) was investigated in this thesis. The concentration of BPA in WDS is100μg/L. BPA was chlorinated by sodium hypochlorite (approx.0.7mg/L in WDS) under the conditions:pH=7.3±0.3, flow velocity of1.0m/s, water temperature of25℃±1℃, and ductile cast iron pipe (lined with cement). The halogenation products were identified by EI/GC/MS and GC. Some BPA congeners,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 earlier60min. This result was different from previous studies. The existence of bromide ion and bromate may affect the formation of byproducts. In the further halogenation, some other halogenation products including2,4,6-trichlorophenol (T3CP), C9H10Cl2O2, bromodichlorophenol, and dibromochlorophenol were found. Finally, after halogenation for2h, most of the above products were disappeared and lots of trihalomethanes (THMS) were found. The halogenation process of BPA in WDS may include three stages:(1) halogenation on the aromatic ring;(2) chlorine or bromine substitution followed by cleavage of the a-C on the isopropyl moiety with positive partial charge and β’-C on the benzene moiety with a negative partial;(3) the benzene ring is opened, than C-C bonds were broken and the hydrogen on the carbon atoms were substituted by chlorine and bromine.