Research Of Risk Assessment & Pollution Control For Drinking Water Distection By-Products

With the public health triumph of the 20th century in chemical disinfection of water for dramatic decreasing in waterborne diseases, chronic exposure to a very large number of chlorinated disinfection byproducts(CDBPs),which formed through reaction of the chlorine disinfectant with naturally occurring inorganic and organic material in the source water. The health effects and risk of DBPs have been focused in the range of world.This thesis provides an overview of CDBPs research on pollution control and risk assessment. The purpose is to address concerns related to CDBPs pollution control technology and health risk from levels of CDBPs in drinking water to impossible control technology to exposure within Qiantangjiang watershed in Zhejiang province, China.. Seven types of CDBPs were studied including THMs (CHC13, CHCl2Br and CHClBr2) and HAAs (MBAA, DCAA, BCAA and TCAA) in thirteen drinking water plants, located in Jiangshan Harbor, Qu River, Lan River, Xinan River, Fenshui River, Fuchun River, Puyang River in the watershed. The research results are showed as follows:(1) The levels of CDBPs in 13 drinking water plants with chlorine disinfectants of the watershed were relatively low, and there were significant differences between total CDBPs levels and CDBPs type.the levels of HAAs were higher than THMs at 83.3% of drinking water plants; the average levels of HAAs and THMs in the finished water were 5.87μ.g/L and 3.34μg/L, respectively in winter; the levels of HAAs were between 0.44 and 13.72μg/L and the levels of THMs were between 0.21 and 15.23μg/L; CHC13 was the most detected THMs, and MBAA and TCAA were the most detected HAAs; the total CDBPs levels in Lanxi of Lan River were the highest, and secondly in Longyou of Qu River, Fuyang of Fuchun River, Duanyiqiao of Puyang River and Nanxingqiao of Qiantang River.(2) The dissolved small molecular weight organic compounds and big molecular weight aromatic substance were the main organic compounds in the source water of Qiantang River. The dissolved organic carbons (DOC) in the source water of Qiantang River were mainly distributed lower than 2K Dalton molecular weights, which the proportion was 52.2%; secondly, the proportion of the molecular weights distributed between 5K and 10K Dalton was 18.9%; according to the UV-254 detection the proportion of the molecular weights that were>100K Dalton was 97.9%. The molecular weights of THMFP were mainly below 2K Dalton, but the molecular weights of HAAFP were between 2K and 5K Dalton.(3) A kind of safety activated carbon-chitosan water-cleaning adsorbent was modified. The diameter of the adsorbent was 1 to 1.5 mm, and the specific surface area was 303.8 m2/g. This adsorbent had very high cleaning efficiency for THMs, and the efficiencies for CHC13 and CHBrCl2 were 79.67% and 87.66%, respectively; the adsorption equilibrium time was only three hours; both pH and temperature have little influence on the cleaning efficiency. This modified technology has obtained the Chinese invention patent in 2005.(4) Both THMs and HAAs can induce apoptosis. All the seven CDBPs can induce obvious apoptosis on crucian carp(Carassius auratus) lymphocytes in vitro for two hours at the exposed levels of 0.1μg/L and 10μ.g/L. The low exposed level (0.1μg/L) induction experiments showed that typical morphological characteristics of early apoptosis could be found after the induction by MBAA, BCAA and DBCM which were low chlorine substituted compounds, however typical morphological characteristics of later apoptosis could be observed after the induction by TCAA, BCAA, CHCl3 and BDCM which have 2-3 chlorine atoms in the molecular structures. According to the quantitative determination by flow cytometry, the apoptosis induction abilities of all the seven CDBPs were TCAA>CHCl3>BDCM>DCAA>DBCM>BCAA>MBAA.(5) The exposure health risk of THMs in the watershed of Qiantang River was low. The average cancer risk of THMs in the watershed was 3.59×10-5, but the cancer risk of THMs in Fuyang area was up to 1.48×10-4. Among all the THMs, CHClBr2 was the main carcinogenic factor with the cancer contribution efficiency of over 60%. The non-cancer risk assessment results also showed that the average risk index in the watershed was 6.99×10-8, and Lanxi and Zhangzheng were the highest with the risk index of 2.33×10-8 and 1.08×10-8, respectively.