The purpose of this study is to evaluate the drinking water quality of Kaohsiung city and its cancer risk potential to residents using city water. In this study, water qualities from different locations and seasons were collected and compared with drinking water quality standards. Total trihalomethanes (TTHM), which is the byproduct of disinfection process, has become one of the major concerns due to its high cancer risk potential. TTHM is composed of trichloromethane (TCM), dichlorbromomethane (BDCM), dibromochloromethane (DBCM), and tribromo methane (TBM), and the drinking water standard for TTHM is 0.1 mg/L. Effective on July 1, 2006, this standard will be revised to 0.08 mg/L, which is adopted from U.S. EPA. In this study, tap water quality data were provided from the technical office of Environmental protection Bureau, Kaohsiung City. These data were collected quarterly in 2004 and 2005 from 50 locations in the city water net system. Moreover, health and risk assessment models developed by US Environmental Protection Agency (EPA) were used for cancer risk calculation. Results from the water quality evaluation indicate that drinking water quality meets with the standards regulated by government. Except for TTHM, results show that sampling locations and seasons did not have significant influence on the variations in other water quality parameters. Results of health and risk assessment of TTHM show that inhalation is the major route of risk exposure, which contributes 80.84% of the cancer risk. The dermal contact only contributes about 0.36% of the cancer risk. Among those four components of TTHM, TCM had higher detected concentrations. However, the major cancer risk came from BDCM and DBCM. Results reveal that the Chijin District (located at the end pipe area) of Kaohsiung city had the highest TTHM cancer risk (3.82¡Ñ10-4), whereas Sanmin District (located at the front pipe area) got the lowest risk (4.10¡Ñ10-5). The averaged TTHM health risk for the general public in Kaohsiung is about 1.50¡Ñ10-4. This calculated risk is much higher than the acceptable risk value (¡Ø10-6) recommended by US EPA. Thus, more stringent standards and more effective treatment technologies should be adopted by related authorities.

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The purposes of this study include: (1) investigating the reasons why drinking water quality degrades during transportation in the distribution system and developing an easy and effective tool to evaluate the status of distribution system; (2) investigating residents¡¦ satisfaction with advanced treated drinking water. It is found that the main reason of drinking water degradation is that most people don¡¦t flush the drinking water storage facilities routinely. It is also found that although most respondents are satisfied with advanced treated drinking water, nearly 40% of local residents still buy bottle water instead of drinking tap water. Therefore, Taiwan Water Supply Corp. (TWSC) should let people know the importance of flushing water storage facilities routinely and what TWSC has done to improve drinking water quality. The LSI (Langelier Saturation Index) of most water samples is negative, which means that the drinking water is corrosive when too much hardness is removed to comply with the regulations. A simple, efficient and cost-effective method is developed to provide TWSC sufficient information to solve the problems regarding water quality degradations in distribution systems. By using contour maps of different water quality parameters, TWSC can easily identifies locations with potential problems and easily assesses the necessity and appropriate locations of building re-chlorination stations, even though the lack of information regarding pipeline material, hydraulic conditions, thickness of biofilm¡Ketc.

Prior to full-scale implementation of process modifications at the Brantford WTP, a pilot-scale treatability study was conducted to investigate intermediate ozonation/AOP and to determine the most suitable granular media (anthracite, GAC, and Filtralite®) for deep-bed biological filtration. The primary objectives of this research were to provide insight into the destruction of natural and synthetic organics and assess ozonated and halogenated DBP formation. Ozone alone was unable to achieve the 1-log removal target for geosmin or MCPA, unless disinfection-level dosages were applied. No improvement was observed when adding hydrogen peroxide. A major obstacle to the implementation of ozonation in bromide-laden source waters is the formation of bromate. There is a direct correlation between ozone dose and bromate formation and by applying ozone dosages at disinfection levels, bromate is likely to exceed regulatory limits. However, adding hydrogen peroxide reduced the amount of bromate formed, and in most cases levels fell below regulatory limits. A linear correlation was established between bromate inhibition and increasing H2O2/O3 ratio at constant ozone dose. Amongst the three filtration media investigated, only GAC achieved 1-log removal for geosmin and MCPA. The superiority of GAC over anthracite and Filtralite® was attributed to its adsorption affinity. Filtralite® and anthracite media were both ineffective for MCPA removal due to its non-biodegradable nature under conventional water treatment conditions. At a 1 mg/L-ozone dose, GAC and Filtralite® filters achieved a 1-log geosmin removal. In contrast, a 1.44 mg/L ozone dose was required to meet this target with anthracite. The tandem of ozone followed by biological filtration was very effective for the control of distribution system TTHM production regardless of filter media, with levels well below current and anticipated provincial regulatory limits. The combination of intermediate ozonation followed by deep-bed biological filtration is well suited for treating Grand River water. Scale-up considerations include pairing the proper filter media to the size of the ozone generator. The best two treatment scenarios were: Option 1: select GAC media and size the ozone generator to produce a 1 mg/L dose. Option 2: select anthracite media and size the ozone generator to deliver a 2 mg/L dose.

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