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Literature indicates that when the concentration of NH-N of raw
water exceeds 0.5 mg/L,prechlorination treatment is not
suitable. For some source waters for public water supply in
Taiwan,including both surface water and groundwater, the
concentration of NH-N has been higher than 0.5 mg/L. However,
the most popular local water strategy adopted by the treatment
plants is superprechlorination, which oxidizes organics, iron,
manganese, and NH-N. Many reports already show that both
natural and artificial organics in water can react with
chlorine to produce halogenated organics, many of which are
known as carcinogens. At first,this study discussed of the
effect of prechlorination on Feng-shan raw water by using
different levels of prechlorination, and then coupling this
treatment with the conventional water treatment processes,
including coagulation, sedimentation, filtration. This study
compared the residual NPDOC and turbidity of the finished water
in order to evaluate the influences of prechlorination on
dissolved organic compounds and turbidity removal during
conventional water treatment processes. Secondly, the effect of
changing the chlorination site, i.e. before or after
conventional coagulation, sedimentation, filtration, on
turbidity and dissolved organic removal and THMs and AOX
concentrations of the finished water was studied.
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