The fulvic acid-like substance detected at excitation 345 nm / fluorescence 430 nm was measured as the fluorescence intensity of the samples from water purification process of the 8 plants in Japan. The fluorescence intensity was decreased during the process. The decreasing ratio of fluorescence from the resource was larger than that of DOC in most treatment processes. In addition, it was found that the fluorescence intensity could be detected more sensitively than DOC in the organic substance change relating to the residual chlorine consumption in the distribution system. Furthermore, it was thought that the transition of the peak wavelength of the fluorescence spectrum generated in the treatment process showed the sorting effect of low molecular weight substances by physical treatment such as aggregation and precipitation. Consequently, it was suggested that the detection method of fulvic acid like substance by fluorescence analysis might be useful for understanding the change of organic substance in the water treatment process and controlling residual chlorine.

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