Seasonal dynamics of concentration of phenylpyrazole insecticide compounds, fipronil (FIP), fipronil sulfone (FIP+O) and fipronil sulfide (FIP-O) were surveyed through the upstream of the Sengari Reservoir for Kobe City. As a result, high concentration of FIP, FIP+O and FIP-O were detected immediately after rice planting. In the laboratory examination, FIP and FIP+O were promptly changed to fipronil sulfone chloramine ((FIP+O) Cl) after addition of sodium hypochlorite. On the other hand, the degradation of FIP-O were very low, and (FIP+O) Cl was not generated. Each of fipronil substance, FIP, FIP+O and FIP-O was effectively removed through activated carbon (powder activated carbon and granular activated carbon) treatment. However, removability of (FIP+O) Cl was low. Therefore, it is concluded that activated carbon treatment before the chlorine addition is effective to remove FIP compounds during water purification.

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In updating the existing facility due to aging etc., in addition to existing water purification treatment technology, it is necessary to consider new technology introduction as well. In this paper, in recent years, the applicability of membrane filtration technology with remarkable technological progress to our water treatment is evaluated. The raw water of Osaka city is surface water which is highly utilized in upstream area. We collaborated with two private companies concerning the investigation of the membrane filtration technology. The two companies have some knowledge of membrane filtration technologies. As a result of the investigation, the combination of coagulation and ozone was optimal as the pretreatment, and the total system using membrane filtration could secure the same water treatment as the advanced water purification treatment. From the viewpoint of operation and maintenance, the membrane filtration treated water quality is stable in experiments assuming accidents such as water volume fluctuations and power outages, and the applicability of membrane filtration technology to water purification treatment in Osaka city is highly evaluated.

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[in Japanese]

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