In the present study, we investigated the effect of mixed injection of different powdered activated carbons (PACs) on improving the removal performance of 2-methylisoborneol (2-MIB). Three PACs (one conventional PAC and two improved PACs) were selected, and the adsorption rates of these PACs were evaluated in real raw water of an existing drinking water treatment plant. The results indicate that both two improved PACs had superior 2-MIB adsorption rates compared with the conventional PAC. The reductions in PAC injection rates through the mixed injection of conventional and improved PACs under a contact time of 30 min were investigated using real raw water with an initial 2-MIB concentration of 100 ng/L. The results revealed that the mixed injection of these PACs was effective for substantially decreasing the total PAC injection to achieve 90% removal of 2-MIB; 40 mg/L was required when the conventional PAC was injected alone, whereas conventional PAC 12 mg/L + improved PAC 8 mg/L was sufficient for achieving the removal rate mentioned above. The estimation of costs associated with PAC adsorption process suggests that the mixed injection scenario is economically competitive under improved PAC to conventional PAC unit price ratios between 3.8～4.5.

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　In this study, a facile and accurate method was developed for detecting hydrazine in tap water without a concentration step, using benzaldehyde derivatization-liquid chromatography-tandem mass spectrometry. The conditions for benzaldehyde derivative formation including the yield of derivatization reaction with benzalazine as the product were investigated, and a highly accurate method for detecting hydrazine at 0.0005 mg/L in tap water was successfully developed. Moreover, various storage methods for hydrazine were evaluated, and the addition of both sodium thiosulfate and phosphate is proposed as an effective method for preserving hydrazine in tap water samples.

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[in Japanese]

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[in Japanese]

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