An A/O SBR fed with acetate was operated at pH 7.0 after the inoculation of activated sludge capable of enhanced biological phosphate removal (EBPR). Glycogen-accumulating organisms (GAOs) were predominant in acetate uptake on the 19th day of operation. The operational pH was then increased to 8.2. Accordingly, the acetate uptake activity of GAOs gradually decreased as intended, whereas phosphate release activity improved. To estimate acetate uptake rate with addition of acetate more than that in the A/O SBR operation, an anaerobic batch test was conducted. Higher amounts of acetate added led to significantly high acetate uptake rates that were not consistent with phosphate release rates only when the acetate uptake activity of GAOs was relatively low in the A/O SBR operation. In other words, an acetate concentration higher than the usual influent concentration probably stimulates the acetate uptake activity of GAOs. These results suggest that a rapid increase in the acetate uptake rate of GAOs affects the sudden deterioration of EBPR.

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In this study, we assessed the calcium nitrate reagent for possible application to the improvement of marine sediments, which are pollutants from organic matter produced through long-term pearl culture. A preliminary study was carried out using the calcium nitrate reagent with a simple laboratory experimental instrument. As the results, 1) the AVS concentration in sediments was reduced, 2) the production of hydrogen sulfide from bottom sediments was prevented, and 3) the possible elution control of phosphorous compounds from bottom sediments was observed. The addition of calcium nitrate to the organically polluted marine sediments could enhance the denitrifying activities.

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To characterize dissolved organic matter (DOM) in natural waters, a procedure called dissolved organic carbon (DOC) fractionation analysis is useful, in which DOM is fractionated into hydrophobic-hydrophilic fractions using XAD-8 resin of an acrylic ester polymer, and into acid-neutral-base fractions using ion exchange resins. However, the difficulties in XAD-8 purification and handling have limited the use of the fractionation procedure to a few research groups; thus, we have developed a new fractionation procedure using PS-2 cartridges packed with purified styrene divinylbenzene copolymer resins, instead of XAD-8. Recovery studies of model compounds such as humic and fulvic acids were conducted to compare the fractionation properties of PS-2 with those of XAD-8. The added hydrophobic and hydrophilic compounds were found at recoveries of 81∼103 % in the hydrophobic and hydrophilic fractions, respectively. The results of the recovery tests showed that PS-2 and XAD-8 have the same fractionation properties for hydrophobic DOM and hydrophilic DOM. By using a similar conditioning of PS-2 cartridges in the solid-phase extraction of the water samples, the blank DOC level in this procedure was easily reduced to 0.4∼0.5 mgC · l^-1, corresponding to the levels obtained using purified XAD-8. For the repeatability of the fractionated DOC measurement, the relative standard deviation was ca. 10% when the measured DOC level was higher than threefold of the blank DOC; it was ca. 30% when the measured DOC level was between two- and threefold of the blank DOC. It was found from the data for the application to river and lake waters that the obtained composition data of hydrophobic DOM and hydrophilic DOM agreed with the reported composition data obtained using XAD-8. This procedure using PS-2 can be used for the hydrophobic-hydrophilic fractionation of DOM in natural water samples as an alternative to the conventional procedure using XAD-8.

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Methyl isothiocyanate (MITC) is a fumigant used to control nematodes, fungi, and insects in agricultural soils. Most of MITC used for agriculture is released into the environment. To examine the degradation behavior of MITC in an aquatic environment, a biodegradation test using an activated sludge was carried out. This test revealed that MITC is hardly mineralized, but converted to six metabolites, which were determined to be 1,3-dimethylthiourea, 3-methylamino-5-oxa- thia-2,7-diaza-2,6-octadiene, 3-methylamino-4,5-dithia-2,7-diaza-2,6-octadiene, methylamine, elemental sulfur, and carbon disulfide. The first three compounds have never been detected or predicted as products even in soil.

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