Continuous denitrification experiments were carried out in an aerobic canal using water-insoluble fatty acid compounds as hydrogen doors. After about one year, the results showed that total nitrogen (T-N) removal efficiencies were 10 to 40% and maximum removal rates were 1920 to 5760mg-N·m^-2·d^-1 per unit area from April to Jun. Statistical analysis revealed that sufficient nitrification treatment was the most important factor for maintaining a high removal rate. Denitrification medias, which gathered denitrification bacteria with precedence, showed high denitrification activity even in aerobic conditions such as those of a canal. In this experiment, a maximum of 20.4% nitrogen was converted into gases, and 1.2%, into sediments.

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The analyses of specific ultraviolet absorbance (SUVA) and excitation emission matrix (EEM) were applied to characterize algogenic organic matter (AOM) produced by Microcystis aeruginosa at low nutrient concentrations and at three different N/P ratios. The production of dissolved organic carbon (DOC) during stationary phase was 3.6-5.8 times as much as that during exponential phase at any N/P ratios, while the components with ultraviolet absorbance at 260nm (E260) were remarkably released during the exponential phase at N/P=20. The ΔE260/ΔDOC value during the exponential phase at N/P=20 was 5.1 l·Abs·mgC^-1·m^-1, which was significantly higher than the reported values for AOMs. Six peaks of fluorescence intensity on EEM maps were identified and one of them (called “Pα” at 230 nm/430 nm (excitation/emission)) had never been reported as a fluorescence peak before. Peak profiles of AOMs on EEM maps were characterized by 1) the presence of Pα, 2) the absence of P3, 3) the relatively high fluorescence intensities at P1 and P2, and 4) the higher fluorescence intensity at P4 than at P6. EEM maps were divided into four zones according to the position of important peaks. The presence of unidentified peaks was discussed based on the relationship between fluorescence peak intensity and the integral value of fluorescence within each zone.

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Selective cultivation of denitrifying phosphate-accumulating organisms (DNPAOs) was conducted using a sequencing batch reactor (SBR) under different electron acceptor conditions. A new biological nutrient removal process configured with anaerobic/aerobic/anoxic conditions was successfully operated in a single SBR. The supplementation of carbon substrate at the start of the aerobic condition was effective for the simultaneous removal of phosphorus and nitrate by DNPAOs.

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A simple method was developed to recover high P content fraction in enhanced biological phosphate removal activated sludge. The method was based on the concept of centrifugal separation in sucrose solution with different density. The quinone profiles of the fractionated samples were analyzed to determine quinone biomarkers for phosphate-accumulating organisms. Addition of 4% paraformaldehyde and lowered temperature around 4°C protected the activated sludge from lysis due to the osmotic pressure of the solution. Homogenization for 15 min was appropriate for the dispersion of the flocs by a homogenizer (φ2cm, 3500rpm). Using 50.0%, 51.2% and 52.4% sucrose solutions, the activated sludge was fractionated appropriately. In the case of 51.2% sucrose solution, relatively high P content activated sludge and low P content one were fractionated. Comparing their quinone profiles, the high P content one had higher fractions of Q-8 and MK-7.

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Experiments were conducted to decompose three dyes, rhodamine B, methylene blue and erythrosine, in water using a reactor with a gas corona discharge. In this reactor, the gas corona discharge was contacted with the treated water to supply short-lived radicals and ions directly to the water surface, resulting in the production of aqueous reactive species. It was found that these dyes were degraded by this method. Total organic carbon which was not significantly decreased by ozonation without pH control was also decreased by the present method. The decomposed compounds seem to be oxidized to CO₂ as final products.

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