We have developed a simultaneous analytical method for pesticides by gas chromatography mass spectrometry (GC/MS) , liquid chromatography mass spectrometry (LC/MS) or liquid chromatography-inductively coupled plasma mass spectrometry (LC/ICP/MS) . We applied this method to 195 pesticides that are frequently used or are “Complementary Items” in drinking water in Japan, and found that 192 of them could be analyzed. The recovery rates of the compounds from the river water and groundwater samples were within the range of 70-130%, with relative standard deviations of less than 20%. Considering the degradation by chlorination, the target pesticides were classified into 10 categories on the basis of the reaction rate constant. The structures of transformation products generated by chlorination were predicted using the mass spectrum and accurate mass that were obtained by liquid chromatography time-of-flight mass spectrometry (LC/TOF-MS) .

Although many types of biological treatment processes have been introduced in Japan, it is unclear whether these processes can reduce the toxicity of municipal wastewater. In this research, an algal growth inhibition test using the green alga Pseudokirchneriella subcapitata was applied to municipal wastewater before biological treatment and to the final (or secondary) effluents obtained from four kinds of wastewater treatment plants that introduced, for example, an oxidation ditch process. As a result, it was confirmed that the growth-inhibiting effect of the wastewater was decreased through the oxidation ditch process, conventional activated sludge process, and anaerobic-oxic activated sludge process. On the contrary, the effect still remained even after the treatment by the anaerobic-aerobic filter process. It was also revealed that the ability of biological treatment processes to reduce the growth-inhibiting effect in winter became less effective than in summer. Much more information on the reduction ability of biological treatment processes are required because it has been suggested that the ability depends on the biological treatment process and the season.

To evaluate the properties indicated by biological oxygen demand (BOD) and chemical oxygen demand (COD) in lakes and rivers, we compared the BOD and COD with total organic carbon (TOC) in the waters of Lake Biwa, its inflowing river, and various discharge effluents. Biodegradation tests were also conducted to investigate the relationship between biodegradability, BOD, and COD. No correlation was observed between BOD and labile organic matter obtained by the 100-day biodegradation test. The BOD shows only a small part of biodegradable components. The BOD is strongly related to particulate organic matter, indicating that the initial biodegradation is largely due to the decomposition of particulate organic matter. Although the COD values in the lake and its inflowing river waters are roughly equivalent to half of TOC, COD and TOC data have high correlation and similar variance. The COD distribution reflects the fluctuations of organic matter in the lake and rivers. However, the COD detection includes 1) overestimation at low concentration, and 2) partial detection based on properties of organic matter. The different COD detection rates depending on the concentration and quality of the samples considerably affect the estimated amounts of organic matter in the lake and its watershed, particularly in the low concentration range.

The operation performance of an improved self-agitated anaerobic baffled reactor with a fixed carrier was investigated by a continuous experiment of treating simulated food waste adjusted to a 5% total solid (TS) concentration. The objective of this study was to enhance methane fermentation and effluent water quality at 35 ℃. The effect of chemical oxygen demand measured by potassium dichromate (COD_Cr) loading rate on the treatment performance was evaluated by shortening the HRT from 50 days to 10 days. As a result, the improved reactor was stably operated until the COD_Cr loading rate increased to 9.56 kg m^-3 d^-1 . In addition, the improved reactor showed better organic removal efficiency and conversion ratio from the substrate than these the CSTR and self-agitated anaerobic baffled reactor without a fixed carrier.

The vertical distribution of denitrification rates in sediment and the seasonal variation of denitrification rates were investigated by measuring denitrification rates using sediment core samples of Lake Kasumigaura maintained under natural conditions. The nitrogen removal rate caused by denitrification was calculated by using those data. Denitrification mainly occurred in the surface layer (top 1 cm) of the sediment. The denitrification rates decreased from the upper to the lower part in Lake Kasumigaura, and showed spring and autumn maxima. The amounts of denitrification in the sediment were estimated as 638 kgN d^-1 in the western part (Lake Nishiura) and 325 kgN d^-1 in the eastern part (Lake Kitaura) of the lake. Nitrogen removal rates caused by denitrification in the sediments corresponded to 5% in L. Nishiura and 6% in L. Kitaura of the annual nitrogen load to each lake, averaged from 2006 to 2010.