A submerged anaerobic membrane bioreactor (SAMBR) combining anaerobic digestion and membrane separation has recently attracted attention, because of its potential to recover methane and reduce sludge production in wastewater treatment. In this study, a lab-scale SAMBR that treats suspended solids containing synthetic sewage was continuously operated for 106 days at room temperature (25°C) to investigate the effect of hydraulic retention time (HRT) on its treatment performance and microbial community. HRT was changed from 48 to 6 hours in 4 steps. At HRT of 12 hours, the chemical oxygen demand (COD) and biochemical oxygen demand removal rates were 94%, and 95% respectively, and 64.6% of input COD was converted to methane. On the basis of the results of cloning analysis, Methanosaeta and Methanoregula were found to be the two dominant Archaea genera, in the reactor. In the clone library of Bacteria, many unclassified bacteria have been detected, and about 21% of facultative anaerobic bacteria have been detected among all the clones.

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The effect of the chemical oxygen demand/sulfate (COD/SO₄^2-) ratio on the anaerobic treatment of synthetic chemical wastewater containing sulfate, acetate, and ethanol was investigated using a UASB reactor. The experimental results show that at a COD/SO₄^2- ratio of 20 and a COD loading rate of 25.2 g-COD·L^-1·d^-1, the COD removal rate was maintained at as high as 87.8%. However, at a COD/SO₄^2- ratio of 0.5 (sulfate concentration 6000 mg·L^-1), a COD removal rate of 79.2% and a methane production rate of 0.20 L-CH₄·g-COD^-1 were obtained. The conversion of influent COD to methane dropped from 80.5% to 54.4% with a decrease in the COD/SO₄^2- ratio from 20 to 0.5. At all the COD/SO₄^2- ratios used, over 79.4% of the total electron flow was utilized by methane-producing archaea, indicating that methane fermentation was the predominant reaction.

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N-nitrosodimethylamine (NDMA) is a probable human carcinogen formed as a by-product of the chlorination and ozonation of water. It is photodegradable by UV irradiation, but its reformation is suspected when chlorine is added to UV-irradiated water. In this research, the photodegradation of NDMA by irradiation with excimer, low-pressure (LP), and medium-pressure (MP) UV lamps was investigated using NDMA solutions with an initial concentration of 100 ng·L^-1. To examine the effects of coexisting matters on the photodegradation and reformation of NDMA, Suwannee River NOM and/or nitrate was added to the test solutions at concentrations below the drinking water standard in Japan. The rates of photodegradation by using the excimer, LP, and MP UV lamps were 8.7, 2.7, and 2.3 cm²·J^-1, respectively. The photodegradation rate was reduced by coexisting matters at about 40-90%, 7-50%, and 20-60% for the excimer, LP, and MP UV lamp, respectively. The increase in NDMA formation potential by chloramination was 5 ng·L^-1 or less, regardless of the coexisting matters.

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Utilizing a U-shaped black light source designed to irradiate UV light in multiple directions and a flat-type reactor made of fluorocarbon resin, we have proven that up to approximately 50 mg-C·L^-1 of organic compounds can be completely decomposed to CO₂. The optimum conditions were over 5,000 mg·L^-1 of anatase-type titanium oxide, pH of 3-5, heating of the sample to 60-80°C, and circulation of 100-200 cm·min^-1 of gas to increase the light exposure area and to suspend the titanium oxide inside the reactor. Also, the produced CO₂ was completely absorbed by alkaline 0.05-0.1 mol·L^-1 strontium chloride solution, and measured as the turbidity of strontium carbonate particles. Adopting this new principle, we have produced a prototype of a compact and low-cost TOC analyzer, and have tested the performance for various organic compounds in solution, sewage, and industrial wastewater, for examples. By this measurement method, the amount of inorganic carbon in water can also be analyzed.

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A rapid and quantitative polymerase chain reaction (PCR) method for determining the numbers of two fecal pollution indicators, E. coli and Enterococcus was developed. The quantitative detection of E. coli and Enterococcus was performed on the basis of the uidA and 23S-rRNA gene sequences, respectively. A linear relationship was observed between the log concentration of each gene and the threshold cycle value obtained from the PCR amplification curve. Using these standard PCR curves, the concentrations of E. coli and Enterococcus were measured in environmental water samples collected from a wastewater treatment plant and four bodies of water located in the northern part of Japan. Measurements by the real-time PCR method were compared with E. coli and Enterococcus counts determined by cultivation methods such as membrane filter and MPN analyses. The PCR method gave quicker results and higher E. coli and Enterococcus counts than the traditional cultivation methods. These higher counts suggested the ability of the PCR method to detect DNA from both culturable and nonculturable or dead bacteria. Regression analysis of these measurements showed significant positive correlations between the PCR method and the traditional cultivation methods with correlation coefficients of over 0.7.

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