Human urine can be diverted from faeces by urine diversion toilets. Nutrient recovery from diverted urine has been a growing concern recently, because urine contains many nutrients. Phosphorus in urine can be recovered as a precipitate of MAP (i.e., struvite, MgNH₄PO₄·6H₂O) by adding magnesium salt under alkaline conditions. In this study, we (1) developed a plant for struvite recovery from urine using a urine diversion toilet, (2) investigated the characteristics of the plant's urine collection, urine storage and struvite formation, and (3) analyzed the precipitates formed in the plant. In this report, we present the phosphorus flow in the plant. The plant was mainly composed of a urine diversion toilet, a storage tank and a reactor. Using the toilet, 94.8% of the urine excreted into the toilet was collected and stored in the storage tank. The composition of the stored urine became stable 19 days after the start of urine storage, and 20.8% of the phosphorus in the urine excreted into the toilet was precipitated with other precipitates during urine storage. The reactor recovered 85.0% of the phosphorus in the influent of the reactor, which was 62.0% of the phosphorus in the urine excreted into the toilet. It was considered that most of the recovered phosphorus in the reactor was in the form of struvite.

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An anaerobic syntrophic substrate-degrading coculture system was used to isolate uncultivated methanogens that can provide hydrogen at a very low partial pressure. Primary enrichments for methanogens were prepared from ten environmental samples with ethanol, butyrate, and propionate, which are degraded by syntrophic association with anaerobic syntrophic bacteria and hydrogenotrophic methanogens. For comparison, enrichments with hydrogen at a high partial pressure were also prepared with the same inoculum. To identify methanogens in the enrichments, we applied 16S rRNA gene-based clone analysis to all the enrichments. The clone analysis revealed that almost all the clonal sequences obtained from the hydrogen enrichments were closely related to those of previously isolated methanogens, such as species belonging to the genera Methanobacterium and Methanospirillum. However, several clones retrieved from the syntrophic substrate-degrading enrichments were affiliated with uncultured lineages within the order Methanomicrobiales and with the candidate order Rice Cluster I. After several attempts at isolating the methanogens, we successfully isolated a methanogen affiliated with Rice Cluster I, and obtained a highly purified culture mainly consisting of a methanogen belonging to the family ‘Methanolineaceae’. These results indicate that anaerobic syntrophic substrate-degrading coculture system could be used as an effective method of isolating uncultivated methanogens.

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The structure of a microbial community during a two-phase circulating process for the hydrogen and methane fermentation of potato was investigated using a molecular biological approach. The process was performed using a mixing tank, a thermophilic acidogenic reactor (55°C) and a mesophilic methanogenic reactor (36°C) connected in series with the recirculation of methanogenic mixed liquor to the mixing tank. A continuous experiment was conducted by changing the process hydraulic retention time (HRT) stepwise from 56 days to 30 days, then 20 days and 15 days. A stable and high-rate hydrogen and methane fermentation was possible at a process HRT of 20 days with a hydrogen production rate of 3.6 l·l^-1·d^-1 and a methane production rate of 3.4 l·l^-1·d^-1. Denaturing gradient gel electrophoresis (DGGE) with 16S rRNA gene-targeted polymerase chain reaction (PCR) analysis was employed to identify the structure of a microbial community at various conditions for each reactor. Thermoanaerobacterium thermosaccharolyticum and Clostridium sporosphaeroides were considered to be the major hydrogen-producing bacteria in the thermophilic acidogenic reactor, whereas Methanosarcina siciliae and Methanoculleus bourgensis were considered, respectively, to be the acetate-utilizing and hydrogen-utilizing methanogenic archaea in the mesophilic methanogenic reactor.

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The microbial community responsible for treating municipal sewage sludges (excess, anaerobic digested and solubilized sludge) by slurry composting was examined. The sludges were kept under isothermal aerobic conditions for two or three weeks, and then its microbial community was analyzed using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) or a PCR cloning assay targeting the 16S rRNA gene. The result of PCR-DGGE indicates that the microbial community changed significantly within one week. The number of detected clones indicated that Bacteroidetes- and Firmicutes-related organisms predominated. Their ratios were 32% and 48% in the excess sludge, 64% and 16% in the anaerobic digested sludge, 78% and 6% in the solubilized sludge, respectively. The predominance of these groups was also reported in organic wastes from other composting or degradation processes, particularly the late period of degradation. The microbial community change throughout the experimental period of slurry composting indicated that the Clostridiales-related (phylum Firmicutes) group is associated with particulate organic substrates, whereas the Flexibacter-or Chitinophaga-related (phylum Bacteroidetes) group is associated with dissolved organic substrates.

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In this study, we discuss the storm runoff load for a collective tea field catchment. The study area was Makinohara plateau, in Shizuoka, Japan. The water quality and discharge were measured during a storm period. Heavy rain occurred due to a Bai-u front or cyclone during the rainy and typhoon seasons from June to September. Compared with clear weather days, NO₃-N concentration during heavy rain decreased to 1/3. However the T-P and COD concentrations increased 2∼23 times. The average recovery rate of NO₃-N concentration was 3 mg · l^-1 · d^-1. Hysteresis was observed in the relation between the discharge and the loads. The loads NO₃-N becomes higher when discharge was decreased than when it was increased. On the other hand, the load of T-P showed a reverse tendency, and the load of COD was similar, too. The loads in periods of storm runoff are heavily affected by the amount of rainfall and antecedent conditions.

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