The anammox process, as an alternative to conventional nitrogen removal technologies, has abstracted much attention in recent years. In this study, two column-type reactors using different support materials―net type acrylic fiber (Biofix) and polyester nonwoven―were used for anammox treatment. The nonwoven reactor was operated at 35℃ and the Biofix reactor at 25℃ (peak summer temperature, 31.5℃). Over 330 days of operation, the nitrogen loading rates of the Biofix and nonwoven reactors were increased to 3.6 kg-N/m³/d and 4.0 kg-N/m³/d and T-N removal efficiencies reached to 81.3% and 86.3%, respectively. A protein substance was shown to be the most abundant extracellular polymeric substances (EPS) in the anammox sludge with almost three times more in the granular sludge of the Biofix reactor than in the granular sludge of the nonwoven reactor. Considering the EPS levels and observation by scanning electron microscopy, the anammox granules in the Biofix reactor were denser than that in the nonwoven reactor. Results of DNA analyses indicated that the KSU-1 strain might prefer relatively low nutrient levels, while the KU2 strain might be better suited for the high media concentration. Other kinds of bacteria were also identified with the potentials for consuming the dissolved oxygen in the influent and facilitating anammox bacteria surviving under aerobic conditions.

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The profile of nitrous oxide (N₂O) production was examined for aerated lagoon (AL) and intermittent aeration sequencing batch reactor (IASBR) treating swine wastewater. N₂O production rate was 1.07×10¹～2.03×10³(mgN₂O－N/head/day) in AL and 2.83×10²～1.12×10³ (mgN₂O－N/head/day) in IASBR. The emission of N₂O in aeration phase accounted for over 80％ of all N₂O emission in AL, and almost 100％ in IASBR. In AL, the N₂O emission rate increased in the last aeration phase due to the simultaneous occurrence of nitrification and aerobic denitrification. In IASBR, the N₂O emission was promoted by the accumulation of dissolved N₂O caused by stagnation of denitrificatoin in anaerobic phase and the occurrence of aerobic denitrificatoin caused by high concentration of organic matter carried over from anaerobic phase. It was suggested that the risk of N₂O emission in AL was higher than that in IASBR, because aerobic denitrification was promoted easily in aerobic phase, and the accumulation of dissolved N₂O lead to the gasification in the anaerobic phase in AL.

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Plasma vitellogenin concentration was measured in wild carp captured from Lake Kojima in Okayama Prefecture at monthly intervals over a five-year period. Calculation of the gonadosomatic index (GSI), calculated as gonad-weight/body-weight, and revealed that reproductive development in males and females was seasonally synchronized. Similarly, seasonal changes in the vitellogenin concentration of male carp plasma were similar to the GSI of not only male carp but also female carp except during the breeding season. Since seasonal variations of 17β-estradiol and bisphenol A were not apparent, it is proposed that the vitellogenin concentration in male carp plasma changed relative to the stage of sexual maturity of the carp. Vitellogenin concentrations exceeding 1000 ng/ml in male carp plasma accounted for 1.9% of 210 specimens. The findings showed that the carp inhabiting Lake Kojima do not appear to be affected by estrogen-like substances at present.

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Comprehensive understanding of the occurrence of pathogens in the aquatic environment is important for assessing possible biological health risks associated with water usage. The occurrence of bacterial pathogens in the Yodo and Kita Rivers, Kinki district, Japan, was investigated by using a DNA microarray targeting 1012 species/groups of bacterial pathogens infectious to human, animals, plants, fish, and shellfish. Eighty-seven pathogens were detected in 24 river water samples collected from two rivers, with more than half present in both rivers. The pathogen profile in the river waters varied primarily seasonally. Effluent from wastewater treatment plants, a well-known possible pathogen source, did not significantly affect the occurrence of bacterial pathogens in the monitored basins. Moreover, some of the detected pathogens, particularly non-fecal ones, did not positively correlate with the total coliform count, a conventional hygienic indicator. Therefore, the conventional hygienic indicator for fecal contamination is inadequate for comprehensive determination of the health risks associated with contamination of river water by bacterial pathogens.

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It is known that mlrA, mlrB and mlrC encode microcystin (MC)-degrading enzymes in MC－degrading bacteria. We discovered the mechanism by which transcription of these genes was induced in MC-degrading bacterium Sphingopyxis sp. C－1. We showed induction of the transcription of mlrA, mlrB and mlrC by microcystin－LR (MCLR) and that of mlrA and mlrB by MCLR degradation products (linear microcystin, H－Adda－Glu－Mdha－Ala－OH (tetra peptide) and 2S, 3S, 8S, 9S－3－amino－9－methoxy－2, 6, 8－trimetyl－10－phenyldeca－4E, 6E－dienoic acid (Adda)). Adda played a key role in the induction of transcription of mlrA and mlrB, while the cyclic structure of MCLR was important for the induction of transcription of mlrC. It was found that the MC-degrading bacteria responded to MCLR and its degradation products by degrading microcystin through a sequential chain reaction for expression of MlrA, MlrB and MlrC.

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Influence of allelochemicals from submergent plants for population dynamics of Daphnia were investigated. We checked rate of hatching out from resting eggs of Daphnia and transition of biota of planktonic microorganisms including Daphnia by using filtrated water from cultivation tank of submergent plant. Potamogeton dentatus, P. × inbaensis, P. perfoliatus and P. maackianus activated not only rate of hatching out from resting eggs but density of Daphnia. The other hands, Myriophyllum spicatum, Potamogeton pectinatus, P. oxyphyllus, Najas oguraensis and Utricularia vulgaris var. japonica inhivited population.of Daphnia. These results suggest us that allelochemicals from submergent plants will play an important role for decision of planktonic biota in natural water conditions.

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