樹木のリター（落葉や落枝など）は、森林や水圏生態系の物質循環に重要な役割を担っている。池沼中に落ちた落葉広葉樹（クヌギ）および常緑針葉樹（スギ）の落葉から溶出した物質の水質へ及ぼす影響について、屋外実験池を用いて調べた。実験池水量1m3あたり乾燥葉1kgを100%クヌギ、100%スギおよび各50%の割合で添加し、2008年4月に実験を開始し、10月まで調査を行った。葉に起因するCODMn、TP、TNの溶出速度およびそれらの溶出量は、スギよりクヌギの葉の方が大きく、水質に及ぼす影響は大きかった。クヌギとスギが50%ずつの場合は中間的な特徴を示した。一方、クヌギとスギの葉は、ともに水生生物の生息場所として好ましくない貧酸素状態（DO：＜2mg・L－1）を引き起こし、とくにクヌギの葉は、その状態が1週間以上継続した。したがって、落葉による湖沼の水質悪化を防止するためには、落葉が水塊に入らないように管理する必要がある。水塊に落下した落葉を除去する際は、即日行うことにより溶出量を減らす効果がある。

Bdelloid rotifer are reported to play a promoting role in microbial aggregation and floc formation in activated sludge systems; however, the mechanisms involved in this process are unclear. This study explores the effect of a rotifer secretion (RS) from the species Philodina erythrophthalma on the flocculation and growth of two bioflocculation-producing bacteria isolated from activated sludge. Results show that although the secretion has weak bioflocculability in itself, it can significantly enhance the flocculability of bioflocculation-producing bacteria and promote formation of microbial aggregation and floc. The possible mechanism is that the RS causes an increase in the bacteria densities and extracellular polymeric substance contents. The improvement of flocculability using RS shows an S-curve changing tendency with collection time, and corresponds with the first-order model with secretion dosage. Chemical composition analysis shows that low contents of non-protein organic nitrogen and polysaccharides are found in the RS, which implies that RS acts more like a growth-promoting substance or infochemical than as a nutrient in the promotion of bacterial growth. In conclusion, the findings provide a novel and potential strategy for promoting sludge floc formation using the infochemical secreted by this rotifer.

The objective of this work was to elucidate the impact of different kinds of vegetation in the catchment of a pond on the water quality. The study area covered the irrigation reservoirs distributed over the Hiki hilly areas in Saitama Prefecture. Five reservoirs were chosen for the investigation based on a local survey after pre-selection using the geographic information system (GIS) software. The catchments were composed of different types of vegetation such as deciduous forest (e.g., sawtooth oak “Kunugi”) and coniferous forest (e.g., Japanese cedar “Sugi” or Japanese cypress “Hinoki”). The concentration ranges (mg・l) of DOC, CODMn, total inorganic nitrogen (TIN), and Chl-a in the surveyed reservoirs were found to be 1.6–3.0, 3.9–6.4, 0.52–2.4, and 0.0024–0.011, respectively. In the reservoirs with deciduous forest-dominated catchments, NH4-N/TIN and NO3-N/TIN were >30% and ~60%. However, in the reservoirs with coniferous forest-dominated catchments, NH4-N/TIN and NO3-N/TIN were <20% and ~70%. Thus, the water quality of the reservoirs is dependent on the catchment vegetation, with typical abundance ratios of inorganic nitrogen more likely in those with conifer forest or deciduous forest-dominated catchments.

本研究では近年普及の進んでいる性能評価型浄化槽に着目し,塩素消毒前の工程における大腸菌群の除去効果,および塩素消毒による除去効果を解析した.さらに大腸菌群の除去特性について他の水質項目の除去効果と比較しながら解析した.その結果,調査した浄化槽25基のうち24基で塩素消毒前の大腸菌群数が排水基準値である3,000cfu/mL以下を満たすことが確認された.また,塩素消毒によって全ての浄化槽において1,000cfu/mLを下回るものの,残留塩素濃度が2mg/L以上検出されても大腸菌群数が200cfu/mL以上検出される場合もあった.大腸菌群数はSSと正の相関が,硝化率と高い負の相関が認められ,SSおよび窒素を高度に除去できる浄化槽によって大腸菌群数を低下させることが可能であることがわかった.

In this study, the effectiveness of aerobic granular sludge as seed sludge for rapid start-up of nitrifying processes was investigated using a laboratory-scale continuous stirred-tank reactor (CSTR) fed with completely inorganic wastewater which contained a high concentration of ammonia. Even when a large amount of granular biomass was inoculated in the reactor, and the characteristics of influent wastewater were abruptly changed, excess biomass washout was not observed, and biomass concentration was kept high at the start-up period due to high settling ability of the aerobic granular sludge. As a result, an ammonia removal rate immediately increased and reached more than 1.0 kg N/m(3)/d within 20 days and up to 1.8 kg N/m(3)/d on day 39. Subsequently, high rate nitritation was stably attained during 100 days. However, nitrite accumulation had been observed for 140 days before attaining complete nitrification to nitrate. Fluorescence in situ hybridization analysis revealed the increase in amount of ammonia-oxidizing bacteria which existed in the outer edge of the granular sludge during the start-up period. This microbial ecological change would make it possible to attain high rate ammonia removal.

Incomplete denitrification and ammonia accumulation were found to cause proliferation of filamentous microorganisms in sequencing batch reactors (SBRs) for swine wastewater treatment. Foaming was observed in response to the accumulation of 115.2 and 12.2 mg/L of nitrate and ammonia, respectively. The mixed liquor suspended solids (MLSS) level in SBRs was decreased to 2,000 mg/L and the suspended solids in the effluent reached 200 mg/L when foaming appeared. However, the use of swine waste as an external carbon source for enhanced biological nitrogen removal was found to effectively control the foaming caused by filamentous microorganisms. Therefore, an optimum strategy for the addition of swine waste was designed using integrated real-time control to provide pulse input control of slurry based on the “nitrate knee” in the oxidation–reduction potential profile. In this case, the MLSS concentration was maintained at an average value of approximately 7,550 mg/L, while the SS in the effluent was less than 30 mg/L.

Adsorption and biodegradation characteristics of musty odorous compounds, methylisoborneol (MIB) and geosmin were examined using activated carbon and nonadsorbing cellulose material as biofi lm carriers. Pseudomonas sp. capable of MIB degradation was used as a biofi lm-forming bacterium for the carriers. In the isotherm tests for MIB and geosmin, MIB was effi ciently removed by two types of carbon, and the carbon with wider surface area showed higher removal effi ciency. However, there was no removal effi ciency in the two types of cellulose with diff erent pore size of μm and μm. In the removal eff ects of MIB by carbon and cellulose carriers with Pseudomonas sp., the carbon formed biofi lm viz. biological activated carbon (BAC) could highly degrade MIB by . %, while cellulose-carrier showed MIB removal with . % within hrs, comparing with obvious less removal of . % by the planktonic degrader in water solution. It was found that Pseudomonas sp. aggregated on the carrier could considerably enhance MIB degradation whether the biofi lm carrier was adsorption or not.

Contamination of river sediments by persistent organic pollutants (POPs) is a worldwide concern, and microbial degradation is regarded as an important process for removal of POPs from river sediments. To date, there is still a lack of systematic study on chlordane biodegradation in river sediments, and the information on hexachlorobenzene (HCB) biodegradation in river sediments is very limited in Japan. We investigated the anaerobic biodegradation potential of trans-chlordane (TC), cis-chlordane (CC), and HCB in sediment samples collected at three sites along the Kamogawa River in Saitama Prefecture, Japan. Lag period and biodegradation rates of TC and CC in the three sediments varied greatly with their properties and contamination by TC and CC. In contrast, biodegradation of HCB in all three sediments started immediately with the start of the experiment without lag period, and major differences in biodegradation rates among the sediments were not observed. At the end of 20-week anaerobic incubation in the dark at 30 degrees C temperature, degradation rates ranged from 0.0% to 33.0% for TC, 0.0% to 12.0% for CC, and 47.6% to 59.4% for HCB. Results showed that the high-to-low order of biodegradation in the river sediments was HCB>TC>CC. Although the sediments were collected in the same river, their biodegradation potential varied with properties. Sediment with rich organic content and contamination by TC and CC or HCB was observed to have high biodegradation rates for these pollutants. In addition, biodegradation of TC, CC and HCB was companied by obvious methane generation and drop of oxidation-reduction potential (ORP).

In a biological nutrient removal (BNR) process, the utilization of denitrifying polyphosphate-accumulating organisms (DNPAOs) has many advantages such as effective use of organic carbon substrates and low sludge production. As a suitable process for the utilization of DNPAOs in BNR, an anaerobic/oxic/anoxic granular sludge (AOAGS) process was proposed in this study. In spite of performing aeration for nitrifying bacteria, the AOAGS process can create anaerobic/anoxic conditions suitable for the cultivation of DNPAOs because anoxic zones exist inside the granular sludge in the oxic phase. Thus, DNPAOs can coexist with nitrifying bacteria in a single reactor. In addition, the usability of DNPAOs in the reactor can be improved by adding the anoxic phase after the oxic phase. These characteristics enable the AOAGS process to attain effective removal of both nitrogen and phosphorus. When acetate-based synthetic wastewater (COD: 600 mg/L, NH4-N: 60 mg/L, PO(4)-P: 10 mg/L) was supplied to a laboratory-scale sequencing batch reactor under the operation of anaerobic/oxic/anoxic cycles, granular sludge with a diameter of 500 microm was successfully formed within 1 month. Although the removal of both nitrogen and phosphorus was almost complete at the end of the oxic phase, a short anoxic period subsequent to the oxic phase was necessary for further removal of nitrogen and phosphorus. As a result, effluent concentrations of NH(4)-N, NO(x)-N and PO(4)-P were always lower than 1 mg/L. It was found that penetration depth of oxygen inside the granular sludge was approximately 100 microm by microsensor measurements. In addition, from the microbiological analysis by fluorescence in situ hybridization, existence depth of polyphosphate-accumulating organisms was further than the maximum oxygen penetration depth. The water quality data, oxygen profiles and microbial community structure demonstrated that DNPAOs inside the granular sludge may be responsible for denitrification in the oxic phase, which enables effective nutrient removal in the AOAGS process.

Isolation, stock, and in addition, monoxenic and mass culture of specific species of aquatic oligochaetes, Nais sp., Aeolosoma hemprichi, Pristina sp. and Dero sp. were attemped successfully. Small aquatic oligochaetes are the typical metazoa found frequently in the activated sludge and bio-film from domestic sewage treatment plant operated by low BOD loading. Using a sterilized activated sludge as the metazoan food, the monoxenic growth rate of small aquatic oligochaetes, the effects of temperature, pH, phosphate buffer solution concentration, organic concentration, share stress, food concentration and sort of bacteria as food, on the growth rate were measured. The optimum temperature of cultivation for A. hemprichi, Nais sp. and Pristina sp. were 33, 25 and 30°C, respectively. Phosphate buffer concentration which could grow normally were 1/375M for A. hemprichi and Nais sp., 1/150M for Pristina sp. and 1/7,500M for Dero sp. The optimum pH values in cultivating the oligochaetes ranged from 6 to 8. The growth of Nais sp. could not be observed in much stronger share stress.Specific growth rates (μ) ranged from 0.35 to 0.43 day-1 for A. hemprichi and 0.10 to 0.13 day-1 for Nais sp., respectively when the sludge concentration was more than 500 mg · l-1.

本研究では、水耕生物ろ過法における水量負荷条件が水質浄化能に及ぼす影響、植物の刈り取り (収穫) の栄養塩類の除去に及ぼす影響について検討を行った。また、隔離水界を用いて水耕生物ろ過法による浄化が対象水域の水質および生態系に及ぼす影響を解析し、浄化能力を総合的に評価した。クレソン植栽水路において冬季を除いてT-Nが平均0.98 g・m-2・d-1、T-Pが平均0.10g・m-2・d-1の除去速度が得られた。最適水面積負荷を検討した結果、除去速度はT-Nが水面積負荷5 m3・m-2・d-1に、T-PやChl. aなどが4 m3・m-2・d-1に設定した場合に最大となった。一方、除去率は低負荷条件に比べ、高負荷条件で低下がみられ、目的に応じて水面積負荷の最適化を図る必要があることが明らかになった。刈り取りの処理に及ぼす影響については、適切な刈り取りを行うことで処理水質に悪影響を及ぼさないことがわかった。クレソン植栽水路を用いた処理により隔離水界中のT-NおよびT-P濃度は低く、25日目においてChl.a濃度は41.1 μg・l -1を示し、対照系の隔離水界の77.4 μg・l -1と比べて1.9倍の差が認められた。特にMicrocystis sp. 除去については、10日目においては処理系水界および対照系水界のMicrocystis sp. の個体密度はそれぞれ1.1 × 103 N・ml -1と29 × 103 N・ml -1であった。本浄化システムにおいて栄養塩類を除去できるのみならず、藻類を量的に制御可能であり、さらに質的制御としての有毒藻類Microcystis sp. の除去や増殖抑制に極めて効果的であり、健全な生態系の維持にも効果があることがわかった。

下水の二次処理水の高度処理技術として、浸透流れ方式による人工ヨシ湿地を創出するための植栽基盤、栄養塩除去能力および最適な水面積負荷について検討を行った。空隙率の異なる砂、礫および網状担体をヨシの植栽基盤として用いた場合を比較したところ、砂および礫ではヨシの生育状況が良好であり、高い栄養塩除去能を有することがわかった。砂系での最大の除去速度は、DTNで5.5g・m-2・day-1、DTPで0.5g・m-2・day-1であり、これは限界水面積負荷である0.38m3・m-2・day-1において得られた。一方、礫系では水面積負荷0.60m3・m-2・day-1において、DTN除去速度6.6g・m-2・day-1、DTP除去速度1.1g・m-2・day-1が得られ、高い水面積負荷でも良好な処理水質が維持されることがわかった。砂系は、特に処理水質に優れ、処理性能の季節変動が少ないのに対し、礫系では処理水量の確保に有効であり、処理目標に応じた植栽基盤の選定が重要であることが示された。

After growing mass and monoxenic cultures of three species of small metazoa, Nais sp., Aeolosoma hemprichi and Philodina sp. using sterilized activated sludge as the metazoan food, the effect of six kinds of metals on the specific growth rate of each metazoa was examined. EC50 (effective concentration) was used to define the metal concentration required to reduce the specific growth rate of metazoa to half of that of a control. The EC50 for A. hemprichi, Nais sp., and Philodina sp. were: 0.9, 1.3 and 5.4 mg · l-1, respectively for copper, 0.04, 0.03 and 1.4 mg · l-1 for hexavalent chromium, 3.4, 4.3 and 9.2 mg · l-1 for zinc, 14.0, 7.6 and 33.0 mg · l-1 for manganese and more than 102.4 mg · l-1 under pH adjusted (A. hemprichi and Nais sp.) for alminium and iron. It was noted that concentrations of these metals from the influent of domestic sewage treatment plants were apparently less than values of EC50 mentioned above.