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Anaerobic ammonium oxidation (anammox) is a promising process for NH 4 + -rich wastewaters such as anaerobic digester liquids. In the present study, we investigated various properties of an up-flow column reactor containing anammox granules and fed with a real digester liquid at four different concentrations (Phases 1 to 4). The efficiencies of NH 4 + and NO 2 − removal decreased by up to 32% and 42%, respectively, in the digester-liquid-fed reactor (reactor-DL). When the performance of reactor-DL deteriorated, the community structure, spatial distribution, and in situ anammox activity in the two reactors were further investigated using 16S rRNA gene-based phylogenetic analysis, fluorescence in situ hybridization (FISH), and microelectrode measurements. The phylogenetic analysis and FISH results showed that non-anammox bacteria were predominant in the granule outer layers in reactor-DL, whereas anammox bacteria still dominated the granule interiors. Microelectrode measurements showed clear evidence of NH 4 + oxidation activity in the interiors of granules from reactor-DL. Batch experiments using anammox granules at different acetate concentrations indicated that concentrations up to 50 mM had no effects on the anammox activity, whereas inorganic carbon uptake decreased in the presence of acetate. The present study clearly shows that the anammox activity and anammox bacterial density in the granules were maintained after feeding the digester liquid to the reactor for 140 days.

本研究は, 厨芥のメタン発酵処理を高負荷処理することを目的とし, 水熱反応処理を前処理としたメタン発酵法を開発した。厨芥の水熱反応処理特性に及ぼす処理条件の影響およびメタン発酵の処理性に及ぼす水熱反応処理の影響を検討した結果, 以下の知見が得られた。 (1) 厨芥の水熱反応処理は, 処理温度が高いほど固形物の可溶化が短時間で進むことが確認された。ただし, 処理温度が高いほどガス化による溶存成分の減少が, 可溶化による増加を短時間で上回ることが確認され, DOCが最大となる処理条件は, 160℃, 60minであり, 処理前の1.5倍程度まで増加した。 (2) 粉砕処理のみの厨芥と水熱反応処理した厨芥のメタン発酵処理実験を行い, 処理性を比較した結果, HRT20日では, 大きな違いがみられなかった。しかし, HRT10日では, 水熱反応処理を行うことによりSS, POC, TOC分解率において10～15%程度の向上効果が確認された。また, 粉砕処理のみでは運転の困難であったHRT5日においても, 水熱反応処理を用いることによりSS, POC, TOC分解率がそれぞれ69, 74, 72%で処理が可能となり, 水熱反応処理の利用によるHRT短縮の可能性が示された。

Applicability of a new simple method for estimating heterotrophic plate count (HPC) in environmental samples was investigated. In this method, 0.1-1.0 ml of sample is incubated in a cell equipped with a dissolved oxygen (DO) electrode. The HPC in the sample is estimated from the time required until the DO is depleted (detection time). This method was applied to a pure culture sample and environmental samples to evaluate the validity and reliability of this method.The results indicated that (1) the HPC estimated by this method was in agreement with that determined by the plate count method in environmental samples (r = 0.85), (2) 95 % confidence interval of detection time of this method was shorter than the generation time of bacteria in the samples with HPCs higher than 102-103 CFU·ml-1, (3) In the case in which the same amounts of heterotrophic bacteria existed in the sample cell, the detection time (mean value and 95 % confidence interval) for bacteria captured on a polycarbonate membrane filter (0.2 μ m) was comparable with that for bacteria suspended in the sample cell.Thus, it could be concluded that this simple method could more rapidly estimate the HPC in environmental samples than the conventional plate count method with comparable accuracy and could be sufficiently applied to low-HPC samples.

Biodegradable organic substances in Yodo River water, its coagulated water and the ozonated water were analyzed in terms of the concentration of assimilatable organic carbon (AOC), the apparent molecular weight and the E260 absorbability. The fundamental behaviors of AOC through coagulation and ozonation were investigated. Yodo River water contained a relatively high content of macro organic compounds (>5,000 Da) that did not exhibit E260 absorbing features. However, these compounds were not detected as AOC. Coagulation resulted in decreases in the concentration of AOC by up to 75%, due to reductions in the phosphorus concentration. During ozonation, the AOC concentration increased rapidly with the reduction of E260 and increased slowly following the change of some large molecular organic compounds to small ones. However, 30-50 % of AOC that could be increased through ozonation was reduced by pre-coagulation.In addition, water samples prepared under the condition of different limiting substrates were subjected to AOC measurements and batch incubation tests for bacteria living in Yodo River. Experimental results indicated that the AOC concentration converted to acetate equivalent could not represent the concentration of the available carbon for assimilation. However, its apparent value was probably reflective of the growth potential of bacteria even under the phosphorus limitation. Thus, it was suggested that the apparent AOC concentration is a useful indicator for evaluating the regrowth potential of native bacteria in Yodo River.

This paper deals with the performance of a jet mixed separator (JMS) which has a series of porous plates inserted in the channel perpendicular to a flow. The water passes through holes in the plates, thus creating jets which gently mix the water on itself. Simultaneous flocculation of suspended particles and sedimentation of grown-flocs occur in the JMS, because large-scale eddies in the vertical plane are almost absent in it. The JMS incorporated with inclined tube settlers was applied to the rapid sand filtration system instead of the combination of mechanical flocculator and sedimentation basin. The turbidity of JMS effluent was constantly below 1 TU at the hydraulic retention time of about 1 hour. The JMS without inclined tube settlers was used as physico-chemical pretreatment process for the rotating biological contactors. The BOD and suspended solids concentration of JMS effluent were around 50 and 40 mg/L, respectively at the hydraulic retention time of 45 min.