Ebara Engineering Service Co.

Tokyo, Japan

Ebara Engineering Service Co.

Tokyo, Japan
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Takahashi M.,Nagaoka University of Technology | Takahashi M.,Tohoku University | Ohya A.,Nagaoka University of Technology | Kawakami S.,Nagaoka University of Technology | And 7 more authors.
International Journal of Environmental Research | Year: 2011

The evaluation of treatment characteristics and sludge properties of an upflow anaerobic sludge blanket (UASB) process was investigated using a pilot-scale 1.15 m 3reactor. The UASB, inoculated with digester sludge, was operated at a hydraulic retention time of 8 h at sewage temperatures ranging from 10.6 to 27.7 °C for more than 1100 days. The stable removal efficiencies for total COD Cr and SS were 63 ± 13% and 66 ± 20%, respectively. The average concentration of the retained sludge increased to more than 24.5 gSS/L of the column volume after two years of operation. In summer, the water temperature increased above 20 °C, and biodegradation of solid organic matter was enhanced. The solid retention time was evaluated to be as long as 293 ± 114 days; this is sufficient for mineralisation of solid organic matter, as indicted by a low sludge conversion of 0.029 gVSS/gCOD removed and a growth yield of 0.132 gVSS/gCOD, determined by seasonal sludge profiling. The bacterial communities, based on bacterial 16S rRNA genes in the retained sludge, were significantly diverse. Bacteroidetes and Firmicutes were the dominant phyla of the decomposers of solid organic matter in the library. A Ruminococcus-related clone detected in the Firmicutes phylum acted as a cellulose decomposer.

Miyahara M.,Tohoku Gakuin University | Kim S.-W.,Tohoku Gakuin University | Fushinobu S.,Tohoku Gakuin University | Takaki K.,Tohoku Gakuin University | And 7 more authors.
Applied and Environmental Microbiology | Year: 2010

In contrast to most denitrifiers studied so far, Pseudomonas stutzeri TR2 produces low levels of nitrous oxide (N2O) even under aerobic conditions. We compared the denitrification activity of strain TR2 with those of various denitrifiers in an artificial medium that was derived from piggery wastewater. Strain TR2 exhibited strong denitrification activity and produced little N2O under all conditions tested. Its growth rate under denitrifying conditions was near comparable to that under aerobic conditions, showing a sharp contrast to the lower growth rates of other denitrifiers under denitrifying conditions. Strain TR2 was tolerant to toxic nitrite, even utilizing it as a good denitrification substrate. When both nitrite and N 2O were present, strain TR2 reduced N2O in preference to nitrite as the denitrification substrate. This bacterial strain was readily able to adapt to denitrifying conditions by expressing the denitrification genes for cytochrome Cd1 nitrite reductase (NiR) (nirS) and nitrous oxide reductase (NoS) (nosZ). Interestingly, nosZ was constitutively expressed even under nondenitrifying, aerobic conditions, consistent with our finding that strain TR2 preferred N2O to nitrite. These properties of strain TR2 concerning denitrification are in sharp contrast to those of well-characterized denitrifiers. These results demonstrate that some bacterial species, such as strain TR2, have adopted a strategy for survival by preferring denitrification to oxygen respiration. The bacterium was also shown to contain the potential to reduce N2O emissions when applied to sewage disposal fields. Copyright © 2010, American Society for Microbiology. All Rights Reserved.

Wakako I.-O.,Tohoku Gakuin University | Miyahara M.,University of Tokyo | Kim S.-W.,University of Tokyo | Yamada T.,Tohoku Gakuin University | And 8 more authors.
Seibutsu-kogaku Kaishi | Year: 2013

In bioaugmentation technology, survival of inoculant in the treatment system is prerequisite but remains to be a crucial hurdle. In this study, we bioaugmented the denitrification tank of a piggery wastewater treatment system with the denitrifying bacterium Pseudomonas stutzeri strain TR2 in two pilot-scale experiments, with the aim of reducing nitrous oxide (N 2O), a gas of environmental concern. In the laboratory, strain TR2 grew well and survived with high concentrations of nitrite (5-10 mM) at a wide range of temperatures (28-40°C). In the first augmentation of the pilotscale experiment, strain TR2 inoculated into the denitrification tank with conditions (30°C, ∼0.1 mM nitrite) survived only 2-5 days. In contrast, in the second augmentation with conditions determined to be favorable for the growth of the bacterium in the laboratory (40-45°C, 2-5 mM nitrite), strain TR2 survived longer than 32 days. During the time when the presence of strain TR2 was confirmed by quantitative real-time PCR, N2O emission was maintained at a low level even under nitrite-accumulating conditions in the denitrification and nitrification tanks, which provided indirect evidence that strain TR2 can reduce N2O in the pilot-scale system. Our results documented the effective application of growth conditions favorable for strain TR2 determined in the laboratory to maintain growth and performance of this strain in the pilot-scale reactor system and the decrease of N2O emission as the consequence. © 2012, The Society for Biotechnology, Japan. All rights reserved.

Syutsubo K.,Japan National Institute of Environmental Studies | Yoochatchaval W.,Japan National Institute of Environmental Studies | Yoochatchaval W.,King Mongkut's University of Technology Thonburi | Tsushima I.,Japan National Institute of Environmental Studies | And 7 more authors.
Water Science and Technology | Year: 2011

In this study, continuous operation of a pilot-scale upflow anaerobic sludge blanket (UASB) reactor for sewage treatment was conducted for 630 days to investigate the physical and microbial characteristics of the retained sludge. The UASB reactor with a working volume of 20.2 m 3 was operated at ambient temperature (16-29 °C) and seeded with digested sludge. After 180 days of operation, when the sewage temperature had dropped to 20 °C or lower, the removal efficiency of both total suspended solids (TSS) and total biochemical oxygen demand (BOD) deteriorated due to washout of retained sludge. At low temperature, the cellulose concentration of the UASB sludge increased owing to the rate limitation of the hydrolytic reaction of suspended solids in the sewage. However, after an improvement in sludge retention (settleability and concentration) in the UASB reactor, the process performance stabilized and gave sufficient results (68% of TSS removal, 75% of total BOD removal) at an hydraulic retention time (HRT) of 9.7 h. The methanogenic activity of the retained sludge significantly increased after day 246 due to the accumulation of Methanosaeta and Methanobacterium following the improvement in sludge retention in the UASB reactor. Acid-forming bacteria from phylum Bacteroidetes were detected at high frequency; thus, these bacteria may have an important role in suspended solids degradation.

Miyahara M.,University of Tokyo | Kim S.-W.,University of Tokyo | Zhou S.,University of Tokyo | Zhou S.,University of Tsukuba | And 9 more authors.
Bioscience, Biotechnology and Biochemistry | Year: 2012

The aerobic denitrifier Pseudomonas stutzeri TR2 (strain TR2) has the potential to reduce nitrous oxide emissions during the wastewater treatment process. In this application, it is important to find the best competitive survival conditions for strain TR2 in complex ecosystems. To that end, we examined cocultures of strain TR2 with activated sludge via five passage cultures in a medium derived from treated piggery wastewater that contained a high concentration of ammonium. The results are as follows: (i) The medium supported the proliferation of strain TR2 (P. stutzeri strains) under denitrifying conditions. (ii) Nitrite was a better denitrification substrate than nitrate for TR2 survival. (iii) Strain TR2 also demonstrated strong survival even under aerobic conditions. This suggests that strain TR2 is effectively augmented to the wastewater treatment process, aiding in ammoniumnitrogen removal and reducing nitrous oxide production with a partial nitrification technique in which nitrite accumulates.

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