著者

Sulfikar Ryo Honda Mana Noguchi Ryoko Yamamoto-Ikemoto Toru Watanabe

出版者

Japan Society on Water Environment

雑誌

Journal of Water and Environment Technology (ISSN:13482165)

巻号頁・発行日

vol.16, no.2, pp.94-105, 2018 (Released:2018-04-10)

参考文献数

51

被引用文献数

16

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The influent of municipal wastewater treatment plants (WWTP) can contain micropollutants such as antibiotics, chlorine, detergents, and biocides. In vitro studies have shown that these micropollutants may induce antibiotic resistance in bacteria. Previous studies have reported increases or decreases of antibiotic-resistant bacteria between the influent and effluent of WWTP in an unpredictable manner. Thus, the triggers of resistance induction in WWTP are largely unknown. To investigate the effects of unit operations in WWTP on antibiotic resistance induction, we incubated sixteen strains of Escherichia coli susceptible to amoxicillin or norfloxacin under simulated conditions of the primary sedimentation tank, aeration tank and final sedimentation tank in sterilized and filtered wastewater from each tank at 25°C for 1, 6 and 2 hours, respectively, which are typical hydraulic retention time of each tank. The minimum inhibition concentration towards amoxicillin or norfloxacin was compared before and after incubation to evaluate the occurrence of induction. We found that resistance to both antibiotics was more likely to increase in the aeration tank than in the primary sedimentation tank or final sedimentation tank. The longer contact time with the wastewater and the aeration are factors that appeared to induce antibiotic resistance in an activated sludge process.

著者

Ryo Honda Yuta Teraoka Mana Noguchi Sen Yang

出版者

日本水環境学会

雑誌

Journal of Water and Environment Technology (ISSN:13482165)

巻号頁・発行日

vol.15, no.1, pp.1-11, 2017 (Released:2017-02-10)

参考文献数

27

被引用文献数

23

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Treated sewage is a promising source of nitrogen and phosphorus in microalgae biomass production for carbon-neutral biofuel and chemical products. In this study, Chlorella vulgaris was continuously cultivated in membrane photobioreactors (MPBRs) under short hydraulic retention times (HRTs) and with different numbers of submerged membrane modules to investigate potential microalgae productivity when treated sewage was used as a nutrient source. Microalgae biomass concentrations were independent of HRT in MPBRs with one membrane module owing to microalgae biomass deposition on the membrane. Installation of an additional submerged membrane module effectively reduced deposition on the submerged membrane, resulting in increased microalgae biomass concentration and volumetric productivity. Growth kinetics suggested that HRT is the essential parameter influencing the volumetric productivity of microalgae under nutrient-limited conditions, and that optimization of the biomass concentration, which depends on the surface/volume ratio of the photobioreactor and initial light intensity, is critical to maximization of the volumetric productivity under light-limited conditions.

著者

Rei YAMASHITA Michio MURAKAMI Yuichi IWASAKI Nao SHIBAYAMA Keisuke SUEKI Mahua SAHA Goro MOURI Soulichan LAMXAY Haechong O Yukio KOIBUCHI Hideshige TAKADA

出版者

日本水環境学会

雑誌

Journal of Water and Environment Technology (ISSN:13482165)

巻号頁・発行日

vol.13, no.2, pp.179-194, 2015 (Released:2015-04-10)

参考文献数

49

被引用文献数

3 15

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The release of radiocesium from the Fukushima Dai-ichi Nuclear Power Plant caused environmental contamination. We analyzed sources, behavior, and temporal trends of radiocesium by 1-year monitoring in an urban river, the Ohori River. The concentrations of 137Cs in both particulate and dissolved phases decreased to ~ 16% within 1 year. The partition coefficient in dry weather was estimated to be 3.2 × 104 L/kg. 137Cs concentrations in the particulate phase were higher during wet weather than during dry weather on the basis of both suspended solids (SS) weight and liquid volume. The ratios of 137Cs concentration to deposited 137Cs in the Ohori River (e.g., composite: 0.26 m2/kg-SS in June - July 2012) were higher than those in the Abukuma River, probably because of differences in land use. Source analysis by a chemical mass balance method showed that 22% of 137Cs came from river water in dry weather, 39% from river sediments, and 39% from road dust highlighting urban surface deposits such as road dust as major sources of 137Cs in the river water even 2 years after the accident, and that the wash-off of these deposits increased the 137Cs concentration in the river during wet weather.

著者

Pokchat CHUTIVISUT Wiboonluk PUNGRASMI Sorawit POWTONGSOOK

出版者

日本水環境学会

雑誌

Journal of Water and Environment Technology (ISSN:13482165)

巻号頁・発行日

vol.12, no.4, pp.347-356, 2014 (Released:2014-08-10)

参考文献数

28

被引用文献数

1 12

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Suspended organic sludge from freshwater and biofloc Nile tilapia systems were examined for the presence of denitrifying and dissimilatory nitrate reduction to ammonium (DNRA) activities under nitrate and sulfide stimulation. Initial nitrate concentrations at 25 and 100 mg NO3--N/L were added to the freshwater sludge and biofloc samples to simulate low and high nitrate levels that are normally found in aquaculture systems. The results showed that freshwater sludge and biofloc both had denitrifying activity immediately after nitrate addition. However, ammonium accumulated in the biofloc reactors but not in the freshwater reactors, indicating the activity of DNRA in the high C/N biofloc particles. The influence of sulfide on nitrate reduction was also studied by adding different concentrations of sulfide along with 100 mg NO3--N/L. The results showed that elevated sulfide concentrations partially inhibited denitrification in the freshwater sludge and caused nitrite and ammonium accumulation, in which ammonium formation was probably responsible by DNRA activity. In sulfide-added biofloc reactors, ammonium accumulated at the same level as found in the biofloc reactors without sulfide. Therefore, DNRA bacteria residing in the biofloc aquaculture system were more likely to be heterotrophs that did not use sulfide as their electron donor.

著者

Izarul MACHDAR Muhammad FAISAL

出版者

日本水環境学会

雑誌

Journal of Water and Environment Technology (ISSN:13482165)

巻号頁・発行日

vol.9, no.1, pp.47-52, 2011 (Released:2011-03-31)

参考文献数

9

被引用文献数

2 3

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An oil palm fiber module has been developed to modify a down-flow hanging sponge (DHS) reactor module. The objective of the proposed system is to improve two existing DHS variants of post-treatment unit for UASB treating domestic wastewater, i.e. cube-type and curtain-type sponge as domestic wastewater treatment system for developing countries. This paper describes the potential of oil palm fiber-based DHS (PF-DHS) configuration for sewage treatment. Feasibility of the PF-DHS reactor was evaluated by conducting a six-month continuous operation using actual sewage as feed. The system has been verified to have an excellent organic removal performance achieving 67% of unfiltered COD removal, and nearly perfect SS removal at the HRT of 2 h. It was observed that the organic removal rate was approximately 2.64 kg COD/m3 per day. The result recommended that the proposed PF-DHS reactor would be a promising system to alter sponge-based DHS for domestic wastewater treatment system in developing countries.