- 著者
- Phuc-Nguon Hong Chanreaksmey Taing Phuong-Thanh Phan Ryo Honda
- 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.1, pp.40-53, 2018 (Released:2018-02-10)
- 参考文献数
- 39
- 被引用文献数
- 17
Extracellular polymeric substances (EPS) are reported to be the major foulant in membrane bioreactor (MBR) processes. It is important to understand the EPS fractions which cause irreversible fouling to reduce operation cost and energy consumption in MBR. In this study, we developed polarity-molecular weight profiling, in which EPS components were plotted on two-dimensional matrix of its polarity and molecular weight, and applied it to investigate EPS of bulk sludge and cake layers from a lab-scale MBR. The EPS components were also characterized via three-dimensional excitation-emission matrix (3D-EEM) spectroscopy. The result showed that hydrophilic substances as large as 100 − 670 kDa was found only in loosely-bound EPS (LB-EPS) of bulk sludge but not in that of cake layers nor in permeate. Hydrophobic substances smaller than 20 kDa were mainly found in soluble microbial products (SMP) in bulk sludge. Hydrophilic substances larger than 670 kDa was mainly found in tightly-bound EPS (TB-EPS) of bulk sludge and in LB- and TB-EPS of cake layers. These findings suggest that, after conditioning of micropores of virgin membrane by hydrophobic substances smaller than 20 kDa in SMP, hydrophilic biopolymers as large as 100 − 670 kDa in bulk sludge clog the narrowed micropores inside membrane, causing irreversible fouling.
- 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
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
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.