Wastewater treatment plants are considered to be reservoirs of antibiotic-resistant bacteria (ARB) outside human and animal bodies. To collect the supporting data, we investigated the existence of ARB in the activated sludge process of municipal wastewater treatment by analyzing communities of sludge bacteria that were incubated with high concentrations of antibiotics (ciprofloxacin or tetracycline) , using the next-generation sequencing technique targeting the 16S rRNA gene. Activated sludge samples were taken from aeration tanks at five municipal wastewater treatment plants (MWWTPs) and one university wastewater treatment plant in Thailand and Japan. Bacterial communities in the sludge samples before incubation were similar among the four MWWTPs in Thailand, but obviously different from those in Japan. The composition of sludge bacteria was markedly changed upon incubation. The concentrations of Enterobacteriaceae species in the sludge samples from two MWWTPs in Thailand increased to 71.3 and 81.4% during incubation with ciprofloxacin, indicating high resistance to this antibiotic. No such increases of specific bacteria families were observed during incubation of the sludge samples with tetracycline, but seven of the top ten dominant families of bacteria were common among the samples from three MWWTPs in Thailand, probably owing to the wide range of sludge bacteria resistant to tetracycline.

We investigated water quality and sessile animals in Dokai Bay, Japan, during periods of heavy eutrophication (1991-1992) and improved conditions (2010-2011) to evaluate the usefulness of sessile animals as environmental indicators. Hypoxia disappeared and total nitrogen and phosphorus decreased following the control of industrial discharges into the bay. Reduced eutrophication led to the spread of oxygenated water to the inner bay, accompanied by expanded distributions of marine sponges and bryozoans. In addition, the improvement of water quality appears to have added 40 new species to the community of gastropod mollusks (snails) . The Shannon diversity index for mollusks increased, and the total number of sessile animal species increased to 1.6 times that before water quality improvement. However, the total wet weight of two species of bivalve mollusks, mussels and Japanese oysters, decreased to 1.2% that before the improvement; statistics confirmed that this drastic decrease was a result of increasing water temperature. These results show that the community and population of sessile animals can be used as indicators of eutrophication and increasing water temperature, because of their dependence on environmental factors.

It is a challenge to maintain the granular sludge during the treatment of wastewater containing methanol by UASB, since few methanogens can utilize methanol as a substrate. In this study, for the treatment of actual wastewater containing methanol, the change in the microbial community and particle distribution of granular sludge were observed during the acclimatization process of seed granular sludge for the continuous operation of an UASB (Up-flow Anaerobic Sludge Blanket) system with sludge returning after solid-liquid separation. Methanosarcina-like methanogens in the granular sludge became dominant during the acclimatization, and the dominant species was found to be Methanomethylovorans. After their DNA exceeded 80%, the collapse of the granular sludge progressed and the particle diameter became less than 0.5 mm. However, stable performance still could be obtained because of sludge returning after solid-liquid separation, even after the collapse of granular sludge.

The pesticide list for drinking water in Japan was revised on March 28, 2013, and the acaricide amitraz was listed as a target pesticide. We investigated an analytical method for the simultaneous determination of amitraz, and the metabolites N-2,4-dimethylphenyl-N-methylformamidine (DMPF) and 2,4-dimethylform- amidine (DMF) in water by liquid chromatography-tandem mass spectrometry. The optimal organic solvent content of the standard solution for preparing the calibration curve was 50 v/v% for amitraz, 1-10 v/v% for DMPF, and 5-50 v/v% for DMF to retain high stability and for preservation. In the fact-finding survey of the existence of the three substances in the Tama river, there were places where DMF was detected in trace amounts in May. We investigated the degradability of the three substances by a disinfectant sodium hypochlorite. As a result, amitraz disappeared in approximately 20 h, and DMPF disappeared shortly after addition of the disinfectant. On the other hand, although its amount was reduced by half in around 5 h, DMF decreased gradually afterwards, and its persistence was higher than those of amitraz and DMPF. It was suggested that amitraz and the metabolites DMF in tap water should be measured simultaneously.