Lake Tazawa in Akita Prefecture, Japan, is an acidic lake caused by the inflow of low-pH water from Tamagawa Hot Springs. Because of this anthropogenic acidification, many indigenous fish species and aquatic ecosystem have perished. Although several counter-measures such as artificial neutralization have been implemented against the acidic waters of Tamagawa River flowing into Lake Tazawa, the pH level of the lake remained low. Therefore, a bioassay evaluation of the low-pH lake water is necessary for ecosystem restoration. In this study, short-term chronic toxicity tests were applied to observe biological responses of three trophic levels of aquatic organisms using water samples of Lake Tazawa. As a result, Lake Tazawa water has toxic effect on all tested aquatic organisms. Especially, the fish embryo/larvae was directly affected by low-pH water, while algae and crustaceans were affected not only by low pH but other factors such as fluorine ion and metals. In order to improve the water quality management of Lake Tazawa for ecosystem restoration, further efforts are needed to reduce multiple toxic substances in addition to the pH neutralization of lake water.

Algal water blooms in lakes or reservoirs are often caused by an enrichment of phosphorus. Depending on a bottom environment, dissolved phosphorus (phosphate) can be released into a water column from bottom sediments and accelerate algal and macrophyte nutrient dynamics. This study focuses on phosphorus pollutant loads in stormwater wash-off from roadways. Control of phosphorus discharge from non-point sources in urban areas is important for preventing water pollution. Sources of phosphorus in pollutant loads were explored by comparing first flush runoff with road dust/water mixture and vehicle wash-off water, where characteristics of the particulate and dissolved portions, and the relationship between road dust and wash-off from vehicles were also discussed. It was clear that the concentration of dissolved phosphorus in the vehicle wash-off water was higher than that in the first flush runoff. One of the affecting factors of the dissolved phosphorus was inferred to be the nature of the additives in engine oils or certain types of engines.

The combination of aquaculture and microalgae cultivation with aquaculture effluent is a promising strategy, being economically and ecologically sustainable. This study explored the growth of Chlorella vulgaris and unintentionally cultivated microalgae with and without CO₂ injection. The microalgae were cultivated with aquaculture effluent at the rearing temperature of coho salmon (18.5°C). In addition, we conducted batch and semi-continuous cultivations with unsterilized aquaculture effluent, demonstrating the dominance of C. vulgaris. Carbon was the limiting factor for microalgal growth in the effluent, and CO₂ injection effectively enhanced the C. vulgaris growth. The highest percentage of C. vulgaris (over 99% of the total microalgal cells) was achieved by batch mode, by inoculating different amounts of C. vulgaris cells. This abundance resulted in the complete consumption of PO₄³⁻ in the effluent. A dominant semi-continuous cultivation of C. vulgaris, containing 82 mg/L of suspended solids, was achieved in 23 days. However, the occurrence of zooplankton grazing resulted in a sharp decrease of C. vulgaris. The cultivated C. vulgaris presented a high total content of amino acids, and the amino acid composition suggested that they could be efficiently used as protein sources for coho salmon.

Drinking water refilling stations (DWRS) are a growing business, providing affordable drinking water for middle–low urban households in developing countries in the last two decades. However, quality control including water quality and compliance with regulations, is not fulfilled completely by all DWRS. This study aimed to assess water quality and risk of recontamination of DWRS and compliance with administrative–laboratory testing regulations and factors associated with it. A cross-sectional study was conducted from March-August 2017 in Bandung City, and 229 of 659 DWRS were selected randomly. The water quality and risk of recontamination from refill gallons and outlet taps were examined using cotton swab and membrane filter methods to identify total coliforms/Escherichia coli. Compliance with administrative–laboratory testing regulations was identified based on the regulations of the Ministry of Health. Results found that water quality was unsuitable in 37.6% of drinking water and 34.1% of raw water. The risk of recontamination was found in 40% of refill gallons and 25.3% of outlet taps. Only 10.5% of DWRS complied with administrative–laboratory requirements. Factors associated with compliance were certified training and good management. An integrated system to manage and control the quality of DWRS is needed to prevent the consumption of nonstandardized drinking water.

High concentration (more than 1.0 mgP/L) of phosphorus was detected in groundwater in Aso caldera, Kumamoto. The fact indicates phosphorus can be transported by groundwater flows. The objective of this study is to clarify the characteristics of paddy soil (Andosol) in phosphorus adsorption process. Adsorption capacity of the Andosol was evaluated by continuously-flowing system using the soil column. In addition, soil phosphorus was categorized into five fractions; water-extractable phosphorus (Water-P), phosphorus extracted by sodium bicarbonate and sodium dithionate (DB-P), phosphorus extracted by sodium hydroxide (NaOH-P), phosphorus extracted by hydrochloric acid (HCl-P) and residual phosphorus (Res-P). As a result, it is confirmed that the flow rate of water is an important factor to control the phosphorus adsorption by the Andosol. The lower the flow rate is, the more phosphorus is adsorbed on the upstream soil. On the other hand, when the flow rate was high, phosphorus was evenly distributed in column soil. In addition, the fraction of NaOH-P accounted for 52% of the adsorbed phosphorus, suggesting that NaOH-P is the most important fraction which controls phosphorus adsorption to Andosol.

Polymeric materials are widely used in premise plumbing. To assess the potential of pipe materials to promote microbial regrowth in drinking water, we incubated drinking water in a new cross-linked polyethylene pipe (N-PEX), a new steel pipe lined with powdered polyethylene (N-SPE), and an old steel pipe lined with powdered polyethylene (O-SPE). As a reference, we also incubated drinking water in a carbon-free glass bottle (REF). Free chlorine rapidly depleted to below the quantification limit in the pipe incubations. While the original drinking water contained 0.4 mg C/L of dissolved organic carbon (DOC), the DOC concentration in N-PEX, N-SPE and O-SPE increased to 5.2, 3.1 and 1.7 mg C/L, respectively, after 8 days of incubation. The total cell count (TCC) in N-PEX, N-SPE, and O-SPE increased from <10³ cells/mL to 6.0 × 10⁵, 2.8 × 10⁵, and 3.6 × 10⁶ cells/mL after 8 days of incubation, respectively. On the other hand, the TCC in REF increased to 1.4 × 10⁵ cells/mL after 14 days of incubation. Dominant bacterial groups were different under the different incubation conditions. These results indicated that organic matter migrating from pipe materials promote microbial regrowth and affect the microbial community composition in drinking water.

Sulfate is currently not regulated by Japanese water quality standards but could pose adverse health effects to dialysis patients if it remains in high concentration (more than 100 mg/L) in dialysis water and dialysis fluid prepared at healthcare facilities (HCFs). In this study, we obtained sulfate levels in raw water and finished water at Japanese drinking water purification plants (DWPPs) from “Statistics on Water Supply (Water Quality)” in FY2012-2014, and then estimated increases in sulfate by water purification processes. Impact of water treatment chemicals containing sulfate (e.g., alum for coagulation and sulfuric acid for pH adjustment) was also evaluated by water sampling at selected three DWPPs. In FY2012-14, sulfate levels in finished water were mostly less than 50 mg/L; however, sulfate at 18 out of 1,497 DWPPs exceeded 100 mg/L. Increases in sulfate level by dosing of the water treatment chemicals were typically less than 10 mg/L, and other part of the sulfate in finished water came from raw water. These information on water quality should be shared with medical professionals conducting the dialysis therapies, and it would be worthwhile to collaborate with them in water quality management at HCFs.

The periostracum of corbicula clams is a unique outermost organic layer secreted from the inner surface of the outer mantle. It records the environmental history of corbicula clams which inhabited Lake Biwa. Two types of corbicula clams, yellowish and blackish shells, were studied with X-ray fluorescence element mapping and S, Fe and Mn K-edge X-ray absorption fine structure (XAFS) spectroscopy. It was revealed that the blackish shells grow in the more reducing environment than the yellowish ones. Main constituent of the periostracum is protein-based material, such as cysteine and methionine. The blackish shells contain much higher amount of Fe and Mn impurities. Fe was accumulated as FeOOH along the growth lines. Sulfur exists exclusively as organic molecules with the functional groups of thiol (-SH), which is oxidized to form disulfide (-SS-) by exposure to the oxidizing environment.