Journal of Japan Society on Water Environment

Greenhouse gas emission from Johkasou may fluctuate daily within a day because of the time variation in the influent volume of domestic wastewater. Two Johkasou systems were operated in a temperature-controlled room, and the effects of anaerobic-aerobic circulation were investigated. Whole-day monitoring of CH₄ and N₂O revealed the time variation in the emissions of these greenhouse gases, which was due to the inflow of wastewater. Therefore, the time variation in the emissions of greenhouse gases should be considered for accurate emission reporting. Anaerobic-aerobic circulation operation reduced CH₄ emission by 72% and N₂O emission by 54%, although CH₄ and N₂O emissions transiently increased with the inflow of wastewater. This means a 68% reduction in CO₂eq. In conclusion, anaerobic-aerobic circulation operation for nitrogen removal significantly contributes to greenhouse gas reduction in Johkasou.

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We aimed to clarify environmental factors affecting the distribution patterns of Vibrio vulnificus along the coast of Nagasaki prefecture. V. vulnificus in the Ariake seawater was found to range from 2 to 4 Log MPN/100 mL on average in summer when the water temperature exceeded 25°C. Although this is generally comparable to the bacterial abundance in other coastal waters of Nagasaki, V. vulnificus cells in the western Ariake Sea exceeded 4 Log MPN, reaching 6.4 Log MPN per 100 mL, when the salinity decreased to 3.3-23 psu in the summer of 2006. In a local river that flows into the Ariake Sea (the Funatsu River), V. vulnificus persisted all year round with a relatively high abundance (2-4 Log MPN/100 mL) in the area between the river mouth and the estuarine basin, where the salinity ranged from 8 to 28 psu. From these results, it is suggested that (1) the estuarine basin of local rivers that flow into the Ariake Sea provides V. vulnificus with a stable habitat, and (2) a combination of high water temperature and long-term rainfall in the Ariake Sea in summer creates low-salinity conditions that favor the excessive growth of V. vulnificus.

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