Efforts to Improve Osaka Bay Water Quality and Current Status (2003-2020s)

Efforts to Improve Osaka Bay Water Quality and Current Status (2003-2020s)

In 2003, the Osaka Bay Revitalization Promotion Conference was established in response to the severe water pollution in Osaka Bay. Since the period of rapid economic growth, Osaka Bay has accumulated chemical substances and hazardous materials due to industrial and urban wastewater, leading to eutrophication. Consequently, the frequency of red tide outbreaks increased, and pollutants such as PCBs and heavy metals settled in the sediments, severely impacting the ecosystem. To address this, the Osaka Prefecture, Osaka City, and Hyogo Prefecture took the lead in launching a collaborative water quality improvement project with industry, government, and academia.

Efforts in the 2000s
During this period, specific measures focused on strict industrial wastewater management and tidal flat restoration projects. For example, major chemical companies in Osaka City, such as "Daicel" and "Sumitomo Chemical," enhanced wastewater treatment technologies to reduce the release of hazardous substances. Additionally, in the area around Sakai City, tidal flat restoration projects progressed, aimed at restoring the habitat of aquatic organisms through sediment improvement. Companies like "Osaka Environmental Business Corporation" and "Toyota Motor Corporation" provided technical and financial support, encouraging participation in environmental conservation activities.

Status and Achievements in the 2020s
Entering the 2020s, notable achievements have been seen in the water quality improvement of Osaka Bay, though challenges remain. The Chemical Oxygen Demand (COD) in the bay's inner areas has gradually decreased from 2003 levels, yet as of 2024, it still averages 3.2 mg/L, exceeding the environmental standard of 2 mg/L. Additionally, during the summer, dissolved oxygen (DO) levels in the bottom layer can fall below 2 mg/L, indicating the presence of hypoxic water masses.

Latest Initiatives
In response to these conditions, more advanced technology integration and community collaboration have progressed in the 2020s. Osaka City's Maishima Sludge Center employs the Membrane Bioreactor (MBR) system for wastewater treatment, improving COD, nitrogen, and phosphorus removal efficiency. Moreover, "Sumitomo Chemical" and "Daicel" have implemented Environmental Management Systems (EMS) in their wastewater treatment facilities, aligning with ISO 14001 to tighten emission standards.

Meanwhile, the tidal flat and seaweed bed restoration projects are also advancing. Osaka Prefecture is promoting the preservation and restoration of shallow areas through projects like the creation of artificial tidal flats in Sakai District 2 and the establishment of seaweed beds near Rinku Town. These projects are expected to restore about 50 hectares of tidal flats by 2023. Additionally, local citizen groups, such as the NPO "Osaka Bay Watch Network," contribute to raising public awareness through regular cleaning activities and environmental education initiatives.

Future Prospects
The restoration of water quality and ecosystem recovery in Osaka Bay requires integrated water quality management across the entire watershed. Further technological innovation and collaboration with businesses and citizens are essential to address climate change. The improvement of Osaka Bay's water quality is not only expected to restore fishery resources but also to enhance its value as a tourism resource, providing new benefits to both the regional community and economy.