Environmental impact assessment in the receiving water area by the treated water discharge control according to the regional characteristic

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K12371
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 64010:Environmental load and risk assessment-related
• Research Institution: Saga University
• Principal Investigator: Yamanishi Hiroyuki 佐賀大学, 理工学部, 教授 (20240062)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 季別運転 / 硝化抑制 / アンモニア態窒素 / ノリ養殖 / 下水処理場 / 有明海 / 泥干潟 / 水温

Outline of Final Research Achievements

Flexible operational effects of sewage treatment according to the needs of the region and the impact on the water environment were investigated. The effect of treated water as irrigation water in summer has a low contribution to the amount of the whole canal water, but the increased concentration of nitrogen and phosphorous showed the possibility of reducing the amount of fertilizer applied and using it in the on-site environment such as paddy soil. In winter, the treated water with high nutrient concentration was released to the seaweed farm, and it was confirmed that the treated water had reached the fishing ground at the concentration level required for growth. In addition, as a result of evaluating the amount of nutrients transported in the water area, it was estimated that the amount of nutrient inflow was about the same as the amount of nutrients taken out by seaweed production. However, in the water area where the discharge is small, the effect was small at about 1/10.

Free Research Field

水環境工学

Academic Significance and Societal Importance of the Research Achievements

有明海湾奥部水域には，日本を代表するノリ養殖の一大拠点が形成されている．昨期のノリ生産高も日本一となり，地域産業としての役割も大きい．一方で，ノリ養殖は自然状況に大きく左右されるため，その管理が非常に難しい．特に，ノリの生長を左右する水域の栄養塩管理は毎年の課題となっている．とかく，短期的な漁獲収量に目を奪われやすい状況のままにある実態から，本研究が実施する現地調査・解析およびこれらに基づく現状の問題点の有無など明らかにすることで，懸念の払しょくもしくは現状の早期改善等を科学的な根拠に基づき，とりまとめることに大きな意義がある．