2024 Volume 34 Pages 79-88
The Omuta City Northern Sewage Treatment Plant (STP) in Fukuoka Prefecture conducts seasonal operation to release nutrients into seaweed booth of Ariake Sea. The purpose is to supply the nutrients contained in the discharged water to the seaweed farms in the Ariake Sea in the winter when nitrogen is scarce. During seasonal operation, the STP discharges wastewater containing ammonia nitrogen as its main nitrogen component. However, no detailed field survey regarding the status of nutrients contained in effluent water from the STP reaching seaweed farms has been reported. In this study, we investigated the arrival status of nutrients derived from STP from the Domen River estuary to the sea area where the seaweed farm is located. As a result, based on changes in nutrients concentration at each point over time, it was confirmed that water that had stagnated near the river mouth during high tide had reached the seaweed farm 500 m west of the river mouth as the tide went out. And, based on the ratio of NH4-N to T-N, it is thought that the tidal current reached a point further 1 km away from the river mouth in the southwest direction.
