FIELD OBSERVATIONS ON ACCUMULATION OF ORGANIC SLUDGE AND GENERATION OF SCUM IN NOMI-RIVER FLOWING THROUGH HIGHLY URBANIZED AREA OF TOKYO

Abstract

 After rain events, scum with malodor often appears in the brackish water reaches of urban rivers. In this study, scum generation mechanisms were observed through continuous water quality observation, capturing inflow organic sludge using sediment traps, and camera surveys in the Nomi-river, which flows through the southern part of Tokyo. The results revealed that sludge accumulated in the area around the Sanya-bridge where the riverbed is deepest and generation of anaerobic gas required for floating scum occurs quickly. Regarding the latter, most of the period from rainfall to the observation of scum shows a transition to a strong anaerobic condition by sulfate reduction action for 12 to 24 hours, and the generation of anaerobic gas required for floating scum occurs within 2 hours.