Dispersion of muddy water and pollutant leaching from the bottom sludge in a dredged sludge disposal site

Abstract

Abstract Related to dredged sludge reclaimed in the stabilization pond, river bottom sludge is more rich in organic substances and nutrients than estuary sludge. Average loss on ignition, COD, total nitrogen and total phosphate content of the former were 13.2%, 54 mg g‐1, 5,200 mg kg‐1 and 3,800 mg kg‐1, respectively, but those of the latter were 9.9 %, 36 mg g‐1, 2,600 mg kg‐1 and 1,300 mg kg‐1, respectively. The elution concentration from the bottom sludge has been larger compared with that from estuary bottom sludge. Sludge discharged from the pipe of the discharge rate of 1,000 to 2,000 m3 day‐1 settled relatively quickly and the dispersion of turbidity and COD was small. At a discharge rate of 110,000 m3 day‐1, water quality at the first partition dike was influenced only for one day, while the effluent at the second outlet was not affected. Near the partition dike in the silt fence, turbidity and suspended solid were settled. Hence the inflow muddy water did not seriously influence water quality out...