Removal of Organics from Leachate by the Combined Process of a Facultative Pre-Treatment Pond and an Aerated Lagoon at a Sea-Based Solid Waste Disposal Site

Abstract

Leachate was collected from the sea-based North Port Solid Waste Disposal Site, Osaka City, and a bench-scale treatment of the combined process of a facultative pre-treatment pond and an aerated lagoon was applied for more than 120 days. The maximum BOD removal rate coefficient and COD-manganese removal rate coefficient were 0.090/day and 0.018/day, respectively. These values were obtained when the retention time of the facultative pre-treatment pond was 25 days. But, if the retention time was beyond or below 25 days, both removal rate coefficients were smaller. Therefore, we concluded that the optimum retention time of a facultative pre-treatment pond was 25 days. This was reconfirmed by the Gel-Permeation Chromatography of the treated leachate, a method for evaluating wastewater treatability proposed by Tambo and Kamei (Water Research, 12, 931-950, 1978). Furthermore, the Gel-Permeation Chromatography pattern of the treated leachate in the bench-scale experiment coincided with that obtained by the actual field test. In addition, judging from Tambo's evaluation method, it could be concluded that higher-molecular organics were decomposed biologically into lower-molecular organics at the middle and bottom layer of the facultative pre-treatment pond. BOD and COD-manganese values of below 10 mg/l and about 130 mg/l, respectively appear to be the maximum effective level of the combined process.