Sediment Oxygen Demand of a Leachate Pond at an Offshore Municipal Solid Waste Disposal Site 2 Years after the Site Was Closed

Abstract

Various water quality parameters of a leachate pond at an offshore municipal solid waste disposal site were monitored. The pH, dissolved oxygen (DO), and water temperature at the bottom of the leachate pond were measured during Sep. (the 1st period) and Nov.-Dec. (the 2nd period) of 2011. The results suggested that the stratification of water temperature in the pond had gradually broken down due to convection occurring between the end of the 1st period and the 2nd period. The pH was almost constant at 10-11 during the 1st period and was approximately 11.5 during the 2nd period. The DO was almost zero during both periods. An anaerobic batch experiment with sampled sediment was undertaken to elucidate the mechanism of material leaching from the sediment. DO decreased under all experimental conditions. With respect to oxidation reduction potential (ORP) and total sulfide in addition to DO, the condition most closely mimicking that of the site became the most anaerobic. The average sediment oxygen demand, SOD ave , was calculated using a brief numerical model based on batch experiment data. The SOD ave was 1114.7 mg/m 2 /d, indicating that at least 434 g/d of oxygen must be supplied to the leachate pond to maintain the DO.