Thesis (M.Eng.) - Asian Institute of Technology, 2002

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering.

This study aims to determine the characteristics of leachate from sanitary landfills and lysimeter investigations with respect to the age of landfill, climate, and the operation of landfill. Phitsanulok Landfill and Pathumthani Landfill are selected to be the representatives of sanitary landfill in Thailand. Four-fero cement lysimeters with 1.4 m diameter and 3.5 m depth located at AIT are used in this study. These lysimeters contain distinct content of wastes and different mode of operation. The parameters used to characterize the leachate cover both physico-chemical and chemical properties (organic and inorganic constituents). The characteristics of leachate produced from sanitary landfills in Thailand with 3-4 years operated can be characterized as followed: 1. High pH values and conductivity 2. Dissolved solids are the main fraction of solid in leachate, on the other hand, suspended is very low 3. The organic contents expressed as COD and BOD5 are not so high, BOD/COD are relatively low in the range between 0.10-0.24. This indicates that this leachate contains high molecular weight refractory organic, which are best treated by physico-chemical processes. Low concentrations of volatile fatty acids present, it corresponding to 5-25% of COD and the main fraction of VF A is acetic acids. 4. High concentrations of nitrogen compounds mainly as ammonia and very low concentrations of organic nitrogen. 5. The concentrations of phosphorus are relatively low. 6. Heavy metals concentrations: Pb, Cr, Cu, and Zn are slightly higher than surface water standard type ill. The leachate produced from each cell lysimeters is characterized as followed: reference cell is placed with unprocessed wastes, produced leachate with high strength of COD and BOD, up to 33,000 and 23,000 mg/L, respectively. In contrast, compost cell is placed with pre-treated wastes, produced leachate with low concentrations of COD and BOD, 1,700 and 1, 100 mg/L, respectively. The circulation of leachate can decrease high strength of pollutants as shown in bio-reactor cell. Open dump cell covered with thin layer of sand produced high strength of pollutants. All cells except compost cell have high concentration of volatile fatty acids and the main fraction is acetic acids.