CHARACTERISTICS OF LEACHATE PRODUCED FROM SIMULATION OF LANDFILL IN ATROPICAL COUNTRY

Four different heights of lysimeter were prepared to investigate the l eachate characteristics produced from waste beds. The solid wastes fro m Chiang Mai municipal area were filled into the lysimeters with an in place density of about 0.85 ton/mg(3). The experiment had been started for 853 days from May, 1990 to October, 1992. The leachates were coll ected every week to every month depending on the age of the waste and analysed for pH, conductivity, total solids, suspended solids, total d issolved solids, total volatile solids, alkalinity, acidity, total vol atile acid, Cl-, SO=4, BOD, COD, TOC, TKN and NH3-N. The results showe d that conductivity, volatile acid, total solids, total volatile solid s, COD, BOD and TOC were very high in me first rainy season or in the first dry season, after that, they decrease abruptly, and then gradual ly decrease until the end of the experiment Acidity, alkalinity, suspe nded solids, TKN and NH3-N were high in the first rainy season and gra dually decreased until the end of the experiment High percentage reduc tion of acidity, volatile acid, COD, BOD and TOC concentrations in the leachate produced from lysimeters after one year of waste filling sho wed that the acidogenic phase of the biodegradation process had termin ated and that the major portion of carbonaceous organic matter in the waste bed had been utilised within me first year of the experiment For the deeper waste layer, nitrogenous compounds in the leachate produce d after two years of waste filling were still high due to the low acti vity of nitrification in the waste bed. It was found that the shallowe r waste layer produced lower concentrations of pollutants in the leach ate. Higher amounts of leachate volume and extracted substances per dr y weight of wastes were produced from the shallower waste layer.