Effect of landfill characteristics on leachate organic matter properties and coagulation treatability

This work spans landfill characteristics, leachate organic matter properties, and coagulation chemistry to provide new insights into the physical–chemical treatability of stabilized landfill leachate. Furthermore, leachate organic matter is viewed in terms of dissolved organic matter (DOM) present in the natural environment, and coagulation chemistry is evaluated based on previous leachate and water treatment coagulation studies. Stabilized leachate was collected from four landfills for a total of seven leachate samples, and samples were coagulated using ferric chloride, ferric sulfate, and aluminum sulfate. Landfill characteristics, such as age, leachate recirculation, and cover material, influenced properties of DOM present in the leachate, as measured by specific ultraviolet (UV) absorbance at 254 nm (SUVA254) and fluorescence excitation–emission matrices. The coagulation performance of the metal salts was ferric sulfate > aluminum sulfate > ferric chloride, and DOM removal followed the trend of color > UV254 > dissolved organic carbon > chemical oxygen demand (COD). Finally, a strong association was found between increasing SUVA254 and increasing DOM removal for coagulation of both leachate and natural surface water. Thus, SUVA254 is expected to be a better predictor of leachate treatability, in particular DOM removal, than the traditionally used ratio of biochemical oxygen demand to COD.