Characterization of Landfill Leachates and Sediments in Major Cities of Indochina Peninsular Countries—Heavy Metal Partitioning in Municipal Solid Waste Leachate

In this study, leachate and sediment samples were collected from the leachate drains, ponds and waste pits of three landfills in the Indochina peninsula to investigate the level of contamination of biochemical parameters, especially heavy metals. In-situ and laboratory measurements were conducted, together with site surveys to discuss the effects of site characteristics on leachate qualities. It was confirmed from the investigation that the changes in leachate qualities are mainly caused by the landfill site conditions, e.g., soil cover, the waste compaction level, waste thickness, dumping method, and leachate storage, and that these conditions lead to different levels of dilution and biochemical reaction of the leachate. Most of the biochemical parameters of the fresh leachates were greater than the effluent standards, and showed higher concentrations than those measured for the leachate in large storage ponds. The concentrations of the parameters were higher in the dry season than the wet season for all fresh leachate samples, but no significant seasonal difference was observed in the large leachate storage ponds. The majority of heavy metals were partitioned in the suspended solids, and no clear seasonal change of heavy metal contents was contained in the suspended solids and sediment samples.