Transformations of Leachate as a Result of Technical Treatment at Municipal Waste Landfills

Research on landfill leachate proves that technical activities conducted on the site of the landfill of municipal waste: permanent compaction of waste, making strata between individual layers of waste, landfill degassing, partial reclamation of landfill quarters and landfilling of partially segregated waste, had a significant impact on change of physico-chemical composition of leachates over 32 years of its operation. It was found that there was a noticeable increase of pH which favours processes of elimination of certain mineral impurities including heavy metals. Concentration of phosphorus compounds occurring mainly in the form of phosphates decreased which can be explained by processes of precipitation and sedimentation of those compounds in leachates. There was a substantial increase in the concentration of ammonia nitrogen in individual years of the operation of the landfill in relation to the initial period, which shows the clear nature of reduction conditions in the generated leachate. Maximum concentrations of this parameter was noted after the fourth and fifth year of operation of the object. This promotes generation of landfill gas, which is used on the landfill site to produce electricity. There is still a high level of concentration of chlorides in landfill leachates. However, in relation to the 1983 and 1984 years, much lower concentrations of those pollutants in the evaluated medium is observed in the recent years. Presence of mineral impurities impacts on the sustaining increased parameters of dry residue and high conductivity. It should be noted that all forms of technical activities undertaken in the issue of landfill method of municipal waste disposal have a positive effect in generation of leachates containing currently far less pollutants than in previous years. It is necessary to conduct field monitoring of landfill leachates, permitting effective decisions regarding their treatment.