Biological Treatment of Landfill Leachate

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Abstract
As is known, leachate produced in a municipal solid waste landfill has very high concentrations of organic and inorganic pollution substances. Hence when present in deep or surface waters, it produces serious effects on health because of pollution of drinkable water sources. Therefore, in order to correctly define a management alternative for landfill leachate disposal, an experiment about its joint treatment with domestic wastewater in a biological full scale plant was developed. This treatment method which is the most used in Italy, among the disposal alternatives for leachate, poses problems connected with the definition of correct load rates between the two components (domestic wastewater and landfill leachate). The experiment which it was intended would verify the real feasibility of the treatment, was conducted over a six-month period, on a wastewater treatment plant in Folzano, Brescia, Italy. Experimentation was developed by gradually increasing leachate input and maintaining process conditions under analytical control. In particular, metals adsorption by the sludge and their effect on the efficiency of the process was measured. During the experiment pollution loads on the plant reached much higher values than ones due to domestic wastewater only (for example: the ratio between COD due to leachate and COD due to domestic waste increased to 9:5). Biological systems have shown a remarkable capacity for treating leachate, at least concerning COD while the removal efficiency of nitrogen was negatively influenced by the great leachate flows. In conclusion, these results show an effective applicability of this solution (if the leachate dosage is maintained under certain limits) and suggest the development of some pretreatment (such as ammonia stripping and metals precipitation) able to greatly improve the biological treatment of the leachate.