Landfill leachate treatment: Review and opportunity

In most countries, sanitary landfilling is nowadays the most common way to eliminate municipal solid wastes (MSW). In spite of many advantages, generation of heavily polluted leachates, presenting significant variations in both volumetric flow and chemical composition, constitutes a major drawback. Year after year, the recognition of landfill leachate impact on environment has forced authorities to fix more and more stringent requirements for pollution control. This paper is a review of landfill leachate treatments. After the state of art, a discussion put in light an opportunity and some results of the treatment process performances are given. Advantages and drawbacks of the various treatments are discussed under the items: (a) leachate transfer, (b) biodegradation, (c) chemical and physical methods and (d) membrane processes. Several tables permit to review and summarize each treatment efficiency depending on operating conditions. Finally, considering the hardening of the standards of rejection, conventional landfill leachate treatment plants appear under-dimensioned or do not allow to reach the specifications required by the legislator. So that, new technologies or conventional ones improvements have been developed and tried to be financially attractive. Today, the use of membrane technologies, more especially reverse osmosis (RO), either as a main step in a landfill leachate treatment chain or as single post-treatment step has shown to be an indispensable means of achieving purification.     

Indicating the parameters of the state of degradation of municipal solid waste

This study related to the analysis of the physical (granulometry and composition) and chemical (organic matter, organic carbon and nitrogen contents) characteristics, as well as those relating to release (leaching tests and determining the methanogene potential) of several domestic wastes, with an aim of evaluating stabilization indicators. Values thresholds for a known stabilized waste were thus deduced by correlation (% paper-cardboard = 0-1; % volatile solid (VS) = 18-19; % OC = 5-6; % fines = 44-45; % degraded components = 75-76, COD of leachate = 141-155 mg O2/L; DOC from leachate = 45-49 mg C/L and 0.9-1 m3 CH4/t of dry waste). However, these values thresholds remain specific to the method employed for the analyses. The results obtained represent a considerable advance in the definition of a waste stabilized state and propose the importance of certain parameters, such as the paper-cardboard content and the measurement of leachates by using the SUVA index for determining a stabilization state.