How the origin of fresh household waste affects its ability to be biodegraded: an assessment using basic tools and its application to the city of Kara in Togo.

Waste biodegradation has been largely investigated in the literature by using conventional tests like the BMP test and the respirometric test, whereas only few studies deal with the use of leaching tests in combination with biological activity measurements. Consequently, this study used an improved leaching test to evaluate the biodegradability of two deposits of fresh household waste from the city of Kara in Togo. The first deposit came from households in neighborhoods located in the outskirts of the city and the second consisted of fresh waste, mainly composed of business waste and household waste, collected in the urban center and aimed at being deposited in the landfill. A physicochemical characterization of the two deposits completed the leaching test. The biological activity was monitored by measuring O(2) consumption and CO(2) production. pH, DOC/OM, VFA/DOC ratios and the SUVA index was measured in the leaching juice to assess both the state of degradation of the waste in the deposits and the ability of the organic matter to be mobilized quickly and to be easily assimilated by microorganisms. The biodegradability of waste from the city of Kara correlated with their origin even though the physical characteristics of the two deposits studied differed greatly.

Optimization of municipal solid waste leaching test procedure: assessment of the part of hydrosoluble organic compounds.

Despite national recycling campaigns, the amount of municipal solid waste (MSW) to be treated remains very important in France with almost 39% of the waste produced going to landfills. Therefore with the increasing concern over sustainable development and energy valorization, it seems essential to optimize current treatment methods and develop new preparation techniques of the waste. Nevertheless an important first step to take into account is to evaluate the waste using a different method than biogas production. In this perspective, the leaching test (LT) could be used as a tool to evaluate the ability of a waste to mobilize organic and mineral compounds. This research aims at optimizing a leaching test protocol mainly adapted to organic waste in order to be used on MSW to assess the fractions of both fast and slow mobilized organic matter. Several leaching tests have thus been implemented, optimized and compared in terms of accessible organic matter in the waste. Results have shown that the test conditions have a great influence on the mobilization of pollutants. The duration of the test affects mainly the quantity and quality of organic molecules extracted. The renewal of the eluent does not properly simulate the conditions of a landfill. The results would be used to assess the performance and the efficiency of new ways of waste pretreatment.

Study of organic matter during coagulation and electrocoagulation processes: application to a stabilized landfill leachate.

Organic matter contained in leachates appears to be a relevant indicator of waste evolution. Among the physico-chemical treatments applied to stabilize leachates, coagulation-flocculation is considered a classical process and electrocoagulation can be developed. Electrocoagulation tests were carried out in a laboratory pilot using aluminium plates and compared to classical coagulation-flocculation with aluminium ions and to electrolysis alone. The leachate used in this study came from the landfill of Crezin (Limoges, France) and it presented low biodegradability and high concentration of macromolecules. To assess the efficiency of the chemical and electrochemical processes, we specifically studied Organic Matter (OM) by using two protocols: adsorption on XAD resins and fractionation by ultrafiltration. Biodegradable Dissolved Organic Carbon (BDOC) measurements were applied to the fractions extracted by XAD resins and were also used as an indicator of the efficiency of the treatments. Residual organic matter concentration was the same for the two processes but its composition appeared different after electrocoagulation: a higher percentage of small hydrophilic organic molecules which seemed to be less biodegradable than the initial organic matter was observed.