Enhancing the Anaerobic Treatment of Municipal Solid Waste through Leachate Recirculation: A Case Study of the Alsulay landfill in Riyadh

Abstract

Anaerobic bioreactor landfills stand out as the prevailing approach for managing municipal solid waste. Among the various techniques employed in bioreactor landfills to address leachate treatment and prevent groundwater contamination, leachate recirculation emerges as a highly effective method. Implementing leachate recirculation not only eliminates the need for separate leachate treatment but also mitigates the risk of groundwater contamination. This strategic application significantly elevates the overall performance of landfills in terms of municipal solid waste (MSW) treatment and the generation of landfill gas. Leachate recirculation acts as a catalyst for accelerating waste degradation, resulting in a higher rate of landfill gas production. Furthermore, the landfill gas produced through leachate recirculation exhibits a greater proportion of methane compared to systems without recirculation. In essence, the integration of leachate recirculation not only optimizes the efficiency of waste treatment but also enhances the quality and quantity of landfill gas output.
The objective of this study is to enhance the efficiency of the Alsulay landfill by investigating the feasibility of recycling leachate water. The approach involves reapplying the treated leachate to the waste with the intention of expediting waste analysis.
To simulate the conditions found in municipal waste, a sample of cooked food, akin to organic components, was introduced. Four reactors (bottles) were set up, each containing a sample of food, a percentage of filtration water, and a percentage of anaerobic bacteria. Additionally, two reactors were prepared: one with food and anaerobic bacteria (without filtration water), and the other with filtration water and anaerobic bacteria (without food). This resulted in six reactors. A standardized quantity of anaerobic bacteria (10 ml) was added to all reactors due to the anaerobic nature of waste decomposition in landfills. The concentration of anaerobic bacteria was maintained at 4000 milligrams per liter.
The reactions were closely monitored, and various properties, including pH, total suspended solids (TSS), total solids (TS), and chemical oxygen demand (COD), were measured.
Microbial activity led to a substantial decline in pH levels across all reactors containing food waste and juices, resulting in the production of volatile fatty acids and a decrease in pH to approximately 3.60.
Within the initial two days of the experiment, the concentration of TSS in reactors containing leachate water and food waste decreased from 26 g/L to 20 g/L, representing an approximate 23% reduction. Following this initial drop, TS concentrations exhibited a significant decline. Notably, the concentration of COD decreased during the digestion of food waste.
The findings indicate that adding 40 ml or more of filtered water per liter contributes to the rapid digestion of 25 grams of food. In contrast, when adding 20 ml or less of filtered water, the decomposition did not occur as efficiently.