Coupled experimental assessment of physico-biochemical characteristics of municipal solid waste undergoing enhanced biodegradation

Abstract

Seven municipal solid waste (MSW) specimens with variable initial waste compositions were biodegraded in large (d = 300 mm, h = 600 mm) laboratory landfill simulators under leachate-recirculation-enhanced anaerobic biodegradation conditions to investigate changes in the biochemical and physical characteristics of solid waste, leachate and biogas during biodegradation. The evolution with time of the monitored characteristics of the three phases was presented and the characteristics empirically correlated. The impact of the initial composition of waste on the biodegradation process was quantified. Although removal of soluble compounds in leachate, and methane (CH4) generation from waste was practically completed after around 300 days, changes in vertical strain, total unit weight and volumetric moisture content of waste continued in decreasing rates even after 1000 days. Methane generation potential (L0) of the waste was correlated to the percentage of biodegradable waste prior to degradation expressed by parameter B0. Maximum methane generation rate (rCH4,max) increased with increasing L0 and maximum soluble chemical oxygen demand in leachate. Final strain (or settlement) of waste due to anaerobic biodegradation (εB,f) increased with increasing B0 and L0. The compression ratio was found to vary during the process, although it is commonly assumed to be constant. The maximum long-term compression ratio increased with increasing εB,f and rCH4,max. The total unit weight at submerged and field capacity states and volumetric moisture content of waste were also dependent on the initial composition and compression (quantified by strain) of waste. The trends presented in this study contribute to the quantitative understanding of coupled processes during enhanced biodegradation of MSW of variable waste composition.