Temperature effects in modeling solid waste biodegradation

Microbial growth models are often used to evaluate anaerobic biodegradation processes and estimate gas generation rates from solid waste decomposition in sanitary landfills. Temperature effects on anaerobic processes have been commonly evaluated in anaerobic digestion studies by deriving mathematical expressions relating media temperature to biokinetic parameters of microbial growth models. Such expressions have not been derived or are rarely used in estimating gas generation rates from solid waste landfills. The first part of this paper presents a review of gas generation-microbial growth modeling techniques applied in simulating biodegradation and gas generation processes in solid waste landfills. The review includes a description of solid waste hydrolysis with temperature effects on hydrolysis rates and biokinetic parameters. The second part of the paper describes the incorporation of kinetic expressions into a gas generation-microbial growth model. Model simulation results were in good agreement with data from a landfill field test. The model indicated that hydrolysis rates of waste constituents were the rate limiting step in the methanogenic process. Temperature had a greater effect on the modeled system at the beginning of the simulation. At later stages, steady state conditions prevail and temperature effects were minimal. The model can be used to estimate methane generation rates from solid waste landfills and more importantly, identify control parameters in a landfill environment.