THERMOPHILIC ANAEROBIC DIGESTION OF WASTEWATER SLUDGE

Abstract

Sludge management is the highest operating cost in municipal wastewater treatment. Anaerobic digestion (AD) is used to stabilize the sludge and reduce biosolids generation. Hydrolysis kinetics limit the rate of anaerobic digestion and must be improved to increase the overall process rate. In this study a new sludge characterization analysis was used to evaluate hydrolysis in a lab-scale pretreatment process operated at 55℃, 65℃, and 75℃. The experimental results were used to develop a new AD mathematical model, the hydrolysis digestion model (HDM). The model developed is easier to use, as the number of processes and variables were reduced by half, in comparison to existing models. The model variables can be measured using standard sludge characterization analysis, and the hydrolysis reactions included the fermenting microorganism to more accurately model the two-phase hydrolysis model. Model simulations were found to be a good fit of the experimental results, accurately predicting the rate and extent of hydrolysis in the pretreatment digester.