Monitoring the role of aceticlasts in anaerobic digestion: Activity and capacity

Abstract

Aceticlastic methanogens are seen as a key to digester capacity and stability. This paper develops and applies an assay to measure digester stability by measuring the maximum aceticlastic methane production rate ( V max,ac). The V max,ac in combination with acetate concentrations was found to be an effective digestion monitoring tool to indicate process upsets. At steady state, thermophilic, first stage and short SRT digesters generally had a greater V max,ac than mesophilic, second stage or long SRT digesters. The ratio of the V max,ac to the plant aceticlastic methane production rate, termed the Acetate Capacity Number (ACN), is a measure of the excess capacity of the digester. Either V max,ac or ACN can be used to estimate the capability to handle higher organic loading rates. Monod modeling was used to predict V max,ac, ACN and maximum VS loading rates for mesophilic and thermophilic digestion and for staged digesters to better understand expected digestion capacity and stability.