Measurements of the specific methanogenic activity of anaerobic digestor biomass

Abstract

A specific methanogenic activity test was tested for its use as a simple procedure suitable for measurement of the activity of the various physiological groups of microorganisms involved in the terminal processes of methanogenesis from complex organic matter. Activity was estimated by supplying sufficient substrate (acetate, propionate, butyrate, H2 or none) to saturate the catabolic systems of the various physiological groups, whereafter the specific methane production rate was determined. Activity was defined as the substrate-dependent methane production rate per unit mass of volatile solids biomass, i.e. the rate with a saturating concentration of substrate present when the background methane production rate had been diluted to an insignificant level. When the digestor was perturbed, the concentration of unused substrate in the biomass obscured the effect of added substrates on the test batches. It was generally found that if the background level of substrates could not be sufficiently lowered by dilution, substrate specific activity tests, as commonly described in the literature, were useless.