Product inhibition in sludge digestion

Abstract
Hydrogen and acetate inhibit the microbial degradation of propionate and ethanol in digesting sludge. Propionate oxidation is more sensitive than ethanol oxidation to product activities. This difference can be explained on thermodynamic grounds. It is concluded that the limiting factors for complete anaerobic mineralization of biodegradable organic matter in digesting sludge are to be sought in the boundary conditions for the exergonic oxidation of propionate. The different ecological significances of hydrogen and acetate as inhibitory agents of fatty acid degradation in sludge digestion are discussed. Hydrogen partial pressure and alkalinity are recommended as parameters in monitoring sludge digestion.