Incorporating the inhibition effect and hydrolysis kinetics into the mathematical model of waste activated sludge anaerobic fermentation

Abstract

Anaerobic digestion is a well-known biological treatment process. It uses less energy, consumes fewer nutrients, converts organic pollutants into methane gas, and produces a small quantity of biomass. The interactions among the various microbes in this complex biological system are poorly understood, and as a consequence, mathematical models are inadequate. This review discusses the principles of biokinetic models published in the literature on anaerobic fermentation as part of the anaerobic digestion process for waste activated sludge. Biokinetic models for anaerobic fermentation have been developed to predict cell growth, substrate consumption, and gas production throughout the process. We explore how the hydrolysis stage, which is a multi-step process that involves the breakdown of carbohydrates, proteins, and lipids, may be included in current biokinetic models. Because there is no single analytical method for accurately determining the biokinetics of anaerobic fermentation of waste activated sludge, the incorporation of hydrolysis parameters and inhibition effects are proposed to improve the estimated trends of process variables as a function of the design variables.