ENV TECHNOL, 21(1), 2000, pp. 87-96
The influence of thermochemical pretreatment of a microbial biomass has been evaluated in terms of COD solubilization and anaerobic biodegradability. Influence of pH, temperature and pretreatment time were investigated. Optimal conditions for COD solubilization were pH=12, 140°C for 30 minutes. In these pretreatment conditions, up to 70% COD solubilization has been achieved. pH of pretreatment was found to be a key parameter whereas temperature and pretreatment time had only minor influence on COD solubilization. Biodegradability batch tests revealed that in all the pretreatment conditions tested, the anaerobic biodegradability of the pretreated substrate was limited. Continuous experiments run with a substrate pretreated at 140°C, pH 12 for 30 minutes led to similar limitations since no acclimatation was observed. The hypothesis proposed was that some inhibitory molecules have been released or that some intramolecular reactions have been induced during the thermochemical pretreatment, leading to the formation of refractory compounds.