Effects of toxicants on the performance of a two-phase anaerobic digestion process treating raw primary sludge

This studyinvestigates the current state of anaerobic digestion, discusses the main limitations and bottlenecks that can inhibit anaerobic digestion processes and cause upset or failure, and examines the performance of a two-phase anaerobic digestion process treating raw primary sludge. A brief review of anaerobic digestion as a process, as well as parameters that must be monitored inorder maintain effective process performance: pH, temperature, C/N ratio, retention time, organic loading rate, bacterial competition, nutrient content, toxicants, solids content, and mixing/agitation isinitially outlined. The discussion then focuses onammonia, a specific inorganic toxicant and its mechanism of toxicity in anaerobic digestion. Finally, the performance of a bench-scale two-phase anaerobic digestion process operating at mesophilic and ambient temperature to treat raw primary sludge is examined in relation to pH, total and free ammonia concentration, and methane production. It is concluded that methane production in the bench-scale anaerobic digestion system was negatively affected by fluctuations in pH which led to an increase in free ammonia concentration inhibiting the newly adjusted ambient temperature microbial community. In short, this investigation highlights the importance of pH control for achieving and maintaining optimal anaerobic digestion performance.