Metal Ion Inhibitors and Other Inorganic Toxicants in Anaerobic Biological Treatment Process of Industrial Effluents: A Critical Review

Because of its manifold advantages over pollution control and energy recovery, the anaerobic digestion process is increasingly being used for treatment practice for industrial wastes. It is also advantageous over aerobic treatment for low sludge production and low energy requirements. However, process instability, low biogas yield, and the presence of inhibitory substances are the problems that often encounter in anaerobic digestion, preventing it from being widely applied. Anaerobic degradation is sensitive to toxicants and a wide range of inhibitory substances are the primary cause of anaerobic digester upset or failure since they are present in substantial concentrations in wastes. Extensive efforts were made over the years to identify them, their mechanism of toxicity and the controlling factors of inhibition in anaerobic digestion. In this review, we present a detailed and critical summary of research conducted on the inhibition of anaerobic processes by inorganic toxicants and heavy metals. The inhibitors commonly present in anaerobic digesters include ammonia, sulfides, various light metal and heavy metal ions