Anaerobic digestion inhibition indicators and control strategies in processes treating industrial wastewater and wastes

Based on a literature review, a set of inhibition indicators is presented for each stage of anaerobic digestion according to the behavior of certain parameters: the reduction of the soluble COD/total COD ratio; the low volatile fatty acids (VFA) production; the accumulation of VFA and low acetate production; and the low methane production. Moreover, we present several preventive and recovery strategies for each stage considering the detected inhibition indicator. Some of the preventive strategies are the acclimation of microorganisms to degrade organic-matter in the presence of certain inhibitors, the enrichment of the inoculum with various additives (e.g., sulfate-reducing bacteria, electron donors, mineral adsorbents or nutrients), the dilution of the influent, and the prior removal of the inhibitors. Some of the proposed recovery strategies are the reduction of the inhibitor concentration by removal strategies (e.g., precipitation, adsorption, and sulfate-reduction), intermittent feeding, and decrease of the total influent volume. Lastly, we present the challenges and future perspectives of applying the inhibition indicators and control strategies.