Screening of early warning indicators for full-scale dry anaerobic digestion of household kitchen waste.

Process monitoring is an essential measure to achieve efficient and stable performance in anaerobic digestion, thus requiring identification of effective early warning indicators. However, the application of early warning indicators to full-scale dry anaerobic engineering biogas plant still remains elusive. This study evaluated the effectiveness of common early warning indicators (including CH 4 , CO 2 , H 2 S, volatile fatty acids (VFAs), alkalinity (ALK), total ammonia concentration (TAN) and free ammonia concentration (FAN)) in monitoring the instability of anaerobic digestion process at a practical engineering plant. The results showed that the individual indicators could not provide a sufficient early warning time before the digester fell into failure collapse. In comparison, the coupling indicators (the ratio of CH 4 /CO 2 , CH 4 /pH, and CH 4 /H 2 S) had sensitive response to perturbation, which could regard as a potential early warning indicator, with the early warning time of 6, 7 and 10 days, respectively. Moreover, the VFA/ALK could be used as auxiliary indicators due to the limitation of complex detection methods. In addition, the result also indicated that the application of some warning indicators needs to be further verified, when transferring the result of laboratory scale to the practice application scenarios. This study provides insight into the stable operation of dry anaerobic engineering. [Display omitted] • The commissioning process of a full-scale biogas plant was investigated. • Household kitchen waste was digested at dry thermophilic condition. • The digester was inhibited and failed when the OLR increased to 15 kgVS/(m³·d). • The digester instability was primarily caused by the over-acidification. • The ratio of CH 4 /H 2 S and CH 4 /pH were selected as early warning indicators. [ABSTRACT FROM AUTHOR]