Hydrogen utilization rate: A crucial indicator for anaerobic digestion process evaluation and monitoring

• A volumetric device and a test procedure were developed for measuring sludge HUR.
• HUR were highly influenced by sludge concentrations because of H2 mass transfer limitation.
• The critical value of sludge concentration for HUR test was concluded to 1 gVSS/L.
• HUR exhibited a good relationship with the TSMA and reactor performance.
• HUR was proved to be a critical indicative parameter for anaerobic process evaluation.

Hydrogenotrophic methanogens had been considered as key species for the anaerobic digestion (AD) of industrial wastewater and municipal sludge. However, how to evaluate the activity of the hydrogenotrophic methanogens was less studied. In this study, a volumetric device and a test procedure were developed for measuring the specific hydrogen utilization rate (HUR) of anaerobic sludge. Results showed that HUR values were highly influenced by sludge concentrations because of limitation on H2 mass transfer. The critical value of sludge concentration in the test bottle should not be higher than 1 gVSS/L. Under such condition, the kinetics of HUR would not be limited by H2 mass transfer and the maximal value of HUR could be obtained. Field survey confirmed that HUR exhibits a good relationship with specific methanogenic activity (SMA) and reactor performance. An anaerobic system with a relatively high HUR was found to be beneficial for maintaining H2 partial pressure in an appropriately low level. Moreover, such system was thermodynamically favourable for the syntrophic degradation of volatile fatty acids. As a crucial parameter of the anaerobic process, HUR could be used as a key indicator for evaluating and monitoring AD processes.