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

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.

[Effects of F/M on the uptake, storage and utilization of carbonhydrate in ASBR].

Substrate utilization in a glucose-fed anaerobic sequencing batch reactor (ASBR) under different F/M ratios was investigated. Glucose added was quickly taken up by fermentation bacterial in anaerobic digestion, then partly degraded directly to volatile fatty acid (VFA, accounted for 34%-38% of COD-fed) and partly accumulated transiently in the cell as glycogen (accounted for 41%-46% of COD-fed) and degraded to VFA in the following. The bacterial accumulation capacities increased with F/M. The maximum specific storage capacities could reach as high as 116.8, 81.1 and 62.4 mg/g as F/M (COD/VSS) was controlled in 0.27, 0.20 and 0.14 respectively. VFA production rate slowed down due to glucose storage, which resulted in low VFA accumulation and guaranteed a stable operation in ASBR under high loading rate.