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

Comparative study of the performance of an anaerobic rotating biological contactor and its potential to enrich hydrogenotrophic methanogens

“…It has been indicated that the propionic acid accumulation is dependent on hydrogen partial pressure or hydrogen uptake rate rather than pH . As the AnRBC showed very low levels of propionate under shock loads with glucose based media and even with propionic acid, it reflects very good hydrogenotrophic methanogenic activity in the AnRBC.…”

“…Despite being an attractive technology, anaerobic treatments of wastewaters suffer from poor operational stability, mainly because of the extreme sensitivity of the microorganisms to various operational parameters such as pH, temperature, toxic compounds, etc . In addition, hydrogen is also recognized as an important process intermediate, because of its effect on the substrate conversion potential of all major anaerobic bacteria groups . This is attributed to the volatile fatty acid (VFA) oxidizers present in syntrophic association with hydrogen‐utilizing (hydrogenotrophic) methanogens via the interspecies hydrogen transfer.…”

Influence of zero valent scrap iron (ZVSI) supply on methane production from waste activated sludge

“…With the increase of ZVSI, the yield of H 2 increased and reached the greatest of 12.3 ± 1.5 mL at 1.0 g-ZVSI/g VSS. It was reported previously that high H 2 content (or partial pressure) was detrimental to methane production [29] because of the associated CO production [48] and/or the impeded thermodynamical conversions of propionate and butyrate into acetate [31], which inhibited acetoclastic methanogenesis (Methanosaeta and Methanosarcina [29]). Notably, H 2 did not accumulate continuously herein even at the highest dosage of ZVSI 1.0 g/g VSS, but was quickly consumed during the following biological process (especially at 35°C), during which no H 2 was detected.…”

“…In a study nano ZVI at 1 mM and above reduced methane production by higher than 20%; at 30 mM, nano ZVI greatly increased soluble COD and volatile fatty acids (VFAs) along with an accumulation of H 2 , leading to a reduction of methane by 69% [29]. The toxicity principles of nano ZVI may include: (i) fast H 2 production and accumulation, which impedes the thermodynamical conversions of propionic and butyric acids into acetic acid [31] and methanogenesis (H 2 threshold of 23-75 nM for methanogens [32]); and (ii) disruption of cell membranes via reductive decomposition of ZVI [29,33], which inhibits methanogenesis. Clearly, up to date, the behaviors of ZVI in anaerobic systems are still inconsistent and sometimes contradictory.…”