The effect of the supplementation with a primary carbon source on the resistance to oxygen exposure of methanogenic sludge

Abstract

Anaerobic methanogenic consortia have a considerable resistance to oxygen exposure. Yet, most research has been focused on the study of the tolerance to oxygen of anaerobic immobilized biomass. Less is known on the potential of the anaerobic suspended biomass for withstanding exposure to oxygen and the effect of a primary degradable substrate on such resistance. Thus, the objective of this work was to determine the effect of the amount of a primary degradable substrate (sucrose) on the resistance of a methanogenic suspended biomass to oxygen exposure. It was found that the inhibition of disperse anaerobic sludge by oxygen exposure decreases when the concentration of the supplemented carbon source increases. This is in agreement with the fact that aerobic respiration of the added substrate by the facultative heterotrophic bacteria, always present in this type of sludge, has been found in previous studies as one of the main mechanisms protecting methanogens against O2. From a practical point of view, this suggests that aeration of anaerobic systems should be possible without inhibiting the activity of methanogenic bacteria if an adequate ratio between oxygen and COD feeding is maintained. Such a ratio will depend however on the wastewater initial COD concentration.

Sulfur-oxidizing bacteria in environmental technology

“…Anaerobic bacteria can tolerate the presence of very low oxygen concentrations both in a granular sludge (Kato et al, 1994), and suspended culture (Estrada-Vázquez et al, 2003). Using micro-aeration, it is possible to reduce hydrogen sulfide in biogas to less than 500 mg/Nm 3 without reducing efficiency of anaerobic fermentation (Fdz-Polanco et al, 2009).…”

Biological H2S removal from gases

“…Previously, methanogens were assumed to be strictly anaerobic; however, recent research shows that in a mixed culture, methanogens are either able to tolerate a limited amount of oxygen or can be protected by facultative anaerobic bacteria. This protection was observed both in suspended as well as granular sludge (Estrada-Vazquez et al, 2003;Kato et al, 1993;Shen & Guiot, 1996).…”

Biodegradability of Nonionic Surfactant Used in the Remediation of Groundwaters Polluted with PCE

“…The biofilm structure of the biomass can protect the methanogenic archaea growing in the internal part of the biofilm from the exposure to nitrate, due to mere physical shield and biochemical protection related to nitrate consumption in the outer layers of the biofilm (Estrada-Vazquez et al, 2003;Garibay-Orijel et al, 2006b;Kato et al, 1997). The stratification of methanogenic archaea in the inner parts of biofilms and granules (Lanthier et al, 2002;Santegoeds et al, 1999;Saravanan and Sreekrishnan, 2006).…”