Improving Anaerobic Digestion of Sewage Sludge by Hydrogen Addition: Analysis of Microbial Populations and Process Performance

Abstract

The effect of hydrogen pulse addition on digestion performance of sewage sludge was evaluated as a means for studying the increase in efficiency of methane production. Microbial communities were also evaluated to get an insight of the changes caused by the operational modifications of the digester. An energy evaluation of this alternative was performed considering the theoretical process of coupling bioelectrochemical systems (BES) for the treatment of wastewater along with hydrogen production and the subsequent anaerobic digestion. The addition of hydrogen to sewage sludge digestion resulted in an increase of 12% in biogas production over the control (1353 mL CH4 d−1 at an injection flow rate of 1938 mL H2 d−1). The liquid phase of the sludge reactor and the H2 supplemented one did not show significant differences, thus indicating that the application of hydrogen as the co-substrate was not detrimental. High-throughput sequencing analysis showed slight changes in archaeal relative abundance after hydrogen addition, whereas eubacterial community structure and composition revealed noteworthy shifts. The mass and energy balance indicated that the amount of hydrogen obtained from a hypothetical BES can be assimilated in the sludge digester, improving biogas production, but this configuration was not capable of covering all energy needs under the proposed scenario.

Diversity and Abundance of Microbial Communities in UASB Reactors during Methane Production from Hydrolyzed Wheat Straw and Lucerne

“…In a study of UASB processes operating with molasses wastewater, Eubacteriaceae was found to be one of the dominant phyla in the total bacterial community, and its relative abundance increased from 19.1 ± 6.2% to 30.5 ± 8.7% when OLR was raised from 3.6 to 5.5 COD g/L/d, but started to decrease again with continued increase in OLR [94]. Eubacteriaceae contains many acetogenic members that tolerate rather high content of acetic and propionic acids, and growth of members of this family has also been shown to be favored by H 2 supplementation [68][69][70]95,96]. Thus, one possible hypothesis could be that high OLR gives a high flow of substrate (and H 2 ), which in a certain range is beneficial for members of this family.…”

Biogas Production from Organic Wastes: Integrating Concepts of Circular Economy

“…Temperature accelerates the rate of degradation, leading to a shorter time needed to complete the full conversion of the substrate. There are several reports in the literature describing the influence of these parameters when operating under mesophilic and thermophilic regimens [28][29][30] and successfully evaluating different types of wastes, such as swine manure [31,32], sewage sludge [6,33,34], and lipid-rich wastes such as slaughterhouse wastes [35,36]. However, digestion is a complex process and may suffer from instabilities that are mainly associated with accidental overloading in the form of the presence of inhibitors such as sulfur compounds, high ammonia concentration, and volatile fatty acids (VFAs), or inadequate temperature control.…”

“…Results regarding this protocol are extremely disperse, obtaining a great diversity of effects in the anaerobic microflora. Martínez et al [33] reported improvements in biogas production with the addition of H 2 gas into a digester treating sewage sludge. Still, the increase in biogas yield was mainly explained by the activity of homoacetogenic microbes, causing the conversion into acetate and subsequently favoring the acetoclastic pathway.…”

Anaerobic Digestion for Producing Renewable Energy—The Evolution of This Technology in a New Uncertain Scenario

“…The evaluation of anaerobic digestion of sewage sludge with different substrates has been widely reported in the literature [ 32 , 33 , 34 ], and it is still under extensive research. There are plenty of reports evaluating the co-digestion of sewage sludge with solid organic wastes, high strength organic streams and different compounds acting as supplements to favor organic degradation [ 35 , 36 , 37 ]. Regarding this last subject is the addition of conductive carbon materials—char, graphene, graphite, activated carbon—to the digestion process that has gained recent interest.…”