Abstract: Anaerobic biotechnology is used to treat municipal wastewater sludge and many industrial wastewaters. In the process, microbes degrade pollutants and convert them to biogas containing methane. The methane gas can be used for heat and energy generation. Therefore, the process includes both wastewater management and renewable energy generation. Often, the Anaerobic Digestion Model #1 (ADM1) is employed to help design and understand anaerobic treatment systems. Fundamental model inputs include maximum Monod substrate utilization rate constants (km). Unfortunately, the kinetic constant values can actually vary greatly, based, in part, on the exact microbial community present in the engineered process (i.e., the identity of microbes and the numbers of each). Unfortunately, there are no standard, simple methods to measure the kinetic values since determining the concentration of active microbes in a given trophic group. is difficult. Having a method to determine active trophic group microbial concentrations as well as kinetic constant values would help us understand the process and design/model anaerobic bioprocesses. In this talk, a novel respirometer method to determine Monod kinetic constant and active biomass concentrations will be presented. Using the technique, the maximum specific acetate utilization rates for biomass from more than 20 full-scale anaerobic bioprocesses was found to vary greatly. Surprisingly, some biomass samples exhibited extremely high acetate utilization rates (>40 g COD/g CODx-d), whereas flocculant municipal biomass rates were similar to the ADM1 default value of 8 g COD/g CODx-d. Rate data were compared to genomic data and results supported the hypothesis that acetate oxidation (i.e., the conversion of acetate to H2 and CO2) is more prevalent in well-functioning digesters than assumed. Granular biomass was especially rich in acetate oxidizing potential, and this may also be supported by significant interspecies electron transfer in granules. The important link between microbial community composition and bioprocess function will be highlighted. Just as the human gut microbiome varies from person to person and can influence health, anaerobic digester microbiomes can vary and influence process function.
Biosketch: Daniel Zitomer, Ph.D., P.E., BCEE, Fellow WEF is professor and chair of the department of civil, construction and environmental engineering at Marquette University (Milwaukee, WI). Dr. Zitomer teaches and performs research regarding wastewater management, renewable energy and anaerobic biotechnology for industrial and municipal wastewater. He also consults with industries and municipalities regarding wastewater management. He is a fellow of the Water Environment Federation (WEF) and received the 2008 WEF Fair Distinguished Engineering Education Medal. He is site director of the National Science Foundation Industry/University Cooperative Research Center on Water Equipment and Policy and is a member of the NSF Great Lakes Water Innovation Engine technical committee. Dr. Zitomer received his BS in civil engineering from Drexel University (Philadelphia, PA) and his MS and Ph.D. degrees in environmental and water resources engineering from Vanderbilt University (Nashville, TN).
Andrew Liguori
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