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Nabaterega, Resty

University of British Columbia

Volatile fatty acid (VFA) production from municipal sludge via anaerobic fermentation is a promising venture to reuse the sludge for resource recovery while ensuring the economic and ecological sustainability of wastewater treatment plants. However, information on optimum digester operating conditions to maximize VFA, especially acetic acid, remains unclear and incomparable. The current study investigated the impact of digester sludge retention time (SRT), temperature, pH, sludge composition, and their combinations on optimizing VFA production via anaerobic fermentation of municipal sludge in semi-continuous flow acid fermenters (AFs). A fractional factorial experimental design and response surface methodology were used to optimize VFA production from municipal sludge in the AFs based on the four critical parameters individually and interactively. To explain the mechanisms of VFA production dynamics, this study also explored batch non-methanogenic microbial activity assays (i.e., specific acidogenesis, acetogenesis, and hydrolysis) and linked them to VFA yields. The present study also modified the International Water Association Anaerobic digestion model No.1 (ADM1) to simulate the experimental VFA production. The fractional factorial design and response surface methodology successfully optimized VFA production in the AFs. A second-order polynomial model with an R-squared of 0.83 and an adjusted R-squared value of 0.84 was derived. The optimal model conditions for VFA production were 3-days SRT, 45°C, pH of 8.1, and sludge composition (VS/TS ratio) of 0.92. Under these conditions, the model simulated a 3.47-fold increase in VFA production, nearly identical to the experimental value of 3.48-fold. Furthermore, the AF had high activities in the non-methanogenic assays. These results suggested that batch non-methanogenic activity assays could provide quantitative information regarding the presence and activity of cultures in continuously fed anaerobic digestion utilizing more complex substrates, such as municipal sludge. Additionally, the modified ADM1 implemented in the AQUASIM 2.0 modeling platform successfully simulated the experimental VFA production.

Text

2023-01-18

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/83665

Civil Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/