Scholarly Work - Center for Biofilm Engineering
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/9335
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Item Greenhouse gas production from an intermittently dosed cold-climate wastewater treatment wetland(Elsevier BV, 2024) Ayotte, S. H.; Allen, C. R.; Parker, A.; Stein, O. R.; Lauchnor, E. G.This study explores the greenhouse gas (GHG) fluxes of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) from a two-stage, cold-climate vertical-flow treatment wetland (TW) treating ski area wastewater at 3 °C average water temperature. The system is designed like a modified Ludzack-Ettinger process with the first stage a partially saturated, denitrifying TW followed by an unsaturated nitrifying TW and recycle of nitrified effluent. An intermittent wastewater dosing scheme was established for both stages, with alternating carbon-rich wastewater and nitrate-rich recycle to the first stage. The system has demonstrated effective chemical oxygen demand (COD) and total inorganic nitrogen (TIN) removal in high-strength wastewater over seven years of winter operation. Following two closed-loop, intensive GHG winter sampling campaigns at the TW, the magnitude of N2O flux was 2.2 times higher for denitrification than nitrification. CH4 and N2O emissions were strongly correlated with hydraulic loading, whereas CO2 was correlated with surface temperature. GHG fluxes from each stage were related to both microbial activity and off-gassing of dissolved species during wastewater dosing, thus the time of sampling relative to dosing strongly influenced observed fluxes. These results suggest that estimates of GHG fluxes from TWs may be biased if mass transfer and mechanisms of wastewater application are not considered. Emission factors for N2O and CH4 were 0.27 % as kg-N2O-N/kg-TINremoved and 0.04 % kg-CH4-C/kg-CODremoved, respectively. The system had observed seasonal emissions of 600.5 kg CO2 equivalent of GHGs estimated over 130-days of operation. These results indicate a need for wastewater treatment processes to mitigate GHGs.Item Multiscale Flux-Based Modeling of Biofilm Communities(Society for Industrial & Applied Mathematics, 2020-01) Zhang, T.; Parker, A.; Carlson, R.P.; Stewart, Philip S.; Klapper, I.Models of microbial community dynamics generally rely on a subscale description for microbial metabolisms. In systems such as distributed multispecies communities like biofilms, where it may not be reasonable to simplify to a small number of limiting substrates, tracking the large number of active metabolites likely requires measurement or estimation of large numbers of kinetic and regulatory parameters. Alternatively, a largely kinetics-free framework is proposed combining cellular level constrained, steady state flux analysis of metabolism with macroscale microbial community models. This multiscale setup naturally allows coupling of macroscale information, including measurement data, with cell scale metabolism. Further, flexibility in methodology is stressed: choices at the microscale (e.g., flux balance analysis or elementary flux modes) and at the macroscale (e.g., physical-chemical influences relevant to biofilm or planktonic environments) are available to the user. Illustrative computations in the context of a biofilm, including comparisons of systemic and Nash equilibration as well as an example of coupling experimental data into predictions, are provided.