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UBC Theses and Dissertations

Community analysis and mixotrophic study of one-stage Anammox system Kang, John


A knowledge gap exists regarding the kinetics and the microbial community of a combined partial nitritation/anaerobic ammonium oxidation (Anammox) system. In this study, a combined system was enriched for a period of 1 year in a SBR setup using synthetic reject water. The system successfully washed out the nitrite oxidizing bacteria (NOB) population using a combination of temperature control, dissolved oxygen (DO) control and sludge wasting. The reduction in NOB population was confirmed through the reduction in the effluent nitrate concentration and fluorescence in-situ hybridization (FISH) studies. With a 50 day sludge retention time (SRT) period, the system achieved a nitrogen removal efficiency between 80 – 90%, corresponding to a loading rate of 0.26 kg N/m³-d. FISH was conducted throughout the study to investigate the spatial analysis in floc/granular forms and the relative volumetric fractions of ammonia oxidizing bacteria (AOB), NOB and Anammox. The spatial analysis revealed that the AOB and the Anammox population are evenly dispersed in the granule rather than the inner/outer layer model discussed in literature. The volumetric fraction for Anammox was 33.2% ± 12.3% at 55 day SRT and 31.3% ± 10.7% at 30 day SRT. For AOB, the volumetric fraction was 36.3% ± 9.4% at 55 day SRT and 25.6 ± 7.0% at 30 day SRT. The NOB population was < 6% throughout the study. FISH could not account for the majority of the bacteria as the unaccounted fraction consisted of up to 39%. Volumetric fractions of Anammox sludge enriched in non-synthetic reject water were 26.9% ± 8.3% and 11.2% ± 3.8% for Anammox and AOB, respectively. The unaccounted fraction was higher at 55%. Mixotrophic tests were conducted using acetate, propionate and primary effluent as electron donors. Both nitrate and nitrite, as electron acceptors, caused the oxidation of the electron donors. The presence of a lag response is likely attributed to the fact that the Anammox sludge was not metabolically active to the presence of the electron donors until the onset of the batch study. Methanol inhibition studies confirmed that the oxidation of the electron donors was not due to heterotrophic activity.

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