title: Membrane Aerated Biofilm Reactors for Nitrogen Removal from Municipal Wastewater
Creators: name: Bunse, Philipp
Publisher: name: UNSPECIFIED
Year: 2025

description: This dissertation investigates Membrane Aerated Biofilm Reactors (MABRs) for nitrogen removal in the context of municipal wastewater treatment. As part of these studies, several MABR systems were constructed at the laboratory scale. Both hollow fiber and flat sheet membrane configurations were used in the reactors. These were operated and compared under a variety of operating conditions such as feed composition, surface loading, aeration, and scouring. Special attention was given to the comparison of intermittent and continuous aeration pattern, as well as the effect of different scouring frequencies on biofilm control. In addition to the analysis of dissolved nitrogen and organic carbon, the microbial community in the biofilm and the suspended biomass were studied (P1 and P2), the characteristics of the biofilm and sludge production were determined (P1, P2 and P3), and oxygen profiles in the biofilm and nitrous oxide emissions were measured with microelectrodes (P3).
During the studies, short-cut nitrogen removal was achieved in some of the MABRs under suitable conditions. Intermittent aeration and frequent scouring proved to be particularly beneficial to this process, resulting in high total nitrogen removal rates. In the experiments, continuous aeration, regardless of scouring, usually resulted in nitrification of the ammonium, which, together with organic carbon, tended to result in classical nitrogen removal by denitrification.
Analysis of the microbial community by qPCR and 16S amplicon sequencing revealed significant differences between the biofilm and the detached biomass or free-growing cells. Furthermore, the aeration and scouring strategies were shown to have a significant impact on the microbial community of the different MABR systems. The application of a high scouring frequency can help to limit NOB retention and promote AOB abundance in membrane-aerated biofilms due to the detachment of the biofilm. A low scouring frequency promotes NOB retention in the biofilm due to less biomass detachment and thus higher biofilm age. Continuously aerated MABRs were found to be more sensitive to high shear stress than intermittent-aerated reactors. Frequent scouring sheared off more biomass from the biofilm of the continuous-aerated reactor, whereas there were minor differences between the scouring strategies in terms of biofilm detachment in the intermittent-aerated reactors.
Analysis of the biofilm with oxygen microelectrodes revealed unique oxygen profiles depending on the operating conditions of the reactors. It is particularly noteworthy that the different oxygen exposure times and concentrations in the different layers of the biofilm could be precisely analyzed during intermittent aeration. Nitrous oxide emissions from the MABR systems were low compared to some conventional systems, but no hotspots of nitrous oxide production or reduction within the biofilm could be identified.
The studies showed that MABR have a high potential for efficient nitrogen removal in municipal wastewater treatment. Promising operating conditions were found to allow for short-cut nitrogen removal and targeted control of biofilm thickness. These studies provide a basis for future research in the field of MABR systems for municipal wastewater treatment.