Membrane Aerated Biofilm Reactors – How longitudinal gradients influence nitrogen removal – A conceptual study. (1st December 2019)

• Record Type: Journal Article
• Authors: Acevedo Alonso, Vanessa; Lackner, Susanne
• Is Part Of: Water research. Volume 166(2019)
• Publication Date: 2019-12-01
• Subjects: Membrane aerated biofilm reactor -- Biofilm -- Nitrogen removal -- Oxygen gradient -- Substrate gradient -- Multi-compartment model; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2019.115060
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Membrane-aerated biofilm reactors are becoming more important for nitrogen removal in the wastewater sector. One-dimensional (1D) models are widely used to study the performance of such systems; however, 1D models are not able to simulate the longitudinal gradients that exist in the reactor. Although there is experimental evidence that points to the existence of longitudinal gradients simple modeling approaches that consider these gradients are not yet developed. This study proposes a novel multi-compartment model that simulates the longitudinal substrate and oxygen gradients. It assesses the effects of temperature, biofilm thickness, number of compartments, and flow configuration (liquid and gas phase) on the modeling results. Additionally, it compares the capabilities of a traditional 1D model with those of the novel multi-compartment model. Our results show that a classical 1D model predicts a lower total dissolved nitrogen concentration (TDN) in the effluent in contrast to the predictions of the multi-compartment model. In the worst-case scenario, the TDN predicted by the traditional 1D model was three times lower than the prediction of the multi-compartment model. The results delivered by the models differ also in the axial gradients. The traditional 1D model, for example, predicted an oxygen concentration at the membrane surface of 0.4 mg-O2 /l while the multi-compartment model predicted a concentration of 2.9 mg-O2 /l. Finally, the results of this study show that the longitudinal oxygen gradient has an important effect on both, biomass distribution and effluent TDN, whereas the longitudinal substrate exclusively affected the effluent TDN. Graphical abstract: Image 1 Highlights: New MABR multi-compartment model including longitudinal substrate gradients. Longitudinal O2 and substrate gradients notably affect the outcome of MABRs models. Traditional model predicted an effluent concentration 3 times lower than our model. Longitudinal O2 gradient had a bigger effect on the effluent than the substrate one. Biomass composition highly depended on the longitudinal O2 gradient.