Assessing microbial competition in a hydrogen‐based membrane biofilm reactor (MBfR) using multidimensional modeling

Abstract

The membrane biofilm reactor (MBfR) is a novel technology that safely delivers hydrogen to the base of a denitrifying biofilm via gas-supplying membranes. While hydrogen is an effective electron donor for denitrifying bacteria (DNB), it also supports sulfate-reducing bacteria (SRB) and methanogens (MET), which consume hydrogen and create undesirable by-products. SRB and MET are only competitive for hydrogen when local nitrate concentrations are low, therefore SRB and MET primarily grow near the base of the biofilm. In an MBfR, hydrogen concentrations are greatest at the base of the biofilm, making SRB and MET more likely to proliferate in an MBfR system than a conventional biofilm reactor. Modeling results showed that because of this, control of the hydrogen concentration via the intramembrane pressure was a key tool for limiting SRB and MET development. Another means is biofilm management, which supported both sloughing and erosive detachment. For the conditions simulated, maintaining thinner biofilms promoted higher denitrification fluxes and limited the presence of SRB and MET. The 2-d modeling showed that periodic biofilm sloughing helped control slow-growing SRB and MET. Moreover, the rough (non-flat) membrane assembly in the 2-d model provided a special niche for SRB and MET that was not represented in the 1-d model. This study compared 1-d and 2-d biofilm model applicability for simulating competition in counter-diffusional biofilms. Although more computationally expensive, the 2-d model captured important mechanisms unseen in the 1-d model.

Perchlorate, nitrate, and sulfate reduction in hydrogen-based membrane biofilm reactor: Model-based evaluation

“…These findings demonstrated the importance of H 2 supply as a control strategy in operating this single-stage H 2 -based MBfR. As shown in Figure 4B, a too low L H2 would suppress the SO 4 2reduction but compromise the removal of ClO 4 and NO 3 -, while a too high L H2 not only meant energy wastage but also triggered the SO 4 2reduction which agreed with the findings of Martin et al [31]. Under the operating conditions of Scenario 2, a L H2 of around 0.114 g COD m -2 h -2 could be considered most suitable.…”

“…Overall, a thin biofilm (e.g., L f of 50 and 75 µm in this case) was beneficial for the highlevel simultaneous removal of ClO 4 and NO 3 through supporting the coexistence of HDB, PRB, and HB in the biofilm, as shown in Figure 4D. In contrast, a thick biofilm (e.g., L f of more than 100 µm in this case) provided favourable environment and protected space (i.e., inner layer of the biofilm) for SRB, stimulated their growth [31], and therefore compromised the biomass fractions of HDB and PRB in the biofilm, resulting in the increasing SO…”

Resistance and Resilience of Sulfidogenic Communities in the Face of the Specific Inhibitor Perchlorate

“…Amplicon sequencing of planktonic and surface-attached populations revealed a community structure dominated by fermentative and sulfate-respiring organisms in both instances. Anaerobic biofilms are often stratified, with more favorable electron-accepting processes closer to the surface (Sun et al, 2014; Martin et al, 2015); in our system, a lack of alternative electron-accepting processes likely resulted in a heterogeneous, mixed structure. Sequencing data confirmed the inhibition of SRM.…”

Hydrogenotrophic Microbial Reduction of Oxyanions With the Membrane Biofilm Reactor

“…When H 2 is supplied from the base of the biofilm and O 2 and NO3- from the bulk, opportunities increase for O 2 -sensitive microbes such as sulfate- and selenate-reducing bacteria, dechlorinating Dehalococcoides , acetogens, and methanogens to proliferate near the base of the biofilm. This occurs because the base of the MBfR biofilm has low concentrations of O 2 and NO3-, but a high concentration of H 2 (Martin et al, 2015).…”