Abstract
In this study, the membrane biofilm reactor (MBfR) is proposed to achieve simultaneous removal of ammonium, dissolved methane, and sulfide from main-stream and side-stream anaerobic digestion liquors. To avoid dissolved methane stripping, oxygen is introduced through gas-permeable membranes, which also from the substratum for the growth of a biofilm likely comprising ammonium oxidizing bacteria (AOB), anaerobic ammonium oxidation (Anammox) bacteria, denitrifying anaerobic methane oxidation (DAMO) microorganisms, aerobic methane oxidizing bacteria (MOB), and sulfur oxidizing bacteria (SOB). A mathematical model is developed and applied to assess the feasibility of such a system and the associated microbial community structure under different operational conditions. The simulation studies demonstrate the feasibility of achieving high-level (>97.0%), simultaneous removal of ammonium, dissolved methane, and sulfide in the MBfRs from both main-stream and side-stream anaerobic digestion liquors through adjusting the influent surface loading (or hydraulic retention time (HRT)) and the oxygen surface loading. The optimal HRT was found to be inversely proportional to the corresponding oxygen surface loading. Under the optimal operational conditions, AOB, DAMO bacteria, MOB, and SOB dominate the biofilm of the main-stream MBfR, while AOB, Anammox bacteria, DAMO bacteria, and SOB coexist in the side-stream MBfR to remove ammonium, dissolved methane, and sulfide simultaneously.
Highlights
The membrane biofilm reactor (MBfR) for simultaneous removal of ammonium, dissolved methane, and sulfide from the anaerobic digestion liquor is of significant interest because biofilms in the MBfR can retain microorganisms with distinct characteristics, and biomass can be naturally accumulated in the biofilm at different depths
In addition to anaerobic ammonium oxidation (Anammox) bacteria, the presence of nitrite and nitrate produced from ammonium oxidation together with the influent nutrients could stimulate the growth of denitrifying anaerobic methane oxidation (DAMO) microorganisms[18] and sulfur oxidizing bacteria (SOB)[19] within the biofilm
The coculture of ammonium oxidizing bacteria (AOB), Anammox bacteria, DAMO microorganisms, aerobic methane oxidizing bacteria (MOB), and SOB could be integrated in a single-stage MBfR to likely achieve the simultaneous removal of ammonium, dissolved methane, and sulfide from the anaerobic digestion liquor
Summary
Simultaneous ammonium, dissolved methane, and sulfide removal. For the main-stream MBfR, the influent ammonium (50 g N m−3), dissolved methane (50 g COD m−3), and sulfide (30 g S m−3) are significantly removed, with concentrations of 3.6 g N m−3, 0.7 g COD m−3, and 0.3 g S m−3 in the effluent, respectively. The high-level removal demonstrates the feasibility of the proposed MBfR to achieve simultaneous ammonium, dissolved methane, and sulfide removal from both main-stream and side-stream anaerobic digestion liquors.
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