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Description:
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Membrane -aerated biofilm reactors (MABRs ) have emerged as a potential nitrogen removal technology for high -strength , nitrogen dominant waste streams (TOC :N <1 , NH4+ > 500mg /L ) . In particular , the unique properties of a MABR are well suited for extreme and /or isolated environments with carbon limited wastes such as a lunar habitation scenario . Among many other features , the ability of MABRs to degrade carbonaceous and nitrogenous pollutants concomitantly via simultaneous nitrification and denitrification (SND ) in a single -stage vessel has posed this technology as a well -suited candidate for space -based water reuse applications .
Relatively untouched by current MABR research , nitrogen dominant waste streams have been deemed outside the range for significant SND in a MABR without the supply of exogenous consumables ; however , experimental research has not been conducted in order to confirm or disprove this hypothesis . The goal of this current work was to explore the performance limits of treating a space -based waste stream with the MABR technology using experimental studies and mathematical modeling efforts .
The experimental studies entailed investigating the performance of a traditionally designed MABR and a modified MABR (mMABR ) . The mMABR combined oxygen permeable membranes in tandem with inert attachment media theoretically supporting nitrification on the former and denitrification on the latter . The traditionally designed MABR reported average carbon and total nitrogen (TN ) removal rates as high as 0 .33 g -C /m2 -d and 0 .14 g -N /m2 -d , respectively , whereas the mMABR achieved mean carbon and TN removal rates reaching 0 .26 g -C /m2 -d and 0 .22 g -N /m2 -d , respectively . The most notable difference between the two reactors was the ability of the mMABR to support denitrification , which was attributed to the mMABRs combination of co - and counter -diffusion biofilms .
The mathematical modeling study aimed to identify the inherent differences that could be propagated by the range of assumed nitrification and denitrification biochemical pathways for one -dimensional membrane -aerated biofilm models . The overarching conclusion reached as a result of this study was that mathematical simulation results vary based upon the assumed biopathway applied to the model . The results of this study were used to understand the underlying processes that occurred during the MABRs treatment of a space -based waste . |