Determining the optimal transmembrane gas pressure for nitrigication in membrane-aerated biofilm reactors based on oxygen profile analysis

Abstract

The goal of this study was to investigate the effect of transmembrane gas pressure (Pg) on the specific ammonium removal rate in a membrane-aerated biofilm reactor (MABR). Our experimental results show that the specific ammonium removal rate increased from 4.98 to 9.26 gN m−2 day−1 when Pg increased from 2 to 20 kPa in an MABR with a biofilm thickness of approximately 600 μm. However, this improvement was not linear; there was a threshold of Pgseparating the stronger and weaker effects of Pg. The ammonium removal rate was improved less significantly when Pg was over the threshold, indicating that there is an optimal threshold of Pg for maximizing ammonium removal in an MABR. The change in oxygen penetration depth (dp) is less sensitive to Pg in the ammonia-oxidizing active layer than in the inactive layer in membrane-aerated biofilm. The location of the Pg threshold is at the same point as the thickness of the active layer on the curve of dp versus Pg; thus, the active layer thickness and the optimal Pg can be determined on the basis of the changes in the slope of dp to Pg.