Long-term performance evaluation of granular activated carbon fluidization and biogas sparging in anaerobic fluidized bed membrane bioreactor: Membrane fouling and micropollutant removal

Abstract

In this study, fluidization of granular activated carbon (GAC) by the recirculation of a bulk suspension through an anaerobic fluidized bed membrane bioreactor (AFMBR) and biogas sparging from the bottom of an anaerobic membrane bioreactor (G-AnMBR) for treating low-strength wastewater were compared to investigate organic removal and fouling rate. The chemical oxygen demand (COD) removal efficiency obtained by both the AFMBR and G-AnMBR exceeded 90 %, and the proportion of methane in the biogas produced was 60 % at the same hydraulic retention time (HRT). In the AFMBR, the transmembrane pressure (TMP) gradually increased, but a rapid TMP jump was not observed during operational period. In the G-AnMBR, the TMP increased rapidly as the biogas flowrate was 2 and 3 L/min (LPM) at 8 h of HRT while the TMP below 0.1 bar was maintained over 90 d at 4 LPM. Our results also indicated that organic micropollutants, such as Bisphenol A (BPA), Sulfamethoxazole (SMX), and Methylparaben (MeP), were removed by AFMBR almost completely. However, the G-AnMBR showed relatively low SMX and MeP removal efficiencies of 47.6 % and 74.9 %, respectively. The estimated energy required to operate the G-AnMBR was 1.37 kW h/m3, while it was only 0.06 kW h/m3 for AFMBR.