An aerated and fluidized bed membrane bioreactor for effective wastewater treatment with low membrane fouling

Anaerobic fluidized bed membrane bioreactors (AFMBRs) use granular activated carbon (GAC) particles suspended by recirculation to effectively treat low strength wastewaters (~100-200 mg/L, chemical oxygen demand, COD), but the effluent can contain dissolved methane. An aerobic fluidized bed membrane bioreactor (AOFMBR) was developed to avoid methane production and the need for wastewater recirculation by using rising air bubbles to suspend GAC particles. The performance of the AOFMBR was compared to an AFMBR and a conventional aerobic membrane bioreactor (AeMBR) for domestic wastewater treatment over 130 d at ambient temperatures (fixed hydraulic retention time of 1.3 h). The effluent COD of AOFMBR averaged 20±8 mg/L for low-COD influent (150 and 200 mg/L) and 26±6 mg/L for high-COD influent (300 mg/L), with a turbidity of <0.2 NTU. Higher effluent CODs were obtained for the AeMBR (38±9 mg/L) and AFMBR (51±11 mg/L) with the high-COD influent, with similar removals for the low-COD influents. Transmembrane pressure of the AOFMBR increased at 0.04 kPa/d, which was 20% less than the AeMBR and 57% less than the AFMBR, at low influent COD conditions (150 and 200 mg/L). Scanning electron microscopy (SEM) analysis indicated a more uniform biofilm on the membrane in AOFMBR than that from the AeMBR biofilm, and no evidence of membrane damage. High similarity was found between communities in the suspended sludge in the AOFMBR and AeMBR (square-root transformed Bray-Curtis similarity, SRBCS, 0.69). Communities on the GAC and suspended sludge were dissimilar in the AOFMBR (SRBCS, 0.52), but clustered in the AFMBR (SRBCS, 0.63).