Pilot scale study on a new membrane bioreactor hybrid system in municipal wastewater treatment

• The pilot scale GACS-FBBR–MBR was successful in treating municipal wastewater.
• GACS-FBBR is a promising pre-treatment method for membrane bioreactor.
• SVI was below 100 mL/g, indicating the good settling property of activated sludge.
• The hybrid system was successful in mitigating membrane fouling.

A pilot scale membrane bioreactor hybrid system (MBR-HS) was evaluated for municipal wastewater treatment. This novel system comprised of a granular activated carbon-sponge fluidized bed bioreactor (GACS-FBBR) followed by a submerge membrane bioreactor (MBR) with the capacity of 2 L/min. The results indicated that the MBR-HS could effectively remove 90% DOC and 95% NH4–N. PO4–P removal efficiency was remained stable at about 70% throughout the experiment. Specific oxygen uptake rate (SOUR) of activated sludge increased from 0.72 to 2.21 mg O2/gVSS h for the first 10 days and then followed by a steady stage until the end of experiment. Sludge volume index (SVI) was always below 50 mL/g, demonstrated an excellent settling properties of sludge. The system also showed an achievement in terms of low trans-membrane pressure (TMP) development rate. The TMP increasing rate was only 0.65 kPa/day, suggesting GACS-FBBR can be a promising pre-treatment for MBR.