Performance of submerged membrane bioreactor (SMBR) with and without the addition of the different particle sizes of GAC as suspended medium

•The GAC particle size plays a major role on membrane fouling reduction in membrane bioreactor.•The superior organic removal with the addition GAC as suspended medium (95%).•Detailed organic characterisation of MBR effluent for different GAC sizes.•GAC helped reduce the sludge volume index and transmembrane pressure development.•The phosphate in SMBR effluent was removed/recovered (90%) using hydrated ferric oxide.

In this study the effect of different particle sizes of granular activated carbon (GAC) on the performance of a submerged membrane bioreactor (SMBR) was investigated. The sizes of GAC used were 150–300, 300–600 and 600–1200 μm. The SMBR was operated at a filtration flux of 20 L/m2 h. The removal of dissolved organic carbon (DOC) and chemical oxygen demand (COD) with the addition of GAC was 95%. The concentration of biopolymers, humic, building block and low molecular weight neutral and acids in the SMBR effluent was reduced by 20%, 66–76%, 20–50%, 30–56%, respectively. It helped to reduce the sludge volume index (SVI) and transmembrane pressure (TMP) development by 30–40% and 58%, respectively. However, the removal of NH4+ and PO43- was relatively low of 35–45% and 34–43%, respectively. The SMBR effluent was rich in PO43- and was removed/recovered using hydrated ferric oxide (HFO). The removal of PO43- was almost 90%.