The performance of immobilized membrane bioreactor with different membrane operation modes

The immobilized membrane bioreactor (IMBR) was investigated for the removal of organic matter and its membrane fouling condition in treating food processing wastewater. The IMBR contains 5,000 mg/L mixed liquor suspended solids with hydraulic retention time of 24 h. The advantages of IMBR include high sludge retention time, improved removal of COD, ammonia nitrogen, and reduced membrane fouling frequency with much less production of soluble microbial products (SMPs). The results showed that the IMBR was an effective organic matter removal system because it achieved 96–97% removal of COD consistently. The concentration of total SMP in the IMBR was measured at 46.4 mg/L which included 24.8 mg/L of protein and 21.6 mg/L of carbohydrate. Steadily, approximately 33% of carbohydrate and 11% of protein were rejected by the microfiltration (MF) membrane. For this reason, it was concluded that carbohydrate poses a more significant impact on membrane fouling through formation of cake/gel layer than protein. Further, various operating conditions during membrane filtration were experimented which included continuous and intermittent filtration, aeration and non-aeration, and with fiber filter (FF) as pretreatment. It was discovered that while adding an additional FF filtration before MF might improve suspended solid retention, SMP was instead discovered to be the major cause of membrane fouling. In addition, aeration in the membrane tank could significantly improve membrane performance by scouring lightly attached particles from the membrane surface.