Influence of Recirculation Rate on Performance of M embrane Bioreactor Coupling with Ozonation Treating Dyeing and Textile Wastewater

Membrane fouling is a limitation of widespread application of membrane bioreactor (MBR) for wastewater treatm ent. This research focused on organics removal and fouling control by adding alum into MBR sludge to improve permeate quality and prolong the filtration time. The ozonation followed by the MBR treatment and the recirculation rate (RR) from ozonation reactor returning to MBR was studied to enhance the non-biodegradable matters. The applied dosage was 104 mg O3/h and the RR was at 1 and 1.5. It is observed that the removal efficiency of COD a nd color in single MBR was 87 ± 3% and 86 ± 5% respectively. When coupling with ozonation, the removal efficiency of COD was 90 ± 2% and 96 ± 1% for RR at 1 and 1.5. Those of color were 93 ± 4% and 95 ± 5% at the respective recirculation rate. The results indicate that the higher recirculation rate enhanced the COD and color removal. In addition, the fouling rate increased approximately 1.9 and 7.2 times when the membrane flux was double and triple, respectively.