Petrochemical wastewater treatment by membrane bioreactor with behavior modify of membrane fouling through granule activated carbon: A case study

In this study, petrochemical complex wastewater was investigated by submerged membrane bioreactor (MBR). Initial sludge was prepared from returned sludge of petrochemical complex wastewater treatment plant. Applied membrane is of micro-filtration type made of polyvinylidene fluoride with effective surface of 0.004 m2, porosity of 73% and nominal pore diameter of 0.1 μm. Particle size distribution (PSD), soluble microbial products (SMP), and extracellular polymeric substance (EPS) for sludge were measured. In addition Fourier-transform infrared spectroscopy (FTIR), and EPS analysis were performed for determining the properties of the formed cake. Also was measured critical pressure for membrane in the MBR. The critical pressure value was 0.2 kPa. Therefore, the operating pressure was selected 0.12 kPa. This research was conducted in two phases. In the first phase, the pilot worked for 35 days. The results showed that despite the membrane fouling in initial days, the permission of the membrane still had a good efficiency, and after each 7 days, the membrane was cleaned physically and chemically, which showed a recovery of permeate more than 90%. The COD removal efficiency was achieved more than 85% in MLSS=3000±300 mg / L and HRT=14-16 hours. In addition, the TSS and turbidity in the output were below 1 mg/L and 12 NTU, respectively. In the second phase, for reducing fouling, the granule activated carbon was added in the sludge. In the reactor containing activated carbon (R2), membrane fouling was carried out with lower rate and also flux drop was lower about 22% compared to reactor without activated carbon. This phenomenon was due to increasing sludge particle size, SMP reduction.