چكيده به لاتين
Although the membrane bioreactor system (MBR) by the combination of activated sludge process and membrane separation has made it possible to achieve proper performance without the need for sedimentation and disinfection processes, the major problem is premature clogging of membrane surfaces and pores by sediments in the feed. It also encounters sludge, which reduces productivity and increases costs. In this study, the microbial factors affecting membrane clogging and different methods of coping with fouling with a focus on the granulation of sludge are investigated. Granulation of activated sludge experiments in 1-liter sequential batch reactors (SBR) with synthetic wastewater (containing phenol, nitrogen, and phosphate) using two basic types: conventional sludge (AS) (S1) and shattered granular sludge (GAS) (G1). Different feeding strategy was carried out in terms of cycle time (6, 12, and 24 hr), and the organic loading rate (OLR) was 0.5 to 4 kgCOD/m3.day. The performance of system in pollutant removal was examined with regards to chemical oxygen demand (COD), sludge volume index (SVI), Soluble suspended solids (MLSS), soluble microbial products (SMP), extracellular polymeric materials (EPS), ammonium, phosphate, and sludge morphology in the granulation process by image processing. The results showed that the granules obtained from the GAS (G1) reduced the granulation rate to 20 days and doubled the contaminant removal rate, and therefore this base was selected to continue the work. By reducing the feeding cycle time from 24 to 6 hours (G126), not only did the system become more stable and resistant to contaminant stresses, and the granulation rate was reduced to 14 days, but also the SVI was decreased to less than 20 ml/g. The production of extracellular protein and polysaccharide as EPS of sludge increased significantly by 15 mg/g.SS.h, so the appropriate cycle time of 6 hours was selected. By increasing the OLR from two to four (G146 system), the maximum diameter of the granules (based on image processing) increased from 1 mm in the S1 to 2.2 mm in the G126 and 4.48 mm in the G146 and improved sedimentation properties. However, due to the further growth of the aerobic layer of the granules, the ability to remove contaminants was decreased simultaneously. Therefore, it can be concluded that the appropriate OLR in this study in terms of simultaneous removal of all pollutants (phenol, nitrogen, and phosphate) in the shortest granulation time, is equal to 2 kgCOD/m3.day, and in terms of morphologically and sludge volume index, is kgCOD/m3.day 4. In order to investigate the effect of granulation on membrane fouling, the performance of the S1 system was compared with the G126 and G146 systems in a plexiglass MBR with a volume of 5 liters containing PES membrane mixed with MEI-101 nanoparticles. In order to evaluate the membrane performance, water permeability fluxes from the membrane (Ji), protein rejection (R), membrane resistance factors (Ri), and membrane flux recovery ratio (FRR) were measured. The G146 system was able to increase the permeate flux (Jp) by 172%, reduce the system fouling and membrane total resistance by up to 2 times, and increase the membrane FRR by 25%.
