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Study of the MBR System for the Removal of Ethyl Benzene and Styrene from Petrochemical Wastewater and Process Optimization by Reducing Membrane Fouling

Hazrati, Hossein | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 48351 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Shayegan, Jalaloddin
  7. Abstract:
  8. In this thesis was investigated the effect of solid retention time (SRT), Hydraulic retention time (HRT), activated carbon and suspended carrier on styrene and ethylbenzene biological removal and also on membrane fouling. In addition to the typical analysis (COD, MLSS, MLVSS, and SVI), the flocculation ability, sludge particle size distribution (PSD), FTIR analysis, excitation-emission matrix (EEM) fluorescence spectroscopy, soluble microbial product (SMP), extracellular polymeric substance (EPS), microscopic observations, microbial activities, microorganism population, and filamentous bacteria are considered to determine sludge characteristics. This study was done in five sections: in the first section the suspended carrier effect on membrane fouling was only investigated. The results showed that microbial activities were reduced due to the formation of larger flocs in the reactor with carriers (2 percent volumetric). However, the carriers had negligible effect on the chemical oxygen demand (COD) removal as well as the enhancement of the removal efficiency by one percent (from 98% to 99%). Also, the membrane fouling occurred in slower rate in the reactor with carrier. This might be due to the increase of the sludge particles size, and the reduction of cake layer resistance and sludge viscosity. Furthermore, the results showed that SMP and EPS in the reactor with carrier were lower than in the reactor without carrier. Beside, hydrophilic SMPc in the reactor without carrier was more than the reactor with carrier. In the second section was simultaneously investigated the effect of both HRT (10, 15, 20 hr) and carrier on membrane fouling. The results indicated that, the optimum HRT (e.g. 15 hrs.) was achieved in the reactor with carrier during biological removal and membrane fouling minimization. During the optimum HRT, the biological removal efficiency for styrene, ethylbenzene, and COD is 99.8±0.1 %, 99.9±0.1%, and 99±0.8% respectively and the concentration of styrene and ethylbenzene in the exit air reached to the minimum concentration (e.g. 0.2 and below 0.1 ppm, respectively). The fluctuation of the transmembrane pressure (TMP) indicated a slight variation for the reactor with carrier rather than without carrier. It was also determined that with reduction of HRT from 20 to 10 hr membrane fouling increases. Further, the sludge particle distribution in reactors demonstrated that the HRT reduction from 20 to 10 hr decreased the sludge particle size. In addition, the alteration of SMP and EPS in two reactors during all the HRTs showed that the SMP was the main reason for fouling of the membranes and the EPS was not the main factor for sludge flocculation. In the third section was studied the effect of activated carbon on membrane fouling. The results showed that sludge settleability and also sludge specification improved. Therefore the cake layer formation was low and membrane fouling was decreased. Furthermore, SMP reduced significantly due to adsorption of dissolved organic compound by activated carbon. Also dissolved organic matters with low molecular weight (below 1.5kDa) were efficiently adsorbed by activated carbon
  9. Keywords:
  10. Packing ; Powder Activated Carbon ; Hydraulic Retention Time (HRT) ; Membrane Bioreactor ; Petrochemical Wastewater ; Membrane Fouling ; Solid Retention Time

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