پديد آورندگان :
قدك، پيمان نويسنده دانشجوي كارشناسي ارشد، مهندسي عمران محيط زيست، دانشگاه خوارزمي Ghadak, P. , اسدا... فردي، غلامرضا نويسنده دانشيار، گروه عمران دانشكده فني مهندسي، Asadollahfardi, G. , ميرباقري، سيد احمد نويسنده استاد، دانشكده مهندسي عمران و محيط زيست، Mirbagheri, A.
كليدواژه :
, Reverse osmosis , فيلتراسيون غشايي , Membrane filtration , mercury , Refinery wastewater, , اسمز معكوس , پساب نفتي , جيوه
چكيده لاتين :
Oil and gas processing activities cause excess water consumption, which leads to excessive wastewater production. This produced waste water contains mineral and biological compounds which can contaminate water and groundwater. Huge amount of this produced wastewater in Oil-rich countries, which generally are arid countries, drive them to find more effective methods for water reuse as a new water resource. One of the most important water pollution is heavy metal, so investigators are believe that heavy metals impact on environment is more hazardous than radioactive toxicity to ground water and seas. Various physical, chemical and biological methods of waste water treatment are applied in refining and petrochemical industries. Considerable amount of mercury with different operational units’ wastewater is discharge to environment from various refinery units. Since mercury is not biodegradable and tend to accumulate in living organisms, we must be able to control it by using effective methods. Application of membrane filtration is new method for water and wastewater treatment process. In this research, by application of case study method on one of Iranian gas refineries, reverse osmosis membrane system performance under different operating conditions, was studied. For this purpose effects of variable parameters, namely operating pressure (5, 7 and 9 bar), pH (3, 6, 9, 11) and mercury concentration (1, 2, 4, 8 and 12 mg/l) on removal performance were studied. Considering removal performance of mercury, COD, TDS, EC, Turbidity and also membrane flow rate, optimum operating condition was obtained. Base on the results, reverse osmosis membrane performance is highly efficient in optimum condition, namely 7 bar pressure and pH=9, from permeate water quality and economical aspects. By increasing system pressure a significant decline in mercury and COD removal efficiency was observed. removal efficiency of mercury, COD, and TDS in 7 bar pressure condition was 91.35%, 99.55%, and 94.89% respectively and also permeate flowrate was acceptable, so 7 bar was found as optimum pressure. On the next stage of investigation, although by increasing wastewater samples’ pH, a considerable increase in mercury and COD removal efficiency was observed, it cause a dramatic rise in TDS and turbidity in feed wastewater and also in permeate stream. More over high value of pH, namely pH=11 can make membrane subject to fouling. So pH=9 was chosen as an optimum pH. Finally, reverse osmosis membrane performance in encountering with possible shocks and high concentration of influent mercury, was investigated. Although results showed a significant decrease in membrane removal efficiency which subjected to high influent mercury concentration, reverse osmosis membrane system efficiency subjected to conventional mercury concentration of refineries was acceptable in mercury removal. Reverse osmosis membrane performance is efficient in optimum parameters’ value namely 7 bar pressure and pH=9, so removal efficiency of mercury, COD, and TDS was 97.5%, 99.75% and 93.29% respectively.
