بررسي قابليت راكتور بيوفيلمي با بستر متحرك در تصفيه فاضلاب محتوي نفت و گازوييل

Investugation of Moving Bed Biofilm Reactor Capability in Treating Wastewater Containing Petrolium and Gas oil

آب آلوده به هيدروكربن هاي نفتي همواره روي محيط اطراف، آثار منفي و زيان بار زيادي در ابعاد سلامتي جامعه، اقتصادي و محيط زيستي داشته است. بنابراين پژوهش حاضر با هدف مطالعه و بررسي تصفيه پذيري اين نوع آلاينده ها از فاضلاب با استفاده از راكتور بيوفيلمي با بستر متحرك صورت گرفت. ميزان تصفيه پذيري هيدروكربن هاي نفتي با محدوده CODهاي معادل 200 تا 2500 ميلي گرم بر ليتر (محدوده TPH بين 52 تا 400 ميلي گرم بر ليتر) در زمان ماندهاي مختلف به راكتور تزريق و راندمان حذف TPH و COD در اثر فعاليت بيولوژيكي تعيين شد. همچنين به بررسي سازوكار غالب تصفيه، سينتيك واكنش هاي بيولوژيكي، اثر ميكروارگانيسم هاي معلق و درصد پرشدگي آكنه در سيستم MBBR پرداخته شد. نتايج نشان دادند كه بهترين راندمان حذف در COD معادل 1000 ميلي گرم بر ليتر به ميزان 85 درصد، زمان ماند 72 ساعت و با ميزان پرشدگي 50 درصد نتيجه مي شود. ميزان راندمان حذف TPH در محدوده ياد شده روند ملايمي نشان داد به شكلي كه در زمان ماند 72 ساعت كاهش در راندمان حذف از 84 درصد در mg/L50=TPH به 75 درصد در mg/L400=TPH رسيد. نتايج سينتيك واكنش هاي بيولوژيكي نيز نشان از تبعيت راكتور از مدل مرتبه دوم داشت. با بررسي نتايج حاصل مشاهده شد كه سيستم MBBR به دليل داشتن توانايي مناسب در تجزيه هيدروكربن هاي نفتي و راندمان حذف بالاي COD و TPH گزينه مناسبي براي تصفيه اين نوع آلاينده ها است

Wastewater contaminated by petroleum compounds includes a wide range of hydrocarbons with different concentrations. Due to high amounts of toxic multiple cyclic aromatics, this type of wastewater may cause significant damages to water resources and human health, which have to be treated before discharging to the environment. Different processes have been applied for treating these kinds of wastewater. The most conventional systems are biological processes especially activated sludge that is being used in the most of the Iranian refineries. In recent years, biofilm processes have been replaced for treating different types of wastewaters because of bulking and foaming problems in the suspended systems. Due to the least deficiencies and restrictions, these processes have been proved as a reliable method for removal of wastewater pollutants. Therefore, in this study, the capability of treating petroleum wastewater was investigated using Moving Bed Biofilm Reactor (MBBR). This study was conducted in a lab-scale batch plastic rectangular cube pilot (L: 24 cm, W: 17 cm, H: 9 cm). To get a compound similar to petroleum effluent of Tehran Refinery, the mixture of gasoline (C16 - C20) and crude oil (C8 - C37) by the ratio of 1 to 2 was prepared. At first, sewage sludge was adapted with hydrocarbon compounds at COD equal to 100 mg/L (or TPH of 27.4 mg/L). Then petroleum hydrocarbons was injected to the reactor with a COD range of 200 to 2500 mg/L (TPH of 52 to 400 mg/L); and COD and TPH removal efficiency was measured at different retention time. Also the dominant mechanism, kinetic of biological reactions, the effect of suspended microorganisms and carrier filling ratio were studied. The highest COD removal efficiency of 85 percent was obtained at influent COD = 1000 mg/L, HRT = 72 hr and filling ratio = 50 percent. The removal trend of organic compounds from the end of adaptation stage (COD = 100 to 1000 mg/L) at resident time of 8, 12 and 24 hours has been varied between 62 and 48 percent. TPH removal efficiency in aforementioned range, followed a smooth trend; so that in HRT = 72 hr, the removal efficiency reduced from the initial 84 percent at TPH= 50 mg/L to 75 percent at TPH= 400 mg/L. The ratio of COD to input TPH was 3.82 and the range of ratios of COD to output TPH at resident times of 24, 48 and 72 hours were 3.09 - 4.80, 9.00 - 13.89 and 10.80 - 15.63, respectively. The results have shown that Grau and Stover- Kincannon were the best models for describing the biological kinetic data. The results have shown that MBBR system is a proper method for treating petroleum hydrocarbons, due to adequate ability to decomposition of these kinds of pollutants.