Optimization of floating crude oil biodegradation by isolated microorganisms via experimental design method

Introduction: Releasing crude oil in environment tends to some problems such as toxic effects, preventing oxygen exchange with aquatic environment, killing lived creatures in water and etc. Due to these problems, the biodegradation of floating crude oil by isolated microorganisms from environment contaminated by crude oil was studied. Material and Methods: in the first step of this study, by liner culture, microorganisms isolated from soil and waste water contaminated by oil. After isolation of microorganisms, the optimization of biodegradation process was performed by using Tagochi method. The tests were performed twice. Five factors in three various levels used in this optimization. These experiments perform duplicate and finally process by tagochi method for determination of optimum condition. Results and discussion: In this study 14 strains of microorganisms were isolated and purified form environment. All microorganisms were identified as bacteria. Among of those, the microorganism called A-14 had the best removal percentage of floating crude oil (about 89%). The emulsification test (E24) indicated that all isolated microorganisms in this study could produce biosurfactant. The optimum condition was obtained for pH equal 7, the volume percentage of crude oil in water equal 3, nitrogen concentration equal 1 mg/l and hydraulic retention time (HRT) equal 5 days. In the optimum condition the removal percent of crude oil was 93%. In this study crude oil with higher concentration was degraded in the time less than other similar previous researches