Removal efficiency of heavy oil by free and immobilised microorganisms on laboratory‐scale

Abstract

This study explored free and immobilised microorganisms to degrade heavy oil. Two oil-degrading bacterial strains (W-1 and W-2) were isolated from heavy oil wastewater samples collected from Shengli Oil Field in China. W-1 and W-2, identified as Rhosococcus sp. and Bacillus cereus sp., respectively, were tested for their growth behaviour and optimal growth conditions in the laboratory. The obtained results showed that the optimal growth conditions for W-1 and W-2 were identified as pH of 8, temperature of 40 • C, and salinity of 2% and 4%, respectively. The environmental conditions affecting oil-degrading efficiency by W-1 and W-2 were optimised in the media containing 0.3% heavy oil. The results showed that the optimal degradation and optimal growth conditions were similar, and the oil degradation rates of W-1 and W-2 were about 34.6% and 45.3%, respectively after 5 days. W-1 and W-2 capable of degrading oil was immobilised in calcium alginate gel beads containing active carbon and used for degradation of heavy oil. The heavy oil biodegradability of immobilised bacteria improved dramatically, compared with that of the free ones. The heavy oil biodegradation rates of immobilised W-2 were found to be maximal at the same optimal growth conditions of pH, temperature, and salinity as the free ones. The best biodegradation rate of immobilised W-2 reached above 78%, which is 33% than that of the free W-2.

Study on the biodegradation of crude oil by free and immobilized bacterial consortium in marine environment

“…The bacterial consortium not only increases the degradation efficiency of crude oil but also enhances tolerance toward salinity of the bacteria. [13]…”

“…[18] After 7d’s biodegradation, the degradation efficiencies of crude oil (2%, w/v ) of immobilized cells were more than 60% with temperature of 15–30°C, initial pH of 6.0–9.0, salinity of 15%–35%. Immobilization improved microbial tolerance to high concentrations of harmful substances, [13] more obviously occurred when crude oil concentration more than 10% ( w/v ). The degradation of immobilized bacteria went stabilization phase with less degradation time (5 d), compared with that of the free ones (7d) and also increase the efficiency significantly.…”

“…In this study, the performance of preparation calcium alginate bio-carrier was improved by adding activated carbon in the embedding to overcome the low mechanical strength, the lack of mass transfer, [13] and to greatly improve mass transfer because the activated carbon is a porous structure. The objectives of this research are: 1) to start up a lab-scale effective petroleum hydrocarbon degrading microorganisms from oil-contaminated seawater samples for marine oil pollution treatment; 2) to explore the characteristics of the immobilized microorganisms; 3) to investigate the performance of immobilized microorganisms on biodegradation of normal alkanes ( n -alkanes) and polycyclic aromatic hydrocarbons (PAHs) in marine environment.…”

Optimization and Statistical Evaluation of Medium Components Affecting Crude Oil Biodegradation by Some Locally Isolated Bacteria

“…Therefore, adding allogenetic microorganisms and changing degradation conditions (temperature, pH and salinity) are effective methods that can improve the rate of biodegradation. Different microorganisms have different optimum growth conditions and oil degrading efficiencies, and so does the same microorganism in various environments (Bao et al, 2013). The rates of uptake and mineralization of many organic compounds by a microbial population depend on the concentration of the compound (Olivera et al, 1997).…”