Immobilization of diesel-degrading consortia for bioremediation of diesel-contaminated groundwater and seawater

This study investigated the potential application of immobilized diesel-degrading consortia for diesel removal in aqueous environments. The microorganisms were entrapped using polyurethane-polyurea co-polymers, alginate, and activate carbon, and total petroleum hydrocarbon (TPH) degradability were evaluated under freshwater and seawater conditions with diesel oil. The results indicated that immobilized cells remained active after entrapment, but rapid diesel degradation occurred after sufficient suspended cells growth in aqueous medium, suggesting that entrapped cells continuously released freely suspended cells and suspended cells degraded diesel as well. Under phosphorous-sufficient conditions (P/TPH>35%), TPH degradation efficiency was achieved at 80% even at low nitrogen condition (N/TPH<10%). Under phosphorous-insufficient conditions (P/TPH<10%), the better degradation efficiency was obtained only at high nitrogen content (TPH:N > 100:7). The stoichiometric relationship for diesel degradation, nitrogen consumption, phosphorous consumption, biomass production was obtained (100:5:0.9:35). The results of repeated batch indicated that immobilized cells could be repeatedly used for diesel degradation in simulated groundwater and seawater environments for more than 360 days of operation. With a combination of copolymer, alginate, and activate carbon, the entrapped matrix presented advantages on high surface area, high porosity, and high mechanical strength for a long-term operation for diesel bioremediation in aqueous environments.