Biodegradation of the petroleum hydrocarbons using an anoxic packed-bed biofilm reactor with in-situ biosurfactant-producing bacteria.

The present study employed an anoxic packed bed biofilm reactor (AnPBR) inoculated with in-situ biosurfactant-producing bacteria for the biodegradation of petroleum wastewater. Highly acclimated biomass decreased the start-up phase period and with increasing the initial total petroleum hydrocarbon (TPH) concentration from 1.5 to 4 g/L was accompanied by TPH and chemical oxygen demand (COD) removal efficiencies of above 99% and 96%, respectively. Decreasing hydraulic retention time (HRT) from 24 to 6 h caused an increase in the specific hydrocarbon utilization rate value from 0.45 to 1.66 gTPH/g.d. Moreover, dehydrogenase activity, surfactin, and rhamnolipid reached 31.8 μgTF/g.d, 95.1, and 27.1 mg/L, respectively. The biodegradation kinetic coefficients such as K, K, K, Y and µ were 0.784 (d), 0.005 (g/L), 0.138 (d), 0.569 (gVSS/gCOD), and 0.446 (d), respectively. Dropping of bioreactor performance, especially TPH removal efficiency from 99% to 37.6% in the absence of nitrate after 10 days, indicates anoxic metabolism has been the dominant biodegradation pathway. The effluent chromatogram of gas chromatography/flame ionization detector (GC/FID) showed aliphatic, cyclic aliphatic, and aromatic hydrocarbons efficiently degraded. According to the high degradation rate of AnPBR in different operational parameters, it can be recommended for the treatment of oil-contaminated wastewater.