Biological Treatment of Petroleum Hydrocarbons and Polynuclear Aromatic Hydrocarbons in Waste Lagoons
Four lagoons containing approximately two million gallons of mixed chemical washings, principally petroleum hydrocarbons (PHCs) from a railcar repair service facility in Texas, were treated biologically in a timely and cost-effective manner. Floating sludge was removed from the largest of the four impoundments and it was converted into an in situ bioreactor. Analytical results obtained from water column samples collected weekly showed excellent removals of oil and grease, phenolics, and polynuclear aromatic hydrocarbons (PAHs). Concentrations of anthracene, benzo(a)pyrene, fluoranthene, and phenanthrene showed ten-fold reductions within one week. In addition, PHCs were reduced quickly and significantly, with successful biodegradation indicated by decreases in the nC17/pristane and nC18/phytane ratios. These ratios are concentration-independent indicators of PHC biodegradation. Periodic, measured introduction of additional contaminated sludge and water to the bioactive lagoon resulted in predicted increases in contaminant levels followed by significant reductions in the following two- to three-week period. Bacterial numbers remained high throughout the winter months. It is anticipated that continued transfer of material from the adjacent three lagoons will result in complete bioremediation of almost two million gallons of water and sludge in preparation for closure. The cost of these activities is projected at less than $.25 per gallon, and duration of cleanup is projected at one and a half years.