Chemical Enhancement of the Biodegradation of Crude-Oil Pollutants

Abstract

These test results establish two important processes for dealing with oil in an aquatic environment. First, the rate of biological destruction of hydrocarbon can be increased by emulsifying the oil with a suitable chemical agent. Secondly, biological destruction can be further accelerated by seeding the emulsion with microorganisms that can use hydrocarbon as a food source. Introduction This study was conducted to determine the effects of chemical dispersants on the microbial decomposition of crude oil in aquatic environments. Lin and Townsley reported that lignosulfates increase the rate of fermentation of hydrocarbons in water. They attributed the increased rate to the large surface area and to the efficiency of cell-to-oil contact provided by the emulsifier. Not all dispersing agents promote bacterial growth. Some agents are quite toxic and will retard the rate of oil decomposition. Other agents form loose, unstable emulsions and have little effect on the reaction. Biological oxidation of any organic matter is basically the utilization of the substance as a food source. The organic matter is synthesized by bacterial oxidation to new cells and converted to energy and metabolism end products such as CO2 and water. The growth of the microorganism is dependent upon the individual metabolic requirements of the organism, the chemical nature of the organic matter and the physicochemical environment. The growth process is physicochemical environment. The growth process is related to surface area, as the interfacial area increases, the growth rate increases. Thus dispersing oil through a water phase increases both the availability of the organic matter and the surface area. The rate of microbial utilization should also increase. The response of microorganisms to dosage with anionic or nonionic surfactants is highly variable. The structure of the surfactant molecule, its concentration, and the type of solvent used as a carrier influence the toxicity to microorganisms. The surfactants, by their effects on cell membranes, have a marked influence on the uptake of other chemical substances. Experimental Data In the laboratory work for this study, a preliminary evaluation was made to select a suitable method for observing the effects of several chemical formulations on microbial activity in a water-and-oil environment Methods for following oxygen uptake were compared and the Warburg technique was chosen. This technique, using 125-ml reaction flasks and aqueous manometers, provided the required sensitivity and allowed the samples to be large enough to he prepared accurately. prepared accurately. A sample of crude petroleum was used as a "standard" oil throughout the work. The standard was a sweet, paraffin-base oil, weathered to approximate oil stored for several days at atmospheric pressure and ambient temperature. The sample was stored for the duration of the investigation under conditions that prevented further change in composition. Both fresh- and sea-water conditions were studied. JPT P. 16