Removal of oil and grease from synthetic gas station runoff using local sorbents from plant materials

Abstract

Gas station runoff is one of the major sources that contribute oil and grease to receiving waters. Inserts are the devices installed at the inlet of the stormwater catch basins to reduce pollutants including oil and grease. Several commercially available inserts depend on sorbents for the removal of contaminants. However, most of the insert sorbents are synthetic and costly. In this study, the uses of fourteen types of local natural sorbents, specifically plant biomass, which are less expensive and more biodegradable than synthetic sorbents, as insert materials for oil removal from gas station runoff were investigated. Bench scale batch, column, and flume experiment were conducted to evaluate the oil removal capability of biomass sorbents and synthetic sorbents (for comparison). For batch experiment, with mechanical emulsified oil samples, the results showed that oil would rather be attached to the wall of sample containers than sorbents. In case of chemically emulsified oil samples, only small amount of oil was adsorbed by sorbents. The results of the column experiment also ocnfirmed that chemically emulsified oil could not be removed neither biomass nor synthetic sorbent. The flume experiments included oil sorption and desorption tests. The sorbents from the sorption tests were employed in the desorption tests. The results of oil sorption tests showed that Salvinia sp. and polyester fiber were the sorbents that provided the least effluent oil concentrations. For the desorption tests, however, the polyester fiber exhibited the highest amount of oil desorbed. The results from this study provide valuable information on the use of local plant materials as alternative sorbents to remove oil from water runoff.