Interim Private Water Well Remediation Using Carbon Adsorption

Abstract

AbstractGasoline spills or underground tank leaks can cause ground water contamination that affects nearby private wells. The volatile organic constituents of gasoline can render the well water unfit for consumption, based on recommended health advisory limits for benzene, ethylbenzene, toluene and xylenes. Ground water investigations and remedial actions can become prolonged situations, during which the well owner may not be able to use his well. Carbon adsorption can be used as an interim remedial action to remove volatile organics and normalize use to well owners, until long‐term solutions can be implemented. Small‐scale carbon units are adaptable to private well plumbing.Contamination of private wells by a gasoline station near Wausau, Wisconsin, provided the opportunity to test the ability of carbon adsorption to effectively treat well water. The gasoline contamination is an isolated problem within an area of Wausau that is the subject of a state‐led Environmental Repair Fund (ERF) investigation. Long‐term solutions to the gasoline problem have been delayed until completion of present investigations. Carbon adsorption was recommended as an interim remedial measure at two private wells affected by the gasoline contamination.The concentrations and types of organic compounds in the water determine the cost‐effectiveness of using carbon adsorption as an interim remedial measure. Each organic compound has a characteristic affinity for a particular carbon, which ultimately determines the life of the carbon adsorption unit before carbon replacement is necessary. Water quality testing for volatile organics at the private water supply wells indicated the type and concentration of gasoline‐related contaminants.The data were used to conservatively estimate the expected life of the carbon adsorption unit. Continued periodic water quality analyses determine the actual carbon tank life.Data collected as part of the study indicate that the carbon adsorption systems initially functioned beyond their estimated capacities and successfully removed organics from the affected water supplies. One well required additional treatment to optimize effective carbon system performance, and to solve an iron discoloration and taste problem. This well also experienced carbon system breakthrough by volatile organics, which required lowering the carbon tank change interval.