A new simple and low cost in-well air stripping system has been developed at the University of California, Davis for cleanup of groundwater contaminated with Volatile Organic Compounds. The patented Multi-Stage In-Well Aerator (Aerator) was developed for the West Campus Groundwater Cleanup Project as an alternative to expensive and sometimes high maintenance packed tower and stacked tray type air strippers and has operated continuously at this site since October 1995 with an availability greater than 99%. Installation cost was less than 50% of a conventional air stripper and the four well 160 gpm system has treated over 100 million gallons of groundwater thus far and shown measurable cleanup of the contamination. The Aerator system consists of an air compressor, compressed air piping to extraction wells, an Aerator in each well, and piping for in-situ or ex-situ discharge of the treated water. The Aerator uses only compressed air. Electrical wiring is not required. Aerator System Schematic The Aerator itself is constructed almost entirely of common PVC pipe components to resist chemical and biological fouling. It has no moving parts to jam or wear out and can be installed in wells of at least 6" diameter. The Aerator provides multiple stages of air stripping using air lift pumping and gravity flow to draw groundwater through serial aeration passes in both the upper and lower sections of the well as shown in the following sketch. This allows groundwater to be completely treated by air stripping in one pumping pass, which air lift pumping alone cannot achieve. VOC laden off gas and treated water are discharged separately at the surface. The off-gas may be discharged directly to atmosphere or captured for treatment if required. If desired the Aerator may be installed completely below ground if additional head for discharge is not needed when using reinjection, leachfield recharge, or other such methods. Aerator Device Schematic Aerator performance varies based on the diameter of well used, pumping rate, type (volatility) of contaminant targeted for removal, and to a lesser extent the concentration of the contaminants to be removed. At the UC Davis site the prime contaminant is chloroform, which has a much lower volatility than most VOCs such as TCE and Carbon Tetrachloride and is therefore more difficult to air strip. Using 8" diameter wells, all VOCs except chloroform were removed to non-detect at all pumping rates, while chloroform removal varied from about 90% at 50 gpm to 99% at 10 gpm. ore information about the Aerator is available on the Internet at the website listed below or by contacting:
Joseph C. Stagner, P.E. Joseph Stagner is a registered Civil Engineer in California with over 18 years experience in a wide variety of civil and environmental engineering projects. He is currently employed as Manager, Solid Waste Division at UC Davis where he invented the Multi-Stage In-Well Aerator. |