Evaporative pre-cooling of condenser air improves the efficiency of compressor-based cooling, particularly in the hot, dry climate that exists in most of California. When implementing evaporative pre‐cooling technologies, one of the main concerns for end‐users is deposition of minerals contained in the water onto the surfaces of the heat exchanger, condenser coils, or cellulose based media. This project consisted of a laboratory investigation of the performance of two commercially-available non-chemical water treatment systems, as applied to evaporative pre-cooling of condenser air. The major claim of most non‐chemical water treatment technologies regarding the mechanism by which they work is that they precipitate minerals in bulk water and reduce the amount of calcium carbonate scale that forms on heat exchanger surfaces. An experimental method and apparatus was developed to evaluate non‐chemical water treatment products applied to a spray‐evaporative cooling application and to provide results on two specific products. A physical treatment device manufactured by Watts OneFlow extended the life of the heat exchanger under test by 14% over the baseline when installed with a sufficient flow rate through the device. A permanent magnet device manufactured by GMX extended the life of the heat exchanger under test by 28% over the baseline. Execution of the tests and analysis of the results generated additional insight into how future testing can be improved to reduce uncertainty. However, the results obtained to date provide confidence that physical water treatment systems have the potential to reduce scale formation in evaporative cooling systems and should be further investigated.

Single well push-pull tests (PPTs) were used to characterize in situ biodegradation rates of ethanol in groundwater at a leaking underground fuel tank (LUFT) site at Site 60, Vandenberg Air Force Base (VAFB), CA. For the tests, local groundwater was spiked with bromide and ethanol and injected at different times into three different wells throughout the experimental area. The spiked water was allowed to remain in the aquifer for 1 to 15.9 h prior to extraction. Biodegradation of ethanol was not observed within 15 h of the aquifer's first exposure to ethanol near any test well; the ethanol/Br ratio was nearly constant in the extraction samples. Biostimulation treatments (ethanol injections) over the course of 1 to 2 weeks resulted in a linear decrease in ln(ethanol/Br) with time in the extraction samples indicating that ethanol was biodegrading with a first order rate constant of about 0.3/h. After exposing an area to ethanol for 3 months, the biodegradation rate increased further by about a factor of 2. Ethanol degradation rates in the aquifer at this site were temporally variable based on the ethanol exposure history. Our results suggest that PPTs were an effective tool for examining such variability. PPT investigations should be valuable at other locations because ethanol degradation rates in groundwater should vary spatially and temporally depending on the type and timing of fuel releases as well as other factors that control the history of ethanol exposure to an aquifer. © 2011, The Author(s). Ground Water Monitoring & Remediation © 2011, National Ground Water Association.