Edinboro Air Stripping Tower

AIR STRIPPING TOWER

FUNCTION

The air-stripping tower, located on the campus of Edinboro University, has been in operation since December 1, 1997. The purpose of the packed column air stripper is to remove dissolved gases and volatile compounds such as organic solvents from water. The Borough of Edinboro Water Department discovered levels of trichloroethylene (TCE) in the water supply in 1985. The air-stripping tower has since its inception virtually eliminated all traces of TCE and other volatile compounds in the treated water supply. Since December 1997, all tests for these compounds have been negative.

Trichloroethylene and other volatile organics still exist in the Borough’s raw water supply, and their levels fluctuate between eight and eighteen parts per billion (ppb). The maximum contaminant level is five ppb. The Water Department continues to monitor the levels with monthly testing of the raw and finished water to ensure the effectiveness of the air-stripping tower.

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OPERATION

The air-stripping tower works by passing contaminated water through a packed bed in contact with a countercurrent stream of air. The packed bed is designed to promote intimate contact between the air and water so that the maximum transfer of gases and volatiles from the water stream to the air stream can occur.

Water is introduced into the top of the column and, after passing through a specially designed water distributor to ensure even distribution, flows by gravity down through the packed bed which consists of molded plastic, metal or ceramic shapes specifically designed to maximize the contact with the air stream described above. After passing through the bed, the water is collected in a collection pan or holding chamber at the base of the column before being discharged.

Air is introduced at the base of the column above the holding chamber and rises by induced or forced draft through the packed bed. After receiving the contaminants from the water stream, the air is passed through a device to eliminate water droplets from the air stream and is discharged from the top of the column.

The Erie County Health Department was alerted to the fact that TCE was being dissipated into the atmosphere, and Doug Ebert of the Health Department notified the Borough that his department had been in contact with the Bureau of Air Quality Control, informing them of the Borough’s TCE levels. At this time current TCE levels are so low that there is no need to apply for or issue a permit for the discharge of TCEs into the atmosphere. There is no health risk to the environment. The Bureau of Air Quality Control will continue to monitor the Borough’s TCE levels and decide when and if it will be necessary to issue permits and/or take steps to reduce levels if they become too high.

The Tower was equipped to accommodate a carbon filter, which prevents TCEs from dissipating into the atmosphere if deemed necessary by the Bureau of Air Quality Control.

Air stripping, in theory, is a simple process, but to operate at maximum efficiency, all components of the system must be carefully engineered. Changes in operating parameters (process flow rates, contaminant concentrations, etc.) will affect the operating balance of the system and must be examined on a case-by-case basis to determine their influence on process efficiency.

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Water Regulations | Air Stripping Tower

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