PILOT TESTING AND DESIGN OF A HIGH TEMPERATURE AIR
STRIPPING SYSTEM FOR MEK REMOVAL
Kevin M. Sullivan,
Frank Lenzo,
Thomas Johnson,
Environmental Products Division
Hydro Group, Inc.
Linden, New Jersey 07036
INTRODUCTION
The air stripping process has been used successfully in many applications for removal of volatile
organic compounds from groundwater supplies, plant process flows, and waste streams. Air stripping
has advantages such as simplicity of operation, low capital costs, and very low operation and maintenance costs when compared to other methods of volatile organics removal [1,2]. One of the few
limitations on the process is the range of compounds that are strippable—stripping is economically
feasible on compounds such as the chlorinated solvents (TCE, PCE, etc.), lightweight aromatics
(benzene, toluene, etc.) and other easily volatilized compounds. The purpose of this study was to
examine the feasibility of stripping less volatile compounds by raising the process temperature to
increase their volatility. This study was performed in order to design a modular, portable high temperature air stripping system for use at hazardous material spill sites [3,4].
The location that prompted the study was a surface aquifer that was contaminated with Methyl
Ethyl Ketone (MEK). Approximately 11,360 1 (3000 gallons) of pure MEK escaped from a tanker
trailer and penetrated the aquifer. Recovery wells were placed downgradient of the spill to capture
the contaminated plume; after treatment, purified water was to be re-injected near the initial spill
points to flush out the MEK that was held by the soil particles above the water table. Hydro Group,
Inc. (formerly Laynco Environmental Products Division of Layne-New York Company, Inc.) was
contracted to design a full-scale stripping process to treat a 379 1/min (100 gpm) flow of water contaminated with 1000 mg/1 of MEK producing an effluent of no more than 50 mg/1 (a removal efficiency of 99.995%). The time constraints on the project were severe; the entire pilot and design
process was to be completed in 75 days.
Earlier ambient temperature stripping tests by Hydro Group had yielded very poor removal efficiencies. Only a 25% reduction in the MEK levels was achieved using a mobile pilot air stripper
(detailed later in this paper). In comparison this same pilot system has removed up to 98% of more
volatile compounds such as TCE. Since there was virtually no data available on high temperature
stripping, it was decided to perform pilot studies using a sample of water drawn from the most heavily
contaminated well. The water was pumped into a 24,600 1 (6500 gallon) holding tank. Since MEK
floats on water, the sampling pump was placed just below the water surface in the hopes of obtaining
the most heavily contaminated sample. Concentrations at the beginning of the sample recovery were
over 4000 mg/1; these decreased to approximately 700 mg/1 by the end of the sample collection. The
water was yellow and foamy and occasionally a milky-white color. Later analysis showed MEK levels
of about 1000 mg/1 in the raw water used for the testing.
PILOT EQUIPMENT
The pilot-scale equipment was selected to duplicate as closely as possible the final, full-scale installation. The stripping tower used was a portable, packed column pilot unit which had been used
successfully for air stripping studies at over 25 different sites. The 25.4 cm (10") diameter column
has an overall height of 6.4 meters (21 feet), enough to accommodate 4.6 m (15 feet) of packing, a
clearwell, and a mist eliminator. It is constructed of aluminum with steel piping (See Figure 1).
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