Automatic Car Wash Water Recycle System
G. W. HEINKE, Associate Professor
Department of Civil Engineering
University of Toronto
Toronto, Canada
H. K. MIYAMOTO, Research Engineer
G. M. SERNAS, Principal
G. M. Sernas Associates, Ltd.
Toronto, Canada
D. E. HOWARD, Senior Project Engineer
Imperial Oil, Ltd.
Toronto, Canada
INTRODUCTION
Several hundred automatic car wash installations are constructed annually in North
America and in Europe.
Present water consumption of car washes varies from about 100 gal/car (400 1/car)
without any recycle to about 10-40 gal/car (40-150 1/car) with partial recycle. A search of
published information on water quality requirements for washing cars and on wastewater
quality produced no useful information. Because of large water usage and increased
importance of pollution abatement, control agencies in many areas refuse to allow the
construction of car washes unless recycle systems are installed. Imperial Oil Limited
engaged G. M. Sernas Associates and G. W. Heinke to carry out research to assess quality
requirements and existing technology and to prepare and test preliminary designs for total
recycle systems, if feasible. The investigation period stretched over 16 months, during which
one professional engineer worked on the project on a full time basis, and several
professional engineers and assistants on a part time basis. A final report was submitted in
November 1973.
PRESENT RECYCLE TECHNOLOGY
There are basically two types of car washes: the roll-over type and the tunnel type. In
the roll-over type operation, the car enters the bay, then remains stationary while the
brushes move over the car. In the tunnel-type operation, the car is conveyed through a
tunnel, washed by a flood rinse, which is used to loosen the dirt, then, through a set of
brushes, where detergent is added, and onto the final rinse where wax is added and the
soapy water is rinsed off. The tunnel-type is much more common. All car wash operations
investigated in this study, were of this type. A typical layout is shown in Figure 1.
Until recently, only the flood rinse water was recycled, if any recycling was practised.
The authors were unable to obtain statistical information on the extent of recycle, and
number of types used in Canadian or U.S. installations. Of Imperial Oil Ltd. installations in
Canada, the most advanced recycle system is that at Richmond B.D., with somewhat less
sophisticated systems at Bridgeport, Ontario, and Sarnia, Ontario. The Toronto station
tested recycled only flood rinse and brush water. Information received from one oil
company (Houston, Texas) in September 1973, indicates that there are recycled systems
installed in Rockville Center, N.Y.; Miami, Florida; Orlando, Florida; and Lancaster
Pennsylvania. The four systems use hydrocyclones and pressure sand filters. They have
been in operation for only six months.
The most common unit operation used in recycle systems at the present is settling for
the purpose of suspended solids removal. Usually, a large concrete settling tank with several
compartments is used. The sizes vary with the capacity of the car wash but are usually from
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