12    TANK TRUCK WASHING WASTEWATER SYSTEM
John Ball, Professor
Department of Civil Engineering
The University of Alabama
Tuscaloosa, Alabama 35487
Jonathan R. Bonner, Engineer
Ball Engineering, Inc.
Tuscaloosa, Alabama 35486
INTRODUCTION
Tanker trucks transport most of the finished liquid chemical products used in our nation. Thousands of these tankers are on the roads daily, with a large percentage used for multiple products or
carrying liquids that produce a residue during transportation. Both conditions require that the tank be
cleaned after use. Tank truck cleaning is usually performed by the trucking company, a commercial
truck terminal, or a waste handling facility. Although the water generation is usually on the order of
several hundred gallons per washing, the strength and variety of constituents can vary greatly.
This chapter presents a case history of the design, installation, and operating experience of a
wastewater treating system that went on line at a tank truck washing facility in March 1988. The
facility was an expansion of an existing system that originally handled only the water from washing
the outside of the trucks. In addition to expanding the washing capabilities, the company underwent a
major expansion about the same time to a fleet of more than 125 tank trucks. The company is in the
process of adding a second washing location that will haul washwater to the first terminal for
treatment and disposal.
ORIGINAL SYSTEM
Figure 1 presents a sketch of the original truck washing system at the terminal that was used to clean
the outside of the vehicles. A worker would use a hand-held high pressure sprayer that could add
detergent to hot water when the worker activated a button. Washing was performed on a concrete slab
with the water draining into two 1000 gallon sumps operated in parallel. The sumps had open tops so
that a small backhoe could remove silt and sand that would accumulate on the sump bottom. The
water was pumped at intervals from the sumps and hauled by company tank truck to the city
municipal treatment plant. The only control on the washwater was to test the pH prior to discharge.
The city plant was a lagoon system recently upgraded by adding rotating biological contactors.
TANK WASHING REQUIREMENTS
During the expansion of the company from 25 to 125 units, the company decided that some costs
could probably be saved and considerable convenience gained by washing the inside of their own
tankers. Much of the hauling service is performed within a few hundred miles from the company
terminal. Before the system was installed, the trucks had to travel as many as 200 non-revenue miles to
wash the inside of a tanker between product changes. In addition, an experience with a contaminated
shipment traced to improper washing was additional incentive to in-house washing.
OUISIW    IRUCK   ajASHINti  ON, 1
■Q-
Figure 1.   Original washing system.
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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