Section Three
HAZARDOUS WASTE MINIMIZATION AND
TREATMENT
19    REMOVAL OF TOXIC ORGANICS FROM WASTEWATER
GENERATED IN TANK TRUCK WASHING FACILITIES
Choong Hee Rhee, Senior Engineer
Paul C. Martyn, Head, Monitoring Section
Margaret H. Nellor, Head, Industrial Waste Section
County Sanitation Dist. of Los Angeles County
Whittier, California 90607-4998
INTRODUCTION
The Sanitation Districts of Los Angeles County (LACSD) provide sewerage service to most of Los
Angeles County outside the City of Los Angeles. Within this service area are over 9,000 industrial
companies and in excess of four million people. Included within the group of industrial companies are
nineteen tank truck washing facilities.
Tank trucks are known to transport non-sewerable hazardous materials often containing toxic
organics and organic solvents. Between loads, the operators of these vehicles generally have both the
interior and exterior of the tanks cleaned at tank truck washing facilities. Wastewaters discharged
from these facilities typically contain high concentrations of purgeable toxic organics and oil and
grease, which (unless adequately treated) may be discharged to the sewer.
In California, liquid and semi-solid wastes have been effectively banned from solid waste landfills
by revised regulations for the discharge of waste to land [California Administrative Code, Title 23,
Chapter 3, Subchapter 15, Article 2, Section 2520(d)). This restriction in the disposal of liquid and
semi-solid wastes affects all hazardous and nonhazardous landfills (Class I, II and III sites) and
ultimately now wastes are transported and treated. Because of this restriction, there are increased
concerns that incompatible or partially treated wastes could be discharged to the public sewer system
in part by discharges and from tank truck washing facilities.
There are neither federal nor state pretreatment standards or effluent limitations specifically developed for tank truck washing facilities. Consequently, to insure proper regulation, LACSD initiated
studies to control toxic organics found in the wastewaters from these facilities. The study results
indicated that rotary vacuum drums, activated carbon filters, dissolved air flotation units and ultrafiltration processes are capable of satisfactorily removing both toxic organics and oil and grease from
tank truck washing wastewaters.
LACSD is now imposing effluent limitations on tank truck washing facilities which rely on the
above-mentioned treatment processes. Two of the nineteen facilities have completed such treatment
systems. The other seventeen facilities are currently being reviewed and, as needed, will be required to
meet similar effluent limits.
CHARACTERISTICS OF WASTEWATER
The interiors of tank trucks are cleaned between loads when different types of materials are
transported. For example, a tank truck which has hauled crude oil needs to be cleaned thoroughly
before diesel oil or gasoline is loaded. The materials typically transported by tank trucks include crude
oil, diesel oil, gasoline, latex, resin, ethylene glycol, deforming agents, various organic and inorganic
chemicals, and organic solvents such as benzene, toluene and xylene.
In addition to the various types of materials which may have been hauled and subsequently
sewered, LACSD's investigation indicates that most tank truck washing facilities are utilizing cleaning
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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