PRETREATMENT REMOVAL CREDITS AND NATIONAL STANDARDS
IN THE CITY OF CHATTANOOGA
George E. Kurz, Staff Engineer
David A. Summers, Industrial Monitoring Supervisor
Eugene G. Wright, Superintendent
Chattanooga Interceptor Sewer System
Moccasin Bend Treatment Plant
Chattanooga, Tennessee 37405
Shortly after EPA's General Pretreatment Regulations (40 CFR Part 403) were published in 1978 [1], the City of Chattanooga initiated a program to gather data to support
a local credits request to benefit industries served by the city's sewer system. The concept
of local credits was established by Congress so that industries that had to meet EPA's
National Categorical Standards and that were served by POTW (publicly owned treatment
works) would not have to operate redundant treatment systems for pollutants removed by
the POTW. Part 403 provides a mechanism to revise the National Categorical Pretreatment
Standards based on the removal of toxic pollutants at the POTW.
The city was already deeply committed at that time to developing a pretreatment program to satisfy its 201 step II Grant conditions. This committment was most clearly discernible in the revised industrial waste discharge ordinance adopted in late 1978, which
conformed to the language and strategy of the General Pretreatment Regulations, and also
contained specific standards to prevent POTW interference, pass through, and sludge contamination by toxics as envisioned by Section 307 of the Clean Water Act.
Since the regulation was published, the city has conducted eight sampling periods conforming to the Part 403 protocol for establishing consistent removal. Results from six of
those periods will be presented in this paper. In that same period, the POTW staff has
gained considerable experience in running a "403"-type pretreatment program, and is now
in a position to evaluate the benefits versus the cost of battling the regulatory red tape
surrounding the offical granting of local credits to a POTW authority.
CURRENT EPA REGULATIONS
Definitions and Procedures
The procedure for obtaining local credits for the revision of the categorical pretreatment
standards was established in Section 403.7 of the General Pretreatment Regulations. This
section amplified the previous Part 128 regulation of 1973 [2j, which briefly mentioned
revision of national standards by POTWs that were designed for, and did remove "significant" amounts of prohibited pollutants.
The Clean Water Act Amendments of 1977 [3] provided that a POTW could have credit
for all, or any part of the removal of a toxic pollutant, so long as the discharge from the
POTW would not violate a categorical standard or effluent limit that would be applicable
if that pollutant were discharged by a source other than a POTW. Additionally, the influent
levels of such toxic pollutants should be controlled so that sludge use or disposal in accordance with standards in section 405 of the Act would not be prevented.
To implement this section of the law, EPA required that a POTW applicant demonstrate
the achievement of "consistent POTW removal." This removal is defined as the reduction
or alteration of a pollutant in the influent, to a less toxic or harmless state in the effuent,
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