Section Ten
DYE WASTES
71    FATE OF AZO DYES IN THE ACTIVATED SLUDGE
PROCESS
Glenn M. Shaul, General Engineer
Clyde R. Dempsey, Environmental Engineer
Kenneth A. Dostal, Environmental Engineer
Industrial Wastes and Toxics Technology Division
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Richard J. Lieherman, Graduate Research Assistant
Department of Civil and Environmental Engineering
University of Cincinnati
Cincinnati, Ohio 45221
INTRODUCTION
The U.S. Environmental Protection Agency's (EPA) Office of Toxic Substances (OTS) evaluates
submissions to the Premanufacture Notification (PMN) process under section 5 of the Toxic Substances Control Act (TSCA). Azo dyes constitute a significant portion of these submissions. OTS is
concerned because some of the dyes, dye precursors or their degradation products such as aromatic
amines, which are also dye precursors, have been shown to be, or are suspected to be, carcinogenic
[1J. Therefore, EPA's Water Engineering Research Laboratory, Office of Research and Development
has an ongoing study to determine the fate of specific azo dye compounds in the activated sludge
process (ASP).
The objective of this study is to dose pilot plant ASP systems with various azo dyes and monitor
each dye compound through the system, analyzing both liquid and sludge samples. The fate of the
parent dye compound was assessed via mass balance calculations. From these data, it was possible to
determine if the compound was removed by adsorption, apparent biodegradation or not removed at
all. This report presents results to date (5/86) from this study which is being conducted at EPA's Test
and Evaluation Facility in Cincinnati, Ohio.
EXPERIMENTAL PROGRAM
A previous paper [2] described in detail the background, objectives and analytical methods
employed for this study. This paper describes work that used wastewater from the Greater Cincinnati
Mill Creek Sewage Treatment Plant as the influent to three pilot-scale ASP systems (two experimental
and one operational control). Each dye was dosed as commercial product to the two experimental
systems operated in parallel at 1 and 5 mg/L of influent flow (henceforth referred to as the low and
high spike systems, respectively). The principal focus of this work is on the ASP and as such the
primary sludge was not sampled. These selected dosages were based on expected concentrations in
publicly owned treatment works [2]. Table I presents a summary of the operating conditions of the
pilot plant systems. Each system consisted of a primary clarifier, complete-mix aeration basin and
secondary clarifier.
Before each intensive data collection phase, dye recovery studies were conducted in organic free
water, influent wastewater, and mixed liquor. These studies were run in duplicate and each recovery
study was repeated at least once in order to ensure that the compound could be extracted from these
samples. Purified dye standards were analytically prepared from the commercial dye product as per
Tincher [3] since standards are not available from conventional sources. All samples were analyzed by
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