A BACTERIAL BIOASSAY FOR ASSESSMENT
OF WASTEWATER TOXICITY
Kenneth J. Williamson, Associate Professor
Diane G. Johnson, Research Assistant
Department of Civil Engineering
Oregon State University
Corvallis, Oregon 97331
INTRODUCTION
The Federal Water Pollution Control Act of 1972 (PL 92-500) specifically prohibits the
discharge of environmentally toxic substances. In response to this legislation, the Environmental Protection Agency has developed a three level system for sampling, chemical and physical
analysis, and toxicity measurement of industrial wastewaters [1]. These procedures are
designed to specifically determine which control technologies could be used for toxicity
removal. In addition, these procedures are ideally suited for assessment of toxicity to biological treatment of industrial wastewaters.
The goal of Level 1 analyses is to define the pollution potential of a wastewater. Specifically, the acute bioassay portion is designed to determine which compounds or classes of
compounds are probable causes of the toxicity. Level 1 analyses can include testing of
control technologies for effectiveness in toxicity removal. Level 2 testing was formulated
to provide a better characterization of the chemical and physical properties of toxic discharges identified through Level 1 tests. This type of study is most often undertaken to gain
additional information that might identify and quantify the toxic substance(s) involved.
The accomplishment of Level 1 and 2 testing should enable identification of toxic waste-
streams, assessment of potential ecological insult from discharge, and determination of
effective control and/or treatment technologies. Level 3 testing involves further testing of
chronic environmentally toxic effects and probably would not be required for most assessments of industrial wastes.
This multiple level approach was chosen to optimize the use of manpower and funds.
As the level of analysis proceeds from Level 1 to Level 3, the cost and time required soars.
This sequential approach should provide substantial savings of time and funds as compared
to traditional assessment methods.
The focus of Level 1 analysis is a complementary series of biological tests (Table I). A
methodology for these tests is summarized by Iuliucci [2]. These tests provide no specific
identification of the toxicant, but serve as signals for a wide range of potentially toxic responses. The primary difficulty with the application of these tests is the complexity that
results in high costs. The tests often require highly trained personnel, modern laboratories,
and long time periods. A listing of estimated unit costs for these tests is included in Table
I[3]. These costs appear reasonable for a small number of samples; however, the cost of
this assessment program could become prohibitive where wastewater compositions vary
temporally or with process changes.
Over the past 3 years, research has been done at Oregon State University towards the
development of a sensitive and inexpensive Level 1 bioassay using Nitrobacter as a test
organism. Results can be obtained within 4 hours and freeze-drying the organisms allows
shipment of the bacteria to test locations [4]. (Freeze-dried Nitrobacter can be obtained
at a nominal cost from the Department of Civil Engineering, Oregon State University, Corvallis, OR 97331). A supply of freeze-dried cells eliminate the need for developing and
maintaining an active bacterial culture. This feature is ideal for those circumstances where
only short term or intermittent sampling is needed. The estimated cost for a Level 1 biological test using freeze-dried Nitrobacter is approximately $20 to $50. This is less than 1 5%
of the cost of current alternate Level 1 bioassay techniques.
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