27    THE USE OF CHRONIC BIOASSAYS FOR
PULP AND PAPER MILL EFFLUENTS IN WISCONSIN
Michael D. Witt, Natural Resources Administrator
Michael D. Hammers, Environmental Engineer
Robert G. Masnado, Environmental Specialist
Wisconsin Department of Natural Resources
Madison, Wisconsin 53707
INTRODUCTION
The Wisconsin Department of Natural Resources administers the NPDES Permit program in
Wisconsin (WPDES). The Department has operated this program since 1974 under a Memorandum
of Agreement with the U.S. Environmental Protection Agency (EPA).
The goal of the permit program is to protect Wisconsin's surface and groundwater resources from
impacts which would impair their designated uses. To achieve this goal, the Department issues
WPDES permits to municipalities and industries which discharge wastewaters to waters of the State.
These permits contain effluent limitations, monitoring requirements and other conditions which
control the type and amount of wastewater which may be discharged.
Over the last 15 years, emphasis has been placed on the regulation of conventional pollutants such
as five-day biochemical oxygen demand (BOD5) and total suspended solids.
However, as controls for conventional pollutants were successfully implemented, the emphasis of
the permit program shifted towards a new concern, that of toxic substances in wastewater discharges.
As a result of this new emphasis, the Department has initiated the use of whole effluent toxicity tests
in its permit program. Whole effluent toxicity tests are laboratory tests that use living organisms to
quantify toxicity and are commonly referred to as bioassays.
In Wisconsin, the expiration of 36 pulp and paper mill permits in late 1986 and early 1987 presented
an opportunity for the Department to gain experience with recently developed 7-day chronic bioassays. As part of their application for permit reissuance, these 36 permittees were requested to perform
7-day chronic bioassays on their wastewater discharges. The Department believed that the bioassay
results, in addition to the extensive analytical data on chemical parameters normally submitted by the
permittee in the reissuance application, would provide a broader data base to evaluate effluent
toxicity.
The Department's decision during the summer of 1985 to use the 7-day chronic bioassays was quite
timely for a number of reasons. First, EPA had recently published in draft a procedure for 7-day
chronic bioassays. The final report, entitled Short Term Methods for Estimating the Chronic Toxicity
of Effluents and Receiving Waters to Fresh Water Organisms, hereafter referred to as the EPA
manual, was published in December 1985.'
Secondly, in July 1985, the Institute of Paper Chemistry, located in Appleton, Wisconsin, informed
the Department that it was prepared to perform 7-day chronic bioassays on a contractual basis. At
that time, the Institute of Paper Chemistry had already worked with the short-term bioassay for over
a year and had the laboratory capacity to perform most of the 36 bioassays.
Thirdly, the Department did not anticipate that the pulp and paper wastewater discharges would be
acutely toxic. Only chronic toxicity testing would provide adequate information to evaluate effluent
toxicity. This latter conclusion was supported by the effluent characterization recommendations made
in EPA's Technical Support Document for Water Quality-based Toxics Control.2 A draft of EPA's
technical support document was available to the Department in July 1985; the final draft was available in September 1985.
Finally, EPA was, and is, promoting the use of a whole-effluent approach to measure the toxicity of
wastewater discharges.2'3>4 Advantages given by EPA for whole-effluent toxicity testing include:
1) the toxicity of complex effluents is measured without having to identify individual constituents of
257