Executive Summary

The Alliance for Environmental Technology (AET) strongly supports complete substitution of chlorine dioxide in the first stage of bleaching independent of the extent of delignification of unbleached pulp. This view is supported by a panel of esteemed scientists whose reports comprise the body of this submission.

In the recent report, "A Review and Assessment of the Ecological Risks Associated with the Use of Chlorine Dioxide," prepared for AET by the panel and submitted to the US EPA at the February 10, 1994 public hearing, the panel of scientists reached a unanimous opinion. Their report clearly demonstrates that complete substitution of chlorine dioxide in the first stage of pulp bleaching provides considerable environmental benefits.

The study followed the general guidelines of the US EPA's "Framework for Ecological Risk Assessment." The panel believes that the weight-of-evidence from laboratory studies, risk analyses and field observations demonstrates that the chlorine dioxide bleaching process provides the following benefits:

• Eighty percent reduction in the quantity, and ninety percent reduction in the degree of chlorination, of the chlorinated organics detected in mill waste water;

• Decrease in the persistence of these compounds, and their potential for bio-accumulation and food chain transfer;

• Reduction in the potential for negative ecological effects; and

• In particular, virtual elimination of the formation of dioxin.

Based on the existing available data, the panel concluded that chlorinated organics from mills bleaching with chlorine dioxide, employing secondary treatment and with receiving water dilutions typical of most mills in North America, present an insignificant risk to the environment.

In Section 1 of this submission, the panel of scientists have updated the risk assessment with more recent laboratory and actual mill operating data. The conclusions are unchanged. The case for complete substitution of chlorine dioxide in the first stage of bleaching now rests on an even firmer data base.

The Alliance for Environmental Technology supports complete substitution of chlorine dioxide in the first stage of bleaching -- independent of the extent of delignification of unbleached pulp -- to achieve the proposed limits for concentrations of the twelve priority chlorophenols, 2,3,7,8-TCDD and 2,3,7,8-TCDF in bleach plant effluent.

Section 2 of this submission shows that EPA's proposed standards for all twelve priority chlorophenols, 2,3,7,8-TCDD and 2,3,7,8-TCDF can be achieved for conventionally delignified softwood pulp both in laboratory tests and in full scale mill operation. Technology options incorporating extended and/or oxygen delignification are not required to achieve this standard of performance. The key requirement is complete substitution of chlorine dioxide in the first stage of bleaching.

EPA has considered using a Toxic Weighting Factor for AOX in evaluating the cost-effectiveness of various technology options. AET strongly discourages EPA from using a Toxic Weighting Factor for AOX. Section 3 of this submission shows that not only is a Toxic Weighting Factor approach for AOX inappropriate, but also that AOX is an inappropriate parameter upon which to regulate pulp mill effluents. The reasons include:

• 1) toxicity weighting estimates can be made for only 10% of AOX for which toxic loading data are available; 2) an arbitrary choice is made for the remaining 90% of the material comprising AOX; 3) the Toxic Weighting Factor of the whole AOX fraction is dominated by the contributions from two substances (2,3,7,8-TCDD and 2,3,7,8-TCDF), which have extraordinarily high Toxic Weighting Factors; and 4) these two compounds are virtually eliminated in all options incorporating complete substitution of chlorine dioxide in the first stage of bleaching.

• AOX is not a homogenous substance, but a mixture which varies in composition and toxicity; and

• AOX is not a measure of toxicity.

EPA is proposing to regulate Chemical Oxygen Demand (COD), in part, to minimize ecotoxicological risks from pulp mill effluents. As discussed in Section 4 of this submission, the use of a COD effluent guideline to "...control losses and discharges of pulsing liquors and associated wood extractives, which recently have been postulated as the source of toxicity to aquatic systems,"* is a poor regulatory tool for protection against ecotoxicological effects such as mixed function oxidase (MFO) enzyme induction or steroid effects in fish. The reasons include:

• COD, Dissolved Organic Carbon (DOC) and Biochemical Oxygen Demand (BOD) are sum parameters which represent a large number of different chemical substances with different chemical and biological properties;

• Where responses such as MFO induction and steroid effects have been measured, these show a poor correlation with DOC; and

• MFO induction measured under laboratory conditions showed no consistent correlation with DOC concentration (and by implication, COD measurements).

* US EPA. 1993. Development document for the proposed effluent guidelines and standards for the pulp, paper and paperboard point source category. Office of Water. US Environmental Protection Agency, Washington, D.C., October, 1993 EPA-821- R-93-019, pages 7-12.