is incorrect. If the unburned material is measured at 900 ppm, the combustion efficiency would be 99.91 % and if measured a t 1100 ppm, the combustion efficiency would be 99.8%. If the " t r u e " value was 1000 ppm, both values would be in error by 10%, but rounding off the answers to three significant figures would show 99.9% combustion efficiency. Mr. Bond is concerned because "the total flow of flue gas was not and could not be measured according to the EPA Method 2." This is correct. The only satisfactory alternative is to calculate the flue gas flow using the fuel flow and the exhaust gas analysis, which is exactly what was done. This does not result in an "assumed" answer as he states, but a more accurate estimate of flue gas flow than one could determine by a greatly modified EPA Method 2 on a short stack, with nonuniform flow and high-temperature gas. The choice to calculate the flue gas flow by this procedure was proper application of the state of the art in this case because it gave the most accurate answer. Mr. Bond also refers to "scattered readings, frequent calibration and maintenance, very erratic thermocou-
ple readings, and several problems during incinerator o p e r a t i o n s . " I would expect that in a field experiment, under difficult conditions, these problems would be accepted and every attempt made to obtain the best data in spite of them. I would expect similar problems in testing such an incinerator on solid ground. I do not feel that any of the conclusions that Mr. Bond has "flagged" invalidate t h e referenced studies. These studies were trial burning tests for development of permitting procedures for future ocean incineration operations. I do hope that E P A has recognized that there was a possibility for errors in much of the field data and that it has taken such errors into account, along with a generous factor of safety, when it permits ocean incineration of U.S. hazardous wastes to be considered as a viable, low-risk disposal method. Richard W. Boubel Professor of Mechanical Engineering Oregon State University Corvallis, Ore. 97331 Desmond Bond replies: It is pleasing to find that interest in an environmental matter, particular-
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230A
Environ. Sci. Technol., Vol. 18, No. 8, 1984
ly one involving the determination of chemical reaction effectiveness and its instrumentation, has widened to include a professor of mechanical engineering; some points made in the article referenced in his letter should, apparently, be explained. As noted, the article does not discuss the environmental hazards of ocean incineration per se. Certainly, "it picks apart the source testing and process measurements used," to illustrate the invalidity of conclusions reached as to the success of ocean incineration to date. Each waste disposal by that means (except for the first, admitted in its report to have been with uncertain effectiveness) can be seen to be looking back to predecessors to substantiate claims of the acceptability of means of measurements attempted, and of the supposed desirability of at-sea destruction of wastes. The letter's suggestion of combustion efficiency, propounded as 99.91 % when b a s e d on m e a s u r e m e n t of 900 ppm unburned material, sounds somewhat unusual, certainly without relevance here. Say, for instance, a vaporized organic (PCB-containing) waste were to be bled into and mixed with a hot stream of nitrogen, so that the combined flow resulted in a stream with 900 ppm organic (PCBcontaining) waste content; would it be reasonable to conclude that the unfired mixture had achieved a 99.91% combustion efficiency? Method 2 is an essential component of M e t h o d 5, according t o E P A Codes. Without determination—with complete disregard of measurement, in fact—of the particulates contained (Method 5) in the flue gas from ocean disposal of hazardous wastes (the wide incidence of presence of particulates certainly was acknowledged in Vulcanus reports), how can destruction efficiencies be claimed with any degree of accuracy at all? As in reports of Vulcanus waste burns, the Boubel letter expects concessions to be granted because of atsea conditions. Methods, procedures and tests, even equipment formulation and design, either the best practical or good enough, considering the circumstances, can hardly be considered to be appropriate, despite their inadequacy, just because of the imperfect context. Measurements invalidly made, some without the accuracy or the frequency essential when accompanying attempts to destroy a hazardous waste, do not constitute a "no-risk" situation or support claims of a disposal method's adequacy.
