ES&T
LETTERS Alcohol fuels from biomass Dear Sir: The feature article by Ayub Hira and co-workers (ES&T, May 1983, p. 202A) provided an interesting overview of the environmental con cerns associated with ethanol and methanol fuels production. As authors of a paper that was referenced in this article, we concur with Hira et al. that the type of energy process used to drive the fuels conversion process is largely responsible for pollutant emissions from an ethanol fuel production fa cility. One important aspect of the energy process selection that was not ad dressed in the article is the use of a steam cogeneration facility to support the fuel production process energy re quirements. This type of unit—due to its larger size, which is required for supporting both in-plant process steam and electrical needs as well as elec tricity for off-site distribution and sale—typically generates higher un controlled environmental residuals than a boiler designed solely to support on-site process steam requirements. In the paper cited in the article (Chem. Eng. Prog. 1981, 6, 42), Stone & Webster Engineering Corporation (SWEC) employed a coal-fired cogeneration boiler that was designed to provide 7.5 MW of electrical power for export sale, in addition to satisfying 100% of the fuel conversion process steam and electrical energy require ments. Approximately 15% of the fuel thermal input was required to provide the capability for export power sale. Air emissions and coal ash production are therefore approximately 15% higher than for a cogeneration facility without export power capability and are 25% higher than a conventional industrial boiler without any cogen eration capability. Knowledge of this difference in energy processes must be available when environmental residu als from different facilities are com pared, such as in Tables 2 and 5 of the article by Hira et al. Further, SWEC's example plant was designed to meet all applicable air quality regulations. The authors' dis cussion of compliance levels may lead to confusion in two areas: First, com pliance requirements are usually based on a unit rate limit, such as pounds of 394A
Environ. Sci. Technol., Vol. 17, No. 9, 1983
particulate per million Btu heat input, and not on an annual emission basis, such as total tons. Second, emissions from two sources, e.g., the process fa cility and power plant, should be ad dressed as separate sources when as sessing compliance with source-spe cific standards, such as the New Source Performance Standards for industrial boilers. These two compo nents were apparently combined in the authors' compliance test. One minor correction should also be noted. The S 0 2 emission limit is 0.52 kg/10 9 J, rather than the reported 0.05 kg/ 109J. A. J. Mills J. H. Walker R. D. Siegel D. Samela Stone & Webster Engineering Corporation Boston, Mass. 02107 Drinking water contaminants Dear Sir: The guest editorial by Rob ert A. Neal in the March issue of ES&T (p. 113A) touches the very important problem of priorities in the analysis of organics in drinking water. I agree with Dr. Neal, as will many others, that priorities for the analysis of organics in water have to be made. However, the priority scheme proposed by Dr. Neal calls for some remarks. I think we agree that the basic principle for setting priorities should be based on the contribution of a compound to the total toxicity, as de termined by the structure (specific effect) and the concentration. How ever, the consequence of this principle may be that the first priority of organic analysis in water is not necessarily the group of lipophilic compounds in the molecular weight and concentration range, as suggested by Dr. Neal. As is well known, the usual analyt ical techniques for isolation and de tection have very limited possibilities when more polar or higher molecular weight material is involved. As I have shown before and as can be expected, in most cases the amounts of this ma terial exceed the amounts of more lipophilic and lower molecular weight material by several orders of magni tude. According to Dr. Neal, this more polar and higher molecular weight material is not expected to be of high
priority from a toxicological point of view. This may be so, but I would prefer to prove this with experimental evidence. For the majority of organic material in water on a basis of weight, we do not know the identity of the material we are talking about, nor do we know the toxicological importance. I would suggest that the first priority is to know what we are talking about. This means the development and application of methods that allow not only for a complete isolation of organics present, but also for short-term toxicological screening. An integrated evaluation of the results thus obtained, based on physical-chemical and toxicological methods, will provide a stronger basis for setting priorities in the analysis of organics in water. Ir. J.G.M.M. Smeenk M u n i c i p a l W a t e r w o r k s of A m s t e r d a m
Literature (1) Smccnk, J.G.M.M.; Noordsij, A. "Inter pretation Problems in the Analysis of Organic Contaminants in Groundwater"; Presented at First Atlantic Workshop by AWWA and IWSA on Organic Contaminants in Groundwater; Nashville, Tenn., Dec. 8-10, 1982. (2) v.d. Gaag, Μ. Α.; Noordsij, Α.; Oranje, J. P. "Presence of Mutagens in Dutch Surface Water and Effects of Water Treatment Pro cesses for Drinking Water Preparation"; In Proceedings of "Mutagens in Our Environ ment"; Sorsa, M.; Vainio, H., Eds.; Espoo, Finland, June 20-24, 1982; Alan R. Liss, Inc.: New York, N.Y.; pp. 277-86.
Quality control Dear Sir: I am responding to Cliff J. Kirchmer's article entitled "Quality control in water analysis" {ES&T, April 1983, p. 174A). This article provides a timely and valuable review of the topic. In particular I found Kirchmer's review of European con cepts of quality control particularly enlightening. I did, however, find a small but sig nificant deficiency in this otherwise excellent article. In the author's dis cussion of "detection limits" he con spicuously omitted mentioning a "re cent" key paper on the topic. Γ refer to the paper by John A. Glaser et al. (ES&T, December 1981, p. 1426), which addressed the topic of detection limits in an in-depth and serious manner. Not only is it rather careless of the author to omit this important
