cess flow, is self-burning at about 5-7 percentage points less than other sludge incineration methods (Chern. Eng., October 14, 1968, p 114). Normally, the 95% water in thickened sludge is reduced to the 18-25% level, as readers involved with municipal treatment are well aware, by mechanical means such as vacuum filtration or centrifugation filtration, not heat. However, as indicated below, heat treatment prior to mechanical dewatering can be energy productive. Current technology is such that appreciable amounts of fuel are not required and indeed, as reported in the article, installations are currently being built utilizing the closed energy loop system where heat will actually be recovered. Although the project mentioned by Mr. Hannan (Blue Plains, Washington, D.C.) is reported to have projected substantial requirements of fuel. the application of the technology set forth in the article would generate the benefits and energy savings mentioned. Mr. Hannan concludes that there may be no easy answers to sludge disposal, but the ecological truth is that sludge incineration has been found by an increasing number of cities over the last few years to be the most environmentally sound and economical answer to their sludge disposal/reclamation needs. Several major metropolitan studies, done within the balanced framework of Title 1, Section 102, of the Clean Water Act of 1972, have found thermal processing to be environmentally and economically the best solution to sludge disposal problems, both now and projected over the next several decades. In summary, sludge incineration not only removes hazardous materials that are not otherwise being removed from the environmental cycle, but collects in the ash most of the heavy metals in a relatively favorable form, does not introduce any new mercury into the atmosphere that will not be there otherwise, and is an insignificant emission source that can be operated to generate useful heat. Frank P. Sebastian
Senior Vice-president Envirotech Corp. Menlo Park, Calif. 94025
Car emission controls Dear Sir: Overall, the feature on the problem of automotive emissions (September 1974, p 807) seems reasonable. However, Earl T. Hayes strikes an old, tired, and discredited note. I t appears that he has not read the earlier articles. His bugbear of fuel penalty is refuted a few pages earlier, but he sails magnificently ahead with quotations from Arthur Stern that ignore the fact that neither the Los Angeles nor Denver area can meet the Ambient Air Quality Stan-
dards for carbon monoxide and oxidant, even with the 1977 Emission Standard. The situation of Denver is perhaps unique, and it is not considered at all in any of the articles. The altitude of some 1600 meters causes a serious penalty in terms of additional carbon monoxide and unburned hydrocarbons that none of the manufacturers seem seriously to have considered. Dr. Hayes then brandishes a figure of the loss of hundreds of thousands of jobs (the source of this information is unspecified) and states flatly that the achievement of clean air will ruin, bankrupt, destroy, communize, and otherwise inconvenience this nation. And, most horrible of all, it could lead to a steady state economy. I would suggest that Dr. Hayes and his many companions in this persuasion are simply having difficulty in accepting any change from the present highly . unsatisfactory economic situation. I t is undeniable that dislocations will occur-they are occurring right now as the petroleum industry tries to adjust to decreased consumption caused primarily by high prices. The truth of the matter is that the American romance with the automobile has got to end, if not because of the problems of balance of trade, then because of the declining world supply of petroleum, not to mention all of the other raw materials for automobiles. Dr. Hayes’s analogy of the Alaska Pipeline Bill is scarcely applicable; only those who wish to discredit the environmentalists would maintain that the delay in initiating the Alaskan pipeline did not greatly improve its environmental acceptability. This is not to say that the Clean Air Act is without its faults. Both the auto manufacturers and an increasing number of stationary sources have been given additional time in which to comply with emissions regulations, but the cities have not been given corresponding time extensions to reach the Ambient Air Quality Standards. As a result, rather violent interim measures will become necessary to reach compliance during the 1975-77 period. I believe that the American public is wise enough to accept measures truly needed to achieve clean air. I do not believe that they will accept draconian measures that are only necessary for one or two years to meet an arbitrarily set target date. I f it is really essential to reach the Ambient Standards by 1977, then no time extensions should have been given to any pollutant sources. It is here, not in the final emission levels that need to be attained, that the faults of the Clean Air Act lie. James P. Lodge Chairman, Air Pollution Control
Commission Colorado Department of Health Denver, Colo. 80220 CIRCLE 2 ON READER SERVICE CARD
Volume8, Number 13, December 1974
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