sluff off and be carried to the condenser. It is desirable, for the good of the biota of the receiving water, to minimize the chlorine in the blowdown. Regulations quite properly limit this discharge in both time and concentration. Cooling towers are aeration systems, and some of the residual chlorine is probably removed therein. I know of no quantitative test data showing how much of the residual chlorine in its various forms is removed by a cooling tower. I would appreciate any available data on these pages or by private communication.
rwo MODELSTO CHOOSE FRON DR-EL/1 and DR-EL/l a
Donald G. Frier, P.E.
Gilbert Commonwealth Reading, Pa. 19603
Steel update-correction Dear Sir: In the December 1977 issue, p 1225 of your magazine, there appeared reference to our study Environmental Steel Update with the price quoted as $10 for the 250 page study. This information is incorrect. The study sells for $150 and there is a technical summary available for $10.
DR-ELI1
Kare Hornschuch
Council on Economic Priorities New York, N.Y. 1001 I
helping you comply with the strict OSHA air quality standards. The MIRAN-11 Multi-Point Ambient Air Monitor: continually monitors up to eleven locations as far as 400 feet away. is available with alarms towarn of phosgene concentrations exceeding theO.l ppm OSHA standard. has rapid response-one minute per location. provides reliable, unattended operation. requires nocarrier or span gases. For detailed information. writeor phone today. Foxboro/Wilks, Inc., P.O. Box449. South Norwalk, CT 06856. Phone (203)853-1616.
WLKS Foxboro Analytical
CIRCLE 8 ON READER SERVICE CARD
994
Environmental Science & Technology
Research in water use Dear Sir: In a guest editorial ( E S & T , January 1978, p 5 ) . Dr. Daniel A. Okun proposes that more efforts should be in addressing potable water quality standards rather than further research in water reuse. Dr. Okun’s statement emphasizes how inadequate are our current water quality standards. Only some waters that meet current water quality standards are acceptable for use. Waters that meet these standards but are reclaimed from wastewaters are not acceptable for domestic use. And we know most domestic supplies are drawn from waters that contain wastewaters. Indeed, further research on potable reuse of water will give the answers Dr. Okun looks for. He argues that a study D f one waste will not give universal mswers because all wastes are differ:nt. Aren’t all water supplies? Studies In one water supply would then not mswer universal questions either. The quality of undesirable products and chemicals in wastewater is (or, at least it should be) greater than in a water supply. Therefore, these undesirable products should be easier to identify and it should be easier to jemonstrate those processes that remove all of these undesirable products. 4 process that removes the undesirable
DR-ELIla
Compact. Portable. Everything you need in the classroom or out. Both include a direct reading colorimeter. Both have built-in pH meter with electrode. For titrations, the DR-EL/1 is equipped with Hach’s new Digital Titrator; the DR-ELI1 a comes with conventional drop count titrator. Both are ideal for teaching aids. FEATURES Easy-to-follow instruction manual. rn Insertable direct reading meter scales for all colorimetric tests. rn Convenient reagent powder pillows. (These are child-resistant.) rn Exclusive Hach color filter wheel. Eliminates hassle of individual glass filters. rn Unbreakable permanently sealed pH electrode. Never needs refilling. rn Completely self-contained. AC or battery power. ORDER YOURS TODAY! DR-ELH (Cat. No. 1206-10) , . , . . $475.00 DR-ELlla (Cat. No. 1206-20) , , . . $425.00 Prices are F.O.B. Ames, Iowa, and are subject to change without notice. ,
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CHEMICAL COMPANY First in Water Analysis P.O. Box 389 Loveland, CO 80537 U.S.A. C a l TOLL-FREE 800/525-5940 (Colo. residents call collect) 303/669-3050 TWX. 91 0-930-9038 And. Hach Europe Namur Belgium 9
:IRCLE 13 ON READER SERVICE CARD
products from reclaimed water, or a t least reduces them to a lower level, demonstrates a process that can be used for drinking water supplies with assurance that such undesirable products will be removed or reduced to an acceptable level. Water of a quality that meets our drinking water standards should be questionable to Dr. Okun and to all of us because the current drinking water standards are based on using the best available or desirable sources. Most sources presently available are contaminated to some degree, and larger rivers can be greatly contaminated as they contain greater amounts of sewage. Hence these best available or desirable sources do not provide the protection claimed by the current drinking water standards. Why should we accept water quality standards based upon the source of the supply since the sources are the biggest unknown from a quality standpoint? Why should we not improve the water quality standards by developing such criteria as are necessary to ensure protection of the public health? The goal should be to develop one set of comprehensive water quality standards for drinking water regardless of source
of the water. This would do more to improve “the quality of waters now being consumed” than any other thing. The development of such standards can be done by continuing and encouraging additional research on wastewater reclamation for potable reuse. When it is demonstrated that reclaimed water is suitable for potable reuse, then we will have adequate water quality standards suitable for use with any source. Lloyd C. Fowler Santa Clara Valley Water District San Jose, Calif. 951 18
Precipitator update Dear Sir: The McGill Precipitator represents a new generation of electrostatic precipitators. It is fundamentally different from conventional EP’s described in the report ( E S &T , June 1978, p 657) in that there are no hanging discharge wires that require periodic maintenance. Also, because of the method used to create an electrical discharge corona, power consumption is considerably lower. This has been verified by more than fifty precipitators we have currently in operation throughout the U S .
For special applications, we encourage pilot testing, using one of our Mobile Electrostatic Precipitators to determine the proper precipitator size and design considerations. William R. Heifner United McGill Corp. Columbus. Ohio Precipitator report Dear Sir: To my knowledge no vendor of precipitator equipment other than Research-Cottrell subscribes to (1) the alkali/Na20 ratio as a criterion for electrode fouling in hot side precipitators, or ( 2 ) that phosphorus pentoxide is responsible for corona quenching. Yet the article (ES&T, June 1978, p 657), “Keeping Fly Ash Out of the Stack”, authored by Research-Cottrell employees presents these concepts as accepted facts. Is there any independent published corroboration of these concepts or are you merely adding to the disheartening array of precipitator mythology that persistently afflicts customers and vendors alike? David H. Spielberg
UOP, Inc., Air Correction Division Darien, Conn. 06820
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Volume 12, Number 9, September 1978
995
