EPA evaluated ! * - - - - " . -q&- \ /------- - I , a

total organic carbon volatile organic carbon total carbon Dohrmann's DC-50 organic analyzer makes 811 of these measurements accurately and rapidly. Based on proven methods, it avoids interferences and undesirable pyrolysis re- actions that historically have resulted in significant errors. Here's why the DC-50 is the complete solution for the analysis of carbon in water: DIRECT READOUT. Four-digit presen- tation shows carbon content directly in mg/liter or ppm. N o recorder needed! DIRECT MEASUREMENT. A single sample injection gives either Organic Car- bon or Total Carbon content directly, not by difference. I N D E P E N D E N T MEASUREMENT. Volatile Organics are determined sepa- rately from Total Organics to aid in source identification. RELIABLE MEASUREMENTS. Deter- mines important, lightweight volatiles such as low molecular weight alcohols and ke- tones, normally lost by acidification and sparging. FAST: 5 minutes per determination ACCURATE: repeatability of f 1 mg/ liter or f 2% W I D E RANGE: 1 to 2,000 mg/liter (ppm) without dilution PRICE: $7,500, including start-up assist- ance and operator training *

~~

Contact: DOHRMANN Division, Enviro- tech Corporation, 1062 Linda Vista Ave.

Mountain View, CA 94040 (415) 968-9710

ENVIROTECH

Circle No. 22 on Readers' Service Card

1082 Environmental Science & Technolog

Automotive emissions-correction Dear Sir: I was pleased to see the

article on the stratified-charge en- gines (ES&T, August 1973, p 688). There were two small communication errors in the middle column of page 689 where test results on the Texaco Controlled Combustion System pow- ered army vehicle were discussed. These occurred in the last sentence of the first full paragraph. This should have read, "After 50,000 miles, under level road, 40-mph conditions, the numbers were 1.31 g/mile CO, 0.34 g/mile HC, and 0.37 g/mile NOx." Unfortunately, the level of NOx emissions through a communica- tion error is changed from one that passes the 1976 standard then in regulation to a level that does not pass. This standard, you will recall, is 0.4 g/mile for NOx. William T. Tierney Texaco inc. Beacon, N .Y .

Air pollution measurements Dear Sir: The article, "Project

Threshold Verifies Tests," (ES&T, April 1973, p 303) highlights the problem a journal such as yours has in reporting complex technical infor- mation before the experimental de- tails and data analysis supporting the claims made by the investigators are available for review by the scientific community.

Validation of air pollution measure- ment methods by the interlaboratory collaborative testing route, as is being done in Project Threshold, is in its infancy, and the manner in which the many complex problems of sys- tem design, conduct of experiments, and analysis of data are dealt with must be evaluated very critically be- fore sound conclusions can be reached. Unfortunately, full reports on the validation tests carried out in Phase I of Project Threshold are not generally available, and, for this rea- son, claims made for the methods are still in question.

Through the kindness of Walter Cropper, project manager for Thresh- old, we have had the opportunity to review preliminary draft reports on the validation tests for measuring ni- trogen dioxide by ASTM method D- 1607 and sulfur dioxide by ASTM method D-2914 and have been given the opportunity to comment on these test results. While we are in general agreement that the methods are reli- able means for measuring NO2 and SO2 in the atmosphere, we have res-

LETTERS

ervations about the precision and ac- curacy claims made for them and feel that further review of the test re- sults for these methods is still re- quired before such definitive state- ments are justified. We have not re- viewed reports on ASTM methods D-2010 (sulfation rate), D-1739 (par- ticulate matter-dustfall), D-1704 (particulate matter-tape samples), and D-3112 (lead).

Notwithstanding our concern about premature claims, we are strongly in favor of having air pollution measure- ment methods validated and have had a substantial program in prog- ress for several years to standardize such methods. Our emphasis, unlike Project Threshold, has been the standardization of methods of mea- surement required to determine com- pliance with national regulatory stan- dards. John B. Clernents National Environmental Research Center Research Triangle Park, N.C. 2771 1

Nitrogen removal Dear Sir: I read with interest the

informative feature article by C. E. Adams, Jr., on removing nitrogen from waste water ( € S A T , August 1973, pp 696-701). Several processes are reviewed in detail but processes involving oxidation of ammonia with chlorine are only briefly mentioned. Because of their potential usefulness they should have been covered in more detail.

A previous article (T. A. Pressley et al., €S&T, July 1972, pp 622-8) examined the use of breakpoint chlo- rination for removing ammonia from waste water. I t should be noted that this process can be used as the sole ammonia removal process or it can be used to remove residual ammonia from the effluent of a single stage, nitrifying activated sludge system. In either case, there is a secondary ad- vantage in that disinfection is also achieved. A major disadvantage is that partial ammonia removal, which in many cases is all that may be re- quired to meet the criterion which has been set for the receiving stream, is difficult to achieve effi- ciently.

A modifica,tion of the breakpoint chlorination process is possible if only partial ammonia removal is de- sired. Addition of chlorine at less than breakpoint dosages along with pH adjustment so that dichloramine is the principal product of chlorina- tion is an important aspect of this

process. Subsequent contact of di- chloramine with activated carbon re- sults in its conversion to nitrogen gas and hydrogen and chloride ions. Chlorine residuals can be completely eliminated from the effluent by the carbon as well, and thus problems resulting from chlorine residual toxic- ity in receiving waters can be avoid- ed. This process was tested in a pilot plant at Owosso, Mich. (P, A. Atkins et al., Proc. 27th Ind. Waste Conf., Purdue Univ.. 1972, in press) and the basic reactions were studied in more detail by others (R. C. Bauer and V. L. Snoeyink, J. Wafer Pollut. Conir. Fed., in press). There are still many valid questions concerning this pro- cess, but it does appear to have enough promise to warrant its inclu- sion in a discussion of alternative processes. Vernon L. Snoeyink University of illinois at Urbana-Champaign ’

Urbana, ill. 61801

New Washington ediforiai staffers

Gibney and Josephson join ES&T Both Lena Gibney and Julian Jo-

sephson joined the publication in Oc- tober. Mrs. Gibney has degrees from Wilmington College and the Universi- ty of Michigan pius industrial experi- ence at Shell Development Co., Shell Chemical Co., and TracorJitco, Inc. Mr. Josephson has degrees from New York University, the University of Paris, and graduate studies at Catholic University plus experience with the U.S. Naval Oceanographic Office, teaching experience with School of Marine and Environmental Technology of the Florida institute of Technology, and business experience with General Enterprises Corp. Each will soon be contributing to the Out- look section of ES&T.

~

Celesco.

The only SO, monitor actually using the National Bureau of Standards fluorescence technique.

Since the NBS revolutionized SO2 monitoring with the gas fluorescence technique, some manufacturers have slapped a “fluorescent” nameplate on their products. They’d like you to think their instruments use the NBS method. The truth is that only Celesco builds a gas fluorescence monitor under NBS license. While others are frantically playing follow-the-leader, Celesco can offer you all these benefits right now ... Celesco Model 5000 detects SO, and only SO, in source emissions. It gives accurate, instantaneous readings from 0-5000 ppm continuously-even around the clock-without chemical reagents. You can recalibrate the entire system, as often as you want, merely by turning a knob. No shut-downs, no interrup- tion to sample flow. And you never have to use bottled calibrating gas or per- meation tubes. The self-contained Model 5000 weighs just 22 pounds. Low 40 watt power con- sumption makes it ideal for field use. Write us today for free descriptive lit- erature and performance specifications. Celesco Industries Inc., Environmental and Industrial Products Division, 3333 Harbor Blvd., Costa Mesa, CA 92626. 7141

x n Equal Omatunny Emplqw-MIF

Celesco makes things simple. Circle No. 26 01 Readers’ Service Card

Volume 7, Number 13, December 1973 1083