EDITORIAL OFFICE:
NEWS
Room 706, Mills Building, Washington, D . C . TELEPHONE: National 0848 CABLE: Jiechem (Washington) ENTERED a s second class matter a t the Post Office at Easton, Pa., under the Act of March 3 , 1879, as 40 times a year. Industrial Edition monthly o n the 1st; News Edition on t h e 10th and 20th; Analytical Edition o n the 15th of January, April, July, and October. ACCEPTANCE for mailing a t special rate of postage provided for in Section 1103, Act of October 3 , 1917, authorized July 13, 1918.
EDITION
Industrial AND ENGINEERING
Chemistry PUBLISHED BY THE AMERICAN
Volume 10, No. 10
CHEMICAL
PUBLICATION O F F I C E : Easton, Pa. ADVERTISING D E P A R T M E N T :
419 Fourth Ave., New York, N . Y . TELEPHONE: Lexington 2-4186 SUBSCRIPTION t o non-members. Industrial and Engineering Chemistry, $7.50 per year. Foreign postage $1.50, except to countries accepting mail at American domestic rates and to Canada. Analytical Edition only, $1.50 per year. News Edition only, $1.50 p e r year (single copies, 10 cents). Subscriptions, changes o f address, a n d claims for lost copies should b e referred t o Charles L. Parsons, Secretary, Mills Building, Washington, D. C
SOCIETY
May 20,1932
HARRISON E. H O W E , EDITOR
Advantages of Mechanical Removal of Sludge in Water-Softening Plants1 FRANK BACHMANN, Sanitary Engineering Division, The Dorr Co., Inc., Chicago, Ill. T H E DISPOSAL of the large volumes of sludge formed in softening reactions a t water-treatment plants has always been a problem. Formerly practice dictated the passing of t h e chemically treated water through one or more intermittent settling tanks, connected in series or parallel. After the bulky precipitate had accumulated to a predetermined level, the tank or tanks were withdrawn from service for a manual or hydraulic removal of t h e deposit, the flow being diverted to other tanks in the group which had been cleaned after their previous period of service. Thus the tanks passed through successive and repetitive periods of sedimentation, cleaning, and refilling, often with not more than half the tanks performing their intended purpose of sedimentation. A decade or so ago there was introduced the continuous, mechanically cleaned sedimentation tank which mechanically removed the precipitated salts a t the rate of deposition and accordingly did not require periodic shut-downs for cleaning, an inherently weak and objectionable feature of its predecessor. Charles P . Hoover of Columbus, Ohio, was the first t o appreciate the basic idea of the continuous sedimentation tank and made the pioneer installation in the waterworks field a t Newark, Ohio, in 1922, this installation being followed shortly by one at t h e Benton Harbor, Mich., waterworks, designed by Pearse, Greeley, and Hansen, of Chicago. There are today in service not less than 49 mechanically cleaned sedimentation tanks a t waterworks throughout the country, serving 35 different municipalities with a total design capacity of 233 million gallons per day. Practice, as it relates to sedimentation, having changed decisively in a decade from intermittent to continuous operation, it may be relevant to inquire into the advantages that the newer practice has demonstrated over the older. ADVANTAGES O F MECHANICALLY CLEANED T A N K S
REDUCTION IN COST OF BASINS.
The mechanically cleaned
basins remaining continuously in service, duplicate units are not required for carrying the load during the weekly, monthly, or bi-monthly cleanings which were inherent i n the non-mechanical type. T h e percentage of removal of suspended solids being a function of t h e detention period in hours provided, which in turn is a function of the n e t effective volume available, the mechanically cleaned basin operates continuously a t its designed efficiency, whereas the plain basin undergoes a continuous reduction in efficiency from the day i t is placed in service until i t is shut down for cleaning. R A T E OF PRECIPITATION ACCELERATED.
By returning con-
tinuously to the mixing basin a portion of t h e sludge removed, two very definite advantages are secured: (1) The r a t e of settling and consequently the percentage removal of solids are increased, probably because of the additional nuclei presented for floe formation; (2) t h e rate of the softening reaction is accelerated, through a catalytic acceleration, it is believed, or. more probably, a reduction in supersaturation· Continuous sludge recirculation under carefully controlled conditions is best accomplished in mechanically cleaned basins of the continuous type. REDUCTION OF STREAM POLLUTION.
When plain sedimenta-
> RECEIVED April 7, 1932. Presented before the Division of Water, Sewage, a n d Sanitation Chemistry a t the 83rd Meeting of the American Chemical Society, N e w Orleans, La., March 28 t o April 1, 1932.
tion basins are cleaned periodically and several weeks' or months' accumulation of sludge is suddenly sluiced into the stream, an extremely unsightly condition is created, which is visible for several days in the downstream reaches. On t h e other hand, when t h e sludge is removed continuously at the rate of deposition the daily increments are slight and are noticeable only within a few hundred yards of the treatment plant. REDUCTION OF ODOR. Disagreeable odors may b e removed by treating t h e softened water with activated carbon and then resettling for the removal of the deodorant. Using a mechanically cleaned basin for this resettling, the sludge may b e continuously recirculated. This procedure will reduce the quantity of deodorant required. REDUCTION OF WATER Loss. Contrary to the impression of many engineers who regard submergea moving parts as a hindrance rather than an aid to settlement, the gentle blunging action imparted t o the sludge by the rakes releases entrapped water and causes the solids to settle to a moisture content 5 to 10 per cent lower than that in a plain basin, thus increasing the over-all yield of treated water. PREVENTION O F ORGANIC DECOMPOSITION.
"Water (tarrying
in suspension appreciable amounts of organic matter and algae may be polluted and may acquire disagreeable tastes and odors through putrefaction and consequent multiplication of bacteria if these impurities are allowed to accumulate in the sludge deposited i n the sedimentation basin. If, however, the basins are mechanically cleaned, impurities are removed continuously before there has been time for putrefaction o r algae growth. REGULATION OF SLUDGE REMOVAL.
The final density to which solids will settle i s a function of the depth of partially settled sludge above the discharge connection. Furthermore, the power input to the motor driving a mechanically cleaned basin is likewise a function of the depth of sludge through which the rakes must be driven. Accordingly the power input is a reliable and constant indicator of sludge conditions, especially when supplemented b y an overload alarm to advise the operator when the sludge depth h a s reached the maximum safe point. Constant removal of sludge at a rate corresponding t o that of deposition is desirable in order that the moisture content may be held constant and a portion of t h e sludge returned t o the influent for accelerating both the rate of settlement.and t h e rate of reaction. Diaphragm or plunger pumps of the variablestroke type a r e t o be preferred t o spigot o r siphon discharges, as the latter are difficult to regulate and tend to over-run when the sludge becomes thin and clog when i t becomes thick. Mechanically cleaned sedimentation basins may b e arranged in various ways with respect to other equipment for handling water t h a t is hard, turbid, or both. When first used, the mechanically cleaned basm had a comparatively short detention period to remove 90-95 per cent of the precipitate and was followed by a secondary settling basin. Later practice indicates that the trend is toward doing all the settling m mechanically cleaned basins. Where more than one sedimentation tank is used for settling the softened water, it is common practice to provide auxiliary flumes and lines so that one of the units may operate in series, instead of in parallel with the others, when necessary. During storm periods and particularly a t the time of spring freshets, river water often becomes excessively turbid. Consequently.
125 P l a n Your Vacation i n Colorado· Objective—The A . C . S . M e e t i n g i n Denver, A u g u s t 22 t o 2 6 . 1932
NEWS
126
the preset Lliug of tliis watex* in one basin, prior to softening and secondary settling in the remaining basins, reduces the consump tion of chemicals and gives a more uniform feed to the softening part of the plant. Where the precipitate settled in the basins is dewatered and reburaed for reutilization i n the softening reactions, the con tinuous, uniformly dense sludge from the mechanically cleaned basin is distinctly better than the discontinuous, less unitorm sludge from plain basins. Continuous rotary vacuum niters followed by continuous rotary kilns are standard in the chemi cal and industrial fields for lime sludge reburning, and in these fields it has been found necessary to provide them with uni form continuous feeds for best results. A. A. NOYES RECEIVES RICHARDS MEDAL THE THEODORE WILLIAM RICHABDS GOLD MEDAL for 1932 was
presented to Arthur Amos Noyes at a special meeting of the Northeastern Section held May 6 at the American Academy of Arts and Sciences, Boston, IMass. William P. Ryan, chairman of the section, presided and made the formal presentation. A paper giving a survey of the work of Professor Noyes and enu merating his scientific achieve ments was read by Arthur B. Lamb, of Harvard University. The story of the establishment of the medal was told by Lyman C. Newell, of Boston Uni versity. After expressing his gratitude for the recognition ac corded him by the SOCIETY,
ARTBUB A. NOTES
Professor Noyes delivered an address on " U n d e r g r a d u a t e Education for Chemical Re search/1 describing the method used at the California Institute of Technology for selecting the s t u d e n t s o f m o s t research promise, interesting them in discovery, and training them in research early in their undergraduate course.
INSTITUTE OF CHEMISTS MEDAL PRESENTED TO H E R T Y
THE MEDAL of the American Institute of Chemists was pre sented to1 Charles H. Herty at a dinner held May 7 a t The Chemists Club, New York, Ν. Υ., the presentation being made by Francis P. Garvan. Frederick B. Breithut, president of the institute, spoke of Doctor Herty's work. Other speakers were former Senator Joseph E. Ransdell of Louisiana, John H. Finley of the New York Times, Henry W. Jessup, and Marston T. Bogert of Columbia University. [Previous medalists have been Andrew W. and Richard B. Mellon, George Eastman, Mr. and Mrs. Francis P. Garvan, Lafayette B. Mendel, and William Blum. K A N E RECEIVES PHILLIPS M E D A L AWARD THE FRANCIS C. PHILLIPS MEDAL AWABD for 1932 has been
awarded to Howard Kane, -who will receive his bachelor of science degree in chemistry in June from the University of Pittsburgh. The medal was established by Francis C. Phillips shortly after his retirement from the university in 1915 and has been continued by Mrs. Phiilios. Mr. Kane was awarded the medal on the basis of -having received highest honors in chemistry in his class, and has ranked equally high in courses other than chemistry.
EDITION
Vol. 10, No. 10 TENTH
COLLOID
SYMPOSIUM
THE FOLLOWING PAPERS will be presented before the Tenth Annual Colloid Symposium to be held at Ottawa, Ontario, Canada, June 16 to 18, 1932. 1. Wilder D. Bancroft and J. E . Rutzler, Jr. "The Colloid Chemistry of t h e Nervous System." 2. John H . Ferguson. "The Particle Size of Biological Units.·' 3. P . J. Moloney and Edith M. Taylor. "The Adsorption of Diphtheria Toxin and Diphtheria Antitoxin a t Various Interfaces." 4. E . 0. Kraemer a n d F. J. Van Natta. "The Viscosity and Molecular "Weight of Polymeric Materials." 5. W . F. Busse. "The Physical Structure of Elastic Colloids." 6. X . Midgley, Jr. "Separation and Identification of Sol Rubber Hydro carbons." 7. S . E. Sheppard and R. C . Houck. "The Insolubilization of Gelatin by Heat." 8. Oharles Mack. "Colloid Chemistry of Asphalts." 9. C H. "Winning and J. W . Williams. "The Sorption of Organic Vapors by Glyptal Resins." 10. N . S. Grace and O. Maass. "The Sorption of Vapors on Cellulose." 11. R . Richardson and 0 . Maass. "The Sorption of Sodium Hydroxide on Cellulose and Wood." 12. M a y Annetts. "Absorption of Colloids b y Filter Paper." 13. C F. Bardorf. "Review of Research on Cane Wax in R a w a n d Re fined Sugars." 14. E . Hatschek. "The Study of Gels b y Physical Methods." 15. 3 . S. Kistler. "On the Nature of Coagulation, Viscosity, and Thixotropy in Colloidal Systems." , 16. Harry B . Weiser and W. O. Milligan. "X-Ray Studies on t h e Hydrous Oxides; Alumina and Stannic Oxide." 17. E . J. Miller. "The Adsorption of Electrolytes b y Ash-Free Charcoal." 18. Harry N. Holmes, Norvil Beeman, and A. L. Elder. "Removal of Sulfur Compounds from Hydrocarbons by Porous Solids." 19. E . W. H. Steacie and H . A. Reeve. "The Decomposition o f Dimethyl Ether on the Surface of Platinum." 20. E . F. Burton. "Preparation and Use of Metallic Arsenic Colloidal Solution." 21. A . L. Elder and Naoma O. Green. "Colloidal Boron." 22. C H. ~M. Roberts. "A New Theory of Emulsions." 23. Robert C. Williams. "Some Aspects of Boundary Lubrication b y Soap Solutions." 24. F. E. Bartell and Charles E . Whitney. "Adhesion Tension. I l l — A Receding Contact Angle, Pressure of Displacement Method." 25. Otto G . Jensen and Ross Aiken Gortner. "Electrokinetics. X I I — Interfacial Energy a t AkOs-Organic Liquid Interfaces a n d the Molecular Structure of Organic Compounds." 26. Et. L. "White, Frank Urban, and B . A. V a n Atta. "A Correlation of Surface Conductance and Stream Potential." 27. Frank Urban and H. L. White. "Some Applications of tbe Stern Theory."
The National Research Laboratories, where the technical sessions will be held, is located about one mile from the Chateau Laurier, Ottawa's largest and finest hotel, with accommodations for 1O00 guests. This hotel, in the heart of the city, offers the best available accommodations and delegates to trie Colloid Symposium will receive the benefit of regular convention rates. Near the Chateau Laurier the Koxborouçh, an apartment hotel serving meals, provides excellent facilities. The Alexandria Hotel, Bank St., is a little farther away, but offers very good accommodation a t prices somewhat lower than the Chateau Laurier. In addition, there are numerous smaller hotels, tourist homes, and apartment houses. Bequests for reservations should be made directly t o the hotels mentioned. Information regarding other places will be furnished on request by the Ottawa Industrial and Publicity Department, 34 Albert St., Ottawa, Canada. BAILEY TO RECEIVE OSBOBNB M E D A L
CI/TDE H. BAILEY, professor of agricultural biochemistry, University of Minnesota, and cereal chemist in charge of the Section of Cereal Chemistry, Division of Agricultural Biochemistry, Minnesota Agricultural Experiment Station, has been awarded the Thomas Burr Osborne gold medal of the American Association of Cereal Chemists "for distinguished contributions in cereal chemistry." The formal presentation of thé medal will be made b y C. B. Morison, of the American Institute of Baking, at the joint meeting of the association with the Detroit Section
BAKER AWARD ΜΑΓ>Β IN ANALYTICAL CHEMISTRY
THE Β,ΕΟΊΡΙΛΝΤ of the J. T. Baker Chemical Co. Research Fel lowship in Analytical Chemistry, Mid-Western Division, for 1932-33 is Vernon E. Stenger at the University of Minnesota. H e will work under the direction of I. M. Kolthoff on a subject involving co-precipitation*
MENDEL MEDAL AWARDED TO GARVAN
FRANCIS P. GARVAN, president of the Chemical Foundation, Inc., has heen awarded tiie 1932 Mendel Medal b y ViUanova College, in recognition of bus contributions to scientific progress. The medal will be presented at the commencement exercises June 7.
of the AMERICAN CHEMICAL SOCIETY on Monday evening, May
23, a t the Statler Hotel, Detroit. Doctor Bailey will respond with an address dealing with certain phases of his well-known work in cereal chemistry. This medal was established in 1926 b y the American Association of Cereal Chemists "to honor those scientists who have contributed signally to the advancement of our knowledge in this field of specialization—the award to be made only at such times as were justified by unusually meritorious contribution." The first award was made in 1928 t o Thomas Burr Osborne, after whom the medal was named, for his classic studies in the field of plan-b proteins. Doctor Bailey will be the second recipient of the medal.
