LABORATORY AND PLANT: THE DESIGN AND OPERATION OF OZONE WATER PURIFICATION SYSTEMS
Journal of Industrial & Engineering Chemistry
will resulc and t h e low discharge is t h e one which must be expected. H a d the sinuous formula given the lower value of v, the result b y the formula for viscous flow would have been rejected. SIZE O F P I P E FOR VISCOUS LIQUIDS Liquids of even moderate viscosity flowing under lorn heads follow viscous motion unless the pipes be very large. It is very important t o keep in mind the fact t h a t , so long as t h e motion is viscous, doubling the size of t h e pipe increases t h e velocity
... es t h e velocity 4-fold a n d the discharge 16-fold for t h e same pressure drop. For t h e same discharge a pipe twice t h e size requires only one-sixteenth t h e pressure drop and therefore but one-sixteenth t h e power. If a pipe is carrying liquid in viscous motion, increase in size of the pipe IS always well worth consideration, owing t o this very great effect on carrying capacity and power consumption. Decrease in size will ultimately result in converting the flow into sinuous motion, after which the effect of size is greatly lessened, being inversely proportional t o only t h e first power of t h e diameter. S C XM A R Y Liquids flowing through pipes flow either in straight line motion in which case they follow Poiseuille's formula, p = , or in sinuous motion. t h e pressure 8 ,ulz g1.2 drop being represented by p = J1pv2. The flow will gr follow t h a t formula which requires t h e higher pressure drop, t h e higher radius, or gives t h e lower velocity, as the case may be. Both formulae must therefore be employed and t h e result chosen according t o t h e abo77-e rule. for sinuous motion: look up, in suitable hydraulic tables, t h e value of t h e coefficient for water flowing in the same size pipe a t t h e same velocity a n d multiply this coefficient b y t h e expression (0.95 j + 0 . oqjz) wherein z is the viscosity relative t o water of t h e liquid flowing. These formulae have been experimentally substantiated only for use in pipes u p t o 2 in. in diameter and for t h e flow of liquids of viscosity (relative t o water a t zoo) of 20. They are probably safe for use in larger pipes and a t higher viscosities, b u t more exact expressions for these conditions must be determined b y further experimentation. T o obtain the coefficient j of the formula' RESEARCH LABORATORY OF APPLIED CHEMISTRY Although t h e first attempt t o purify water on a practical scale b y means of ozone was made less t h a n thirty years ago, still this gas was generated and its chemical and physical properties have been studied b y many investigators for more t h a n a century. In all probability ozone has been recognized by scientists 1 Chemist and bacteriologist of the Baltimore County Water and Electric Company, A N D ENGIMEERIiVG C H E M I S T R Y T 'ol. 8, NO. 7 since .the earliest ages, if not by name a t least b y its characteristic properties. The first authentic record t h a t we possess of t h e manufacture of this gas was in 1783 when Van Marum: a Dutch scientist, termed it 'la smell of electricity," as a result of its production by this means. I t was not, however, until t h e exhaustive studies of Schoenbein in 1840 t h a t t h e active properties of ozone were well understood or a n y analytical methods were devised for measuring this gas. Schoenbein recognized this active oxidizing agent as a distinct gas t o which he gave t h e name of ozone. For more than fifty years after Schoenbein's researches nothing was accomplished in placing ozone within. the scope of a commercial possibility, although its active and oxidizing power was well known. With t h e development of t h e alternating current generators and transformers, which so materially reduced the cost of production, and t h e increasing knowledge of the bacteriology and chemistry of water, ozone T?"S recognized as a water purification agent of great value. Berthelot, a French chemist, in 1890 undertook, with some degree of success, t o apply this method of water purification, and from then on Europe, as well as America, has been practically flooded with numerous designs of generators and patented appliances for v a t e r treatment. All t h e ozonizers t h a t have been devised are based upon t h e same genera! principle, ziz., t h e production of t h e allotropic form of oxygen, 03, from the oxygen of the atmosphere. This is accomplished by passing a current of air over a brush discharge u-hich takes place between electrodes connected t o a high voltage alternating current circuit; these usually ha\-e a solid dielectric interposed between them. There are, of course, many other ways of generating this gas, b u t none of these processes other t h a n the one described has proven a commercia! success. Numerous theories h a r e been advanced t o account for t h e production of ozone in this manner b u t t h e one generally accepted is based on the theory of molecular m0tion.l This theory, as stated b y Dr. C. P. Steinmetz, regards the chemical effect of all ether radiations recognized b y light, heat and electrical waTTes as more or less specific for various compounds t o definite frequencies of their movement setting up resonance effects upon t h e natural molecular or atomic motion. Pure ozone is colorless, has a distinct and peculiar odor and instantly decomposes a t 260' C. I t can be liquefied b y a pressure of 1840 lbs. per sq. in. and a t a temperature of -103' C. I n this condition it is highly magnetic b u t is not so powerful an oxidizing agent as t h e gas. The great affinity of ozone for organic matter renders it peculiarly suited for water purification, in t h a t it not only removes the bacteria by direct oxidation b u t will eliminate t o a considerable degree other organic substances 'contained therein. A11 ozonation plants for the purification of water consist of two distinct parts-the ozone generator and 1 Engineering S e w , 65 (1910). 488.