INDUSTRIAL AND ENGINEERING CHEMISTRY
704
drop in insulation is most undesirable. Experiments and experience have demonstrated that in certain cases an initial drop in dielectric resistance may be observed; then, provided the core is otherwise satisfactory, the improvement will eventually set in, although possibly a t a reduced rate. Additional factors affecting improvement are moisture content of the dielectric and concentration of dissolved salts in the water. TABLE 111. EFFECT OF CHANGES IN MOISTURE CONTENT Moisture Content
% 4.3 3.3 1.5 0.3 0.1
Specific Resistance at 75O F. Ohm-cm. X 1014 13.5 13.7 11.3 11.7 14.2
Dielectric Constant 3.2 3.18 3.1 3.05 3.05
Little has been said of the dielectric constant of guttapercha, balata, and admixtures, in spite of the fact that it is the most important operational constant of a cable. However, it follows more definite laws than the other characteristics and may be predicted for a mixture with reasonable certainty by an arithmetical computation from the figures of the components. Nonuniformity in the mixture will almost certainly be reflected in its dielectric constant, and since the moisture content is usually affected by changes in processing, the high dielectric constant of the water will cause changes in the capacity of the finished material. It might be expected that the dielectric resistance would be more susceptible than the dielectric constant to changes in moisture content; although this is found to be the case, the variations in the former are very irregular, whereas those
VOL. 31, NO. 6
of the latter are consistent with theory. Table I11 gives the results obtained in a series of experiments on a mixture of normal proportions in which, as far as possible, the only variable was the moisture content.
Conclusions The satisfactory insulation of a submarine cable core is fundamentally complicated by the considerable variation in the characteristics of the different types of raw materials. Furthermore, the characteristics of a mixture of components do not bear any known mathematical relation to those of the components. Finally, the considerable variations experienced in sample to sample of the same type of raw material, by reason of their jungle origin, causes still further complication. I n these circumstances, it is to be deplored that cable specifications are drawn up in such a way as to cause still further difficulties to a manufacturer endeavoring to supply the best cables commercially possible. It is to be hoped, therefore, that this paper will throw some light upon what is generally considered an obscure subject and a t the same time cause serious thought by those responsible for drawing up cable specifications.
Acknowledgment Thanks are due to The Telegraph Construction & Maintenance Company Limited, for permission to publish the information in this paper.
Literature Cited (1) Dean, J. N., India Rubber J.,82, 853-6 (1931). (2) Kemp, A. R.,J. Franklin Inst., 211, 37-57 (1931). PRESENTBID at the 94th Meeting of the American Chemical Society, Rochester, N. Y .
Removal of Ammonia in
Water Treatment A. M. BUSWELL AND MAX SUTER State Water Survey Division, Urbana, Ill. ANY microscopic organisms live and grow in water distribution systems. These organisms are troublesome; they often cause odors and unsightly conditions in the water, although they are nonpathogenic as far as we know. For the latter reason they.have not been subjected to much study by medical bacteriologists. Usually they cannot be grown under artificial conditions and therefore are not attractive material for the general microbiologist. However, increased demands for a more perfect water in any public supply requires that these organisms be eliminated as far as possible from the distribution system. At present, we have little systematic knowledge of these organisms. Most of them are a true and higher form of bacteria (iron and sulfur bacteria), but protozoa and higher organisms, especially nematodes, are also very common. I n general three ways are available to eliminate these organisms: avoidance of contamination, disinfection, and elimination of food supply (starvation).
M
.
Elimination of Organisms Avoidance of contamination requires that the organisms be kept out by the filter. The efficiency of the filter in this respect is rather low. Even if most bacteria, spores, and cysts are kept back in the filter and are to a great extent removed from it in backwashing, a few may pass through. It is also known that nematodes can slowly wiggle through the sand and carry some organishns along. Furthermore, other sources of contamination are possible, such as backsiphoning through plumbing fixtures, and eddy currents a t leaks and through fire hydrant drains. Disinfection is produced mainly through chlorination, but all organisms found seem to be very resistant to chlorine; a t least they are not affected by a chlorine dosage up to 0.5 p. p. m., to which the water in the distribution system is ordinarily limited because of tastes. Another way of practical disinfection for chlorine-resistant organisms is in the use of the lime softening process. The meager observations made so far seem to show that chlorine-resistant bacteria can resist a low p H but not the high pH produced by the lime
JUNE, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
treatment. Water softening combined with chlorination gives, therefore, a wide range of active disinfection. Other means for the limitation of these growths are much needed. It is conceivable that cutting off the food supply will cause their elimination by starvation. All living organisms must have available some food supply which furnishes material for bodily growth and which is also capable of yielding energy through chemical reactions. Iron organisms gain a t least part of the energy needed from the oxidation of ferrous to ferric iron. Similarly, sulfur bacteria use the oxidation of sulfur to sulfate ions or of hydrogen sulfide to water and elementary sulfur. However, in some cases it is 5 found that these organisms or similar ones persist even in the absence of sulfur and with very complete removal of the iron. I n such 4 cases attention may be called to the possir0 bility that the organisms may gain energy 2 from ammonia which is present in many 3 well waters. The energy available from the Q oxidation of ammonia depends on the product formed, as shown by the equations: 2 NH4+ NH4+ NH4+
+ 202 = 2H+ + NOa- +
+
+
HzO - 81,230 cal. 2H+ NOS' / 2 0 ~ H 2 0 - 63,230 cal. '/~OZ H+ l/zNz S/2H20 - 86,670 cal.
+
+
+
705
replace calcium and magnesium ions in the water by sodium ions), carbonaceous zeolites have the property of hydrogenion exchange. They are able to replace any metallic ion by hydrogen ions and thus form acids in the treated water. Ammonia is included in the ions that are removed by carbonaceous zeolites. Tests were made with the tap water of the University of Illinois. This water is aerated and filtered to remove iron and then chlorinated. It is practically a pure carbonate water, free of sulfates, but after heavy chlorination it contains about 5
-w z
v) 0
400%
%
I-
300 UI
200
I
+
GALLONS PASSED
-
100
g
I B
The existence of the process in the second of REMOVAL OF AMMONIA 8Y CARBONACEOUS ZEOLITE these equations is confirmed by the fact that in many distribution systems nitrites can be found, although the raw water contains only ammonia. Calcup. p, m. chlorine ions. On an average, the water contains lations from energy relations show that the energy in the the following metallic ions in parts per million: calcium, ammonia in a million gallons of the University of Illinois water 60.6; magnesium, 28.2; sodium, 56.5; ammonium, 2.7. In SUPPlY would be sufficient to Produce 40 Pounds of baaterial a long run the carbonaceous zeolite (Zeo-Karb, provided by growth (dry weight). This material would Yield 800 Pounds of the Permutit Company) shows two cycles with this type of wet sludge of 95 per cent moisture content and contains only water: first an acid cycle in which 811 metallic ions are reabout 12 per cent of the nitrogen of the ammonia in the original moved, then a sodium cycle in which the carbonaceous zeolite water. Evenif we do not anticipate that the biological reaction acts as a noma1 zeolite, removes only the hardness produeuses all the ammonia available, we can nevertheless assume that ing metals, and replaces them with the sodium extracted durthe m ~ m o n i aWill furnish energy and nitrogen for a great ing the acid cycle. The boundaries between the cycles are amount of organic sludge. Elimination of the m ~ m o n i a not sharp, and there is somewhat a gradual change from one from the distribution system will therefore help to reduce action to the other. This can also be found relative to the reconsiderably the after-growth in pipe lines. moval of ammonia. I n the acid cycle practically all the ammonia is removed, Elimination of Ammonia In the effluent an average is found of only 4.4per cent of the ammonia in the raw water. At the end of the acid cycle, when It was first thought that the ammonia could be eliminated the total solids increase, the ammonia content increases also by the formation of ammonium magnesium phosphate. To to an average of 13.2 per cent of that in the raw water. Durstudy this possibility, two series of experiments were run on ing the sodium cycle very little ammonia is removed, the &liter samples with trisodium phosphate as the source of phoseffluent containing on an average 77.8 per cent of that of the phate ions. Since trisodium phosphate is also used as a water raw water. At the end of the sodium cycle as soon as the softener, lime was employed to soften the water and to aid hardness increases, the carbonaceous zeolite seems to be unthe phosphate to react with the ammonia. Neither the triable to retain the ammonia; at least an increase in ammonia sodium phosphate nor the lime alone had any effect on the amwas found then, the content of the effluent averaging 120 monia. Even if the trisodium phosphate and lime were introper cent of that of the raw water. duced a t practically the same time, no effect on the ammonium content could be found within experimental error (actual reCarbonaceous zeolites, if regenerated with sodium chloride, duction from 1.6 to 1.52 p. p. m. ammonia nitrogen). If act like siliceous zeolite in removing the hardness from the the lime was introduced first and, after 20 minutes of reaction water. Probably in this case they will also remove ammonia time for the lime softening, twice the necessary amount of triduring the sodium cycle, a t least a t the beginning of the cycle. sodium phosphate was added to bind the ammonia, a slight But to obtain full benefit of the special properties of the carreduction of the ammonia from 2.0 to 1.3 p. p. m. was found bonaceous zeolites they should be used only in the acid cycleas the best result. Apparently trisodium phosphate reacts i. e., after regeneration with an acid. It is during this acid too easily with calcium to be effective for the removal of cycle that the carbonaceous zeolites form an excellent and reammonia. liable means for reducing the ammonia content of the water The recent development of carbonaceous zeolites offers a to a very low amount, averaging in these tests 0.12 p. p. m. possibility for the Of ammonia' Ordinary PRESENTED at the 96th Meeting of the American Chemical Society, Milsilica zeolites have the property of base exchange (that is, they waukee. wis.
