Cold Lime-Soda Water Softening EXPERIENCES WITH SPAULDING PRECIPITATORS S. B. APPLEBAUM The Permutit Company, New York, N. Y .
T
HE art of cold lime-soda water softening is over a hunexisting large Springfield, Ill.,municipal lime-soda water softendred years old. Its history has been given in prior pubing plant, of older design, where these tests were conducted. Later a large-scale test (11) was made by installing a prelications (1, 2, 4, 6), and the contributions made by cipitator in one of the two existing mixing basins and thus Spaulding have also been discussed (4, 6-11). His aim in comparing the old and new processes with the same chemical developing the precipitator was a better utilization of the dosage. The results are given in Table I. sludge in promoting speed and completion of the reactions. Prexlous designers had appreciated the value of sludge but The precipitator design was then adopted for the new had failed to accomplish effective contact of sludge and water. Springfield plant a t a considerable saving in cost ($22,000 per The emphasis in many previous designs was on sedimentation million gallons instead of $30,000 t o $40,000 for earlier plants). It was put into operation in November, 1936. and on efficient means of removing the settled sludge. Spaulding proposed to put the sludge to work by avoiding its settling, by conditioning the sludge particles, by keeping all the sludge Experiences at Springfield, Ill. continuously in suspension with positive mechanical agitation This first large precipitator Dlant consists of three conand high uDward velocities. bv controlling the height and ciete units (Figures 1 and 2). d e n s i c y of t h e s u s p e n d e d " The capacity is 12 million galsludge by proper sludge blowlons per day (m. g. d.). As off, and finally by separating planned, the first two units the sludge from the water by were in parallel as the first decreasing the upward velocity Lime softening was discovered over a stage, followed by recarbonarather than by settling. Incihundred years ago, but the first large plant tion and passage through the dentally, this eliminated the was installed about fifty years ago. Imthird unit as the second stage. ex p e n si v e sludge-collecting The units are 68 feet in diamemechanisms. provements in design have been gradually ter a t the top, 44 feet 6 inches The efficient action of sand made since, but in the last decade progress at the bottom, and 24 feet 6 filters in removing hardness in this art has been more rapid. inches high. At 12 m. g. d. the from settled water after partial The Spaulding precipitator is so designed velocity a t the top is 1.25 recarbonation was much more that a positive mechanical agitator, operatgallons per minute per square than mere straining. Contact foot with 90-minute detention ing over the entire bottom of the tank, with the surface of the sand in the first stage and 2.5 gallons grains had a powerful effect in keeps the sludge particles suspended and per minute per square foot with stimulating completion of the prevents their settling out. After thorough 45-minute detention in the r e a c t i o n s . S p a u l d i n g (6) mixing of chemical, water, and sludge, the second stage. aimed to devide a suspended mixture rises upward through a suspended A minimum slope of 52" t o sludge filter in the settling basin the horizontal was found adsludge filter zone, so arranged that the to produce similar effects. visable to avoid sludge deThe first laboratory model upward water velocity continually deposits. To maintain this slope, consisted of a funnel hung in a creases. The height and density of the a simple funnel would have incylinder with an agitator at sludge filter are controlled by regulated devolved too high a tank. Therethe bottom. The water and sludging and the upward velocity. When fore, the design of one cone chemical mixed with retained inside another was adopted the water reaches a certain level, i t sepasludge, and the mixture rose (Figure 1). The same feature into the funnel. Clear water rates from the sludge and emerges clarified of decreasing velocity in the emerged at the top. The and completely softened. sludge filter zone was thus obconical funnel was selected to This design permits reducing the size t a i n e d w i t h lower h e i g h t . contain the sludge filter beof the settling tank from 3 to 6 hours of Vertical radial baffles in the cause, as the mixture rose, the sludge filter still the currents retention down to 1 hour, saves chemicals, upward v e l o c i t y d e c r e a s e d created by the agitators. After until i t was no longer able to and results in a softer, clearer, and more 3 months of operation, recarsupport the sludge particles. stable effluent. Frequently recarbonation bonation was found unnecesThus the water separated from may be omitted. Illustrations of various sary because excess lime was the sludge, and the effluent designs of precipitators installed and cheminot needed and the effluent was mas clear. The results obtained sufficiently stable. Table I1 cal results obtained are given. exceeded anticipation. I n 20 gives more recent results and minutes better results were proshows that the chemical effiduced than after 8 hours in the 678
1NDC'STRI.kL 4 S D EUGINEERING CHEMISTRY
MAY, 1940
TABLE I. COXPARISON O F OLD LIME-SODA PROCESS WITH K E n . SPACLDIKG PRECIPITATOR IN LARGE-SCALE TESTS AT SPRISGFIELD,
ILL.=
Carbonate Hardness as CaCOa 111 EWuent
Detention Period .Minutes
P.p . m.
...
R a w a-ater Old mixing basin Old settling basin
18i
io
46 481
64
-
Old total
Bpauldiria and Timrtnus i l l , Figure 21.
SLUDGE CONTAC FILTER W I T H SLOPING S I D E
FIGURE1.
DESIGSOF
THE
The next large municipal plant to adopt the precipitator design was Minneapolis. I n 1938, Jensen (S), of the Water Works Department, described their 4-year experimental work with models of the older design with rectangular basins and cylindrical clarifiers, as well as of the precipitator. The source of supply is the Mississippi River which is somewhat turbid and often highly colored ET as well as hard. In the past the city had merely clarified the water with alum and Gterilized it with chlorine but water softening had been under consideration for some time. As a result of the test work the precipitator design was adopted for t'he new plant, and twelve concrete units, having a combined AGITATORS capacity of 120 m. g. d. are now nearing completion. They are of the same general design SPRINGFIELD PRECIPITATOR PLANT
ciency is practically 100 per cent; i. e., the lime dosage is no greater than the theoretical dosage. The sludge is allowed to concentrate in the precipitator to 0.1-5 per cent by weight. The usual range is 1-2 per cent. This strength is maintained by blowing sludge from the precipitator either intermittently or continuously. The sludge is discharged into an external concentrator where the strength is increased to 5-15 per cent by quiescent settling. The decanted water is recovered, and water and chemical are thus saved. An external concentrator was used because it served three precipitators, but other plants are using internal sludge concentrator compartments with equal success. Two simple tests are made-(a) t o determine the sludge strength by weighing a definite volume, (b) to locate the top of the sludge by lowering a sampling thief. Successful results TABLE 11.
Experiences at Minneapolis
55
58
New precipitator total
can be obtained with a wide range of sludge depth, but the deeper and more concentrated the sludge, the more complete is the chemical reaction (7). However, the turbidity of the effluent increases slightly with increasing sludge density. Table 111 shows the effect of different concentrations and tlepths of sludge on the chemical results and turbidity. The results were better on August 24 than on September 6 because the sludge was more concentrated and deeper. The higher flow on August 24 caused the deeper sludge hed. This proves the value of t,he sludge filt'er.
..
527
679
AVERaGE
FIGURE 2. PHOTOGRAPH OF OSE
MONTHLYC ' H E M I C I L
-Sept., In
'38out
-Dec., In
PREClPlT \TOR O P E H ~ T I S GD '38--Out
-,Jan., In
Chemical D a t a , P. P. >I. Total hardness a s CaCOa 164 82" 176 80" 177 Ca hardness aa CaCOa 32' 107 35a 108 M g bardnesn as CaCOt 65 " 50' 69 450 09 M e orange alkalinity 119 38 131 38 129 Phenolphthalein alkalinity 0 20 0 19 0 Turbidity 19 5 11 1.6 12 Free COz as Cog 2 0 3 0 3 93% C a O fed 86 99 Alum fed 7 14 Copperas fed 0 ... 0 93% CaO required theoretically6 86 102 R a t i o of actual t o theoretical, 70 100 97 a Filtered; t h e other "out" figures represent precipitator effluent as applied t r , t h e filters. b Theoretical 83% CaO = (COz X 2.3 methyl orange alkalinity T Alg reduction hydrates 9 3 % with little variation, seldom exceeding 1 2 % .
... ... ... ... ...
+
... ... ... ...
... ... ... ... ...
+
'39Out 850 37" 480
39
20 1.0
0 102 13 0 09
103
OF THE
A T 4T ~
SPRISGFIELD CxIrs
SPRISGFIELD, ILL.
-Feb.. In 176 104 72 134 0 28 4
..: ... ... ... ...
'39--
Oit
.-.Ipr11, In
'39---
Out
83a 335 50a
38 18
1.8
n loo 12 0 103 97
+ 0.46 x a l u m fed) :%; lime a t Springfield averageh
INDUSTRIAL AND ENGINEERING CHEMISTRY
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VOL. 32, NO. 5
-
-
Perrnutit Exlleriences with Precinitators TABLE111. EFFECTOF SLUDOE DEPTWAND CONCENTRATION ox EFFLUENT C ~ X P O S ~ T AT I O SPRINGFIELD' N Height
of Sludge
Date
in 1938
Sludge Density S... bbuwt.
Filler
above Port
Ft.
2.4 8/24 9/5 5.5 Q/G 1.5 From Spaviding (7).
12 9 4
Rate of
Flow M.0.d. 10 7 7
-Effluent-Me Phenolorange Phthalein alkaaikalinity iinity P.o.m. P.P.m. 32 36 40
18 21
The Permutit Company recognized the merit of Spaulding's contribution in the precipitator design and obtained a license under his patent late in 1937. Since then research work has been carried out in the application of the precipitator to various waters and in the improvement of design for nen units as well as for the remodeling of existing scttling tanks. Illustrations will be given of designs installed during the last two years, as well as the chemical results and economies obtained. These economies met with such favor that up to September, 1939, a total of seventy precipitators had been installed or were under construction. They have a total capacity of 125,750 g. p. m., equivalent to 181 m. 6. d. Of these, fortythree are in the municipal and twenty-seven in the industrial field. Many are of large capacity, although a considerable number are for capacities as low as 5 gallons per minute (g. p. m.), which produces water of low alkalinity for the carbonated beverage industry.
Turbidity P.v.~. 2.6 9.5 2.0
as the Springfield units. The diameter is 85 feet at the top and 58 feet at the bottom, and the depth is 23 feet. Figure 3 shows the plant during construction. The rate will be 1.25 gallons per minute per square foot at the top when the total flow is 120 m. g. d. It is proposed t o reduce the hardness of the water from 170 down to 75 p. p. m. without using excess lime.
FIGURE 3.
MlNNEAPoLtS P L A N T UNDER
TABLEIV. Installation
A . Feigv Falls.
CONS'PRUCTION
CHEMICAL RESULTSOF PRECIPITATORS B. Woadstook, Ill.
C, Shelby. Ohio
Minn.
Rated OBmcity. g. P. m. Chemical a n ~ l ~ s ip. s i). m. Tots1 hardnes. 68 CeCDi CB hsrdneas aa CaCO, MLIhardness s8 CaCOs
Melhyl nranm alkalinity Phsnolphtlmlein alkalinity Free cos 8 s co,
Chemical dosa~eD. p. m.
93% lwdrafed'lime fed T@e"ret'asl lime requirements dl"m
Ferriaul [anhrd. Fa(SOd,]
2080
_-.Raw Treated 180 56 124
68 12 56 70
2s
120 80 0
_-_-
0
1300 _~~_______
2030
_L.____ liar Tresled Kar Treated 410 250
90 50 40 78 30 0
160
3s4 0
608 391 217 273 0
220 110 110 26 9 0
13 -~ 45
D. Ssniiaiium in
_--
Ohio
157
... 4
470 475
La
..
... ... ..
83
76
_ 1 -
Ears
Treated
270
67 26 41 166 75 0
193 77 375
0 20
A
157
E, Industrial Plant in Miah. Treated
Raw a17
0
62 22 40 84 50
23
0
136 101 290
I _
... ... ...
...
...
... ..
..
MAY, 1940
lNDUSTRIAL AND ENGINEERING CHEMISTRY
681
the existing three tanks t o the precipitator type, to gain both increased INLET WATER. capacity and improved results. With the cooperation of the purchaser and UPPER COLLECTOR OUTLET Stone & Webster, a design was finally COLLECTOR B O X evolved (Figure 4) of a double-deck sludge filter zone with a common mixing zone, which utilized the great VENT PIPES height of the tanks most effectively. L O W E R COLLECTOR Double-decking practically doubles the capacity obtainable from a single SLUDGE CONCENTRATOR POCKETS deck of the same area. Before remodeling, each tank was capable of SAFFLES __ softening GOO g. p. m.; as remodeled the capacity is 2000 g. p. m. One of the large tanks was remodeled and AGITATOR placed in satisfactory operation at the end of 1938. Since then the SLUDGE OUTLETS other two tanks have been likewise DRAIN. remodeled so that the three tanks together have a capacity of 6000 g. p. m. h G U R E 4. IIOUBLE-DECKER DESIGN AT BATONK O U G k After one tank was remodeled, it5 performance was compared with Table IV lists a few preciprtators, their capacities, and analythat of the other two unremodeled tanks. Table V gives the ses of the raw and treated waters. I n two cases the actual comparative results. Even though the remodeled tank and theoretical chemical dosages given are equal and thus handled three times as much capacity, its effluent was indicate 100 per cent efficiency. Cases A, D, and E show how superior. This installation also shows that precipitators can low the calcium may be reduced and thus approach the handle turbid water satisfactorily because the Mississippi theoretical solubility of calcium carbonate a t these temperaRiver a t Baton Rouge is one of our most turbid supplies. tures. Case C illustrates reduction in alkalinity, and case E reduction in magnesium with low hydroxide. Performance in any case depends on the aim of the treatTABLE b7. COMPARATIVE CHEJIICAL RESULTS O F A PLAIA m e n b i . e., whether maximum reduction is desired in alkaSETTLING TANK WITH A SIMILAR T A N K CONVERTED T O A PRECIPITATOR^ linity, calcium, or magnesium. Municipal precipitators are Effluent Effluent often not operated to produce the lowest hardness obtainable Raw of Plain of PreImprovebecause the desire is to save chemical. Table I V also shows Water Tank cipicaror ment, % equally successful results for small and large plants; cases ... 600 1800 200 Flow rate, g. p. m. 118 115 CaO fed, p. p. m. A, B, and C are twenty to thirty times as large as cases D and 10 IC1 Ferrisul fed, p. p. m. CITATOR
DRIVE
E.
Experiences with a few installations of special interest will be described in the following paragraphs.
Gulf States Utilities Company, Baton Rouge, La. An installation had been designed by Stone & Webster Engineering Corporation about ten years ago t o soften Mississippi River water for high-pressure boiler feed purposes. T h i s p la nt c on si st ed essenAGITATOR DRIVE tially of three vertical \ steel continuous lime treatment tanks, 34 feet in diameter and 50 feet high, followed by a number of intermittent batch system settling tanks, then by acid treatment, Anthrafilt (washed screened anthracite coal) filtration, and zeolite softening. Recently t h e capacity of the plant had to be increased. I n order to save the addition of a number of new lime treatment tanks, an investigation mas made of the possibility of remodeling FIGURE 5.
Chemical results. p. p. m. as CaCW 186 106 Hardness 1.14 49 Me orange alkalinity Phenolphthalein alkalinity 0 30 Caustic alkalinity 0 11 142 “2 Turbidity a
92 34 20 6 13
13
30 ...
...
11
Water a n d chemicals mixed in coninion mixer aheaa of both tanks.
OPEN FLUME 10 CARBONATION B A S I N
-4-l
I.
DESIGN OF THE WOODSTOCK PLANT
II
INDUSTRIAL AND ENGINEERING CHEMISTRY
682
Experiences at Woodstock, Ill. This plant is another example of the conversion of an existing lime-soda plant to the precipitator type. The original plant was installed several years ago for a capacity of one m. g. d. It consisted of a mixing chamber, 12 feet 6 inches square and 12 feet deep, followed by two clarifier basins 29 feet 6 inches square and by 15 feet deep, recarbonation, and filtration. Figure 5 shows how the capacity was increased to about 3 m. g. d. with a minimum of expense. Figure 6 is a photograph of the completed installation. A steel pyramidal funnel was inserted in each of the tanks, and an agitator was installed a t the bottom. This corresponded closely to Spaulding’s original laboratory model, except that the funnel was pyramidal rather than conical. The plant was put into operation a t the end of 1938; Table VI gives the comparison of the chemical dosage and other operating data which shorn the improvement obtained while handling the same raw water supply, despite the fact that the capacity was tripled. ECOSOVIE~ EFFECTED BY COSVERTING EXISTING \\-ATER SOFTENER TO SPAULDING PRECIPIT4TOR TYPE^
T 4BLE VI
Old Plant Rated capacitv, m. 6. cl Lime used. p. p. m. Alum used, p. p. m. Sludge blowoff, % Filter wash water, % 5
1 0 313 21 6 3
l f t e r Coriversion t o Precipitators
Saving
?’&
3 0
..
445
13 38
13 3 50 0.6 83 Same raw water used and same hardness removal accomplished.
I n addition, another economy which was welcomed in thi? plant was the abandoning of the original recarbonation. The recarbonation equipment was difficult to control and required considerable attention. Instead of recarbonating, the precipitators are operated by split lime treatment, as described later in this paper.
Experiences a t Fergus Falls, Minn. A municipal installation of a new precipitator plant was designed by Joseph E. Young, of the Water & Light Commission, with the advice of Spaulding, and was installed in 1938. It consists of two cylindrical concrete precipitators with inner steel double cones; top diameter of the cylinder was 32 feet and the depth about 11 feet. The two units are connected to operate either in parallel or series. They handle a river supply which reaches freezing temperatures. Its composition is unusual in its high magnesium content compared to calcium. It v a s necessary to reduce the magnesium to a low figure in order to obtain an effluent of the desired hardness of 4 to 5 grains per gallon. Since the permissible upward velocity is lower at freezing than a t higher temperatures, the units were each rated at 1.5 m. g. d. in winter and 3 m. g. d. in summer. When the units are operated in parallel in summer, the available capacity is 6 m. g. d. Table IV gives the analyses of the raw and treated water and the chemical dosage required. The plant has been operated with the two precipitators in parallel during the winter and with recarbonation ahead of the filters. During the past summer the plant has been using split lime treatment; the two units operate in series and omit recarbonation. The chemical results in Table IV are representative of this operation; in this case alsq the
VOT,. 32, NO. 5
actual lime dosage is equal to the theoretical, which demonstrates perfect utilization.
Available Precipitator Designs Thus the following precipitat’or designs are available to suit varying space conditions for new installations as well as to permit remodeling of existing tanks of various proportions : 1. The Springfield design (Figure 1). 2. The Louisiana double-deck design (Figure 4).
3. The Roodstock design of square outer tank with vertical walls and inner pyramid (Figure 5 ) . 4. Cylindrical outer tank and inner cone, either as a simple funnel or as a double cone, such as used at Fergus Falls. a. Rectangular outer tank with vertical walls, the agitator shaft being horizontal instead of vertical and permitting installation in long narrow basins (Figure 7). Two such installations have been designed. One is in operation and the other under construction.
Permissible Detention Period and Upward Velocity The precipitator large-scale tests a t Springfield, Ill., indicated better results in 20 to 30 minutes than with the older designs of several hours’ detention. Nevertheless, it is good practice to recommend a detention period for precipitators of not less than one hour, to have a reasonable factor of safety. Of this one hour, at least half should be devoted to contact with sludge. The permissible velocity a t the top of the precipitator is affected by temperature and composition of the sludge. At, freezing temperatures a velocity a t the top of 1.25 g. p. m. per square foot has been found correct for the average sludge containing the usual proportions of calcium and magnesium. A great many municipal plants use more water in summer than in winter. Consequently the units may be designed for a smaller winter capacity a t the lower flow rate per square foot, and the same units can fortunately handle the greater capacity required in summer with ease. This results in economy of investment, The higher the ratio of calcium to magnesium in the sludge, the higher the permissible rates of flow. Calcium carbonate precipitates in the sludge are more crystalline and heavier than the magnesium hydroxide precipitates. If t,he sludge consifits of calcium carbonate alone, as in the
MAY, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
683
enters the first stage. The effluent of the first stage therefore contains considerable hydroxide excess which accomplishes good magnesium removal. A portion of the raw water is by-passed around the first stage and enters the second stage. The carbon dioxide and bicarbonate present in this by-passed raw water converts the excess hydroxide in the effluent of the first stage into carbonate. Consequently, less lime is employed than with single-stage treatment, in which excess lime is added to all of the water and the excess is neutralized by recarbonation. Split lime treatment is particularly effective with precipitators because of the efficient removal of calcium carbonate in the second stage. Even for single-stage treatment i t is frequently desirable to use two precipitator units for greater flexibility, interconnected to operate either in parallel or in series. This will take care of varying raw water compositions. FIGURE7. HORIZONTAL AGITATORDESIGN
-4daptability to Variable Rates of Flow second stage of split lime treatment plants, then a rate of 2.5 g. p. m. per square foot and a detention period of 30 minutes may be employed. Further data are being collected on the effect of various sludge compositions on this permissible velocity. The area at the top of the sludge filter where the water separates from the sludge is much less than the area a t the top of the precipitator where the water is finally drawn off. This is due to the sloping sides of the clear water space above the sludge. An additional factor of safety to prevent sludge carry-over is thus provided by the Spaulding design. This was discussed in a recent paper by Klassen and Spafford (4). A sharp line of demarcation separates the top of the sludge filter and this clear water. With sludge filters using vertical instead of sloping sides, this factor of safety of further decreasing the velocity above the sludge is lost.
The question has often been raised a s to whether precipitators must be operated at a constant flow rate (4). The answer is negative. Figure 8 shows the behavior of the sludge filter a t various flow rates. Because of the sloping sides more particles, and consequently more spaces between the particles, are present in each successive layer from top to bottom of the sludge filter. The sum of these spaces determines the over-all upward velocity which decreases as the water rises. When the flow increases, the sludge rises, but it
Single-Unit us. Double-Unit Plants To determine whether single-stage or two-stage split lime treatment is preferable, a study must be made of the raw water and treated water analysis desired, as well as the chemical costs involved. If the raw water contains a high amount of magnesium which must be reduced to a low figure to obtain a desired low total hardness, then excess lime may be required. The amount of this excess lime required is much less with precipitators than with the older plants because of the greater efficiency of the precipitator design. Nevertheless, some excess lime may be required, in which case two-stage split lime treatment is recommended. However. it is possible to use a single-stage precipitator even in such cases if one of the three following operating methods are employed : Recarbonating the excess hydroxide to bicarbonate. This results in an effluent of greater carbonate hardness than can possibly be obtained by the two-stage method. Employing soda ash with the lime to offset this increased carbonate hardness. Recarbonating the excess hydroxide to carbonate and precipitating this carbonate on the filter sand. This has been common practice in some plants but has resulted in increased maintenance cost due to incrustation. It is thus usually a question of balancing extra investment against extra operating cost. The split lime treatment not only saves the extra soda ash just mentioned but also saves lime. I n the split lime treatment, a portion of the raw water, together with all the lime,
BEDA T VARIOUSFLOW RATES FIGURE8. SLUDGE comes to rest a t a level such that the lower upward velocity no longer supports the sludge particles at the higher flow. When the flow decreases, the sludge recedes, but owing to the funnel shape, equilibrium is again restored at a slightly reduced level. Thus there is always present a considerable depth of sludge to accomplish the desired contact between sludge and liquid.
Sludge Recirculation Approximately the same strength of sludge exists in the mixing as in the sludge filter zone. This is due to the fact that the sludge not only rises from the mixing into the sludge filter zone but also returns in the reverse direction, especially the larger particles. As the small particles agglomerate into larger ones, they are able to fall through the stream rising into the port entrance of the sludge filter zone. That a free interchange of sludge between the zones takes place is evident from a simple example. Assume a plant capacity of 100 g. p. m. precipitating 20 grains per gallon of solids, or 100 x 20 = 2000 grains of solids each minute. This is blown off either continuously or intermittently from the sludge concentrator. But since the sludge in the mixing zone has a strength, for example, of 1.5 per cent by weight or 15,000 p. p. m. or 870 grains per gallon, the solids rising through the port would be 100 X 870 = 87,000 grains per minute, or over forty times
IXDUSTRIAL -4ND ENGINEERING CHEMISTRY
684
VOL. 32. NO. 5
as much as is precipitated. Unless there was a considerable circulation of sludge downward through the port, the mixing zone would soon lose most of its sludge. Since the mixingzone sludge does not decrease in strength, this recirculation of sludge must take place.
tor design is applicable for this purpose in such cases, but instead of lime or soda ash, such coagulants as alum, copperas, or Ferrisul are employed.
Distribution of Mixed Water into Sludge Filter Zone
Behrman, A. S., and Green, W. H., ISD. ENG.C H E M .31, , 128-33
Another feature of the precipitator design is the uniformity of distribution of the mixed water into the sludge filter zone. I n all of the precipitator designs described, sludge filter bottom port opening is of relatively small area, usually about one twelfth of the area of the top of the tank. Whether this port consists of the apex of a single funnel or the annular shaped port in Figure 1, it effects a uniform distribution of the mixed water into the sludge filter zone, with the aid of the agitator. Thus, channeling and short-circuiting through the sludge filter are avoided. Most of the precipitator installations have been made for lime-soda water softening. Some plants, however, have been installed for the removal of turbidity and color from surface supplies where softening is not needed. The same precipita-
Literature Cited (1939).
Hoover, C. P., “Water Supply and Treatment”, pp. 82-86, Washington, D. C., Natl. Lime Assoc., 1936. Jensen, J. A., J . Am. Water W o r k s h s o c . , 30, 1847 (1938). Klassen, C. TI’., and Spafford, H. A , , Ibid., 31, 1734 (1939). Sheen, R. T . , Beta, W. H., and Betz, L. D., Maryland-Delaware Water Works and Sewerage .4ssoc., Cumberland, Md., May, 1939.
Spaulding, C. H . , J . Am. Water W o r k s Assoc., 29, 1697 (1937). Spaulding, C. H., Ohio Conf. Water Purification, Ann. Rept. 18, 52 (1938).
Spaulding, C. H., 8 0 . Dak. Water & Sewerage Conf., Watertown, S. Dak., Sept., 1938. Spaulding, C. H., 27th Ann. Meeting, S. W. Section, Am. Water Works Assoc., Oct., 1938. Spaulding, C. H., Water W o r k s & Sewerage, 85, 153 (1938). Spauldinp, C. H., and Timanus, C. S., J. Am. Water W o r k s Assoc., 27, 326 (1935).
PRESENTED before the Division of Water, Sewage, and Sanitation
Chemistry
at the 98th Meeting of the American Chemical Society. Boston. Mass
COAL BY-PRODUCTS Yellowing of indene-coumarone is attributed to the development of a highly unsaturated molecular structure, representative of a class of compounds known as fulvenes. Hydrogenation prevents the formation of these highly colored bodies in the resinous mass by preventing a series of reactions beginning with entry of oxygen and its expulsion later as water. Bleaching with hydrogen destroys the fulvene originally present, which results from process operation. Influence of pressure, temperature, catalyst concentration, time, completeness of reaction, distribution of hydrogen have been determined. Water-white resin is now produced on a small scale with operating conditions of 1000 pounds per square inch pressure, 200” C. (392’ F.), 70 per cent resin concentration, and a cycle of 20 hours. F T H E most recent advances in the chemistry of synthetic resins, the theoretical studies applied to indenecoumarone polymers have been highly successful in originating new and modified polyindene resins. This paper is concerned entirely with practical developments, specifically with the influence of the factors involved in the introduction of hydrogen by metallic catalyst into the resin polymers a t a multitude of points in the molecule. Commercial resin of today can be produced in standard grades with very pale color. This initial color is intriguing, but despite the apparent visual perfection, these resins are
0
1 The
fint paper in this aeries appeared in April (f).
The Hydrogenation of Indene-Coumarone Resins’ WILLIAM H. CARMODY, HAROLD E. KELLY, AND WILLIAM SHEEHAN Carmody Research Laboratories, Inc., Springfield, Ohio
undependable as to color stability. The development of dark color is attributed to the formation of a fulvene structure throughout the mass ( I ) . This color behavior and other minor characteristics have been noted in these resins, but there was no coordinating theory until recent study revealed the simple interrelations. The foregoing explanation deals with the role of the double bond and the methylene group in the indene polymers. The remaining portion of these resin molecules is apparently immaterial to the development of fulvene structure and takes part in secondary roles during hydrogenation. Owing t o the number of aromatic rings in the structure of these resins and to the certainty of their saturation, other aspects enter into the problem besides that of mere hydrogenation of the solitary alkene linkage in the terminal indene unit of the polymer. The numerous possible points of hydrogen entry bring about a complexity of reactions. Based on the number of indene units (each having an aromatic nucleus) in one mole weight of the commercial grade of resin, it is possible to introduce, on an average, 42 atoms of hydrogen. Study of the situation has permitted the distribution of the hydrogen to be determined, and it is definitely known t o react in the manner described in the following paragraphs.
