INDUSTRIAL AND ENGINEERING CHEMISTRY
1290
Summary The preparation of picric acid by simultaneous oxidation and nitration of benzene (the ~F701ffenstein-Botersreaction) has been investigated over a series of several hundred experiments. The procedure involved tho reaction of benzene with a nitric acidcatalyst mixture, separation of the product from the cooled reaction mixture, and make-up of the latter to serve as the reaction liquor for the next run. The reaction was tested on two scales, the first in glass apparatus using 100 grams of benzene per run, and the second in metal equipment using 1250 grams of benzene per run. The main results obtained may be summarized as follows: The yield of picric acid of satisfactory setting point consistently obtained was 1.5 parts from 1 part of benzene (a 50% yield).. The consumption of nitric acid was 1.68 parts of nitric acid per part of picric acid produced in the small scale runs, and 1.44 parts of nitric acid per part of picric acid in the larger scale runs, The difference may be attributed t o a more efficient fume-recovery system in the latter case. The optimum amounts of the catalyst metals were 0.28 mole of mercury, 0.015 mole of manganese, and 0.005 mole of aluminum, for reaction with 100 grams of benzene. The mercury concentration was somewhat critical; amounts below that specified necessitated a longer reaction time, and larger amounts increased the inorganic salt content of the reaction mixture to a point where concentration by distillation was interfered with. The by-products of the reaction included significant amounts of dinitrobenzenes as well as the nitrobenzene previousIy known to be produced. The dinitrobenzenes, if allowed to accumulate in the reaction liquor, contaminated the product, lowered yield and setting point noticeably, and when separated after each run carried with them a substantial quantity of mercury. Avoidance of these difficulties constituted the most troublesome part of this investigation. The evolution of oxides of nitrogen was not a t a uniform rate, but relatively high toward the end of each run. This necessitated a fume-recovery system of a size out of proportion to the reaction vessel. This might in practice be dealt with by having one fumerecovery system common to two or more reactors. Corrosion troubles were encountered with the Duriron equipment used for the larger scale work, and stainless steel would apparently have been much more satisfactory. LITERATURE CITED (1)
Badische Anilin- und Soda-Fabrik, Ger. Patent 153,129 (Feb.
(2)
Bamberger, E., Ber., 30,506-14 (1897).
27, 1903).
Vol. 40, No. 7
(3) (4)
Blechta, F., Chem. L i s t y , 14,161-5 (1920); 1 5 , 60 (1921). Blechta, P., and Patek, I C , 2. gee. Schiess.- undSprengstofw., 22,
(5)
Boters, O., and Wolffenstein, R., U. S. Patent 923,761 (June
314-7 (1927).
1, 1909). (6) Brewster, T. J., Brit. Patent 131,403 (June 26, 1918); 1,380,185 ( M a y 3 1 , 1921). (7) Broders, unpublished work at the arsenal of Saint-Fons, France, during 1916, cited by Desvergnes (13). (8) Carmack. M., J . Am. Chem. SOC.,69, 785 (1947). (9) Davis, T. L., Ibid., 14,1588-91 (1922). (10) Davis, T . L., U . S. Patent 1,417,368 (-May23, 1922). (11) Davis, T. L., Worrall, D. E., Drake, N. L., Helmkamp, R. W., and Young, A. M., J. Am. Chem. SOC.,43,594-607 (1921). (12) Debourdeaux, Compt. rend., 136,1668-9 (1903). (13) Desvergnes, L., Chimie Ce. industrie, 22,451-61 (1929). (14) Dhar, N., J . Chem. Soc., 111, 694-6 (1917). (15) Divers E , Ibid., 75,82-3 (1899). (16) Farbenfabriken vorm. Friedr. Bayer & Co., Ger. Patent 161.954 (17) (18)
(March 19, 1904). Jorisben, W. P.,Z.angew. Chem., 12,521-5 (1899). Jorissen, W. P., and Reicher, L. T., 2. physik. Chem., 31, 14363 (1899).
(19) (20) (21) (22) (23) (24) (25)
Macdonsld, D. B., Brit. Patent 17,525 (Dee. 15, 1 9 1 5 ) ; 126.675 (Dee. 15. 1915). Macdonald, D. B.', and'calvert, J., Brit. Patent 126,062 and 126,084 (Dec. 4 , 1916). Marshall, A,, "Explosives," Vol. 111, p. 80, London, J. & A. Churchill, 1932. Prochaaka, J., Chem. Listy, 15, 59-60 (1921). Rarny, P., Biit. Patent 125,461 (Aug. 12, 1916). Reid, H. S.,and Lodge, W. C., private communication concerning secret research in 1916-18. Smith, L. I., and Taylor, F. L., J . Am. Chem. SOC.,57, 2460
(1935). (26) Vignon, L.. Bzdl. soc. chim.. 27, 547-50 (1920), (27) Villiers, A., Compt. rend., 124, 1349-51 (1897). (28) Westheinier, F., J . Am. Chem. Soc., 69, 773 (1947). (29) Wolffenstein, R., and Boters, O., Ber., 46, 586-9 (1913). (30) Ibid., 589-99 (1913). (31) Wolffenstein, R., and Boters, O., Ger. Patent 194,883 (Aug. 4 , 1906); 214,048 (Aug. 21, 1907); French Patent 380,121 (July 22, 1 9 0 7 ) ; Brit. Patent 17,521 (July 31, 1907). (32) Zakharov, A . I., J . Chem. I n d . (U.S.S.R.),4, 960-4 (1927); 5 , 2 6 - 7 (1928); 6 , 698-9 (1929); 8, 30-7 ( 1 9 3 1 ) .
RECEIVED January 21, 1947. This work (carried out a t the request of t h e National Research Council of Canada) was a joint effort of the Departments of Chemistry and Chemical Engineering of the University of Toronto, with some aid from the Ontario Research Foundation and the Bciioo of Engineering Research, University of Toronto. The work represents the Ph.D. dissertation of D. C. Downing.
Variations in B.O.D. Veflocitv Constants of Sewage Dilutions J
C. C. RUCHHOFT, 0. R. PLACAIC, JOHN F. ICACHNIAR, rlND C. E. CA4LBERT U . S. Public Health Service, Cincinnati 2, Ohio
I
N A R E C E N T study (1) of the biochemical oxygen demand (B.O.D.) of sewage from military areas, in which this laboratory cooperated, it was found that the mean velocity constant was considerably higher than the value of 0.1 a t 20' C., which is generally accepted for domestic sewage. I t was also noted that the K values for military sewage dilutions varied considerably. These findings were not in agreement with the generally accepted theory t h a t the 5-day B.O.D. is directly proportional t o the strength of the sewage. Also, although military sewage might be stronger than domestic sewage, on the basis of the general theory of biochemical oxidation there should be no essential difference in the rates of biochemical oxidation of domestic or military sewages. To determine the causes of the high K values and the
variation in these values, a n intensive study was made of some of the factors that might be involved, such as time of storage, condition of storage, dilution water, and application of blank corrections. Some of the more important data and findings are assembled in this report. In this study the B.O.D. a t 20" C. of fifty-nine samples of domestic, military, and hospital sewage was measured daily over a period of 10 days. The domestic sewage used was a Cincinnati sewage originating from a densely populated section of the city. It was essentially free of industrial waste, had a 5-day B.O.D. of approximately 450 parts per million (p.p.m.), and was received in a fresh state. The hospital sewayes were obtained from two sources, the C. S. Public Health Service Narcotic Hospital,
.
July 1948
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Variations in the magnitude of biochemical oxidation reaction-velocitv constants of sewage dilutions were studied and are discussed. Determination and interpretation of these constants are important in sewage and industrial waste disposal. At the present time all sewages, effluents, industrial wastes, and pollution in streams are measured on the basis of 5-day biochemical oxygen demand on the assumption that this is proportiohal to the total strength of the waste. K (the reaction velocity constant) is commonly accepted as being 0.1. This study of fifty-nine sewage samples on which daily biochemical oxygen demand observations were made gave K values from 0.04 to 0.29 with a mean closer to 0.15 than the accepted value of 0.1. The importance of minimal amounts of nitrification as a cause of deviations in K is shown, and an improved technique for interpreting velocity constants is indicated. The fallacy of applying blank seed corrections in the conventional manner is demonstrated.
-
Lexington, Ky., and the U. S. Army Convalescent Hosptial, Fort Thomas, Ky. The military sewages were obtained from five posts in the East Central States area during the course of studies of military sewage treatment plants. The majority of the samples were obtained from the Lookbourne Army Air Base, Columbus, Ohio, and the others from Camp Atterbury, Ft. Benjamin Harrison, and Baer Field, Ind., and the Erie Proving Grounds, Lacarne, Ohio. I n all but thirteen of the samples Theriault-Nichols (3) water was used t o prepare the sewage dilutions; formula C water was used for the remainder. I n al1,cases the distilled water that was t o be used for dilution water had been stored for a t least 5 days at room temperature. The carboys were then transferred to the 20" C. incubator, and stored for at least 2 days more t o bring the temperature t o 20" C. and satisfy any demand. At sometime during storage in the incubator all of the mineral salts required t o prepare the dilution water, except the ammonium sulfate, were added from two solutions. The ammonium sulfate was not added until the day the water was used. These details may be considered pertinent in view of the nitrification data which are discussed later. The alkaline-azide modification of the Winkter procedure was used throughout in the determination of dissolved oxygen t o counteract the effect of nitrites. All samples were water-sealed and run in duplicate in each dilution. The constants for the formulation of the unimolecular reaction were derived using the slope method proposed by Thomas (4, which is based on a least squares treatment of the differential equation of the reaction I n certain cases the results were checked by the method of least squares@), although this was too tedious a procedure to be used on all samples. Whenever possible each 10-day series of B.O.D. data was analyzed by three applications of the Thomas dope method, a s follows: method A, using data for the first 7 days, observed at 1-day intervals; method B, using all 10 days; and method C, using 10-day observations at 2-day intervals. These three methods of calculation were used because it was desirable t o obtain as fair a statistical comparison as possible, and t o accomplish the following results: (a) show that the same statistical trends are present, regardless of the method of computation; (6) minimize any effects due t o nitrification by using data covering the first 7 days only; and (c) minimize any possible effects due t o the use of the Thomas slope method. It can be shown, using equal time intervals, t h a t the slope method might appreciably affect K where slight errors of observations occur in certain values of y. Our three methods of calculation will tend to counteract any such effect by causing different observations t o assume these important values.
1291
The constants derived by the three procedures from all data that was complete for 16 days are shown in Tables I, 11, and 111. The values given in Tables I, 11, and I11 are in pairs of dilutions except for the first and last series in each table. If for simplicity we compare the mean, maximum, and minimum values of K and L in each series, we find t h a t the statistical trend is the same for all classes of sewage. This is demonstrated by the similar vaIues obtained for the root mean square deviation obtained for the series by each method of calculation. Specifically limiting our observations t o those calculated by method A (Table IV) as being presumably the most reliable data, and studying these trends, we find: @) There is a wide variation in K values obtained through the incubation of numerous sewage dilutions. The minimum and maximum K values of the Cincinnati sewages examined were 0.074 to 0.230, the hospital sewages were 0.055 to 0.223, and the military sewages were 0.053 t o 0.213. The similarity in the range of variation is evident. (6) There is no essential difference in the mean K value regardless of the source of the sewage. The mean K values obtained for Cincinnati, hospital, and military sewages, in that order, are 0.152, 0.169, and 0.143. (c) Referring t o the pairs of dilutions, in general the lowest concentration gives the lowest K value. One other thing is apparent-namely, that mean results obtained by method B are similar for all classes of sewages, but are lower than the other mean values. The inclusion of some nitrification could conceivably cause this effect. Table IV is a summary including samples from all sources which were run in two dilutions. K values were derived for the data through the first 7 days. The similarity between the maxi'mum, minimum, and mean of sewages from various sources is apparent. The mean K value of all samples is 0.149. From the preceding data it seems unwarranted t o assign a constant K
TABLEI. COMPARISON OF B.O.D. REACTION VELOCITYCONSTANTS CALCULATED FOR TENSAMPLES OF CINCINNATI SEWAGE A, Based on 1-Day Intervals
conon,, for 7 Days Series 4 19 20 21 22 37 38 39 40 58 Mean Max. Min. u
% '
.. ..
,.
..
K
0.074 0.177 0.188 0.155 0.230 0.126 0.151 0.084 0.184 0.147 0.152 0.230 0.074 0.048
B , Based on 1-Day Intervals for 10 Days
K
L
680 672 654 735 697 578 521 712 47 1 642 636 735 471
L
0.093 0.140 0.169 0.153 0.205 0.116 0.147 0.091 0.106 0.077 0.130 0.205 0,077 0.042
. ..
C, Based on 2-Day Intervals for 10 Days
L
K
639 744 684 698 683 590 524 667 594 893 672 893 524
0.082 0.153 0,238 0.182 0,229 0.147 0.191 0.111 0.158
533 728 643 673 687 535 486 644 590
0 166 0.238 0.082 0 051
613 728 486
...
.. .
..
...
TABLE11. COMPARISON OF B.O.D. REACTION VELOCITY CONSTANTS FOR TENSAMPLES OF HOSPITAL SEWAGE A , Based on 1-Dav Intervals conon.,for 7 Days
Source and Series
%
B,Based on 1-Dav Intervals for 10 Days
K
L
0 . 2 3 3 179 0 . 1 2 6 266 0 . 1 5 8 160 0 . 0 5 5 725 0 . 2 2 2 268
0.017 0.087 0.147 0.040 0.205
735 271 166 921 280
0 . 2 0 4 674 0 181 660 0 179 743 0 176 735
0 . 1 7 7 708 0 172 675 0 179 743 0 178 730 0 107 344 0,131 0.208 , 0,017 .. . 0.065
K
L
C, Based on 2-Dav Intervals for 10 Days
K
L
U.S.P.H.S.Hasp.,
Lexington, K y . 8 51 53 55 56 U. S. Arm-.y u--ILVUIJ., Ft. Th,"mas, . Ky.
1/z
1 z/;
40
26 27 28 31
Mean Max. Min. .a
1 z/; /a
. .
. ,.
0.169 0,223 0.055 0.053
,
,.
..
., ., .. .. . .. .
.... . .. .
0 . 1 3 3 303 0 . 1 4 6 227 0 . 1 2 1 184 01232
274
0.199 0.197 0 189 0 196 0.119 0.170 0.232 0,119 0.041
697 667 754 740 341
.
. .
INDUSTRIAL AND ENGINEERING CHEMISTRY
1292
Vol. 40, No. 7
A few of thc niany types of curves obtained iii the incubation of raw 01 priinary sewage dilutions are shown in Figure 1. Those to the left, of the figure are norinal unimolecular type curves. -4v Nos. 31 and 28 represent a first stage only. Nos. 8 and 14 have t y 1-Day On B, Based 1-DayO n C, Based 2-DayO n Intervals Intervals Intervals second st,age with definite point,s of inflection. The curves t,o the conon., for 7 Days for 10 Days for 10 Days right represent some of the unusual types encountered. No. 5: Source and Series % K L K L I, shows nitrification only, and 10, although appearing t o represent. Lockbourne A.4.F. Base a first stage unimolecular reaction, does not actually do so but, can 41 '/z 0.053 412 0,109 260 0.101 284 best be represented by a straight line after the fifth day. In 42 1 o.ijs 241 0.122 273 0.176 246 curve 2, the third-day point seems to follow a different trend. 47 46 44 1 0.166 245 0.113 284 0.131 281 This can be attributed t o analytical error. It may also be a point 2 Ft. Benj. Harrison of inflection because it happens frequently enough t o appear 33 */z 0.103 236 0.123' 210 0.136 208 34 I 0.157 205 0.160 203 0.158 205 significant, and after this point the curve follows a straight line Camp dtterbury formulation. A similar effects is seen in No. 37 where two 36 ;Ip reasonable curves may be drawn by disregarding certain points. When data obtained from two dilutions of ten sewages are Baer Field 1 '/z 0,134 800 0,022 2755 .. . , ,. presented, as in Table VI, some interesting conclusions may be, 2 I 0.155 759 0.136 809 ... .. noted. The lower concentration gives the lowest K value in Erie P.G. 10 I 0 , 0 6 6 348 0.111 245 0,111 249 most, cases. The only instances where this is not true are series Mean .. 0.143 ... 0.129 0.154 ... 49-50, where higher dilutions were used, and 25-2.6, and 27-28, hlax. . .. 0.213 ., ,, .. 0.174 ,. 0.101 0.277 .... ., where no evidence of nitrification was apparent. It is significant, Min. . 0.053 0.022 .. a .. 0.049 . . 0.041 . . 0.050 also that the coefficient of variatiorv is greater in the lowest concentration. These dat'a suggest' that variation in TABLE Iv. i 7 A R I A T I O N S I N ITALUES O F K AND L FOR DIFFERENT TYPES OF SEW.4GES may be attributed t o incubation conK Values Based on I-Day Intervals No. for First 7 Days L Values centration and nitrification. The data of Concn., Source Samples % Max. Min. Mean u Cva Max. Win. presented in Tables VI1 and VI11 were Cincinnati 14 1/g& 1 0.230 0,074 0.156 0.044 2 8 . 2 735 290 obtained t o study these factors. Hospital 11 Same 0.223 0.065 0.168 0.059 3 8 . 1 743 160 Lockbourne A.A.F. base 12 Same 0.293 0.040 0.137 0.040 29.1 664 208 Daily B.O.D. determinations €or Baer Field, Erie P.G.. F t . Benj. Harrieon, 11 Same 0.213 0.053 0.143 0.049 34.0 800 128 10 days of a series of dilutions of Camp Atterbury the same sewage are shown in Tabla ,411 samples 48 Same 0.293 0.040 0.149 0.056 37.6 800 128 VII. These dilut,ions range from 5 Coefficient of variation = = .mean 0.2% t g 2.6%. Kitrite determinations were made daily, and some of these dat'a are shown in Table IX. The data fall into two classes, one value t o sewage dilutions, but if the mean of a large number of that is completely consistent', and q#nother composed of insamples is a correct statistical measurement, and for routine consistent data. All of the cohsistent data are shown above work such a figure is desirable, these data indicate that the value the rules. Theoretically all data should be the same exof 0.15 is more nearly correct than the commonly accepted value cept for dilution factor difference. .From these data it ie of 0.10. plain that there is a limiting 1-oncentration above which alii I n Table V these same conclusions are arrived at independent data are consistent, and below which they are not. For t,his of any curve-fitting procedures. Thirtyone samples, free from nitrification or with nitrification a t a minimum, a$ judged by the plotted results, were used for this comparison. The maximum, minimum, and mean ratios of the 3- t o a-day, 5- t o a-day, and 5- to 7-day observations are shown in the left-hand side of the table. The right-hand side shows those theoretical ratios comparable t o the experimental means, The variations in K are again apparent in the range of ratios. The mean experimental ratios are significant. The 3- t o 2-day mean ratio of 1.289 correrponds t o a K of 0.15; the 5- t o 3-day ratio of 1.254 is equivalent t o a K of approximately 0.16; this confirins the conclusions reached by the Thomas slope curve-fitting procedure. The 5- t o 7-day mean ratio of 0.871 corresponds to a K of 0.12, still higher than 0.1, 0 but lower than the other ratios. It 2 7 6 8 I O 0 2 4 6 8 will be shown later t h a t this is due Time in D u p t o a slow nitrification which becomes Figure 1. Experimental Data on a Series of Sewages Illustrating Variation# significant after the fifth day. in the Form of Curves Ohtained
TABLE 111. COMPARISON OF B.O.D. REACTION VELOCITYCONSTANTS FOR TWELVE SAMPLES O F MILITARY SEWAGE
:,%g::;
::::;i!g
z:; z::',;
~:~~~z:i
z; ::;
:zi
z:;: :$:
..
.
.. .
'
1 1 1 1 1 1 1 1 1 1 1 ~
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1948
TABLE V. Ratio of B.O.D. 2 day 3 day 5 day 7 day
--
TABLE
Source and Series Military 41-42 45-46 47-48
49-50
particular sewage the limiting concentration is between 1.0% and 1.4%. Below this point the data are unduly affected by nitrification, and, in the lowest concentration by another factor, apparently seeding, which permits the data t o fall intoa random pattern. These data are plotted in Figure 2. The curves of concentrations from 2.6% to 1.4% are similar in appearance, are unimolecular in form, and have
VARIATIONSIN RATIOSO F DAILYB.0.D. AND COMPARISON WITH THEORETICAL RATIOSFOR DIFFERENT VALUESOF K
Experimental Data (31 Samples)
Av.
Theoretical Ratios for K Value of 0.12 0.15 0.17 0.20
Max.
Min.
Mean
deviation
0.10
1.717
1.145
1.289
0.078
1 352
1.327
1.293
1.273
1.65
1.07
1,254
0.088
1.371 1.333
1.274
1 , 2 4 3 1.20
0 969
0.679
0.871
0 065
0.854
0.903
0.918
VI.
COMPARISON O F
Concn.,
%
K
0.875
VALUES FOR T W O
SEWAGE
& 1
& 1
0 053 0.059
0.159 0 180
0.109 0.088
0.122 0.174
0,101 0.250
1/z& 1 1& 2
0.130 0.166
0.293 0.155
0.157 0.155
0.153 0.160
0.130 0.185
1/z 1/z
1.244
K and L values t h a t are in very good
0 937
DILUTIONS I N TENSAMPLES
K Values for Low and High Concn. 1-Day inter1-Day inter2-Day intervals, 7 days Val& 10 days vals, 10 days
Comments
0.176 0.277
Points slightly erratic Slightly erratic nitrification 10th day 0.160 Same 0 184 Nitrificationbegan about 9th day
0.126
0.151
0.116
0.147
0.147
0.191
39-40
0.084
0.184
0.091
0.106
0.111
0.158
19-20
0.177
0,188
0.140
0.169
0.153
0.238
0.204 0.179
0.181 0.176
0.177 0,179
0.172 0.178
0.199 0,189
0.197 0.186
........ ............
0.103
0.157
0.123
0.160
0.136
0.158
l%nitrificationlOthday
Military 33--34 Mean Max. Min. 0.
CY
1/2
& 1
.... ....
agreement. The plot of the 1% data shows definite nitrification and a trend t o a lower K and higher L. All concentrations below 1% do not follow a unimolecular pattern and are greatly affected by nitrification, as denoted by the heavy black points. Small amounts of nitrification may have a greater effect on K values than is Ordinarily This is true particularlv in lower concentrations. Bv actually determining the nitrite nitrogen values along with the daily B.o.D., it is possible t o eliminate those data which should not be included in the consistent group, even though such selection is not very apparent by inspection or by plotting. I n other words, what could be called marginal nitrification m a y s t i ~ ~ b e s u f f i c i e n t f o at~beecKt
OF
Cincinnati 37-38
Hospital 25-26 27-28
Slightly erratic nitrification 9-10th days 1/z% erratic, 1% nitrifyjng 8-9th days Nitrificationbegan7-8th days
..............
0.128 0 , 1 8 2 0.135 0.154 0.160 0.192 0.204 0.293 0.179 0.178 0.250 0.277 0.053 0 , 1 5 1 0.091 0.106 0.101 0.158 0.053 0,041 0.032 0.024 0.046 0.038 41.4 22.5 23.7 15.8 28.8 19.8
1293
value greatly. A method for deciding which data should be included andwhich not used because of nitrification, is illustrated in
..............
.............. ..............
..............
0 O
0
0
0
0.20%
? I
,.'
0
PI
E ~ p e 4 n e n ~ aPoinh / Acfive ffifr/ficof/on 600
mc/,,/a
.
P/of o f Unrmdradur ,%of@
0.0 9/
Time in Daya Figure 2.
B. 0. D. us. Time for Series B Dilutions of Cincinnati Sewage, May 7, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
1294
CUMULATIVE DAILYB.O.D.asbUP TO TENDAYSFOR SERIESOF DILUTIONS OF SAMESEWAGE [Cincinnati sewage (series B); cotton-filtered: T - S dilution water; 20" C.]
TABLE VII. Days Incubation 1 2 3
4 5 6
7 8 9
10
----0.2%
60 105 - 115 195a 215 195 210 270 (230) (320)
B.O.D. a t Sewage Concn. of--0.75% 1.0% 1 . 4 % 1.8% 69 51 59 64 101 99 97 105 132 119 125 125 (164) 141 144 148 (191) 156 152 157 (221) 153 152 (257) (181) 161 162 (327) (235) 166 170 (447) (272) 166 180 (499) (325) 176 175
0.5% 56
__ 108 (144) (164) (206) (208) (254) (302) (308) (472)
2.2% 59 100 123 137 143 149 153 154 166 173'
.
2.6% 67 102 122 137 150 155 157 160 165 170
A T . of Consistent Data 60.6 102.1 123 .O 141.4 151.6 154.6 158.3 162.5 169.3 173.5
Figures above rules represent consistent data, below rules, inconsistent data, Figures in parentheses denote active nitrificahon oxygen demand. Denotes incipient nitrificat,ion oxygen demand.
T.4BLE
VIII.
CUAfUL-4TIVE DAILYB.O.D.',* UP T O TENDAYSFOR SERIES O F DILUTIONS OF SAMESEWAGE
Vol. 40, No. 7
By plotting the observed B.O.D. values, Y, n, the presence of nitrification would not be suspected until the ninth day. If this observed Y,+ B.O.D. is used t o derive the constants for the so-called first stage, a K of 0.118 and an L of 5.20 is obtained. However, if the observed B.O.D. values during the first 10 days are corrected by the oxygen equivalent of the nitrite formed, a K value of 0.16 and a n L of 4.5 are obtained. I n other words, the correction for nitrite formation increases the K value, which purports t o be representative of the rate of carbonaceous oxidation by about 357,. +
DISCUSSIOIV AND SUhIhI4RY
On the basis of this study, it is [Cincinnati sewage (series A) ; cotton-filtered; T-X dilution water: 20° C.] suggested that many of the B.O.D. Days Av. of data that have been used for the deriIncuba- -----------B.O.D. a t Sewage Concn. of------------. Consistent tion 0 2% 0 . 6 % 1 . 0 % 1.4% 1.8% 2 . 2 % 2 . 6 % 3 . 0 % Data vation of velocity constants heretofore __ 108 110 120 123 119 117 115.6 1 (75) 112 may, or may not, have included some 2 (120) 183 188 193 199 213 212 210 199.7 nitrite formation. Consequently many 3 (160) 247 244 254 263 272 269 253 2.57 ..4 309 304 302.6 297 298 4 (235j E (312) previously derived Ir' values may have 351' 333' 344 ,., (341.0) 5 (415) (352) (352) 331' been affected by nitrite formation. 6 (425) (415) (396) (348) 363' 371' 381' .. . (371.6) The time of onset and amount of 7 (405) (447) 0 (407) (415) -..... 8 (49s) (558) (416) (40+) ., . nitrification are shown t o be important @ (630) (702) (640) (459) .. . (601) ... ,.... factors in the variation of the dea Figures above rules represent consistent d a t a ; below rules, inconsistent data. rived velocity constants. The true * Figures in parentheses include active nitrification B.O.D. carbonaceous demand rates can be Includes incipient nitrification B.O.D. obtained only on samples of dilutions which have been analyzed and found to contain quantities of nitrite which Table I X . These data show the nitrite nitrogen figures obtained represent oxygen demands below the probable error of t h e on the 2.273 and 1.0% dilutions previously discussed in connection observed B.O.D. Considerably more work must be done with Table VI1 and Figure 2 . The observed increase in nitrificabefore the incidence of nitrite formation in selvage dilutions tion is shown in column 2. Column 3 gives equivalent oxygen for various incubation periods is known, and before the range demands of these figures in p.p.m. Column 5 gives the range of of velocity constants for the true carbonaceous demand can. be determined, probable error based on the known precision in this laboratory and the observed demands given in Table IV. The precision in this In this study of velocity constants of more than fifty sewage laboratory is somewhat less than 570 but was taken as a n even samples, a considerable variation in K values was encountered. The K values ranged from 0.04 t o 0.29 and had a mean value of 5% for these calculations. It is apparent immediately that nitrification is not significant so long as it remains below the probable error. Stated in another m-ay-if column 3 minus column 5 results in a negative sign, then the data are unaffected TABLEI X . COMPARISOSOF MAGNITUDE OF NITRIFICATION by nitrification; if this sign is positive, then that particular point OXYGENDEMAND WITH RAXGEOF PROBABLE ERRORIT TOTAL must be included Jtith the inconsistent data. The amount of B.O.D. nitrification that may cause this difference is small, especially in Range NitrificaObsvd. Oxygen Total Oxygen of Probable tion O.D. Increase Demand lower concentrations with loner total oxygen demands. I n in Nitrite Equiv. to Demand Error in Minus Table I X the data for a 2.2% sewage dilution show that the B.O.D., Error in Time, Nitrogen, Increase in (B.O.D.), P.P.M. B.O.D.* Days P.P.Rl. P.P.M. P.P.M. oxygen demand equivalent to the increase in nitrite did not exceed the probable error in the B.O.D. until the tenth day. Cincinnati Sewage 2.2'%, Series B-7, Nitrification Absent 1.30 0 .os 1 0.001 0.003 I n contrast t o this, the data for the 1.07, sewage show that the 2.19 0.11 0,003 2 0.001 oxygen demand equivalent to the increase in nitrite equaled the 2.70 0.14 3 0,002 0.007 .3.02 0,16 4 0.003 0.010 probable error in the B.O.D. by the fourth dag, and increased 3.15 0.16 5 0.003 0.010 3.28 0.16 6 0.004 0.014 until it LTas more than five times greater than the probable error 3.37 0.17 7 0.004 0,014 on the ninth day. 0.17 . 0,028 3.39 8 0.008 0 . 1 8 0.090 3.65 9 0.026 The plot for these B.O.D. data (the 1% dilution in Figure 2) 10 0.076 0.266 3.81 0.19 indicates that one would not suspect material nitrification until Cincinnati Sewage l . O % , Series B-4, Nitrification .ictive the eighth day. As a matter of fact, nitrification exceeding the 0.05 0.51 0.006 0.02 probable error in the B.O.D. determination had been going on 0.08 0.99 0.002 0.01 0.07 1.19 0.02 since the fifth day. This illustrates the need for nitrite deter0,007 0.07 1.41 0.07 0.019 minations t o indicate the onset of nitrification in B.O.D. deter0.08 0.11 1.56 0.031 1 . 6 4 0.08 0 . 1 4 0,042 minations, if derivation of reaction constants is t o be undertaken. 0.09 1.81 0.32 0.092 0.12 2.35 0.39 0.112 The decided effect of the small quantities of nitrites that may 0.14 2.72 0,172 0.60 be formed on the resulting K and L values is shown in Table X by a hypothetical set of B.O.D. values and nitrite nitrogen Column 3 minus column 5 . values, which normally occur frequently on the basis of our data.
I.,
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+
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1948
TABLE
ON
x.
AND
'
EFFECTOF NITRIFICATION B.0.D. CALCULATED CARBoNACEoUs B*o*D*
THEORETICAL
Yo,
Yn,
Nitrite Nitrogen Equiv.
to Yn,
Probable Error P.P.M. in Y e , Oxygenb P.P.M. 1.42 0.07 2.39 0.12 3.06 0.15 3.54 0 17 3.89 0.19 4.15 0.20 4.36 0.21 (4.55)C 0.21 (4 74) 0.22 (5 00) 0.22
Y O+
n,
Time, P.P.MSn P.P.M. P.P.M. Days OxweOxygen Nitrogen 1 1.39 0.03 0.009 2 2.35 0.04 0,011 3 3.01 0.05 0.014 4 3.47 0.07 0.02 5 3.79 0.10 0.03 6 4.01 0.14 0.04 7 4.16 0.20 0.06 8 4.26 0 29 0.08 9 4.34 0.40 0.12 10 4.39 0.61 0.18 a For Y c , K = 0.160,L = 4.50. For Y c + n, K = 0.118,L = 5.20. 0 Figures in parentheses include active nitrification B.O.D.
Minus Y* Probable Error in
-
-
7
f + +
0.15. This variation was unpredictable and was apparently independent of the origin of the sewage (military, hospital, or domestic). A statistical comparison of the values found in a series of two dilutions showed t h a t the higher concentration of * sewage on the average gave the higher K value, and that the Coefficientof variation was greater on the lowest concentrations, Careful studies of several series of dilutions of the same sewage showed t h a t t h e data could be divided into two groups, one of which was consistent and the other inconsistent. Examination showed t h a t each inconsistent value was one in which the oxygen demand equivalent of the nitrite nitrogen exceeded the Drobable in the B.0.D. data. In other words, the in K were observed to result from the unpredictable formation of amounts of nitrite after incubation periods of 3 days 01 more in
1295
some series, and dilution was an important factor in the onset of nitrification. The nitrite formation occurred earlier and more frequently in the lower concentrations of sewage. The oxygen demand equivalent of the nitrite formation was so small t h a t it could not be recognized by plotting the observed B.O.D. results. The great effect of the formation of small increments of nitrite on the K value derived from a series of observations was demonstrated. The conclusions which may be based on this study are: 1. The general theory of clear-cut carbonaceous and nitrogenous stages in the B.O.D. reaction needs further study and considerable revision, particularly in its application t o stream pollution problems. 2. Application of blank seed sample demands as correction factors is a n erroneous procedure and should be avoided. 3. Nitrite and dissolved oxygen determinations should be made on all B.O.D. series t h a t are t o be used for the determination Of reaction constants' 4. Much work remains t o be done on other factors besides dilution that may affect the onset of nitrification in sewage
LITERATURE CITED
(1) N a t l . R e s e a r c h Council, Sewwe Works J., 18, 791-1028 (1946). (2) R e e d , L. J . 9 a n d T h e r i a u t t , E. J . 7 J * PhW. Chem.7 35, 950-71 (1931). (3) Ruchhoft, C. c,, worksJ , , 13, 669-80 (1941). (4) T h o m a s , H. A., Jr., Ibid., 9, 425-30 (1937); 12, 504-12 (1940).
sewage
RECEIVED October 18, 1946. Presented before the Division of Water, Sew. age, a n d Sanitation Chemistry a t the 110th Meeting of the AivBRICAN CHEMICAL SOCIETY, Chic-ago, Ill. Published by permission of the Surgeon General's Office, u.8. Public Health Service, Federal Security Agency.
System Calcium OxidePhosphorus Pentoxide-Sulfur TrioxideWater at 15.3" C. A. N. CAMPBELL AND J. W. COUTTS, When sulfuric acid is added to tricalcium phosphate, the number of possible solid phases is large. The three common phosphates of calcium give rise to five or six, depending on the degree of hydration. The occurrence of calcium sulfate a8 a solid phase complicates matters because this substance can exist in at least three, possibly four, forms, some of which, however, are claimed to be metastable. In addition to this, the possibilities of the formation of solid solutions (16) and of double salt (31) have been mooted. The problem of determining what solid phases coexist with solution, under various conditions of acidity and temperature, is one of considerable importance to industry, agriculture, and geology.
T
HE only previous investigation of the complete fourcomponent system, calcium oxide-phosphorus pentoxidesulfur trioxide-water, is that of Cameron and Bell (7), carried out a t 25' C. The present investigation was undertaken at 75.3" C.; a temperature in the region of which the industrial process for the manufacture of phosphoric acid from phosphate rock is operated. The system calcium oxide-phos-
University of Manitoba, Winnipeg, Canada
phorus pentoxide-water has been studied by Elmore and Farr ( I d ) at, among other temperatures, 75 O C. The authors' results are in close agreement with those of Elmore and Farr; in other words, the presence of calcium sulfate has little or no effect on the concentrations of solutions or the nature of the solid phases, except t h a t the number of the latter is increased by the presence of gypsum, anhydrite, or hemihydrate. The literature of this subject is vast and merits a brochure dedicated t o it. The bibliography given with this paper is believed to be the most complete bibliography extant. EXPERlMENTAL
MATERIALS. Analyzed tricalcium phosphate from the J. T Baker Chemical Company was used for the experiments of series 1. Commercial tricalcium phosphate, as has been pointed out by several investigators, seldom has a composition which corresponds exactly to the formula Ca3(P04)2. This was confirmed by the authors when i t was found t h a t a n extract of a sample of tricalcium phosphate supplied by another manufacturer gave a conductivity almost ten times as great as the Baker product. E o foreign radicals, however, were detected; the increased conduc-
