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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
grades were analyzed b y t h e hydrolysis method described above as well as by t h e digestion method for t h e sake of comparison. I n t h e digestion analyses i t should be noted t h a t t h e copper was determined b y weighing t h e oxide in place of t h e volumetric method given above. Also t h e zinc was precipitated as sulfide in the presence of ammonium Eormate and formic acid instead of ammonium acetate and acetic acid. I n confnrmity to t h e usual custom, the results of t h e analyses are stated in terms of milligrams of metal per kilo of gelatin or parts per million. HYDROLYSIS METHOD DIGESTION METHOD
cu p.m. NO. 1................ 1................ 1................ 2 2 3 3i:O 3.. 26.6 4 .............. 20.0 4 .............. 24.0 5 24.0 5.. 22.4 5 20.0
............... ............... .............. ............ .............. ............ ..............
Zn P.p.m. 1341.0 1341 .O 1341.0 126.0 128.0 96.4 104.0 64.0 56.0 77.9 80.3 80.3
cu Zn P . P . ~ . P . P . ~ . 1341 .O 1340.0
,. .. .. ..
3i:O 32.0 20.0 20.0 24.0 24.0
..
lii.0 3.4 96.4 68.0 56.0
80.3 80.3 76.0
The copper was separated b u t was not determined in Samples I a n d 2 because a t first it was intended only t o investigate the determination of zinc. I n order t o test the method further, measured quantities of standard solutions of zinc and copper were added t o weighed amounts of Sample 5 . T h e hydrolysis and analyses were made as described above with t h e following results: SAMPLP, TAKENCu Added Grams Mg.
Zn Added Mg.
Cu Found Mg.
Zn Found Mg.
It should be observed t h a t t h e amount of zinc and copper in 2 0 g. of Sample 5 gelatin as determined by averaging the results obtained by previous analysis. has been deducted from t h e results given above. The results obtained with these trial analyses show t h a t t h e method is accurate. I n order t o obtain satisfactory results, i t is most important t h a t the directions be followed in every detail. Furthermore, great care must be taken t o eliminate by filtration any non-volatile matter which may separate during t h e course of t h e analyses, before proceeding t o make t h e final precipitation of the zinc or copper sulfides. Also, t h e Gooch crucibles used must be prepared so t h a t they will not lose weight during the filtration and ignition of t h e sulfides. BUREAUOB CHGMISTRY DEPARTMENT OF AGRICUGTURE WASHINGTON, D. C.
THE DEOXYGENATING EFFECT OF THE EFFLUENT FROM THE MILES ACID PROCESS OF SEWAGE TREATMENT By F. W. MOHLMAN Received July 12, 1918
Experiments with t h e Miles acid process of sewage treatment were conducted a t t h e New Haven Sewage Experiment Station under t h e direction of Prof. C. E, A. Winslow, from June I, 1917, until May I, 1918,in comparison with three other processes which have been considered for New Haven conditions.’ 1
Eng. News Record, 79 (1917), 18.
325
Some very interesting facts were established during this work regarding t h e Miles acid process. The Miles patent, No. 1,134,280claims t h a t the Miles process “ ( I ) consists in introducing-an inorganic acid as the sole effective agent” and “(3) consists in introducing sulfurous acid into the sewage.” Sulfurous acid seems t o have a selective toxic action on bacteria which is more intense t h a n is obtained by the same hydrogen-ion concentration of sulfuric acid. The effect of the sulfurous acid is augmented by t h e germicidal power of the bisulfites formed from the bicarbonates. Therefore, from the standpoint of effective disinfection, sulfurous acid is preferable t o sulfuric. It also has the decided advantage of being cheaper, when made as needed, by burning sulfur or pyrites and conducting the gas into a part of the sewage, which can then be used for acidifying the remaining sewage. We have applied compressed sulfur dioxide t o t h e sewage as i t flowed into a settling t a n k through a galvanized iron pipe about 2 0 f t . long. The settling t a n k was 16 f t . long, 4 f t . wide, and 4 ft. deep. T h e detention period was 4 hrs. when treating 10,000 gal. of sewage per day. After acidification the sewage contains bisulfites a n d some free sulfurous acid. It also contains lime and magnesium soaps, which are attacked by the acid, liberating the free f a t t y acids. As the sewage passes through t h e tank, part of t h e bisulfites a n d sulfurous acid is oxidized t o bisulfates and sulfuric acid. I n t h e effluent there is a mixture of sulfurous acid, sulfuric acid, bisulfites, RHSO3 (R indicating S a , K, Ca, Mg, or Fe), and bisulfates, R H S 0 4 . T h e oxidation takes place a t t h e expense of t h e dissolved oxygen in t h e sewage, and some oxygen is also supplied by absorption of atmospheric oxygen from t h e surface of t h e liquid. The oxidation may easily be followed by determining total sulfur dioxide in both bisulfites and sulfurous acid by titration, using an excess of iodine solution. By titration with standard sodium hydroxide, using methyl orange as indicator, all of the sulfuric acid b u t only half of the sulfurous acid is determined. This is due t o t h e fact t h a t t h e reaction H z S 0 3 NaOH = N a H S 0 3 HzO takes place, and N a H S 0 3 reacts neutral t o methyl orange. T o get accurate results as t o the total acidity, all sulfurous acid should first be oxidized t o sulfuric acid or else the sulfur dioxide in the sulfurous acid must be determined. Titration with standard sodium hydroxide using phenolphthalein as indicator includes t h e acidity due t o bisulfites a s well as t h a t due t o sulfurous acid a n d sulfuric acid, as N a H S 0 3 reacts acid t o phenolphthalein. By a combination of the three titrations t h e exact state of oxidation of t h e sulfur dioxide may be followed. These facts must be remembered in determining t h e acidity of t h e Miles effluent, as erroneous results may be reported when titrating with methyl orange when the effluent contains unoxidized sulfur dioxide. We have usually attempted t o carry the free acidity t o 50 p. p. m. (as CaC03). Preliminary tests made on February 14, 1918, showed a total content of 118 p. p. m. of sulfur dioxide
+
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in t h e effluent. I n order t o determine whether this sulfur dioxide would use up t h e dissolved oxygen in t h e diluting water if i t were discharged into t h e New Haven harbor, various mixtures of t h e effluent with sea water from t h e harbor were made. No special care was taken t o exclude atmospheric oxygen during t h e mixing. Partial analysis of the sea water and effluent is given in Table I. TABLE I-PARTIALANALYSISOF SEAWATERAND EFFLUENT Sea Water Temperature, deg. C . . . . . . . . . . . . . . . . . . . 4 Chlorine, p. p. m 10,000 Dissolved oxygen, p. p. m . . . . . . . . . . . . . . 12.0 Sulfur dioxide, p. p. m . . 0.0 Alkalinity, p. p. m 77
Effluent 10
....
........................
0.8 118 -134 (acid)
................. .......................
As soon as possible after dilution, dissolved oxygen and sulfur dioxide were determined in t h e mixtures. The results shown in Table I1 were obtained. TABLE 11-MIXTURE I
Effluent Dissolved oxygen. 0.8 Sulfur dioxide.. ,118
..
OF
Sea Water 12.0 0
SEA WATER A N D THE MILES EFFWENT 1 Effluent 1 Effluent 1Effluent 1Effluent 2 Water 4 Water 9 Water 19 Water 1 .o
5.0
8.8
8
0
0
11.0 0
A great decrease in t h e dissolved oxygen took place in t h e dilutions containing 2 0 per cent or more of t h e effluent. Table I11 shows the reduction in dissolved oxygen due simply t o dilution, t h e amount required for ox:dation of t h e sulfur dioxide in each dilution, a n d ’ t h e difference between the latter and t h e former, t h e oxygen taken up from t h e air in completing t h e oxidation. TABLE111-OXIDATION
OF SULFUR DIOXIDE BY DISSOLVEDOXYGEN
. . . . . . . . 12.0
Sea Water. Effluent . . . . . . . . . . . . . 1 Effluent, 2 HzO.. .. 1 Effluent, 4 He0 ..... lEffluent, 9 H z O 1 Effluent, 19 Hs0.
..... ....
0.8 1.0 5.0 8.8 11 . O
......
. . . . . .
8.3 9.8 10.8 11.4
7.3 4.8 2.0 0.4
0.0 118.0 31.0 24.0 11.8 6.0
0.0 29.5 7.7 6.0 2.9
1.5
... ...
0.4 1.2 0.9 1.1
From these results it is probable t h a t there is immediate quantitative oxidation of t h e sulfur dioxide, according t o t h e reaction SOz 0 = SOs. I n this reaction one part per million of oxygen oxidizes 4 p. p. m. of sulfur dioxide. The oxidation takes place immediately after dilution is made. I t was also determined t h a t not only t h e sulfur dioxide present as sulfurous acid is oxidized, b u t also t h a t present as bisulfite. The seriousness of this fact may well be imagined. If a certain sewage has an average alkalinity of 1 7 5 , which is not high, and sulfur dioxide is applied t o give an acidity of 50, t h e effluent would contain about 2 0 0 p. p . m. of SO2, t h e 2 5 remaining parts probably being oxidized while passing through t h e t a n k . These 2 0 0 parts of sulfur dioxide will reduce 50 parts of dissolved oxygen upon dilution, or in terms of dilutions a t summer temperatures, one volume of effluent will immediately reduce all of t h e oxygen in 5 t o 7 volumes of sea water. An oxygen demand of 50 p. p. m. is not high, as most sewages have biochemical oxygen demands of from zoo t o 300 p. p. m., b u t t h e serious aspects of t h e discharge
+
Vol.
11,
NO.4
of this effluent into diluting water is t h a t t h e oxygen is absorbed immediately according t o a definite chemical reaction, while t h e biological consumption does not t a k e place nearly so quickly, allowing much longer time for dilution and dispersion. It is not improbable t h a t there might be a distinct zone of de-aerated water at t h e outfall of the effluent from t h e Miles process. I n order t o determine whether t h e sulfur dioxide might be oxidized before t h e effluent is discharged, a n aerating t a n k was constructed by Mr. Harold G. Wynne, of t h e City Engineer’s office, who assisted in t h e experimental work. This tank, as shown in Fig. I , consisted of two concrete draintiles 3 0 in. in diameter, placed one above t h e other, with a filtros plate one foot square cemented into an iron plate at t h e bottom. Air was blown through this,plate from a Nash hydro-turbine, t h e pressure being measured by a mercury manometer and t h e volume being measured by a gas meter. The t a n k was used both on t h e fill-and-draw a n d continuous plan. When used intermittently it was filled with effluent and t h e air started, samples being withdrawn a t intervals a n d analyzed for sulfur dioxide, t h e quantity of air being measured a t t h e time each sample was withdrawn. Results of an average experiment of this kind are given in Table IV. TABLE IV-A%RATION OF THE MILES EFFLUENT Date.. March 4, 1918 220 gal. Quantity of effluent.. Quantity of a i r . . ...................... 21 . O cu. Et. a t 6 . 4 in. mercury Quantity of free a i r . . . . . . . . . . . . . . . . . . . . 2 5 . 5 cu. f t .
.............................. .................. Time Min. 0 10 20 30 40
so2
P. P. m. 78.1 71.7 53.8 23.0 10.2
Reduction Per cent
..
8 31 70 87
Air
Cu. ft. per gal. 0 : Oi9 0.058
0.087 0.116 Effluent mixed with sea water, before and after aeration, dissolved oxygen determined immediately. -Dissolved oxygenSAMPLE Before After Effluent.. .................... 1,4 5.8 Sea W a t e r . . . . . . . . . . . . . . . . . . . . 14.2 1 Effluent, 2 Sea W a t e r . . . . . . . . 4 . 4 ii.8 1 Effluent, 4 Sea W a t e r . . . . . . . . 7.4 11.8
The results of this experiment have been substantiated b y various other experiments on t h e filland-draw plan. The t a n k was next used as a n aerator on t h e continuous-flow plan. The effluent from t h e Miles t a n k was passed through t h e t a n k as shown in Fig. I, having a detention period of 3 1 min. Samples of t h e influent were taken a t 3 and 9 A . M . and P . M . , and of t h e effluent 30 min. later. The average results of these experiments are shown in Table v. TABLF:V-CONTINUOUS AGRATION O F THE MILES EFFLUENT --Sulfur dioxideReduction Air Date Influent Effluent Per cent Cu. ft. per gal. 54 0.10 3/6/18.. . . . . . . . . . . . . . . 99.1 44.9 0.10 79 14.4 3/7/18.. . . . . . . . . . . . . . . 7 0 . 4 0.11 3/8/18., . . . . . . . . . . . . . . 7 2 . 3 80 14.4 0.10 92 3/9/18.. . . . . . . . . . . . . . . 6 9 . 1 5.2 0.10 46.4 3/1 0/ 18, . . . . . . . . . . . . . . 81.3 43 36.1 55 0.06 3/11/18.. . . . . . . . . . . . . . 8 0 . 9 0.10 10.2 3/31/18 . . . . . . . . . . . . . . . 81 53,s 37.4 65 0.10 4/1/18.. . . . . . . . . . . . . . . 108.5 26.5 71 0.10 4/2/18. . . . . . . . . . . . . . . . 90.9 72 0.10 19.8 4/3/18.. . . . . . . . . . . . . . . 7 1 . 0 95 0.10 4/4/ 18. . . . . . . . . . . . . . . . 9 2 . 2 4.5 0,097 70 23.6 78.1 -4VERAGE. . . . . . . .
These results are quite similar t o those obtained on t h e fill-and-draw plan, with 30 min. aeration, except t h a t slightly more air is necessary. T h e close agreement in sulfur dioxide content in t h e effluent is ac-
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M ' ? e I1
//
u
Meter
PLAN .VIEW
"I1i1
ELEVATION
FIG. 1-TANK USED FOR A ~ R A T I OON B EFFLUEKT FROM
cidental. I n each method 7 0 per cent of t h e sulfur dioxide was removed in 30 min. aeration, but with 97,000 cu. f t . of free air per million gallons of effluent when operating continuously, as compared with 87,000 cu. f t . per million gallons on the fill-and-draw plan. T h e aera.ted effluent did not de-aerate the diluting water t o a n appreciable amount a t any time, and thus could be discharged into t h e harbor with safety. Bacterial counts made by Mr. W. S. Sturges before and after aeration showed t h a t there was practically no change in t h e bacterial content. Laboratory experiments in which wood plates were used for diffusing t h e air indicated t h a t the amount of air. required could be reduced considerably b y diffusing t h e air very finely. This experience is similar t o t h a t found in the activated sludge experiments a t Milwaukee, but it is probable t h a t this oxidation, which is purely chemical, is even more affected by t h e fineness of division of t h e air t h a n is t h e oxidation in t h e axtivated sludge process, which is biological. T h e quantities of air used in t h e experiments with t h e filtrose diffuser were from one-fifteenth t o onetwentieth of those used in the aeration with activated sludge, so it is probable t h a t t h e cost of this aeration would be low. T h e tank used for t h e aeration was too shallow t o be very efficient, and it is believed t h a t the results obtained in these experiments could be greatly improved b y further work. While this aeration will make a Miles plant more complicated and t h e process more costly, it does not necessarily condemn t h e process, as t h e aeration period is very short and
THE
MILESACIDPROCESS
the amounts of air necessary b u t a small fraction of those required in t h e activated sludge process. CONCLUSIOKS
I-The Miles acid effluent contains unoxidized sulfur dioxide. 11-This sulfur dioxide is oxidized a t t h e expense of t h e dissolved oxygen in the water in which t h e effluent is diluted. 111-The sulfur dioxide may be oxidized before dilution b y aeration for a short time with relatively small quantities of air. After this aeration t h e effluent will not de-aerate large volumes of diluting water. DEPARTMENT OF HEALTH HAVEN,CONNECTICUT
NEW
DOUBLE SALTS OF CALCIUM AND POTASSIUM AND THEIR OCCURRENCE IN LEACHING CEMENT MILL FLUE DUST By E. ANDERSON Received August 13, 1918
T h e recent development of t h e cement potash industry has served t o direct attention t o certain double salts of potassium and calcium which have heretofore been of interest chiefly t o t h e scientific investigator. Of these t h e potassium mono-calcium sulfate, KzS04.CaS04.PIz0, or syngenite, is perhaps most familiar, b u t t h e potassium penta-calcium sulfate, KzS04.j C a S 0 4 . H 2 0 , is equally important. The occurrence of these salts in t h e natural potash deposits and t h e fact t h a t they can be easily made artificially from their simple constituents indicates t h e possi-
