Detergents in Water Supplies JAMES C. VAUGHN AND RALPH F. FALKENTHAL South District Filtration Plant, Department o f Water and Sewers, City o f Chicago, 111.
The Task Group of the American Water Works Association classifies general problems of detergents as: foam on settling basins, taste and odor, coagulation and sedimentation, presence of iron, foaming of finished waters, and quality deterioration in distribution system. Coagulation with alum and activated silica was helpful at Appleton and Osawatomie. Chlorine dioxide was helpful at Wheeling. Activated carbon is effective in removing detergents, but tremendous quantities are required and there i s a dosage limitation. Ferrous sulfate-lime coagulation has some effectiveness. Recent work at the South District Filtration Plant indicates that if the water i s first treated with a rosin-acid amine, the detergent may be effectively removed b y alumsilicate coagulation. Partially settled sediment from filtration plant settling basins added to water has been effective in detergent removal. Finely divided silica sand and limestone have no effect. Some physical forms of precipitated calcium carbonate are effective.
NCREASED use of synthetic detergents in the past decade has created problems in water treatment. Detergents, principally those used in households, pass relatively unchanged through the usual sewage treatment processes. Therefore, water supplies that are subject t o considerable re-use can, in periods of low flow, accumulate an appreciable detergent content. The Task Group of the American Water Works Association, organized t o investigate the general problem of detergents, classifies the problems presented as follows: foam on settling basins, taste and odor, coagulation and sedimentation, iron, foaming of finished waters, and quality deterioration in the distribution system. Appleton, Wis., was the first to report trouble of this type (1). The water would not coagulate and floc would not settle. A moldy or mildewy taste resisted removal by activated carbon and was more pronounced a t the consumer’s tap than a t the plant. This condition still prevails. Osawatomie, Kan. , reported similar troubles in early 1953 (3). After several months the Ohio River as far as Evansville, Ind., experienced the same difficulties to a lesser degree (6). Ottumwa, Iowa, had a similar experience during 1953 and 1954 (6). At the South District Filtration Plant ammonium sulfate containing 1.25% alkyl aryl sulfonate as an anticaking agent at the concentration used in plant operation interfered with coagulation and produced objectionable taste and odors. Utica, Mich., reported foaming troubles in November 1954 (4). Samples taken from the Clinton River (Utica’s water supply) showed 0.28 to 1.57 p.p.m. of anionic detergent. The Southwest Sewage Plant of the Sanitary District of Chicago reported that the detergent content of the plant influent, for a short period, ranged from 1.48 to 2.48 p.p.m., while the outfall ranged from 1.84 to 3.00 p.p.m. A single pair of samples from the Calumet Plant showed: influent, 2.24 p.p.m. and outfall, 3.24 p.p.m. Water from the Illinois Drainage Canal receiving effluents from the Northside and Southwest Sewage Plants (activated sludge plants) had a detergent content ranging from 0.80 t o 2.00 p.p.m. Three steam plants using this canal water had boiler foaming troubles. The water from some of these boilers showed a detergent content ranging from 7.4 to 18.0 p.p.m. The American Water Works Association organized a discussion panel on the effects of synthetic detergent pollution before ita
I
February 1956
Water Purification Division in 1949 (1). The Osawatomie experience was told by Culp and Stoltenburg before the division in 1953 (2). It was apparent that the problems created for water treatment plants by the tremendous increase in detergent use were becoming too widespread and complex for individual solution. Therefore a task group was created to investigate the general problem. I t s first progress report was given in 1954 ( 3 ) . In beginning its work the task group surveyed the continental United States and the Province of Ontario, Canada, to determine to what extent problems were created by detergents in water supplies, if the amount of detergents present had been determined, and what methods of treatment had been effective. A Committee of Synthetic Detergents was appointed in England May 12, 1953, with Sir Harry Jephcott as chairman.
Evaluation of Methods of Removing Detergents The South District Filtration Plant in Chicago has continued quantitative evaluation of methods of removing detergents from water. The substances used were: activated carbon, aluminum sulfate, ferrous sulfate, dolomitic limestone, chlorine dioxide, bentonite, slaked calcium oxide, activated sodium silicate, finely divided silica sand, partially settled sediment from the settling basins in the filtration plant, and a primary rosinamine acetate. These compounds were evaluated singly for the most part, but in some cases in a combination of two or more substances. I n all cases 20 p.p.m. of detergent (a commercial brand, considered 100% anion-active) was used. Six samples were prepared for each test. The samples were mixed for 30 minutes, allowed to settle for 15 minutes, and then filtered. The effectiveness of the chemical used for removing the detergent was measured by the methylene blue-chloroform extraction method, using a Klett-Summerson colorimeter. The residual detergent values were plotted against the chemical dosages, and a curve was formed, from which the optimum removal of the detergent for the chemical applied was determined (Figure 1). Carbon Test. The data on the carbon test are given in Table I. Figure 1 shows that a dosage of 75 p.p.m. of activated carbon added t o water containing 20 p.p.m. of commercial detergent will reduce the detergent t o below 3.9 p.p.m., which is the critical
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241
POUNDS PER M/LL/QN 6ffLLONS Figure 1.
Table I.
Sample 1 2 3
4
6 6
Carbon Test
Carbon Added Lb,/ million gal. P.p.m. 0 ion 100 500 ... 1000 I500 2000
Detergent Remaining, P.P.M. 20 0 14 0 I1
0 12 12 ~~
~~
5 1
60
120 180 240
Table 11.
Removal of detergents from water by chemicals
1 4
1 . 11 0 fi
Detergeii t Renioved Per p.p.rii. carbon P.p.m. added 0.0 f6i n0 n 0 ' .in .50 14 6 14.6 0 224i 18 (3(7 18 9 18.9 199 .44 1
0 l i i, 0 11
o . 0n88 0
Aluminum Sulfate Test Detergent ____ Removed-
Aluminum Sulfate Added Lb:/ million Sample gal. P.p.m.
Detergent Remaining, P.P.M.
prr
P.p.m.
Per p.p.m. alum added
8.40
P H 8.80 1 2
3
? 0
0 in0 150 200 300 500
0
12 16 24 36 60
Table 111.
20 13 13 13 13 13
n
7 3 3 3 3
Lb,/
Saanvle 1 2
3 4
5 6
242
100 150 200 300 500
P.p.ni.
0 12 IF 24 36 60
3 7 7 7 7
0 52 0 42 0 28
n io
0 11
Table iV.
Ferrous Sulfate Test
Ferroiis Sulfate Added
million gal. 0
0 6 6 6 6 6
point as found by Cross ( I ) and CuIp ( 8 ) . Dosages above 96 p.p.ni. remove little or no additional detergent. The data were rearranged according to the Freundlich equation, X , / N = K(C)l'n,by Paul Haney, chairman of the American Task Group on detergents, and found to fit the equation very well. This arrangement is plotted on Figure 2. Aluminum Sulfate Test. Aluminum sulfate and activated sodium silicate were used a t a ratio of 10 parts of alum to 1 of silicate. Lime water was added to maintain a constant pH value. It is apparent from Table I1 that a t pII 8.40 there is little effective removal at, an alum dosage above 48 p.p.m. and the highest practical dosage is 42 p.p.m. At' the optimum dosage of 42 p.p.m., 6.6 p.p.m. of detergent were removed. At pH 8.80 the highest effective dosage of alum is 16 p.p.m., and the highest practical dosage is 12 p.p.m. At this higher pH the alum-activated silica is more effective. '4t the optimum dosage of 12 p.p.m., 6.3 p.p.m. of detergent were removed. Ferrous Sulfate Test. Ferrous eulfate and chlorine were used at a ratio of 7 parts of ferrous sulfate to 1 part of chlorine, the chlorine being added t o oxidize the ferrous sulfate. Lime xvater was added to maintain a constant pH value of 9.1 (Table 111). At the optimum dosage of 12 p.p.m. of ferrous sulfate, 9.5 p.p,m. of detergent were removed. This is somexvhat more effective than alum-silicate coagulation (see Figure 1). Chlorine Dioxide Test. At the optimum doeage of chlorine dioxide (36 p.p,m.) odor reduction was measured. The threshold
Iletergent Reinaining, P.P.M. 20 0 10 5.
10 3
10 0 9.9 9.8
Detergent Rriiioved Per p.p.m. FeSOl P.p.in. added 0 9 .J 0 ' 79 9 7 10.0 10.1
10.2
O.(il
0.42 0.28 0.17
Chlorine Dioxide Test
Chlorine Dioxide Added Lb.1 million Sample gal. P.p.m. 1 0 0 2 3 4 3
F
ion
200 300 400 500
12 24 30 48 60
Iletorgent Remaining, P.P.M. 20.0
INDUSTRIAL AND ENGINEERING CHEMISTRY
12.9 12.2 12.0 11.8 11 8
n e t r r p c n t Rcinovcd Per p.p.rii. ClO? P.p.m. added 0 7.1 0: no 7.8 0.32 8.0 8.2 8.2
0.22 0.17 0.14
Vol. 48, No. 2
STREAM POLLUTION PROBLEMS adding a small amount of acetic acid, or it can be procured in the water-soluble acetate form. Unfortunately, the primary rosin-amine and its acetate form are strong skin irritants and the manufacturer recommends that they not be used in potable water supplies, A check on the ammonia content of the treated samples indicated that appreciable amounts of the rosin-amine mere left in the water after reaction with the detergent. The completion of the reaction requires an excess of the rosin-amine.
[
8
,
,,,,,,I,
0.010.1
L,
,
,
,
I
,,,,
~
,,,;,,I
lo
10
100
SYNTHETIC D E T E R G E N T RCHAINING-
acm.
Table VII. Settleable Sediment Added &b:/ million Sample gal. P.p. I l l .
C
Figure 2.
Data from carbon tests rearranged by Freundlich equation
odor of the original sample was 14 (hot-dechlorinated). The odor of the sample after treatment with 36 p.p.m, of chlorine dioxide was 7 , a reduction of 5070, and the odor was changed from pungent chemical to musty earthy. However, the dechlorinating agent of itself produced an odor. It was necessary to dechlorinate the sample before determining the residual detergent by the methylene blue method; otherwise the excess chlorine bleached the dye. I n general, the by-products of this treatment were so complex as to make it impractical a t the high dosages employed.
Table
V.
0
2 3 4 5 6
200 300 400 500
Bentonite Test
Sample 1 2 3 4 5 6
Primary Rosin-Amine Acetate Test Detergent Remaining, P.P.M. 20.0 7.9
2.0 0.6 0.3 0.0
Detergent Removed Per p.p.m. PR8.4 P.p.m. added 0 12.1 10:OS 18.0 5.00 19 4 3.23 19.7 2.35 20.0 1.85 ~~
~~~
A dosage of 10.8 p.p.m. of primary rosin-amine acetate reduced the detergent content of 20 p.p.m. to 0 (Figure 3). This primary rosin-amine is a cationic material which neutralizes the anionactive material in the detergent, so that it can be readily removed by coagulation. The use of bentonite in conjunction with this material aids in removing the detergent. The primary rosinamine is insoluble in water. It can be dissolved in water by February 1956
0 1:o1 0.66
12.1 13.5 14.9 15.4 16.2
0.41 0.32 0.27
Ferrous Sulfate-Treated Water 0 20.0 0 12 8.1 11.9 24 5 4 14.6 36 6.1 13.9 48 5.5 14.5 GO 3 5 16.5
100
I
I 80
0
c)
1:oo 0.61 0.39 0.30 0.28
so
I PePrS et# X,iL/W I
, I
26
100
100
BOO
I 1 400
d2
-
0
5w
POUNDS PEPM/LL/ON G~ALLOKJ
Figure 3. Primary Acetate I+./ million gal. P.p.m. 0 0 10 1.2 3.6 30 50 6.0 70 8.4 90 10.8
Detergent Reinoved Per p.p.rn. sediment P.p.m. added
Settled Sediment Test. Sediment from the settling basins in the South District Filtration Plant was used with 90 pounds per 1,000,000 gallons of alum and 15 of lime. The sediment as removed in the daily basins desedimentation process was allowed to settle for 1 hour before use in the test. It was assumed to be 100% active material and to weigh 8.345 pounds per gallon. Sediment from both alum-treated water and iron-lime-treated water was used (Table VII).
Bentonite Test. Bentonite was used with coagulation dosages of 90 pounds per 1,000,000 gallons, of alum and 15 of lime. The bentonite reached its maximum adsorption a t a dosage of 12 p.p.m., a t which point 10 p.p.m. of detergent were removed. This is equivalent to 0.83 p.p.m. of detergent removed for each part per million of bentonite added. Beyond this point the efficiency falls off markedly. Primary Rosin-Amine Acetate Test. Rosin-amine acetate was used with dosages of 90 pounds per 1,000,000gallons, of aluminum sulfate, 15 of lime, and 10 of activated sodium silicate. Table VI.
Detergent Remaining. P.P.1M.
Alum-Treated Water 0 20.0 12 7.9 24 6.5 36 5.1 48 4.6 3.8 60
0 100 200 300 400 500 1
Sediment Test
Removal of detergents from water by various substances
As can be seen from Figure 3, sediments from water coagulated with aluminum sulfate and with chlorinated ferrous sulfate were equally effective in the removal of detergents. In either case a dosage of 60 p.p.m. reduced the original dosage of 20 p.p.m. of detergent t o below the 3.9 p.p.m. trouble-making level ( 1 ) . As yet no attempt has been made t o find the saturation point of the sediment for detergent adsorption. As this sediment is always available in relatively large quantities a t any water plant, the rather high dosage requirement of 60 p.p.m. is not important. On the days that the sediment samples used in the tests were collected, the raw water treated with alum had a turbidity of 19 p.p.m. Dosages were (pounds per million gallons of water): alum 91; activated carbon, 13; chlorine, 6.3. The raw water treated with chlorinated ferrous sulfate and lime had a turbidity of 13 p.p.m. Dosages were: ferrous sulfate 69; activated
INDUSTRIAL AND ENGINEERING CHEMISTRY
243
/
ALUM TREATED W T E R O
0 24
0 IZI 135
48
149 154
80
162
38
FERROUS
38 40
w
032 027
xi0 7 9
6 5 5 1 4 5
38
SULFATE-LIME TREATED WATER A
-
0
I2 z1
-
IO1 OS5 041
li4 14 6 139 145 165
I37
0 81 039
81
0%
55
028
35 9,
/ SYNTHETIC
DETERGENT
REYAINYC
- afl,
"C
Figure
4.
Data from settled sediment tests according to Freundlich equation
plotted
carbon, 15; chlorine, 6.1. The effectiveness and economy of this method of detergent removal make it well worth trying on a plant scale.
Effectiveness of Settled Sediment The question arises as t o w h r srttled sediment is effective in detergent removal. The answer lies in an analysis of the results previously obtained, some of them several years ago. On Figure 2 the data from the test on removal of detergents by activated
carbon (Table I ) have been plotted according t o the Freundlich equation. As can be seen, these data fit the equation very well, all the points falling close t o a straight line. Substances removed from water by activated carbon are presumably adsorbed onto its very great surface area. If the data from the settled sediment tests (Table VII) are also plotted according to the Freundlich equation (Figure 4), the points also fall close t o a straight line. The points established by the data from the alum sediment, the iron-lime sediment, and the equivalent dosages fall close to the same straight line. This would indicate that the removal of anionic detergent? from water by settled sediment is an adsorption phenomenon, the effectiveness of any material depending on the total surface available, per unit of substance applied. The data from the alum-activated silica and the chlorinated ferrous sulfate test, when plotted according t o the Freundlich equation, also give a straight line. That the removal of anionic detergents from water is generally an adsorption phenomenon is further confirmed by the fact that inert nonporous materials with limited total surface areas, such as finely divided silica sand and dolomitic limestone, are not a t all effective. However, precipitated calcium carbonate, a porous material with an appreciable total surface area per unit of material applied is effective (12 p.p.m. applied t o 20 p.p.m. of anionic detergent in water removed 10.8 p.p.m. of detergent). Further experiments on problems created by the presence of detergents in mater supplies included determination of the effect of low concentrations of detergent on the pH of water.
C
3x D
tM
b
Figure 5 .
p H values of detergents a t various concentrations Laboratory-distilled water used as dilution water
244
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 48,No. 2
STREAM POLLUTION PROBLEMS
i
-
a00
I
IO
5
1 5
20
DE7iZRGEN7- CO/VCENTX?UT/'N fpp@ Figure 6.
pH values of detergents a t various concentrations
Treated water from South District Filtration Plant used as dilution water
Figure 5 shows the p H of varying concentrations of a number of detergents on distilled water. Sample F is a 100% anionic material. Samples H and J are built detergents containing nonionic surface active compounds. I n Figure 6 t a p water is the diluting medium. This is of interest only in estimating the general effect of detergents. I n the original investigation reported by Cross ( I ) , two of the detergents investigated a t the South District Filtration Plant were industrial base materials containing 100% anion-active compounds. Recently a test was performed with lauryl sulfate in raw water. A concentration of 3 p.p.m. gave an objectionable taste and odor. At 5 p.p.m. the odor was very strong, foam occurred, and there was interference with coagulation. In a parallel test using a 100% nonionic detergent base, objectionable taste and odor were apparent a t 1 p.p.m. concentration. At 3 p.p.m., the taste and odor were worse and interference with coagulation occurred. It is apparent that the surface aetive compounds are, a t least in part, responsible for the problems created in water supplies by the presence of detergents. As yet, the effect of the phosphate consitituents of detergents on water treatment has not been investigated.
Conclusions Chlorine dioxide is effective t o a limited degree in reducing the taste and odor produced by detergents, but high dosages are required. A cationic material (a primary rosin-amine) is effective, but cannot be used in potable water supplies, as it is a strong skin irritant. Activated carbon is effective, but very high dosages are required and beyond a certain point it is ineffective. Coagulation with aluminum sulfate, activated silica, and chlorinated ferrous sulfate are effective t o a limited degree. The alum-silica treatment is most effective a t pH 8.80. Settled sediment, concentrated by an hour's further settling, is most effective in removing detergents from water supplies. February 1956
Sediment from treated water and iron-lime treated water is equally effective. Certain physical forms of precipitated calcium carbonate are effective t o a limited degree. A volcanic clay such as bentonite is effective to a limited degree. Plotting the data from the carbon and settled sediment tests according t o the Freundlich equation indicates that the removal of detergents from water is a surface adsorption phenomenon. The tests with bentonite and precipitated calcium carbonate, and the coagulation tests with alum-silica and ferrous sulfatelime combinations confirm this. The surface active constituents of commercial detergents are in part responsible for the problems created by the presence of detergents in water supplies.
Acknowledgment The authors wish t o express their appreciation for the helpful suggestions and the materials supplied by K. A. Steel, K. A. Steel Chemicals, Inc., Arthur Klem, American Colloid Co., K. A. Wagner, Hercules Powder Co., Walter Walker, Marblehead Lime Co., and Paul Haney, Black & Veatch. They are also indebted t o Paul Haney for assistance in interpreting data on carbon adsorption.
Literature Cited (1) Cross, J. T., J. Am. Wuter Works Assoc. 42, 17 (1950). (2) Culp, R.L., and Stoltenberg, H. A., Ibid., 45, 1187 (1953).
(3) J. Am. Wuter Works Assoc. 46, 751 (1954). (4) Mich. Wuter Works News 19, No.4,6 (1954). (5) Poole, B. A., Director, Bureau of Environmental Sanitation, Indiana State Board of Health, and Ahrens, G. C., Superintendent, Ottumwa Water Works, Ottumwa, Iowa, personal communication. RECEIVED for review April 25, 1955.
INDUSTRIAL AND ENGINEERING CHEMISTRY
ACCEPTED July 29, 1 9 5 2 .
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