Drinking
ater Taste and
CORRELATION WITH ORGANIC CHEMICAL CONTENT
F. M. MIDDLETON,
Robert A. Taft Sanifary Engineering Cenfer,
Education, and Welfare,
U. S.
U. S.
Department of Health,
Public Health Service, Cincinnati, Ohio
WALLACE GRANT, Wesf Virginia Wafer Service Co., Charleston, W. Va. A. A. ROSEN, Robert A. Taff Sanitary Engineering Center, Education, and Welfare,
U. S.
U. S.
Deparfment of Health,
Public Health Service, Cincinnati, Ohio
Serious tastes and odors in the drinking water of a municipal supply have been caused b y organic wastes in the water source. Threshold odors from 100 to several thousand were observed in the raw water. Organic materials were recovered from the raw and finished water in concentrations from 45 to 3000 parts per billion, showing a direct variation with the odor thresholds and an inverse relationship to river flow. Aromatic hydrocarbons and oxygenated neutral materials were the most odorous classes o f substances isolated from the water; a few parts per billion of these materials were detectable b y odor. The results illustrate some o f the techniques available for the study of organic contaminants affecting water quality.
THE
city of K t r o , T5’. Va.. has been confronted with serious taste and odor problems in the water supply for a number of years. This situation is principally due to the city’s location on the Big Kanaivha River, 10 miles below the highly industrialized area of Charleston, 15’. Va. The odor problems have been described by Haynes and Grant ( 3 ) ,as well as water-treatment methods employed a t the Nitro plant. The object of this study was to determine the kinds and quantities of organic chemicals in the raw and finished water a t Nitro affecting taste and odor and to relate the factors of flow and threshold odor to these materials. Taste- and odor-producing organic materials may reach waters from runoff, discharge of domestir and industrial wastes, and the growth and decay of aquatic plants and animals. I n addition to taste and odor effects, these chemicals may impair water quality for industrial uses and interfere with water-treatment processes. Whether such materials in the concentrations encounteied have physiological effects on man is not known. Certainly, materials that survive natural purification and all known water-treatment methods are of interest to water works officials and health authorities. The carbon filter method ( 2 , 6) was used for the concentration and recovery of the organic materials from the water. Threshold odors of the r a F and finished water viere determined a t regular intervals during the period of study (August 1951 t o February 1953). An attempt was made t o identify the materials most responsible for odor. I n addition to studies of chemicals and odors, the organic material recovered was tested on white mice for possible cancer-producing effects.
Carbon Filter Studies Sixteen expeiimental runs Fere made on the S i t r o water using the carbon filter for collection of the samples. Certain run7 included both raw and finished water for purposes of comparison. Table I shows the recoveries of organic materials obtained as a result of these tests and the per cent reduction of the organic materials accomplished by the water treatment. Water treat-
268
ment consisted of high pressure aeration, coagulation, filtration, chlorination, and application of active carbon. Recoveries of organic materials from the raw water ranged from 170 to 3050 parts per billion (p.p.b.). The 3050 p.p.b. recoverv occurred following a spill of industrial waste. However, the raw water commonly contained 500 to 1000 p.p.b. of the organic materials. The finished water yielded 46 to 1Oi5 p.p.b. of materials. Thc quantities recovered represent only chloroform-extractabk materials and comprise an indeterminate portion of the total materials present. Highly volatile materials which may be a factor in the raw water a t S i t r o would be lost, but i t is believed that the principal taste- and odor-producing materials are re-
Table
1.
Period
Dates From To
Organic Material Recovered from Raw and Finished Water a t Nitro, W. Va.
1
8/21/51
lO/5
2 3 4 5
10/9 10/28 11/14 11/29
101’27 11/13 11/ 2 8 12/16
6 7 8
12/17 4/13 4/22
1/5/52 4/21 5/13
9 10 11
5/20 6/17 7/22
6/16 7/11 811
12
10/30
l1/5
13
11/18
11/24
14
12/22
12/28
15
1/14/53
1/23
16
219
2/18
pzetrz, Gal.
Kater
10,905 10,905 4,945 5,595 3,365 4,390 5,017 3,555 1,260 2,235 10,008 10,260 9,945 3,095 1,017 1,200 1,010 1,155 1,025 1,005 1,178 1,080 2,065 1,410 2,115
Raw Finish e d RawRaw Raw Raw Finished Raw Raw Raw Finished Finished Finished Raw Finished RawFinished Raw Finished Raw Finished Raw Finished Raw Finished
INDUSTRIAL AND ENGINEERING CHEMISTRY
$f:$$s Recovered Grains P.p.b. 41 90 7.45 25.05 22 68 5 54 2.58 2.70 2.29 2.55 3.25 3.72 3.14 2.59 5.85 1.76 8.90 4.12 5.35 3.44 11.66 3.61 2.38 3.46 3.77 2.70
1013 184 1340 1070 460 156 142 1717 _ .. 540 388 QR “1
81 46 500 457 1830 1075 1220
885 3060
810 580 440 705 340
Reduction, Raw t o ~ i ~ i ~ h ~ d ,
%
si:0
.. I .
..
8.9
.. ..
74 5
.. 8.6
41.2 27.4 73.5 24.1 51 5
Vol. 48, No. 2
STREAM POLLUTION PROBLEMS covered by this method. Studies of pure compounds using the carbon method have indicated that recoveries of 75 t o 95% may be expected. Recoveries from the filters are comparable, as all were treated in a similar manner. As both raw and finished water were included in a number of test runs, it was possible t o estimate the effectiveness of the water treatment a t Nitro in the removal of organic material. The extent of removal ranged from 9 t o 82%. The principal odor-reduction methods a t Nitro were aeration and application of active carbon in amounts based on the tests and judgment of the chemist and plant operator. Carbon dosages varied from 26 to 258 pounds per million gallons during this study. The materials present change in quality and quantity and may vary widely as t o the ease with which they are removed. Better efficiency is obtained in removing the most odorous portion of the organics than in reducing the over-all organic content.
Table II.
Period 1 2 3 4 5 6
7 8 9 10 11 12 13 14 15 16
Average Threshold Odor Numbers on Raw and Finished Water a t Nitro, W. Va.
Dates From To 8/2 1/5 1 10/5 10/9 10/27 10/28 11/13 11/14 11/28 11/29 12/16 12/17 1/5/52 4/13 4/21 4/22 5/13 5/20 6/16 6/17 7/11 7/22 8/1 10/30 11/5 11/18 11/24 12/22 12/28 1/14/53 1/23 2/18 2/9
No. of Observations 5 3 2 2 3 3 2 3 4 4 2 1 1
1 2 1
* v * Threshold Odor Number Raw Finished 646 25 1,620 109 3,536 170 884 73 835 34 123 8 114 11 193 8 109 29 645 15 23 2,040 42 1,060 278 6,250 12,500 156 262 39 2 240
Reduction in Odor,
% 96.0
93.5 95.5 92.0 96.0 93.5 90.0 96.0 73.5 97.5 98.5 97.5 95.5 99.0 85.0 89.0
Odor Studies
Threshold odor tests ( I ) were made a t regular intervals on the raw and finished water. During the period of this study, nbutyl alcohol was used as a “standard” odor substance t o measure the observers’ sensitivity. A correction factor was applied to obtain threshold numbers comparable t o those that would be obtained by an observer of unchanging sensitivity. For each series of odor tests corresponding t o the periods of carbon filter operation, the corrected geometric average threshold was com-
5
R
Flow Relationships
16
,I
SAMPLING
Figurel.
puted. Table I1 shows the threshold odors of the raw and finished water and the per cent reduction in odor resulting from the water treatment. The raw water threshold odors ranged from 110 to 12,500 and the odor range in the finished water was from 2 t o 300. The reduction of odor achieved by the treatment plant varied from 74 t o 99% and usually exceeded 90%. Figure 1 shows graphically the per cent reduction of the concentration of organics and the per cent odor reduction from the raw t o finished water a t Nitro. The extremely intense odor characteristics of the materials in the raw and finished water are indicated by computing the ratio of the recovery of materials in parts per billion t o the threshold odor. This in effect indicates the parts per billion of materials present a t the threshold odor level. For the raw water these concentrations were from 0.2 t o 5 p.p.b. and for the finished water the range was 1 t o 26 p.p.b. Figure 2 shows the relationship of the threshold odor and organic content of the raw and finished water. These data indicate that the principal odorous constituents of the raw water are being substantially reduced by the water treatment. Significant quantities of other organic materials remain in the finished water. The substances remaining are much less odorous than those that were removed.
r--
r
I
Organics in water are obiectionable not only from the standpoint of taste, odors, and other features, but they are causing deterioration of costly anion exchange resins used in demineralization. It is always difficult to identify or classify complexed mixtures of organic materials. The technique presented here is CI favorable approach to classification.
PERIOD
I
Reduction of odors and organic materials resulting from water treatment
February 1956
If the pollutional load on the river were constant, odors and the concentration of organic materials would vary inversely with the river flow. Domestic sewage discharge is relatively constant, whereas industrial discharges may be variable. It is a common practice to discharge lagooned materials a t times of high water. I n addition, heavy runoff and stirring of bottom sediments may add t o the organic load. Biochemical oxidation may change the quantity and character of the organic materials and is more effective during warm weather. The flow of the river is plotted on a chart showing threshold odors and quantities of organic materials recovered from the raw water (Figure 3). All figures are averages computed for the time interval which corresponded t o the period of operation of the carbon filter. From periods 2 through - 6 the river flow was increasing. The organics recovered decreased during the same time interval, as would be expected.
INDUSTRIAL AND ENGINEERING CHEMISTRY
269
'ooOF-T 1
I
l
l
LEGEYO 0 - R AW W A T E R
9 00
0
Table 111.
WATER
o.FINlSHED
BOO
0
1 v)
W
IL
400
1
+
300
*ool 100
Period
1 0 4
O I n j
0
200
IO0
l o0
1
4 5 6
7 8 11 12 13 14 15 10
I
1
Distilling Temg. a t l p 1 4 Mm. Hg, C .
300 4 0 0 5 0 0 6 0 0 700 800 O R G A N I C C O N T E N T - p.p,b.
900
1000
Id
Correlation of threshold odors and organic content in raw and finished water
Table V.
However, for periods 2, 3, and 4 the threshold odois increaspd, leveled off a t period 5, and dropped to low levels at periods 6, 7, and 8. When the river flow decreased again in periods 11, 12, and 13, the odors and organics showed corresponding increases. During period 14 an accidental spill of industrial waste occurred. This event is reflected by the largest odor threshold (12,500) and the largest recovery by the carbon filtei (3050 p.p.b.) during this study. When the effects of the spill had passed, recoveries and odors were diminished by increased river flox. It is of interest t o coinpute the odor load and the chemical load of the river. The odor load is a factor relating the threshold odor to the flow. If dilution were the sole factor influencing odor, a constant figure for odor load would be obtained. T h e chemical load is exprcssed in terms of pounds per 24 hours of material in the river, computed froin the flow and quantities recovered by the carbon filter. These data are presented in Table 111. The odor load is fairly consistent and sharply reflects the industrial waste spill a t period 14. It is concluded that the river flow 20 COO 1 1 correlates fairly well with the odor in the water a n d t h e quantity of chemicals present. Unusual events such IL as spills, dumpings, or changes in the m kinds of chemicals present may inI 3 z fluence the conditions t o a significant degree. The finished n-ater odor 0 IL a thresholds and the quantities of recovered materials closely follow the 0 0 same variations noted in the raw W water.
%
Density Refractive index Carbon, % IIydrogen, 70 Unsnponifiable, % Nitrogen n o t detected
Description CGlGrkSS 011 Colorless oil Light yellow liquid Dark bron-n liquid
19
95 100 to 105 Residue
IC
17,200 11,500 20,400 18,700 11,500 24,000 56,700 57,500 6,800 16,300 39,600 119,000 60,500 85,500
Yield,
65 to 70
la lb
1
Chemical Load, Lb./24 Hr.
Vacuum Distitlation of Filter Extract
Table IV. Fraction
I
Raw Odor Load Raw Threshold T.O. X F l o h Recovery, Odor X 108 P.P.B. 646 1.3 1013 1,620 1.7 1340 3,536 8.0 1070 884 4.3 460 835 7.4 156 123 2.1 170 114 1.4 540 193 3.5 385 2,040 3.4 500 1,660 1.8 1830 6,250 24 1220 12,500 59 3060 202 3.3 580 240 3.5 705
2,030 1,030 2,280 4,900 8,800 16,900 12,600 17,926 1,640 1,070 3,900 4,680 12,500 14,550
1
2 3
o o
0
Figure 2.
I
Odor and Chemical Load on Kanawha River
Flow hllllioh Gal./Day
23 2o 38
Properties of Fractions 1 a to 1 d la lb IC Id .0.924 0.917 0.945 0.975 1.482 1.548 1.559 1.565 75.5 80.5 79.1 82.6 10 5 13.5 11.9 12.1 59.2 45.0 04.1 87.3 in a n y frsction b y micro-Dumas inethod
may be ajiunicd that cliaiiges iii manufactiiririg prowsses and products occurring during the period of this study caused corresponding changes in the chemical composition of the organic pollutants. The organic mixture recovered from the carbon filter and remaining after solvent removal was a dark brown jelly having a heavy, sn-eetish odor that was disagreeable. This material was separated into fractions, by applying vacuum fractional distillation t o one sample and by subjecting a second sample t o organic group separation according t o solubility classes ( 2 ) . Fractional Distillation. A 13.7-gram portion of the filter extract (sample 1) FTas distilled in vacuum at 12 to 14 mm. of mer-
~
*
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