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Trace inorganics in rural potable water and their correlation to possible sources
14awr R,,scarch Vol. 12. pp. 257 to 261 ~q~ Pergamon Press Ltd. 1978. Prinlcd in (Jrcat Ilrilain
IXl43-1154 7~ 1~4/II-0257SI)2(Xl (I
TRACE I N O R G A N I C S IN RURAL P O T A B L E WATER A N D THEIR C O R R E L A T I O N TO POSSIBLE S O U R C E S S. S. SANDHU, W. J. WARREN and PETER NELSON Water Laboratory, South Carolina State College, Orangeburg, SC 29117, U.S.A. (Received 10 April 1977, in revised form 15 August 1977)
Abstract--Ninety-eight water samples, comprising about 10".~, of the total sources available to rural homes in Hampton County, South Carolina, were randomly selected and analyzed for inorganic constituents. Chemical contamination is widespread in this area and many people are using substandard quality water. A noticeable number of water samples showed unacceptable levels of arsenic, iron, manganese and mercury. Iron and collodial material were chiefly responsible for turbidity in 19~'~of the water sources. Acceptable levels of cadmium, chloride, copper, lead, nitrate, phosphate, sodium, total solids and zinc were detected in most of the samples. Statistical analysis indicated that leachings from septic tanks were at least partially responsible for the contamination of shallow water supply sources with nitrate, phosphate, chloride and arsenic. Iron, lead and manganese appear to have come from corrosion of antiquated plumbing in older homes.
INTRODUCTION Studies in the past (Hammerstrom et al., 1972; Kopp & Kroner, 1969; Schroeder & Balasa, 1966; U.S. Department of Health Education, and Walfare, 1962-63, 1966; & Krenkel, 1974) have shown micro amounts of arsenic, cadmium, copper, iron. lead, manganese, mercury and zinc in public water supply systems as well as in interstate carrier water supply sources. Metal ion concentrations in these water sources were generally acceptable (U.S. Department of Health, Education & Welfare, 1962) except for a few reservoirs (Angelillo, 1961). Water supply wells in rural areas have been found to have high levels of nitrates (Harris & Brecher, 1974) as a result of possible seepage from septic tanks. Excessive nitrates in drinking water has been reported to cause infant cyanosis (Subcommittee on Air and Water Pollution, 1970, Part 2). A few investigations have suggested that lead pipes and goosenecks in house plumbing systems were the principal sources of lead in municipal drinking water (Goldberg, 1974; Kehoe et al., 1940). The potential for chemical pollution of groundwater has been discussed by Walker (1969), who found in Certain selected cases that pollutants readily entered groundwater through substrata, crevices, or limestone or dolomite aquifers. The crevices allowed rapid flow of contaminants without significant dilution by groundwater (Kingston, 1943). Because of the nature of soil reactions, certain chemical species released from septic tanks exhibit greater mobility through soil and greater pollution potential than others (Miller, 1957). Groundwater contamination by seepage of chloride, nitrate, sulfate, and phosphate from septic tanks has been found to be common and widespread over much of Long Island (Thomas &
Schneider, 1970). Private sewage disposal systems in the Ohio drainage basin contribute 38,2501bs of phosphate per year to Hoover Reservoir (Birch, 1969). JUSTIFICATION The proportion of rural people in South Carolina is rather small, but in Hampton County where this survey was conducted, the proportion of rural residences (residences not located in an incorporated municipality) is about 58~ or 9500 people (McLean, 1970). Most of the drinking water in this county therefore comes from private water supplies, many of which do not meet the minimum specifications normally prescribed for public water systems. The location of the survey area is shown in Fig. 1. Hampton County is bordered by the Savannah River. The soils are generally sandy and waterlogged and a considerable amount of agricultural chemicals is used for crop production (Personal CommunicaNorth Carolina
~ , ~ i ~ .Spartanburgp'~ South arolina Columbia Orangeburg •
" ~ / /
~.~
~ J
"~ ~x Chor~e,~/-
~
Hompton,T"
Fig. I. Location of study. 257
Atlantic
oceoo
S. S. S A N D H U ,
258
W. J. WARREN
lion, 1972}. Consequently, there is a distinct potential for contamination of groundwater. The South Carolina Department of Health and Environmental Control closely monitors public potable waters for biological contamination, but water systems checked were generally not tested for any chemical pollutants (Harris & Brecher, t974). This study was undertaken to thoroughly investigatc the type and extent of physical and chemical contaminants in private rural water supplies, to determine if private drinking waters meet the 1962 federal criteria for public water supplies (U.S. Department of Health, Education and Welfare, 1962) and to determine if the sources responsible for the decline of water quality can be identified. EXPERIMENTAL
MATERIALS
AND
METHOD
Water samples were randomly selected from rural sources of drinking water in Hampton County. SC. The number of samples taken represented sources available to 10'~,, of the county's population. The following information regarding the water supply system and household was obtained: (1) location, (2) family income, (3) education, (4) type of water source, including the well depth, (5) age and type of plumbing, (6) type of human waste disposal system, (7) septic tank distance from the source, (8l water table depth, (9) general condition of sanitation related to water supply, (,10) terrain and land use of watershed above the water source, where relevant, (I 1) location of any industry in the vicinity, (12) waste dumping sites and (13) types and amounts of agricultural chemicals used. One-liter water samples were collected, in Pyrex glass jars with screw-on Teflon caps, and stored on ice. All necessary precautions for trace analysis were taken throughout the work. The temperature and pH of the samples were taken at collection time. At the end of the day the samples were brought to the laboratory and stored overnight at 4'C before being analyzed. Standard methods were used for the chemical and physical examination of water. Chlorides were determined by the argentometric method. Nitrites were converted to nitrates, and then total nitrates were determined by the phenoldisulfonic acid method. Total phosphates were determined by the vanadomolybdophosphoric acid colorimetric method. Total residues were determined by evaporation of suitable aliquots in Pyrex dishes. Turbidities were determined by nephelometry (American Public Health As-
and
PETER NELSON
sociation, 1971). Sodium was determined using specitic-iou electrodes {Orion Research. lnco, 1972J. Aliquots of water samples were then preserved with nitric acid and directly aspirated, under standard conditions, into a Perkin-Elmer Model 306 atomic absorption spectrophotometer for the evaluation of copper, iron. manganese and zinc. Duplicate 100ml amounts of every third acidified water sample werc concentrated to 10ml by evaporation on a water bath in preparation for the determination of arsenic, lead and cadmium, using a sampling-boat-system technique. Mercury in the water was determined, on duplicate samples, b~ flameless atomic absorption spectrophotometry (Pcrkin Elmer Corp. 1970).
RESULTS
AND
DISCUSSION
The water samples collected for analysis in the present survey were drawn from a variety of private supplies--drilled wells, dug wells, both open and covered, hand-pumped wells, hand-drawn wells, and an artesian well. The largest group (75°4) was the covered wells, which generally were over 20m in depth and had some type of electrical pumping unit and a solid heavy covering such as a metal cap or a concrete slab. The only other large group (201'o) was the "open" wells, which seldon exceeded 15m in depth and generally had hand-operated delivery systems and little or no protective covering. All samples came from sources where it was not possible to treat the water in any way prior to its use in the home. The chemical and physical characteristics of potable waters, along with their mandatory limits, are summarized in Table 1. Nineteen percent of the samples showed turbidity above the acceptable limit of 5 units established by the health agency (U.S. Department of Health, Education and Welfare, 1962). A few of the water samples (11?~o) appeared turbid at the time of collection. The colloidal organic matter or clay seemed to be responsible for this turbidity. No attempt was made to measure the amount of these constituents. The remaining samples did not show any abnormalities at collection time but when kept overnight, another 8% developed turbidity, possibly
Table 1. Chemical and physical characteristics of rural drinking waters Range Ippml
Samples assayed
MandatoD* heahh limil [ppl'nl
Percent exceeding health limit
Componem
Mean. p p m
Arsenic Cadmium Chloride Copper Iron Lead Manganese Mercur) Nitrate Phosphate Sodium Total Residues Zinc
0.0768 0.0005 6.27 0.0608 0484 0.0014 0.0431 0.0016 0.761 0.2046 1.990 157.7
< 0.002 < 0.00001 < 0.2 < 0.1 < 0.1 < 0.0001 < 0.050 < 0.00I 0.04 < 0.20 0.010 20.(]0
0.183 -0.0013 55.0 -0.3 -3.7 -0.0175 -0.41 -0.024 -3.73 - 4,65 ~16.00 356.00
33 33 98 98 98 33 98 33 98 98 98 98
0.354
< 0.01
~2.18
98
5.0
0.0
pH Turbidity Units
7.7 3.99
4.7 < 0.1
-8.0 -48.7
98 98
4-8 5
0.0 19.4
0,05 0.01 250.0 1.0 0.3 0.05 0.05 001 45.0 --500.0
* U.S. Department of Health, Education and Welfare, Drinking Water Standards, 1962.
27 3 00 O0 O0 40,8 00 34.7 15.2 0,0
O0
Trace inorganics in rural potable water
259
Table 2. Linear regression analysis of data in Table 1 and well characteristics (Fryer, 1966) y
A
Significant at P = 0.01 Iron, p p m
0.62 p p m
Iron. p p m
0.72ppm
Chloride. ppm
Significant al P = 0.05 age of well. _~r arsenic, ppb pH Significant at P = 0.10 Lead. ppb Lead. ppb Arsenic. ppb
Y=A+B.X+C.Z B
C
age of well. yr
- 0 . 0 2 ppm/$10~/yr
H*, moles I -I
0.062ppm/unit
7.05 p p m
1.69 x 10"~ppm mole- ~I " I -0.04 ppm/m - ~
well depth, m
- 0.018 p p m / m
7.56yr.
- 0 . 3 4 yr/$10J/yr,
income. $10J/yr.
- 0 . 3 3 yr/m
- 0 . 0 1 3 ppb 6.55
9.4 ppb 26.34 ppb 0.64 ppb
1.4 × 10 -5 ppm/yr,
X
0.011 ppb/ll0~/yr, 6.5 x 10-J/m
- 0 . 0 1 2 ppb/ m - 2.62 ppb - 3 x 10 -4 ppb/m
Z
R
annual income $ I 0~/y r lurbidily. unit septic tank to well distance, m
0866
well depth, m
0.611
0.821 0.676
income, $10~/yr, well depth. m
0406 0.384
well depth. m pH septic tank to well distance, m
0.344 0.227 0.181
B and C are coefficients, derived from the slope of the plane or a line, which indicate the direction and magnitude of change in the dependent variable (Y) for a given change in the independent parameters (X) and (Z). A is the y-axis intercept and is a constant, statistically derived by assuming that the values of the independent parameters are zero. R is the product-moment coefficient of linear correlation and is an index which measures the strength of the observed linear regression. as a result of oxidation and precipitation of iron (II) (Stum& Morgan, 1970). The odor and color were characterized only by sight and smell. Though no obnoxious odor was detected, some waters containing iron or suspended matter were repugnant and seemed unacceptable for human consumption. The majority of the waters were slightly alkaline, having an average pH of 7.7. Arsenic was detected in about 91~ of the samples, and 27% exceeded the mandatory health limit (U.S. Department of Health Education and Welfare, 1962). Similar results for tap water (Schroeder & Balasa, 1966), public and private water supplies (U.S. Department of Health, Education and Welfare, 1962; Sandhu et al. 1975), have been reported in the past. It is believed (Subcommittee on Air and Water Pollution, 1970, Part 4) that drinking water from many locations frequently exceeds the established health limit for arsenic. Cadmium was not detected except in two samples out of 33 tested. Copper, lead and zinc were detected in almost every sample, but their concentrations never exceeded the established health limits though lead concentration ranged between 10-50 ppb in about 7~o of waters. It is well established that under certain circumstances (Harris & Brecher, 1974; Kehoe et al., 1940; Goldberg, 1974) drinking water has had unacceptable levels of lead. Iron was found in about every sample and the health limits (U.S. Department of Health, Education and Welfare, 1962) for iron and manganese were exceeded in 41 and 34% of the samples respectively. Although the presence of excessive amounts of iron and manganese in water for home use presents little or no immediate health problem for the consumer, many users complained about the rust, brown color and unpleasant taste of their waters. A few water samples exceeded the health limit for mercury.
Chloride, nitrate, phosphate, total solids and sodium were found in about every sample, but the concentrations were generally low and posed no health problem to the consumer. Statistical analysis of data A number of persons in the survey area were using standard water, but beyond the unpleasant taste and rust, most people were unconcerned and unaware of its quality. The consumer had no conception of the possible sources polluting his water. Information collected about the households and the well characteristics was used, in conjunction with chemical and physical data of Table l, to compute multiple linear correlations, Table 2. This was done to identify the possible factors affecting the water adversely. There are many complex and interdependent variables that could significantly affect the quality of rural drinking water. Iron concentration in water supply sources was significantly related to consumer income, well depth, age of the well, hydrogen ion concentration, and turbidity. The hydrogen ion concentrations and level of turbidity were generally good indicators of the expected iron concentrations. A hydrogen ion concentration equal to or greater than 10-4moles 1-t. i.e. pH4, appeared to produce a very rapid increase in iron concentration. The statistical analysis suggested that the corrosion of the antiquated plumbing in older homes of relatively low income families was responsible for high iron levels in water. The statistical analysis also indicated that newer wells, generally associated with higher income families, had relatively low iron concentrations. A significant correlation between the chloride concentration in well waters and well depth and its distance from the septic tank was also observed (Table
260
S. S. SANDHU. W. J, WARREN and PETER NELSON
2). This implies that a shallow well located relatively close to a septic tank had higher chloride concentration. Septic-tank-to-well distance and the well depth showed a weak correlation with nitrate and phosphate concentration in water. This suggested that chloride, phosphate and nitrate probably reach the groundwater through septic tank seepage. Chloride ions are quite mobile in soil and have been used as a measure of pollutant diffusion in groundwater (Kaufman & Orlob, 1956). The presence of chloride in well waters and its statistical relation to the water supply source parameters indicates its origin from the septic tank. Lead concentrations in water supply sources showed a significant negative correlation with pH and a negative correlation with well depth. Also there was a positive correlation between the well depth and pH. This implies that the deeper wells with relatively higher pH should have lower lead levels. It has also been suggested that lead generally comes from goosenecks and other soldered joints in the plumbing system. The newer wells were comparatively deeper and were generally owned by relatively richer families. The homes of the richer families had plastic plumbing systems, which may explain the lower lead levels in waters drawn from deeper wells. Table 2 data also suggested that higher-income families generally had newer and deeper wells and thus were able to tap superior quality groundwater. Arsenic showed a significant positive correlation with family income and no relation to well depth or age, indicating that arsenic levels in water are not related to the deterioration of the water supply system. There was a weak, but significant (P = 0.1), negative correlation between arsenic concentration and the well-to-septic-tank distance, suggesting that the septic tanks of rich persons were responsible, in some way, for the augmented levels of arsenic in water. Arsenic probably may come directly from septic tank leachings or hydrostatic pressure of the septic tank may redound to the movement of soil arsenic into the well water. The implications of potential groundwater pollution by arsenic from synthetic detergents have been discussed (Angino et al., 1970). Under normal conditions the phosphate and arsenic compounds are readily and rapidly absorbed in soil and travel only short distances, but the presence of surfactants does change the soil characteristics and induces an increased mobility of pollutants in soil (Cardenali & Stoppini, 1974). Well waters from Long Island were found significantly polluted with alkylbenzene sulfonates (Thomas & Schneider, 1970) and if surfactants can leach from septic tanks and reach groundwaters, probably other contaminants can follow. It has been suggested (Minear & Patterson, 1973) that if the septic tank drain field fails to work effectively in removing the pollutants from the percolating water, the chemical pollutants can travel tong distances in ground and have a distinct impact on contaminating groundwater.
o~/ \ \ 8runson
coU
147~k~°/4
CoUeton County
1.4
N
I
~
~
Hampton
-oun,y
77
f,,4
258
Fig. 2. Distribution of mercury in rural potable water around Varnville in Hampton County. Mercury concentrations are given in parts per billion (ppb). It was also noted that the higher-income families generally had higher levels of arsenic in their water supplies. Based on the assumption that higher-income families probably have more built-in home laundering facilities, it was speculated that increasing arsenic concentration in their water sources was due to heavy use of detergents and a greater frequency of home laundering. Groundwater pollution by septic tanks has been referred to in the literature as a common occurrence (Thomas & Schneider, 1970). Less than 50% of the septic tanks studied in Illinois, Michigan, Ohio and Wisconsin worked satisfactorily as waste disposal systems (Kiker, 1958). The diffusion of pollutants from the point of origin--septic tank--to the nearby water source might have been further aggravated by the occasional heavy rains (average rainfall 48.0in.) and the flooding of the survey area by the Savannah River which has been reported to be fairly contaminated with all sorts of chemicals (Geraghty et al., 1973). Mercury concentrations did not show any correlation either with the well characteristics (depth, etc.) or the socio-ecomomic status of the household. This suggested that these parameters had no bearing on the mercury levels of water. Mercury contamination apparently occurs for other reasons. Data indicate that high-level mercury samples were localized in the Hampton-Varnville area (Fig. 2). It is difficult to pinpoint the source of mercury in these water supplies, but there are several small industrial plants, including an electronics firm, located in this area. CONCLUSIONS
About one-third of the families in the survey area were using substandard water. Metallic contamination was quite common and in certain cases the levels of arsenic, iron, manganese and mercury were far above acceptable limits. The consumer corn-
Trace inorganics in rural potable water plained about the turbidity, brown color and unpleasant taste of his water. Nitrate, phosphate, chloride, copper, lead, sodium and zinc were found in most of the water samples but their concentrations were always low. Statistical analysis of the data suggested that iron, lead, and manganese appeared to have come from corrosion of antiquated plumbing by soft water in older homes. This problem could be eliminated or considerably reduced by use of plastic pipes in home plumbing systems. Leaching from septic tanks was partially responsible for the presence of arsenic, chloride, nitrate and phosphate in relatively shallow well waters. Acknowledgements--We wish to thank Dr. R. L. Hurst, Vice-President of Research, Planning and Extension, for his interest and encouragement. We also thank Dr. W. Stancliff of Claflin College for his help in preparing this manuscript. This study was financed under 1890 Research Program of CSRS. REFERENCES
American Public Health Association, American Water Works Association and Water Pollution Control Federation. (1971) Standard Methods for the Examination of Water and Waste Water, 13th edition, pp. 1-362. American Public Health Association, Washington. Angelillo B. (1961) Manganese in drinking water. Ingiene Moderna 54, 3-34. Angion E. E., Mangnuson L. M., Waugh T. C., Gallen O. K. & Berdfelt J. (1970) Arsenic in detergents: Possible danger and pollution hazard, Science 168, 389-390. Birch T. J. (1969) Sources of pollution in the drainage basin contributing to the eutrophication of Hoover Reservoir. Ph.D. thesis, Ohio State University, Columbus, Ohio. Cardenali A. & Stoppini Z. (1974) Effects of detergent-polluted waste water on the hydrological characteristics of agricultural soils. II Structure Stability. Ann. Fac. Agar, Univ. Studi. Peruoia 29, 349-368. Fryer H. C. (1966) Concepts and Methods of Experimental Statistics, pp. 420--450. Allyn and Bacon, Boston, Mass. Geraghty J. J., Miller D., Van Der Leeden F. & Troise F. L. (1973) Water Atlas ok[ the United States, pp. 51, 65. Water Information Center, Washington. Goldberg A. (1974) Drinking water as a source of lead pollution. Environmental Health Perspectives 7. U.S. Dept. Health, Education and Welfare, Pub. No. 72-218, Public Health service NIH, Washington. D.C. Hammerstrom R. J., Hisson D. E., Kopfler R. C., Mayer J., McFarren E. F. and Pringle B. H. (1972) Mercury in drinking water. J. Am. War. Wks. Ass. 64, 60-69. Harris R. H. & Brecher E. (1974) Is the water safe to drink': Consumer Rept, 436--449. Kaufman W. J. & Orlob G. T. (1956) Measuring groundwater movement with radioactive and chemical tracers. d. Am. Wat. Wks Ass. 48, 559-572. Kehoe R. A., Cholak J., Hubbard D. M., Bambach K., McNary R. R. & Story R. V. (1940) Experimental studies
261
on the ingestion of lead compounds. J. Ind. Hyg. Toxicol. 22, 381-386. Kiker J. E. (1958) Fringe area sewerage problems, d. San. Engng Div. ASCE. 84, Paper No. 1714. Kingston S. P. 0943) Contamination of water supplies in limestone formations, J. Am. Wat. Wks. Ass. 35, 1450-- 1562. Kopp J. & Kroner R. C. (1969) Pollution Surveillance Report. Federal Water Pollution Control Administration, U.S. Government Printing Office. Washington. Krenkel P. A. (1974) Heavy Metal in Aquatic Environment. pp. 68-119. Pergamon Press, New York. McLean E. (1970) Advance Report. Census of Population, South Carolina. PC (Vl)--revised. Minear R. A. & Patterson J. W. (1973) Septic tank and groundwater pollution. In Groundwater Pollution, pp. 53-71. Underwater Research Institute, St. Louis, Missouri. Miller J. M. (1975) Underground waste disposal and control. J. Am. Wat. Wks Ass. 49, 1334-1340. Orion Research Inc. (1972) A Whole New Technoloyy ]br Chemical Measurements. FORUM IM400/2711, Orion Research, Cambridge, Mass. Perkin-Elmer Corp. (1970) Analytical Methods Jot Atomic Absorption Spectrophotometer. Perkin-Elmer, Ay 05 FP4, Norwalk, Conn. Personal Communications (1972) County Extension Agent, Hampton County, South Carolina. Sandhu S. S., Nelson P. & Warren W. J. (1975) Potablc water quality in Georgetown County. Bull. envir. Conturn. Tox. 14, 465-472. Schroeder H. & Balasa J. J. (1966) Abnormal trace metals in man: Arsenic, d. Chron. Dis. 19, 85-106. Stumm W. & Morgan J. (19701 Aquatic Chemistry, p. 534. Wiley-lnterscience, New York. Subcommittee on Air & Water Pollution of the Committce on Public Works, United States Senate. (1970) Water Pollution--Part 4, United States Senate. Ninety-first Congress, Second Session. pp. 1388-1405. U.S. Govcrnment Printing Office, Washington. Subcommittee on Air & Water Pollution of the Committee on Public Works, United States Senate. (1970) Water Pollution--Part 2, United States Senate, Ninety-first Congress, Second Session. pp. 662-671. U.S. Government Printing Office, Washington. Thomas H. E. & Schneider W. J. (1970) Water as an Urhan Resource and Nuisance. U.S. Geological Survey Circular 601-D, Washington. U.S. Department of Health, Education and Welfare, Public Health Service. (1966) Keep Your Drinking Water Safe. Publication No. 1511. U.S. Government Printing Office. Washington. U.S. Department of Health, Education & Welfare, Public Health Service. (1962-63) Drinking Water Quality of Selected Interstate Carrier Water Supplies. Public Health Service Publication No. 1049-A. U.S. Government Printing Office, Washington. U.S. Department of Health, Education and Welfare. Public Health Service (1962) Drinking Water Standards. Public Health Service Publication No. 956. U.S. Government Printing Office, Washington. Walker W. H. (19691 illinois groundwater pollution. J..4m Wat. Wks Ass. 61, 31-9.
IXl43-1154 7~ 1~4/II-0257SI)2(Xl (I
TRACE I N O R G A N I C S IN RURAL P O T A B L E WATER A N D THEIR C O R R E L A T I O N TO POSSIBLE S O U R C E S S. S. SANDHU, W. J. WARREN and PETER NELSON Water Laboratory, South Carolina State College, Orangeburg, SC 29117, U.S.A. (Received 10 April 1977, in revised form 15 August 1977)
Abstract--Ninety-eight water samples, comprising about 10".~, of the total sources available to rural homes in Hampton County, South Carolina, were randomly selected and analyzed for inorganic constituents. Chemical contamination is widespread in this area and many people are using substandard quality water. A noticeable number of water samples showed unacceptable levels of arsenic, iron, manganese and mercury. Iron and collodial material were chiefly responsible for turbidity in 19~'~of the water sources. Acceptable levels of cadmium, chloride, copper, lead, nitrate, phosphate, sodium, total solids and zinc were detected in most of the samples. Statistical analysis indicated that leachings from septic tanks were at least partially responsible for the contamination of shallow water supply sources with nitrate, phosphate, chloride and arsenic. Iron, lead and manganese appear to have come from corrosion of antiquated plumbing in older homes.
INTRODUCTION Studies in the past (Hammerstrom et al., 1972; Kopp & Kroner, 1969; Schroeder & Balasa, 1966; U.S. Department of Health Education, and Walfare, 1962-63, 1966; & Krenkel, 1974) have shown micro amounts of arsenic, cadmium, copper, iron. lead, manganese, mercury and zinc in public water supply systems as well as in interstate carrier water supply sources. Metal ion concentrations in these water sources were generally acceptable (U.S. Department of Health, Education & Welfare, 1962) except for a few reservoirs (Angelillo, 1961). Water supply wells in rural areas have been found to have high levels of nitrates (Harris & Brecher, 1974) as a result of possible seepage from septic tanks. Excessive nitrates in drinking water has been reported to cause infant cyanosis (Subcommittee on Air and Water Pollution, 1970, Part 2). A few investigations have suggested that lead pipes and goosenecks in house plumbing systems were the principal sources of lead in municipal drinking water (Goldberg, 1974; Kehoe et al., 1940). The potential for chemical pollution of groundwater has been discussed by Walker (1969), who found in Certain selected cases that pollutants readily entered groundwater through substrata, crevices, or limestone or dolomite aquifers. The crevices allowed rapid flow of contaminants without significant dilution by groundwater (Kingston, 1943). Because of the nature of soil reactions, certain chemical species released from septic tanks exhibit greater mobility through soil and greater pollution potential than others (Miller, 1957). Groundwater contamination by seepage of chloride, nitrate, sulfate, and phosphate from septic tanks has been found to be common and widespread over much of Long Island (Thomas &
Schneider, 1970). Private sewage disposal systems in the Ohio drainage basin contribute 38,2501bs of phosphate per year to Hoover Reservoir (Birch, 1969). JUSTIFICATION The proportion of rural people in South Carolina is rather small, but in Hampton County where this survey was conducted, the proportion of rural residences (residences not located in an incorporated municipality) is about 58~ or 9500 people (McLean, 1970). Most of the drinking water in this county therefore comes from private water supplies, many of which do not meet the minimum specifications normally prescribed for public water systems. The location of the survey area is shown in Fig. 1. Hampton County is bordered by the Savannah River. The soils are generally sandy and waterlogged and a considerable amount of agricultural chemicals is used for crop production (Personal CommunicaNorth Carolina
~ , ~ i ~ .Spartanburgp'~ South arolina Columbia Orangeburg •
" ~ / /
~.~
~ J
"~ ~x Chor~e,~/-
~
Hompton,T"
Fig. I. Location of study. 257
Atlantic
oceoo
S. S. S A N D H U ,
258
W. J. WARREN
lion, 1972}. Consequently, there is a distinct potential for contamination of groundwater. The South Carolina Department of Health and Environmental Control closely monitors public potable waters for biological contamination, but water systems checked were generally not tested for any chemical pollutants (Harris & Brecher, t974). This study was undertaken to thoroughly investigatc the type and extent of physical and chemical contaminants in private rural water supplies, to determine if private drinking waters meet the 1962 federal criteria for public water supplies (U.S. Department of Health, Education and Welfare, 1962) and to determine if the sources responsible for the decline of water quality can be identified. EXPERIMENTAL
MATERIALS
AND
METHOD
Water samples were randomly selected from rural sources of drinking water in Hampton County. SC. The number of samples taken represented sources available to 10'~,, of the county's population. The following information regarding the water supply system and household was obtained: (1) location, (2) family income, (3) education, (4) type of water source, including the well depth, (5) age and type of plumbing, (6) type of human waste disposal system, (7) septic tank distance from the source, (8l water table depth, (9) general condition of sanitation related to water supply, (,10) terrain and land use of watershed above the water source, where relevant, (I 1) location of any industry in the vicinity, (12) waste dumping sites and (13) types and amounts of agricultural chemicals used. One-liter water samples were collected, in Pyrex glass jars with screw-on Teflon caps, and stored on ice. All necessary precautions for trace analysis were taken throughout the work. The temperature and pH of the samples were taken at collection time. At the end of the day the samples were brought to the laboratory and stored overnight at 4'C before being analyzed. Standard methods were used for the chemical and physical examination of water. Chlorides were determined by the argentometric method. Nitrites were converted to nitrates, and then total nitrates were determined by the phenoldisulfonic acid method. Total phosphates were determined by the vanadomolybdophosphoric acid colorimetric method. Total residues were determined by evaporation of suitable aliquots in Pyrex dishes. Turbidities were determined by nephelometry (American Public Health As-
and
PETER NELSON
sociation, 1971). Sodium was determined using specitic-iou electrodes {Orion Research. lnco, 1972J. Aliquots of water samples were then preserved with nitric acid and directly aspirated, under standard conditions, into a Perkin-Elmer Model 306 atomic absorption spectrophotometer for the evaluation of copper, iron. manganese and zinc. Duplicate 100ml amounts of every third acidified water sample werc concentrated to 10ml by evaporation on a water bath in preparation for the determination of arsenic, lead and cadmium, using a sampling-boat-system technique. Mercury in the water was determined, on duplicate samples, b~ flameless atomic absorption spectrophotometry (Pcrkin Elmer Corp. 1970).
RESULTS
AND
DISCUSSION
The water samples collected for analysis in the present survey were drawn from a variety of private supplies--drilled wells, dug wells, both open and covered, hand-pumped wells, hand-drawn wells, and an artesian well. The largest group (75°4) was the covered wells, which generally were over 20m in depth and had some type of electrical pumping unit and a solid heavy covering such as a metal cap or a concrete slab. The only other large group (201'o) was the "open" wells, which seldon exceeded 15m in depth and generally had hand-operated delivery systems and little or no protective covering. All samples came from sources where it was not possible to treat the water in any way prior to its use in the home. The chemical and physical characteristics of potable waters, along with their mandatory limits, are summarized in Table 1. Nineteen percent of the samples showed turbidity above the acceptable limit of 5 units established by the health agency (U.S. Department of Health, Education and Welfare, 1962). A few of the water samples (11?~o) appeared turbid at the time of collection. The colloidal organic matter or clay seemed to be responsible for this turbidity. No attempt was made to measure the amount of these constituents. The remaining samples did not show any abnormalities at collection time but when kept overnight, another 8% developed turbidity, possibly
Table 1. Chemical and physical characteristics of rural drinking waters Range Ippml
Samples assayed
MandatoD* heahh limil [ppl'nl
Percent exceeding health limit
Componem
Mean. p p m
Arsenic Cadmium Chloride Copper Iron Lead Manganese Mercur) Nitrate Phosphate Sodium Total Residues Zinc
0.0768 0.0005 6.27 0.0608 0484 0.0014 0.0431 0.0016 0.761 0.2046 1.990 157.7
< 0.002 < 0.00001 < 0.2 < 0.1 < 0.1 < 0.0001 < 0.050 < 0.00I 0.04 < 0.20 0.010 20.(]0
0.183 -0.0013 55.0 -0.3 -3.7 -0.0175 -0.41 -0.024 -3.73 - 4,65 ~16.00 356.00
33 33 98 98 98 33 98 33 98 98 98 98
0.354
< 0.01
~2.18
98
5.0
0.0
pH Turbidity Units
7.7 3.99
4.7 < 0.1
-8.0 -48.7
98 98
4-8 5
0.0 19.4
0,05 0.01 250.0 1.0 0.3 0.05 0.05 001 45.0 --500.0
* U.S. Department of Health, Education and Welfare, Drinking Water Standards, 1962.
27 3 00 O0 O0 40,8 00 34.7 15.2 0,0
O0
Trace inorganics in rural potable water
259
Table 2. Linear regression analysis of data in Table 1 and well characteristics (Fryer, 1966) y
A
Significant at P = 0.01 Iron, p p m
0.62 p p m
Iron. p p m
0.72ppm
Chloride. ppm
Significant al P = 0.05 age of well. _~r arsenic, ppb pH Significant at P = 0.10 Lead. ppb Lead. ppb Arsenic. ppb
Y=A+B.X+C.Z B
C
age of well. yr
- 0 . 0 2 ppm/$10~/yr
H*, moles I -I
0.062ppm/unit
7.05 p p m
1.69 x 10"~ppm mole- ~I " I -0.04 ppm/m - ~
well depth, m
- 0.018 p p m / m
7.56yr.
- 0 . 3 4 yr/$10J/yr,
income. $10J/yr.
- 0 . 3 3 yr/m
- 0 . 0 1 3 ppb 6.55
9.4 ppb 26.34 ppb 0.64 ppb
1.4 × 10 -5 ppm/yr,
X
0.011 ppb/ll0~/yr, 6.5 x 10-J/m
- 0 . 0 1 2 ppb/ m - 2.62 ppb - 3 x 10 -4 ppb/m
Z
R
annual income $ I 0~/y r lurbidily. unit septic tank to well distance, m
0866
well depth, m
0.611
0.821 0.676
income, $10~/yr, well depth. m
0406 0.384
well depth. m pH septic tank to well distance, m
0.344 0.227 0.181
B and C are coefficients, derived from the slope of the plane or a line, which indicate the direction and magnitude of change in the dependent variable (Y) for a given change in the independent parameters (X) and (Z). A is the y-axis intercept and is a constant, statistically derived by assuming that the values of the independent parameters are zero. R is the product-moment coefficient of linear correlation and is an index which measures the strength of the observed linear regression. as a result of oxidation and precipitation of iron (II) (Stum& Morgan, 1970). The odor and color were characterized only by sight and smell. Though no obnoxious odor was detected, some waters containing iron or suspended matter were repugnant and seemed unacceptable for human consumption. The majority of the waters were slightly alkaline, having an average pH of 7.7. Arsenic was detected in about 91~ of the samples, and 27% exceeded the mandatory health limit (U.S. Department of Health Education and Welfare, 1962). Similar results for tap water (Schroeder & Balasa, 1966), public and private water supplies (U.S. Department of Health, Education and Welfare, 1962; Sandhu et al. 1975), have been reported in the past. It is believed (Subcommittee on Air and Water Pollution, 1970, Part 4) that drinking water from many locations frequently exceeds the established health limit for arsenic. Cadmium was not detected except in two samples out of 33 tested. Copper, lead and zinc were detected in almost every sample, but their concentrations never exceeded the established health limits though lead concentration ranged between 10-50 ppb in about 7~o of waters. It is well established that under certain circumstances (Harris & Brecher, 1974; Kehoe et al., 1940; Goldberg, 1974) drinking water has had unacceptable levels of lead. Iron was found in about every sample and the health limits (U.S. Department of Health, Education and Welfare, 1962) for iron and manganese were exceeded in 41 and 34% of the samples respectively. Although the presence of excessive amounts of iron and manganese in water for home use presents little or no immediate health problem for the consumer, many users complained about the rust, brown color and unpleasant taste of their waters. A few water samples exceeded the health limit for mercury.
Chloride, nitrate, phosphate, total solids and sodium were found in about every sample, but the concentrations were generally low and posed no health problem to the consumer. Statistical analysis of data A number of persons in the survey area were using standard water, but beyond the unpleasant taste and rust, most people were unconcerned and unaware of its quality. The consumer had no conception of the possible sources polluting his water. Information collected about the households and the well characteristics was used, in conjunction with chemical and physical data of Table l, to compute multiple linear correlations, Table 2. This was done to identify the possible factors affecting the water adversely. There are many complex and interdependent variables that could significantly affect the quality of rural drinking water. Iron concentration in water supply sources was significantly related to consumer income, well depth, age of the well, hydrogen ion concentration, and turbidity. The hydrogen ion concentrations and level of turbidity were generally good indicators of the expected iron concentrations. A hydrogen ion concentration equal to or greater than 10-4moles 1-t. i.e. pH4, appeared to produce a very rapid increase in iron concentration. The statistical analysis suggested that the corrosion of the antiquated plumbing in older homes of relatively low income families was responsible for high iron levels in water. The statistical analysis also indicated that newer wells, generally associated with higher income families, had relatively low iron concentrations. A significant correlation between the chloride concentration in well waters and well depth and its distance from the septic tank was also observed (Table
260
S. S. SANDHU. W. J, WARREN and PETER NELSON
2). This implies that a shallow well located relatively close to a septic tank had higher chloride concentration. Septic-tank-to-well distance and the well depth showed a weak correlation with nitrate and phosphate concentration in water. This suggested that chloride, phosphate and nitrate probably reach the groundwater through septic tank seepage. Chloride ions are quite mobile in soil and have been used as a measure of pollutant diffusion in groundwater (Kaufman & Orlob, 1956). The presence of chloride in well waters and its statistical relation to the water supply source parameters indicates its origin from the septic tank. Lead concentrations in water supply sources showed a significant negative correlation with pH and a negative correlation with well depth. Also there was a positive correlation between the well depth and pH. This implies that the deeper wells with relatively higher pH should have lower lead levels. It has also been suggested that lead generally comes from goosenecks and other soldered joints in the plumbing system. The newer wells were comparatively deeper and were generally owned by relatively richer families. The homes of the richer families had plastic plumbing systems, which may explain the lower lead levels in waters drawn from deeper wells. Table 2 data also suggested that higher-income families generally had newer and deeper wells and thus were able to tap superior quality groundwater. Arsenic showed a significant positive correlation with family income and no relation to well depth or age, indicating that arsenic levels in water are not related to the deterioration of the water supply system. There was a weak, but significant (P = 0.1), negative correlation between arsenic concentration and the well-to-septic-tank distance, suggesting that the septic tanks of rich persons were responsible, in some way, for the augmented levels of arsenic in water. Arsenic probably may come directly from septic tank leachings or hydrostatic pressure of the septic tank may redound to the movement of soil arsenic into the well water. The implications of potential groundwater pollution by arsenic from synthetic detergents have been discussed (Angino et al., 1970). Under normal conditions the phosphate and arsenic compounds are readily and rapidly absorbed in soil and travel only short distances, but the presence of surfactants does change the soil characteristics and induces an increased mobility of pollutants in soil (Cardenali & Stoppini, 1974). Well waters from Long Island were found significantly polluted with alkylbenzene sulfonates (Thomas & Schneider, 1970) and if surfactants can leach from septic tanks and reach groundwaters, probably other contaminants can follow. It has been suggested (Minear & Patterson, 1973) that if the septic tank drain field fails to work effectively in removing the pollutants from the percolating water, the chemical pollutants can travel tong distances in ground and have a distinct impact on contaminating groundwater.
o~/ \ \ 8runson
coU
147~k~°/4
CoUeton County
1.4
N
I
~
~
Hampton
-oun,y
77
f,,4
258
Fig. 2. Distribution of mercury in rural potable water around Varnville in Hampton County. Mercury concentrations are given in parts per billion (ppb). It was also noted that the higher-income families generally had higher levels of arsenic in their water supplies. Based on the assumption that higher-income families probably have more built-in home laundering facilities, it was speculated that increasing arsenic concentration in their water sources was due to heavy use of detergents and a greater frequency of home laundering. Groundwater pollution by septic tanks has been referred to in the literature as a common occurrence (Thomas & Schneider, 1970). Less than 50% of the septic tanks studied in Illinois, Michigan, Ohio and Wisconsin worked satisfactorily as waste disposal systems (Kiker, 1958). The diffusion of pollutants from the point of origin--septic tank--to the nearby water source might have been further aggravated by the occasional heavy rains (average rainfall 48.0in.) and the flooding of the survey area by the Savannah River which has been reported to be fairly contaminated with all sorts of chemicals (Geraghty et al., 1973). Mercury concentrations did not show any correlation either with the well characteristics (depth, etc.) or the socio-ecomomic status of the household. This suggested that these parameters had no bearing on the mercury levels of water. Mercury contamination apparently occurs for other reasons. Data indicate that high-level mercury samples were localized in the Hampton-Varnville area (Fig. 2). It is difficult to pinpoint the source of mercury in these water supplies, but there are several small industrial plants, including an electronics firm, located in this area. CONCLUSIONS
About one-third of the families in the survey area were using substandard water. Metallic contamination was quite common and in certain cases the levels of arsenic, iron, manganese and mercury were far above acceptable limits. The consumer corn-
Trace inorganics in rural potable water plained about the turbidity, brown color and unpleasant taste of his water. Nitrate, phosphate, chloride, copper, lead, sodium and zinc were found in most of the water samples but their concentrations were always low. Statistical analysis of the data suggested that iron, lead, and manganese appeared to have come from corrosion of antiquated plumbing by soft water in older homes. This problem could be eliminated or considerably reduced by use of plastic pipes in home plumbing systems. Leaching from septic tanks was partially responsible for the presence of arsenic, chloride, nitrate and phosphate in relatively shallow well waters. Acknowledgements--We wish to thank Dr. R. L. Hurst, Vice-President of Research, Planning and Extension, for his interest and encouragement. We also thank Dr. W. Stancliff of Claflin College for his help in preparing this manuscript. This study was financed under 1890 Research Program of CSRS. REFERENCES
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