E F F E C T OF D O M E S T I C S T O R A G E T A N K S ON T H E Q U A L I T Y OF D R I N K I N G W A T E R S P A R T 1: C H E M I C A
L A NA L YSIS
I. M. J A W A D , M. R. A L - G H A Z A L I , a n d M. S. H. K H O R S H I D
Biological Research Center, P.O. Box 2371, Jadiriyah, Baghdad, Iraq
(Received February 1988) Abstract. An investigation covering 12 districts of Baghdad city was conducted over 2 yr to monitor the effect of domestic storage practice on the quality of drinking water. Water storage tanks are widely used in Iraq as an additional water source. Tap and stored waters were tested for their chemical constituents i.e. Ca, Mg, Na, K, C1, Zn, Fe, Pb, Cd, and total hardness (T.H.). All the tested elements were within the permissible limits. However, statistical analysis showed a significant variation between the different districts for T.H., Cu, Mg and chloride for both tap and stored waters. Seasonal variations have a significant effect on the levels of some elements. The quality of stored water was not affected by storage practice. Zinc, Pb and Fe were the only elements that showed some variation in the stored waters. This was attributed to the effects of corrosion of the tank metal and the migration of metals from the distribution system.
1. Introduction
Water storage tanks are widely used in Iraq as an additional potable water reservior for domestic use. These tanks are usually insulated and sited on the roofs of houses, tower buildings, hospitals, schools, etc, and fed with tap water from the main water distribution systems. They are cubic in shape and fabricated of galvanized metal. The daily household activities are highly dependent on such stored waters, particularly during the long summer time, due to the provision of warm waters from such tanks. The elevated water temperature during the summer season is attributed to the subtropical climate of the country in which the ambient temperature may reach about 50~ in the shade. Domestic plumbing systems are designed to permit the use of this water beside each tap-point of the main potable water system. Although some people would hesitate to use this water for human consumption, others would readily do so. Such a practice could raise questions concerning the health risk of such waters. Storage tanks contain variable levels of trace metals such as Zn, Pb, Cd, Fe, etc, and since these tanks could be used for up to 20 yr, any evident corrosion would affect the mineral content of the stored waters, Many workers have studied the quality of drinking water in relation to the heavy metals (Craun and McCabe, 1975; Gillies and Paulin, 1982; Ohtsuka et al., 1985). Such metals are probably one of the most harmful and insidious pollutants because of their non-biodegradable nature and their potential toxicity to man at certain levels of exposure and adsorption (Pier and Bang, 1980). Epidemiological studies (Pier and Bang, 1980) suggest a relationship between the mineral content of drinking water and the prevalence of such diseases, as hypertension, cancer, urolithiasis, cardiovascular syndrome, and sudden infant Environmental Monitoring and Assessment 11 (1988) 79-87. 9 1988 by Kluwer Academic Publishers.
80
1. M. JAWAD ET AL.
death syndrome (Schroeder and Kraemer, 1974). However, no data are available concerning the levels of minerals in storage tank water in Iraq. This study was conducted to trace the mineral levels in stored waters in an attempt to evaluate the water characteristics from the chemical and physical point of views.
2. Materials and methods
2.1. STUDY AREA Baghdad city, with a population of about 3 million, was selected to conduct the study due to the wide use of the insulated roof water storage tanks as additional water reservoirs for domestic use. The city is supplied with drinking water from nine water distribution systems around the capital. These plants are supplied with raw water from the river Tigris passing through the city. 2.2. STORAGE TANKS Iraqis use an insulated cube-shaped water tank (Figure 1) fabricated of galvanized metal on roof of their house. Tanks vary in size from 0.6 to 2.0 cubic meter for the usual household water use. A series of connected tanks or a larger (2-6 cu.m.) tank may be used for other larger buildings. Water tanks are usually fed with a tap water input pipe near the top, while the output pipe is located a few inches above the bottom. A hole is made in the center of the top side and fitted with a removable cover to aid in cleaning and visual monitoring of the water quality.
INPUT LOOSE COVER
I
I
MAIN WATER SOURCE
MESTIC USE
Fig. 1.
Diagram of a Domestic Water Storage Tank.
EFFECT OF DOMESTIC STORAGE TANKS ON THE QUALITY OF DRINKING WATERS 2.3.
81
S A M P L I N G REGIME
A total of 220 water storage tanks, distributed around the city covering 12 main districts, were selected randomly for water sampling. The sampling programme was conducted in a way that guarantees resampling from the same district four times a year at different seasons. Samples were collected in triplicate from both input and output pipes after running the water full force for about 60 seconds prior to taking the sample. The 1-L samples were stored in polyethylene bottles precleaned with nitric acid solution, and were transported in an ice chest to the laboratory for processing, The time between the collection and the analysis did not exceed 24 hr. 2.4.
C H E M I C A L ANALYSIS
Water samples were analysed for concentrations of CI, Ca, Mg, Na, K, Fe, Zn, Pb, Cd and Cu in addition to the measurment of total hardness (T.H.). The following methods were applied in the analysis of each element; calcium and magnesium were analysed by titration with EDTA (APHA, 1980), sodium and potassium were measured using a Coming model 400 (U.K.) flame photometer. Iron, zinc, lead, cadmium and copper by atomic absorption with a Pye-Unicam SP9 atomic absorption spectrometer. A blank sample was made for each element determination in order to account for any analytical and instrumental error. Total hardness (as CaCO3) was calculated from calcium and magnesium concentrations: chloride was determined by titration with AgNO 3 (APHA, 1980). Data obtained for each element were subjected to comparison with a pre-prepared standard curve for that specific element. 2.5.
O N - S I T E M E A S U R M E N T S A N D OBSERVATIONS
Temperature and pH of tank water were measured using a digital thermometer and a portable WTW prig0 digital pH-meter, respectively. Metal corrosion and sedimentation at the bottom of the tank was observed visually for each tank tested. All the necessary information concerning the use of tank waters for the household activities were obtained through questionnaires distributed to the residences. 2.6.
S T A T I S T I C A L ANALYSIS
Data were statistically treated by an F-test with a critical probability P < 0.05 and P < 0.01, means (x), standard deviation (S.D.) and standard error (Sx) (Davis, 1973) using an a IBM computer. 3. Results and discussion
Data (Tables I and II) revealed that the concentrations of all elements tested for both input and output waters of the storage tanks were lower than the prescribed limits of the national (Anon., 1974) and international agencies (USEPA, 1983; WHO, 1984).
TABLE I
315 72 32 67 1.99 95 0.067 0.119 0.028 0.002 Trace
.~
According to the Iraqi and W H O standards Significant at 0.01 probability level Significant at 0.05 probability level Not significant.
500 75 50 200 340 250 5.0 0.3 0.05 0.03 1.00
T.H. Ca Mg Na K CI Zn Fe Pb Cd Cu
a: b: c: d:
Permisible limits a
Parameters
51.00 11.57 8.60 15.51 0.15 29.72 0,035 0.063 0.013 0,008 --
S.D. 14.73 3.34 2.48 4.48 0.042 8.58 0.01 0.018 0.004 0.003 --
S~
Winter
6.10 b 16.97 b 7.27 b 11.79 b 6.63 b 13.46 b 0.90 d 1.98 d 4.14 b 17.34 b --
Cal. F-test 333 74 42 69 1.87 103 0.056 0.160 0.025 0.002 Trace
.~ 113.93 11.81 16.20 12.65 0.237 25.198 0.028 0.089 0.015 0.0005 --
S.D.
22.89 3.41 4.68 3.65 0.068 7.274 0.008 0.026 0.004 0.0003 --
S~
Summer
66.33 b 62.51 b 130.78 b 24.64 b 32.72 b 7.19 b 2.55 c 2.54 c 1.42 d 1.61 d --
Cal. F-test
Means (,~), standard deviations (S.D,), standard errors ($2) and the calculated F-test o f input waters of B a g h d a d districts in winter and s u m m e r seasons
t-
>
>
a: b: c: d:
500 75 50 200 340 250 5.0 0.3 0.05 0.03 1.00
limits a
Permisible
306 72 31 66 1.99 93 0.173 0.091 0.033 0.002 Trace
.~
According to the Iraqi a n d W H O standards Significant at 0.01 probability level Significant at 0.05 probability level Not significant.
T.H. Ca Mg Na K CI Zn Fe Pb Cd Cu
Parameters
51.38 11.76 7.80 14.99 0.161 25.57 0.077 0.023 0.016 0.0008 --
S.D. 14.83 3.4 3.25 4.33 0.046 7.38 0.022 0.007 0.005 0.0002 _
S.V
Winter
13.42 b 16.01 b 14.02 b 20.25 b 21.05 b 19.54 b 2.38 c 2.46 c 5.89 b 30.1 b _
Cal. F-test 330 74 43 68 1.86 101 0.148 0.112 0.024 0.002 Trace
~7 116.70 13.25 16.47 12.62 0.237 28.43 0.055 0.038 0.008 0.0007 --
S.D.
33.69 3.82 4.75 3.64 0.068 8.21 0.016 0.011 0.002 0.0002 _
S~
Summer
105.7 b 51.6 b 68.6 b 24.9 b 35.1 b 20.8 b 2.0 c 1.8 d 1.6 d 2.6 c _
Cal. F-test
Means (.V), standard deviations (S.D.), standard errors (S.V) a n d the calculated F-test of the output waters o f Baghdad districts in winter and s u m m e r seasons
T A B L E II
,.-t
0
C >
rr m
0 Z
O > t'n > Z
84
I. M. J A W A D ET AL.
In order to evaluate the effect of storage tanks on the incoming potable waters, it is first necessary to assess the quality of the input waters. The chemical characteristics of the input waters, represented as a mean (x) of the 290 tested samples, together with the standard deviations (S.D.), standard error (Sx), and testing hypothesis (F-test) fot both summer and winter times, are shown in Table I. Results showed that the mean of total hardness (T.H.) and some other elements, e.g. Mg, Na, and Fe, have a higher level during summer rather than winter, which reflects the seasonal changes of water chemistry and the low water levels which occurred during the summertime as a result of evaporation and the lack of rain. Correlations between levels of each element among the different districts of the feed waters (F-test), showed that there were significant differences during both seasons. This can be attributed to the efficiency of each water treatment plant that feeds each specific district, where there are nine water treatment plants feeding Baghdad districts. Another significant result obtained from the analysis of the feed waters was the variation in the chloride concentrations detected within the different districts of the city. Such variation is attributed to the arbitrary chlorine addition practiced at the different water treatment plants (AI-Hashimi et al., 1986). A feature of the chlorine results is the higher levels detected during the summertime compared to winter. This is frequently due to the fact that higher concentrations of chlorine are needed during the summer season to overcome the expected health hazards of increased water temperature, which is favorable to microorganisms. The concentrations of Zn, Fe, Pb and Cd in the feed waters were less variable among districts and seasons. Some of the possible sources of these heavy metals in the drinking waters are the soluble materials chemically weathered from soil and rock and the probable industrial contribution of such metals to the river above the intake of the treatment plants. Furthermore, another possible metal contamination of drinking water, as Ajmal and Uddin (1986) suggested, can be attributed to the distribution system. The levels of elements detected in the stored waters, shown in Table II, showed that they were mostly of the same concentration or lower than the input waters, with the exception of Zn and Pb. It seems that the duration of storage of the water in the tanks could cause precipitation of the suspended particles which results in the relative clarity of the water. Field investigations revealed that muddy precipitations at bottom of tanks, of about one inch thickness, would form within 3-4 months after each cleaning. Thus domestic storage tanks can be considered as an additional precipitation tank (provided they are cleaned regularly) which works as a 'safety valve' for the clarification of waters. Indeed, such precipitation would depend greatly on the frequent use of these waters. On this basis, most insoluble elements were of a relatively lower concentration in the storage tank output waters. In addition, chloride showed an evident loss during water storage. Such a phenomenon is well known and has been demonstrated by other workers
EFFECT OF DOMESTIC STORAGE TANKS ON THE QUALITY OF DRINKING WATERS
85
(AWWA, 1971). This effect was also evident in the Fe concentrations in the ,~utput waters. Statistical analysis (Table II), showed that there was a significant variation for most elements in the stored waters among the different districts during all seasons. Exceptions are for Fe and Pb, which showed variations during the winter season only. The increase in the levels of Zn and Pb in the output waters could be due to the migration of these metals, mainly from tanks and distribution systems. Visual observation showed 60~ of the total studied storage tanks to be corroded to some extent. The tanks are usually fabricated of a galvanized metal in which Zn comprises the major constituent. Furthermore, it has been recognized that various substances deleterious to health can be leached by drinking water distribution systems (Schroeder, 1969). Also, Craun and McCabe (1975) have stated that the water supply system is a major source of metals in drinking waters. Schroeder and Kreamer (1974), indicated that the corrosion in the distribution systems and in the household plumbing also contributes to the metal content of drinking water and that Cd, Pb, Cu, and Zn, which often occur in plumbing materials, have been found to leach in soft drinking waters. Therefore, materials such as galvanized iron and plastic have been recently used in such distribution systems in Iraq, in order to minimize the health hazards caused by the use of lead piping in these systems. The high water temperatures (Max. 45~ recorded during the summer season could enhance the migration of these metals from tanks to waters. F-tests for seasonal effects on input and ouput waters (Table III) indicate an
TABLE l l I Statistical analysis (F-test) of variations in seasonal and in the incoming and stored water concentrations of the tested elements Calculated F-tests Summer x Winter Parameters
Input
T.H. Ca Mg Na K CI Zn Fe Pb Cd
3.144 1.131 2.290 1.748 1.808 1.146 1.770 1.722 2.769 1.150
b c c c c c c c a c
a : Significant at 0.01 probability level b: Significant at 0.05 probability level c : Not significant.
Input x Output
Output
Winter
Summer
4.045 1.080 4.182 1.459 2.013 1.223 3.235 3.140 2.030 1.697
1.264 1.044 1.496 1.205 1.123 1.462 2.192 8.410 1.215 1.035
1.018 1.275 1.220 1.006 1.009 1.043 4.030 4.612 4.630 1.426
a c a c c c b b c c
c c c c c c c a c c
c c c c c c a a a c
86
1. M. JAWAD ET AL.
evident significant variation on T.H. Field investigation suggested that water consumption during the summer was higher than in winter due to the extra demand for such waters in this season, Thus the duration of water storage in these tanks will in consequence be shorter, which may explain the highly significant variation of T.H. recorded in the output waters. This would also apply to Mg variations recorded in the stored waters. Table III also showed an evident significant level of Zn and Fe in the stored waters when comparison between seasons is carried out. In addition, Zn, Fe and Pb also showed a highly significant variation during the summer season when a" general comparison is made between the incoming and stored waters. The role played by the tank's metal on the water quality was obvious. This could be due to several factors e.g. seasonal effects, temperature, corrosion, water storage duration and pH. However, Pb contamination was due to the Pb content of the plumbing pipes, which reflected on the significant variations in the Pb concentration in the input waters between the two seasons. The insolubility of Pb reflected on its presence and on the insignificant variation in concentrations in the output waters.
4. Conclusion The present study showed that the quality of the stored waters in the roof tanks was not greatly affected by storage practice. However, although all the elements tested were within the prescribed limits, the only variation noticed on the stored waters were with Zn and Pb, in addition to Fe, to some extent. Seasonal variations have significant effects on the levels of some elements and on T.H. Therefore, the use of water tanks can be recommended for household water activities, providing a routine cleaning and monitoring of the metal corrosion are observed. On the other hand, microbiological studies should be undertaken, together with the chemical analyses, in order to evaluate the quality of such waters for human consumption.
Acknowledgements Dr. D. S. Daoud of the Scientific Research Council is thanked for his assistance in the statistical analysis.
References Aimal, M. and Uddin, R.: 1986, 'Quality of Drinking Water in the Aligarh Muslim University Campus. Aligarh, U.P. (INDIA) with Respect to Heavy Metals', Environ. Monit. and Assess. 6, 195-205. AI-Hashimi, M. A. I., AI-Naqeeh, S. M., and Saleh, R. M.: 1986, 'Effect of Treatment Stages of Drinking Water in 7 April Project on Some Heavy Metals', Proceedings of the 4th Scientific Conference of the Scientific Research Council, Baghdad., Vol. 5, Part 2. pp. 421--440. Anon. 1974: Drinking Water and Standard Methods for Testing and Analysis. Iraqi Organization for Standarization. No. 417. Ministry of Planning, Baghdad. APHA. 1980: Standard Methods for the Examination of Water and Wastewater. 15th ed., American Public Health Association, Washington, DC.
EFFECT OF DOMESTIC STORAGE TANKS ON THE QUALITY OF DRINKING WATERS
87
Craun, G. F. and McCabe, L. J.: 1975: 'Problems Associated with Metals in Drinking Water', J. Am. Wat. Wks. Ass. 67, 593-599. Davis, J. C.: 1973, 'Statistics and Data Analysis in Geology', John Wiley and Sons, New York. Gillies, M. E. and Paulin, H. V.: 1982, 'Estimations of Daily Mineral Intakes from Drinking Water', Human Nutrition, Applied Nutrion 36A, 287-292. Ohtsuka, R., Hongo, T., Kawabe, T., and Suzuki, T.: 1985, 'Mineral Content of Drinking Water in Lowland Papua', Environment International 11, 505-508. Pier, S. M. and Bang, K. M.: 1980, 'The Role of Heavy Metals in Human Health', in Trieff, N. M. (ed.), Environment and Health, 367-409. Schroeder, H. A.: 1969, 'The Water Factor', New Engl. J. Med. 280, 836-838. Schroeder, H. A. and Kraemer, I. A.: 1974, 'Cardiovascular Mortality. Municipal Water and Corrosion', Archs. Environ. Hlth. 28, 303-311. U.S. Environmental Protection Agency, 1983: National Revised Primary Drinking Water Regulations, Federal Register, October 5, 48(194), Part II. World Health Organization, 1984: Guidelines for Drinking Water Quality. WHO, Geneva.
L A NA L YSIS
I. M. J A W A D , M. R. A L - G H A Z A L I , a n d M. S. H. K H O R S H I D
Biological Research Center, P.O. Box 2371, Jadiriyah, Baghdad, Iraq
(Received February 1988) Abstract. An investigation covering 12 districts of Baghdad city was conducted over 2 yr to monitor the effect of domestic storage practice on the quality of drinking water. Water storage tanks are widely used in Iraq as an additional water source. Tap and stored waters were tested for their chemical constituents i.e. Ca, Mg, Na, K, C1, Zn, Fe, Pb, Cd, and total hardness (T.H.). All the tested elements were within the permissible limits. However, statistical analysis showed a significant variation between the different districts for T.H., Cu, Mg and chloride for both tap and stored waters. Seasonal variations have a significant effect on the levels of some elements. The quality of stored water was not affected by storage practice. Zinc, Pb and Fe were the only elements that showed some variation in the stored waters. This was attributed to the effects of corrosion of the tank metal and the migration of metals from the distribution system.
1. Introduction
Water storage tanks are widely used in Iraq as an additional potable water reservior for domestic use. These tanks are usually insulated and sited on the roofs of houses, tower buildings, hospitals, schools, etc, and fed with tap water from the main water distribution systems. They are cubic in shape and fabricated of galvanized metal. The daily household activities are highly dependent on such stored waters, particularly during the long summer time, due to the provision of warm waters from such tanks. The elevated water temperature during the summer season is attributed to the subtropical climate of the country in which the ambient temperature may reach about 50~ in the shade. Domestic plumbing systems are designed to permit the use of this water beside each tap-point of the main potable water system. Although some people would hesitate to use this water for human consumption, others would readily do so. Such a practice could raise questions concerning the health risk of such waters. Storage tanks contain variable levels of trace metals such as Zn, Pb, Cd, Fe, etc, and since these tanks could be used for up to 20 yr, any evident corrosion would affect the mineral content of the stored waters, Many workers have studied the quality of drinking water in relation to the heavy metals (Craun and McCabe, 1975; Gillies and Paulin, 1982; Ohtsuka et al., 1985). Such metals are probably one of the most harmful and insidious pollutants because of their non-biodegradable nature and their potential toxicity to man at certain levels of exposure and adsorption (Pier and Bang, 1980). Epidemiological studies (Pier and Bang, 1980) suggest a relationship between the mineral content of drinking water and the prevalence of such diseases, as hypertension, cancer, urolithiasis, cardiovascular syndrome, and sudden infant Environmental Monitoring and Assessment 11 (1988) 79-87. 9 1988 by Kluwer Academic Publishers.
80
1. M. JAWAD ET AL.
death syndrome (Schroeder and Kraemer, 1974). However, no data are available concerning the levels of minerals in storage tank water in Iraq. This study was conducted to trace the mineral levels in stored waters in an attempt to evaluate the water characteristics from the chemical and physical point of views.
2. Materials and methods
2.1. STUDY AREA Baghdad city, with a population of about 3 million, was selected to conduct the study due to the wide use of the insulated roof water storage tanks as additional water reservoirs for domestic use. The city is supplied with drinking water from nine water distribution systems around the capital. These plants are supplied with raw water from the river Tigris passing through the city. 2.2. STORAGE TANKS Iraqis use an insulated cube-shaped water tank (Figure 1) fabricated of galvanized metal on roof of their house. Tanks vary in size from 0.6 to 2.0 cubic meter for the usual household water use. A series of connected tanks or a larger (2-6 cu.m.) tank may be used for other larger buildings. Water tanks are usually fed with a tap water input pipe near the top, while the output pipe is located a few inches above the bottom. A hole is made in the center of the top side and fitted with a removable cover to aid in cleaning and visual monitoring of the water quality.
INPUT LOOSE COVER
I
I
MAIN WATER SOURCE
MESTIC USE
Fig. 1.
Diagram of a Domestic Water Storage Tank.
EFFECT OF DOMESTIC STORAGE TANKS ON THE QUALITY OF DRINKING WATERS 2.3.
81
S A M P L I N G REGIME
A total of 220 water storage tanks, distributed around the city covering 12 main districts, were selected randomly for water sampling. The sampling programme was conducted in a way that guarantees resampling from the same district four times a year at different seasons. Samples were collected in triplicate from both input and output pipes after running the water full force for about 60 seconds prior to taking the sample. The 1-L samples were stored in polyethylene bottles precleaned with nitric acid solution, and were transported in an ice chest to the laboratory for processing, The time between the collection and the analysis did not exceed 24 hr. 2.4.
C H E M I C A L ANALYSIS
Water samples were analysed for concentrations of CI, Ca, Mg, Na, K, Fe, Zn, Pb, Cd and Cu in addition to the measurment of total hardness (T.H.). The following methods were applied in the analysis of each element; calcium and magnesium were analysed by titration with EDTA (APHA, 1980), sodium and potassium were measured using a Coming model 400 (U.K.) flame photometer. Iron, zinc, lead, cadmium and copper by atomic absorption with a Pye-Unicam SP9 atomic absorption spectrometer. A blank sample was made for each element determination in order to account for any analytical and instrumental error. Total hardness (as CaCO3) was calculated from calcium and magnesium concentrations: chloride was determined by titration with AgNO 3 (APHA, 1980). Data obtained for each element were subjected to comparison with a pre-prepared standard curve for that specific element. 2.5.
O N - S I T E M E A S U R M E N T S A N D OBSERVATIONS
Temperature and pH of tank water were measured using a digital thermometer and a portable WTW prig0 digital pH-meter, respectively. Metal corrosion and sedimentation at the bottom of the tank was observed visually for each tank tested. All the necessary information concerning the use of tank waters for the household activities were obtained through questionnaires distributed to the residences. 2.6.
S T A T I S T I C A L ANALYSIS
Data were statistically treated by an F-test with a critical probability P < 0.05 and P < 0.01, means (x), standard deviation (S.D.) and standard error (Sx) (Davis, 1973) using an a IBM computer. 3. Results and discussion
Data (Tables I and II) revealed that the concentrations of all elements tested for both input and output waters of the storage tanks were lower than the prescribed limits of the national (Anon., 1974) and international agencies (USEPA, 1983; WHO, 1984).
TABLE I
315 72 32 67 1.99 95 0.067 0.119 0.028 0.002 Trace
.~
According to the Iraqi and W H O standards Significant at 0.01 probability level Significant at 0.05 probability level Not significant.
500 75 50 200 340 250 5.0 0.3 0.05 0.03 1.00
T.H. Ca Mg Na K CI Zn Fe Pb Cd Cu
a: b: c: d:
Permisible limits a
Parameters
51.00 11.57 8.60 15.51 0.15 29.72 0,035 0.063 0.013 0,008 --
S.D. 14.73 3.34 2.48 4.48 0.042 8.58 0.01 0.018 0.004 0.003 --
S~
Winter
6.10 b 16.97 b 7.27 b 11.79 b 6.63 b 13.46 b 0.90 d 1.98 d 4.14 b 17.34 b --
Cal. F-test 333 74 42 69 1.87 103 0.056 0.160 0.025 0.002 Trace
.~ 113.93 11.81 16.20 12.65 0.237 25.198 0.028 0.089 0.015 0.0005 --
S.D.
22.89 3.41 4.68 3.65 0.068 7.274 0.008 0.026 0.004 0.0003 --
S~
Summer
66.33 b 62.51 b 130.78 b 24.64 b 32.72 b 7.19 b 2.55 c 2.54 c 1.42 d 1.61 d --
Cal. F-test
Means (,~), standard deviations (S.D,), standard errors ($2) and the calculated F-test o f input waters of B a g h d a d districts in winter and s u m m e r seasons
t-
>
>
a: b: c: d:
500 75 50 200 340 250 5.0 0.3 0.05 0.03 1.00
limits a
Permisible
306 72 31 66 1.99 93 0.173 0.091 0.033 0.002 Trace
.~
According to the Iraqi a n d W H O standards Significant at 0.01 probability level Significant at 0.05 probability level Not significant.
T.H. Ca Mg Na K CI Zn Fe Pb Cd Cu
Parameters
51.38 11.76 7.80 14.99 0.161 25.57 0.077 0.023 0.016 0.0008 --
S.D. 14.83 3.4 3.25 4.33 0.046 7.38 0.022 0.007 0.005 0.0002 _
S.V
Winter
13.42 b 16.01 b 14.02 b 20.25 b 21.05 b 19.54 b 2.38 c 2.46 c 5.89 b 30.1 b _
Cal. F-test 330 74 43 68 1.86 101 0.148 0.112 0.024 0.002 Trace
~7 116.70 13.25 16.47 12.62 0.237 28.43 0.055 0.038 0.008 0.0007 --
S.D.
33.69 3.82 4.75 3.64 0.068 8.21 0.016 0.011 0.002 0.0002 _
S~
Summer
105.7 b 51.6 b 68.6 b 24.9 b 35.1 b 20.8 b 2.0 c 1.8 d 1.6 d 2.6 c _
Cal. F-test
Means (.V), standard deviations (S.D.), standard errors (S.V) a n d the calculated F-test of the output waters o f Baghdad districts in winter and s u m m e r seasons
T A B L E II
,.-t
0
C >
rr m
0 Z
O > t'n > Z
84
I. M. J A W A D ET AL.
In order to evaluate the effect of storage tanks on the incoming potable waters, it is first necessary to assess the quality of the input waters. The chemical characteristics of the input waters, represented as a mean (x) of the 290 tested samples, together with the standard deviations (S.D.), standard error (Sx), and testing hypothesis (F-test) fot both summer and winter times, are shown in Table I. Results showed that the mean of total hardness (T.H.) and some other elements, e.g. Mg, Na, and Fe, have a higher level during summer rather than winter, which reflects the seasonal changes of water chemistry and the low water levels which occurred during the summertime as a result of evaporation and the lack of rain. Correlations between levels of each element among the different districts of the feed waters (F-test), showed that there were significant differences during both seasons. This can be attributed to the efficiency of each water treatment plant that feeds each specific district, where there are nine water treatment plants feeding Baghdad districts. Another significant result obtained from the analysis of the feed waters was the variation in the chloride concentrations detected within the different districts of the city. Such variation is attributed to the arbitrary chlorine addition practiced at the different water treatment plants (AI-Hashimi et al., 1986). A feature of the chlorine results is the higher levels detected during the summertime compared to winter. This is frequently due to the fact that higher concentrations of chlorine are needed during the summer season to overcome the expected health hazards of increased water temperature, which is favorable to microorganisms. The concentrations of Zn, Fe, Pb and Cd in the feed waters were less variable among districts and seasons. Some of the possible sources of these heavy metals in the drinking waters are the soluble materials chemically weathered from soil and rock and the probable industrial contribution of such metals to the river above the intake of the treatment plants. Furthermore, another possible metal contamination of drinking water, as Ajmal and Uddin (1986) suggested, can be attributed to the distribution system. The levels of elements detected in the stored waters, shown in Table II, showed that they were mostly of the same concentration or lower than the input waters, with the exception of Zn and Pb. It seems that the duration of storage of the water in the tanks could cause precipitation of the suspended particles which results in the relative clarity of the water. Field investigations revealed that muddy precipitations at bottom of tanks, of about one inch thickness, would form within 3-4 months after each cleaning. Thus domestic storage tanks can be considered as an additional precipitation tank (provided they are cleaned regularly) which works as a 'safety valve' for the clarification of waters. Indeed, such precipitation would depend greatly on the frequent use of these waters. On this basis, most insoluble elements were of a relatively lower concentration in the storage tank output waters. In addition, chloride showed an evident loss during water storage. Such a phenomenon is well known and has been demonstrated by other workers
EFFECT OF DOMESTIC STORAGE TANKS ON THE QUALITY OF DRINKING WATERS
85
(AWWA, 1971). This effect was also evident in the Fe concentrations in the ,~utput waters. Statistical analysis (Table II), showed that there was a significant variation for most elements in the stored waters among the different districts during all seasons. Exceptions are for Fe and Pb, which showed variations during the winter season only. The increase in the levels of Zn and Pb in the output waters could be due to the migration of these metals, mainly from tanks and distribution systems. Visual observation showed 60~ of the total studied storage tanks to be corroded to some extent. The tanks are usually fabricated of a galvanized metal in which Zn comprises the major constituent. Furthermore, it has been recognized that various substances deleterious to health can be leached by drinking water distribution systems (Schroeder, 1969). Also, Craun and McCabe (1975) have stated that the water supply system is a major source of metals in drinking waters. Schroeder and Kreamer (1974), indicated that the corrosion in the distribution systems and in the household plumbing also contributes to the metal content of drinking water and that Cd, Pb, Cu, and Zn, which often occur in plumbing materials, have been found to leach in soft drinking waters. Therefore, materials such as galvanized iron and plastic have been recently used in such distribution systems in Iraq, in order to minimize the health hazards caused by the use of lead piping in these systems. The high water temperatures (Max. 45~ recorded during the summer season could enhance the migration of these metals from tanks to waters. F-tests for seasonal effects on input and ouput waters (Table III) indicate an
TABLE l l I Statistical analysis (F-test) of variations in seasonal and in the incoming and stored water concentrations of the tested elements Calculated F-tests Summer x Winter Parameters
Input
T.H. Ca Mg Na K CI Zn Fe Pb Cd
3.144 1.131 2.290 1.748 1.808 1.146 1.770 1.722 2.769 1.150
b c c c c c c c a c
a : Significant at 0.01 probability level b: Significant at 0.05 probability level c : Not significant.
Input x Output
Output
Winter
Summer
4.045 1.080 4.182 1.459 2.013 1.223 3.235 3.140 2.030 1.697
1.264 1.044 1.496 1.205 1.123 1.462 2.192 8.410 1.215 1.035
1.018 1.275 1.220 1.006 1.009 1.043 4.030 4.612 4.630 1.426
a c a c c c b b c c
c c c c c c c a c c
c c c c c c a a a c
86
1. M. JAWAD ET AL.
evident significant variation on T.H. Field investigation suggested that water consumption during the summer was higher than in winter due to the extra demand for such waters in this season, Thus the duration of water storage in these tanks will in consequence be shorter, which may explain the highly significant variation of T.H. recorded in the output waters. This would also apply to Mg variations recorded in the stored waters. Table III also showed an evident significant level of Zn and Fe in the stored waters when comparison between seasons is carried out. In addition, Zn, Fe and Pb also showed a highly significant variation during the summer season when a" general comparison is made between the incoming and stored waters. The role played by the tank's metal on the water quality was obvious. This could be due to several factors e.g. seasonal effects, temperature, corrosion, water storage duration and pH. However, Pb contamination was due to the Pb content of the plumbing pipes, which reflected on the significant variations in the Pb concentration in the input waters between the two seasons. The insolubility of Pb reflected on its presence and on the insignificant variation in concentrations in the output waters.
4. Conclusion The present study showed that the quality of the stored waters in the roof tanks was not greatly affected by storage practice. However, although all the elements tested were within the prescribed limits, the only variation noticed on the stored waters were with Zn and Pb, in addition to Fe, to some extent. Seasonal variations have significant effects on the levels of some elements and on T.H. Therefore, the use of water tanks can be recommended for household water activities, providing a routine cleaning and monitoring of the metal corrosion are observed. On the other hand, microbiological studies should be undertaken, together with the chemical analyses, in order to evaluate the quality of such waters for human consumption.
Acknowledgements Dr. D. S. Daoud of the Scientific Research Council is thanked for his assistance in the statistical analysis.
References Aimal, M. and Uddin, R.: 1986, 'Quality of Drinking Water in the Aligarh Muslim University Campus. Aligarh, U.P. (INDIA) with Respect to Heavy Metals', Environ. Monit. and Assess. 6, 195-205. AI-Hashimi, M. A. I., AI-Naqeeh, S. M., and Saleh, R. M.: 1986, 'Effect of Treatment Stages of Drinking Water in 7 April Project on Some Heavy Metals', Proceedings of the 4th Scientific Conference of the Scientific Research Council, Baghdad., Vol. 5, Part 2. pp. 421--440. Anon. 1974: Drinking Water and Standard Methods for Testing and Analysis. Iraqi Organization for Standarization. No. 417. Ministry of Planning, Baghdad. APHA. 1980: Standard Methods for the Examination of Water and Wastewater. 15th ed., American Public Health Association, Washington, DC.
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Craun, G. F. and McCabe, L. J.: 1975: 'Problems Associated with Metals in Drinking Water', J. Am. Wat. Wks. Ass. 67, 593-599. Davis, J. C.: 1973, 'Statistics and Data Analysis in Geology', John Wiley and Sons, New York. Gillies, M. E. and Paulin, H. V.: 1982, 'Estimations of Daily Mineral Intakes from Drinking Water', Human Nutrition, Applied Nutrion 36A, 287-292. Ohtsuka, R., Hongo, T., Kawabe, T., and Suzuki, T.: 1985, 'Mineral Content of Drinking Water in Lowland Papua', Environment International 11, 505-508. Pier, S. M. and Bang, K. M.: 1980, 'The Role of Heavy Metals in Human Health', in Trieff, N. M. (ed.), Environment and Health, 367-409. Schroeder, H. A.: 1969, 'The Water Factor', New Engl. J. Med. 280, 836-838. Schroeder, H. A. and Kraemer, I. A.: 1974, 'Cardiovascular Mortality. Municipal Water and Corrosion', Archs. Environ. Hlth. 28, 303-311. U.S. Environmental Protection Agency, 1983: National Revised Primary Drinking Water Regulations, Federal Register, October 5, 48(194), Part II. World Health Organization, 1984: Guidelines for Drinking Water Quality. WHO, Geneva.
