According to a survey, around 1.1 billion people in the world have no access to safe drinking water supplies and 2.6 billion people lack adequate sanitation (WHO/UNICEF, 2004). The consumption of unsafe drinking water is the cause of 2.2 million diarrheal disease deaths annually comprising mostly the children (WHO/UNICEF, 2000). A vast majority of diarrhoeal disease in the world (88%) was attributed to unsafe drinking water, sanitation and hygiene (WHO, 2003). Potable water is that water delivered to the consumer that can be used safely for drinking, cooking and washing (DeZuane, 1997). Besides, contamination of drinking water can be at the water source such as water wells, treatment facilities, distribution networks and water tankers and at houses.
Microbiological contamination of water between the source and point-of-use is widespread and significant (Wright et al., 2004). The main sources of microbiological contamination are from human and animal waste, leakage from sewage networks, land disposal of raw sewage effluent without treatment, seepage from septic tanks and pit latrines, improper handling and storage of water at home (WHO, 2010).
Previously, many studies were conducted on the quality of groundwater used for drinking propose and household water quality in the Kingdom of Saudi Arabia or in specific regions of the Kingdom (Mee, 1983; MAW, 1984; Rihan et al., 1986; Bazhair and Alkaff, 1989; Faruq et al., 1996; Al-Saleh, 1996; Abdel Magid, 1997; Alabdulaaly, 1997a, b; Alabdulaaly et al., 2011).
Sadiq and Hussain (1997) reviewed the drinking water quality in Saudi Arabia. They reported that majority of groundwater aquifers, especially in the central and eastern parts, are highly saline and the water requires desalting to become fit for human consumption. The corrosion of utility pipes and leaching of chemicals from PVC pipes could elevate metal concentrations in drinking waters supplied to consumers (Alam and Sadiq, 1989). El-Rehaili and Misbahuddin (1995) reported that houses with galvanized iron plumbing contained higher concentration of iron, copper, chromium, lead, zinc and cadmium in drinking water than those houses with PVC or copper plumbing. They also observed that 34, 23 and 3% of water samples contained Fe, Cu and Pb contents above the maximum permissible limits, respectively.
However, the main concern of consumer is to make sure that the water received is safe and meets the established water quality standards. Previously, free flowing springs were the basis for existence of Al-Ahsa Oasis. Early records on number, location, water quality, water temperature, purity and discharge date back to 1941 and 1951 (Vidal, 1951). Due to urban, rural, industrial and agricultural expansion, the groundwater level decreased significantly. Presently, once free flowing springs have been replaced by wells to fulfill the increasing demand of water for various uses. Also, desalinated water is pumped from the Arabian Gulf to meet the growing demand for water but is mixed with groundwater to improve its quality and quantity.
Therefore, the main objective of this paper is to evaluate household drinking water quality in Al-Ahsa City, Saudi Arabia.
MATERIALS AND METHODS
The study was carried in Al-Ahsa city, Eastern Province, Kingdom of Saudi Arabia. A total of 199 water samples were collected from underground reservoirs, over-head water tanks, municipal water supply network, water tankers and in some locations from wells supplying water to houses from different areas in the city of Al-Ahsa. The following criteria were considered for selecting the study area in the city:
|•||Areas without sewage system and the houses depending on cesspool system for wastewater disposal
||Areas with a sewage system and the houses are connected to the public swage system
||Public places like mosques and schools
Majority of the houses in Al-Ahsa city depend on underground water storage, because there is no regular water supply by the municipal water supply network. To study the quality of water and to investigate the sources of contamination, water samples were collected and classified as follows:
||The 41 water samples were collected directly from the outlet of municipal water supply network before entering the underground or upper water storage tanks. This was done to collect information on quality of water before entering the houses and eliminate the effect of storage facility on water quality. The collection of limited number of water samples was due to limited accesses to water supply line in some houses. However, in majority of the houses, the water supply line was connected directly to the underground water storage tanks. while in many cases, it was not possible to open the underground storage tank or the manhole cover
||The 158 water samples were collected from the tap water in houses and public facilities (schools and mosques) from water coolers used for drinking. Also, the water storage facilities were inspected thoroughly during sampling for any defect or any obvious source of contamination
During the field work, two drinking wells (one well in the city of Al-Hofuf and the other in a village called Bani Maán) were sampled for analyzing major cations and trace elements.
It was noticed during investigation that many residents of Al-Ahsa city do not use the water supplied by Municipal Corporation for drinking but use it only for cooking and cleaning purposes. Because, they suspicious about the quality of the water which may be contaminated at the source, during transportation or during storage in the houses. However, for drinking purposes, they depend on water supplied by water tankers from different companies which use Reverse Osmosis (RO) technology for water treatment. Some people use water treatment devices under the sink to improve water quality.
Physical water quality parameters such as temperature, Electric Conductivity (EC), pH, Dissolved Oxygen (DO) and turbidity were measured at the time of sample collection. The water samples were stored in an ice chest and then transported to the analytical laboratory of National Center for Water Technology (NCWT), King ABdulaziz City for Science and Technology (KACST) for analysis. The validity of laboratory results was checked by the cations and anion balance on equivalent basis. Furthermore, 19 water samples were collected as duplicate from the same places for quality control.
Simultaneously, water samples were also collected for microbiological analysis, stored in an ice chest and brought to the laboratory for bacterial analysis. The water sampling locations are given in Fig. 1.
Water analysis: The standard analytical procedures described in APHA (1992) were followed for analysis of water samples. Temperature, electrical conductivity (EC), pH and dissolved oxygen (DO) were measured in the field using the portable instrument Thermo Scientific Orion 5-Star Plus. Turbidity was measured using HACH Turbidity Meter (Model 2100P).
Different anions (Cl, SO4 NO3 and PO4) and cations (Na, K, Ca and Mg) were determined by ion chromatography (Dionex Ion Chromatograph models DX 300 and DX 500). The carbonates (CO3) and bicarbonates (HCO3) were determined by titration method according to procedures given in USDA (1954).
Traces elements were determined by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) (Optima 2000 DV Perkin Elmer) equipped with an ultrasonic nebulizer model Cetec U 5000 AT.
The microbial quality of water samples was assessed using IDEXX Colilert® as qualitative method showing the presence or absence of coliforms and Escherichia coli (E. coli).
|Fig. 1:|| Location map of drinking water samples in Al-Ahsa city
RESULTS AND DISCUSSION
Water chemistry of the two wells is shown in Table 1 which was considered as an example of groundwater quality for drinking water supply. The TDS (mg L-1) ranged between 1248 and 3230 in Bani Maan and Hofuf well water, respectively. The total water salinity was considerably higher in Hofuf well as compared to the Bani Maan well. The nitrate (NO3) contents (mg L-1) were 24.9 and 43 in Bani Maan and Hofuf well water, respectively. The NO3 contents were higher than the WHO permissible limits of 30 mg L-1 for drinking in Hofuf well water. The chemistry of groundwater in Al-hasa area was studied by Al-Zarah (2008). He investigated 101 wells and found that the order of abundance for cations was Na>Ca>Mg, while that of anions was Cl>SO4>HCO3. The groundwater in the study area was classified as very hard water.
|| Physical and chemical parameters of sampled wells used for supplying drinking water
Maximum, minimum, average and standard deviation for different water quality parameters from water supply lines and household tap waters are presented in Table 2 and 3. The mean values of TDS, chloride (Cl), nitrate (NO3), iron (Fe) and zinc (Zn) were 725.1, 231.2, 11.5, 73.4 and 58 mg L-1, respectively in water samples collected from water supply network to houses in the city. Whereas, mean values of TDS, chloride (Cl), nitrate (NO3), iron (Fe) and zinc (Zn) were 708, 226.4, 10.4, 50.4 and 66.6 mg L-1, respectively in water samples collected from tap water of each house in the city. On percent basis, 85.4% (water supply network) and 79.1% (tap water) water samples exceeded the limits of hardness according to WHO (2011) permissible limits.
||Supply line water quality compared to GCC and WHO guidelines
|*: No guideline, ND: Not detectable
||Household tap water quality compared to GCC and WHO guidelines
|*: No guideline: ND: Not detectable
|| Concentration of major ions in water supply inlet
Similarly, 31.7% (water supply network) and 51.3% (tap water) water samples exceeded the limits for Cl contents according to WHO (2011) standards. The analytical results were compared with the water quality standards of Gulf Cooperation Countries (GCC) and World Health Organization Standards for evaluation. It was found that all the water quality parameters are within the maximum recommended limits for major cations and trace elements according to WHO (2011). On the other hand, all the water samples exceeded the GCC drinking water quality standard for pH and total dissolved solids (TDS). Out of the total water samples, 6.5% exceeded the GCC standard for pH and 13.6% were above the TDS standards. The study results show that water samples did not meet the recommended acceptable limits established by WHO (2011) for some parameters that may not have any direct health effects but have objectionable taste or odor such as pH, turbidity, TDS, Hardness, Na, Cl and SO4. However, data in Table 4 presents the number and the percentage of samples that did not meet the WHO maximum acceptable standard for drinking purposes.
Figure 2-5 show the maximum, minimum and average values of cations, anions, trace elements and heavy metals in water samples collected from the drinking water distribution network (inlet) and the household tap waters. The piper diagram (Fig. 6 and 7) showed that the dominated water type is Na-Ca-Cl-SO4 (114 samples), Na-Ca-Cl-HCO3-SO4 (17 samples), Na-Ca-Cl (15 sample), Na-Ca-Mg-Cl-HCO3 (13 sample) and few samples show the water type as Na-Ca-Mg-Cl-SO4, Ca-Na-Cl-SO4, Ca-Na-Mg-Cl-HCO3-SO4, Ca-Na-Mg-HCO3-Cl and Na-Ca-Cl-HCO3.
Bacterial contamination: Bacteria are present naturally in the environment. Although, the presence of total bacteria are harmless and do not cause diseases but is considered as an indication for the existence of pathogens in water. The presence of Fecal coliform and E. coli indicates that water may be contaminated by human and/or animal wastes and may cause water-born illnesses.
Out of 199 water samples collected from different sources, 117 samples (58%) showed Total Bacterial Count (TBC) known as Heterotrophic Plate Count (HPC).
|Fig. 3:|| Concentration of trace elements ions in water supply inlet
|Fig. 4:|| Concentration of major ions in household tap water
The HPC represent bacteria that are naturally present in the environment and without any health effects. According to EPA (2012), if the concentration of bacteria in drinking water is low, this means that the water system is maintained properly.
The highest total bacteria counts were found in water samples collected from an area without sewage system. However, one of the two wells sampled during the study, shallow well in area without sewage system, showed 738 total bacteria counts (MPN colonies 100 mL-1 water sample) which also showed 7.4 ( MPN colonies 100 mL-1 water sample) Fecal coliform bacteria.
|Fig. 5:|| Concentration of trace elements ions in household tap water
||No. and percentage of sample exceeding the WHO maximum acceptable concentration limits in water supply inlet and household tap water
|| Piper diagram for samples from water supply inlet
Also, 30 water samples from the water supply inlet (water coming from water authority before entering the houses) showed total bacteria counts, with one showed contamination with fecal coliform bacteria. All these water samples, collected from water coolers installed in different elementary schools and mosques showed the presence of total bacteria. Furthermore, one of the three drinking water distribution tankers showed high total bacteria count and tested positive for Fecal coliform bacteria.
|| Piper diagram for tap water
Out of 117 water samples showing Total Bacteria Counts (TBC), only 9 (7.7%) samples tested positive for Fecal coliform, as majority of these samples were from those houses in areas without public swage system. However, only one sample tested positive for E. coli bacteria. On the other hand, the EPA Maximum Contaminant Level Goal (MCLG) and the WHO standard for drinking water stated that the E. coli or thermotolerant coliform bacteria may not be detectable in 100 ml water sample. Although, coliform bacteria by itself may not cause illness but their presence indicates that the water is vulnerable to contamination and may include other organisms (pathogens) harmful for human health after drinking. The presence of E. coli may indicate the presence of disease-causing pathogens, such as bacteria, viruses and parasites. The main source of contamination of household drinking water by total coilform and E. coli in this study may be related to improper sewage discharge along with inferior quality household underground water storage facilities.
The study showed that microbiological contamination of water is more serious problem than the chemical contamination. The bacterial contamination was observed in those water samples collected from tap-water, public water cooler and the underground water tanks. The main source of bacterial contamination seems to be the unhygienic conditions of the water reservoirs, corrosion of water supply network, leakage of sewage effluent into the damaged water supply network or inferior design and poor condition of household water storage facilities.
Overall, the results showed that all the water samples are within the WHO (2011) standard for all parameters. However, water samples did not meet the recommended acceptable range by the WHO (2011) for pH, turbidity, TDS, Hardness, Na, Cl and SO4.
Water samples from the water supply network and the household tap water exceeded the GCC standards for pH and total dissolved solids. Among the total water supply line samples (41 samples) 2.4% were higher in pH and 12.2% higher for TDS than the maximum acceptable limits. Out of the total household water samples (158 samples), 7.6% exceeded the GCC standard for the pH and 14% exceeded the maximum acceptable limits for TDS. Majority of household water samples (82%) were classified as very hard water.
Above all, disposal of wastewater using cesspool is a threat to environment and public health and may be a source of contamination to underground water storage. This study emphasized the importance of proper maintenance of water storage facilities at houses which may be a source of microbiological contamination.
Based on the results and observations in this study, chemical disinfectants of water at the point of use is a good alternative for residents in area vulnerable to contamination. This can be achieved by using 6% sodium hypochlorite solution to kill bacterial contamination. In conclusion, the residents should get their water tested for bacterial quality biannually. Also, regular monitoring of drinking water quality in public places (schools and mosques) for bacterial contamination is recommended to avoid human health hazards.
The authors are grateful to King Abdulaziz City for Science and Technology (KACST) for financial support of Project No. 28-125.