Evaluation of Drinking Water Quality and Treatment from Coolers in Public Places in Madinah City, Saudi Arabia

Abstract

The aim of this work is to prevent the public drinking from water coolers, by using an auto-detection process, if the quality of water is low. Therefore, the proposed water treatment management system for allows the activation of dispensers to provide the best-quality water coolers. The objective is to investigate the quality of the drinking water from coolers in public places in Madinah and to provide clean, safe, and healthy drinking water for the general public. The methodology consisted of performing different analyses, tests, and water treatments, such as physicochemical analyses of the water samples, measurements of the different concentrations of anions, measurements of the concentrations of heavy metals, and bacteriological tests of the water samples. Therefore, 66 water samples were tested, and the experimental values were compared with the reference values given by the World Health Organization (WHO) and Saudi Standards, Metrology, and Quality Organization (SASO) for drinking water. The tests revealed that the physicochemical parameters (pH, EC, TDS, and TH) of different water sources (95.5%) were in accordance with the SASO and WHO values. In addition, all the analyzed water samples (100%) contained permissible levels of nitrates, sulfates, nitrites, and free residual chlorine, as indicated by the results. However, 68.2% of the samples studied had fluoride concentrations below the standard limits. Furthermore, heavy metals such as lead, iron, and others were tested for all water coolers. The measured findings indicated that just one cooler exceeded the permissible limit of 0.3 mg/L for Fe, and the biological contamination testing revealed that 4.5% of the coolers were infected with coliforms. Finally, this research suggests that water coolers should be regularly maintained. Additionally, using the best design for the water desalination process is very important to give the best drinking water quality.

1. Introduction

Water is one of the most essential needs for life. As the global population increases, the need for water will also increase. However, because of different effects and especially human activities, water resources are decreasing, becoming polluted, and still being used unconsciously [1]. Three-quarters of our planet is covered with water, and the human body is mostly made up of water. Water is of vital importance for all living things and plays a key role in many of our bodies’ functions. In fact, our body uses water in all its cells, organs, and tissues to help regulate its temperature and maintain other bodily functions [2]. Because our bodies lose water through breathing, sweating, and digestion, it is important to rehydrate by drinking fluids and eating foods that contain water. Clean water is very important for everyone worldwide. There are many waterborne illnesses that are detrimental and can cause epidemics in societies around the world [3].

In Saudi Arabia, drinking water is provided by water desalination systems and distributed in different public places using water coolers, which are easily accessible by the public since they are placed in public areas such as streets, bus stations, train stations, mosques, and airports [4,5].

Since Saudi Arabia is considered a hot country, especially in Madinah City, where the temperature can reach 55 °C in the summer months [6], the water coolers very much need to be placed in wide areas and in different locations [7]. The water coolers should be kept clean and safe because 80% of diseases come from contaminated drinking water, along with almost one-third of the deaths in developing countries [8].

Hence, a necessity for health protection is to supply the public with a suitable supply of secure drinking water. Developments in water treatment methods have outstandingly increased the quality and especially the safety of water. Nonetheless, the quality of drinking water can be degenerated by toxic chemicals and microbial elements during its transportation and storage before consumption [9].

Water cooler devices are highly affected by the metal fabrication process [10]. In fact, the metal used for these devices could affect the drinking water’s quality, which can be determined by its odor, color, taste, and concentration of organic and inorganic matter [11,12]. Health problems can be caused by drinking water that contains heavy metals such as magnesium (Mg), nickel (Ni), copper (Cu), arsenic (As), lead (Pb), and zinc (Zn). The concentration (mg/L) of such heavy metals in water coolers should be controlled frequently to ensure the safety of the public.

In a study conducted in Riyadh City (Saudi Arabia), 400 water samples from public coolers were analyzed using an inductively coupled plasma (ICP) spectrophotometer.

The results indicated that 95.5% of the samples were within the limit of the standard values of the SASO and WHO, while 4.5% presented high levels of heavy metals (Fe, Pb, and Ni) [5].

Other results showed that 28.6% of the water coolers contained less than 0.5 mg/L of free residual chlorine, while 19.1% contained lead at levels greater than 0.01 mg/L. Additionally, the microbiological results indicated that 14.2% of cooler samples showed a higher total bacterial count than the WHO guidelines [13]. Another study was carried out in Alexandria City (Egypt) on the quality of the water. It was found that 85% of the water cooler samples contained less than 0.5 mg/L of free residual chlorine, 65% of the samples contained lead concentrations higher than 0.01 mg/L, and about 15% were microbiologically contaminated [14]. Another study investigated the quality of water via biological and chemical analyses of public water coolers on selected streets in Sharjah (UAE). The results indicated that all water samples revealed water quality in concordance with the allowable levels of sulfates, nitrates, and nitrites and were microbiologically safe regarding the total coliforms [15]. Physicochemical and bacteriological parameters were analyzed for each water source, and the results were compared with the standard values of the WHO and SASO [16]. Twenty-two samples of drinking water from nine water coolers were analyzed [9], and an absence of coliforms and Escherichia coli was found in the water samples. Another study investigated the quality of water samples and found that 50% of the tested samples contained residual contents outside of the Iranian standards [17], while the pH values in 12.5% of water samples were found to be out of range. Generally, water dispenser pollution can be caused by many factors such as input water pollution, an unsuitable connection of the water dispenser, stagnation of the water, and the existence of cracks in the water dispenser [18]. Another investigation was performed to estimate the contamination of drinking water from bottled water coolers [19]. It was found that in 62% of the water cooler samples, the bacterial count was higher than the standard limit [20]. Otherwise, almost 77% of tested dispenser were contaminated with different types of microbes such as fecal streptococci and coliform microbes, Escherichia coli, and Pseudomonas aeruginosa [21]. Additionally, contamination rates of 54% for E. coli and 17% for S. aurous were found in filtration-treated dispenser water. Currently, about 56% of Mondial’s population is without safe sanitation [22]. Recently, a study investigated the parameters which affect the quality of drinking water. Sixty water dispensers were tested in Walailak university (Thailand). The results show that the total hardness value in 13 of the samples was higher than the limit values, and the microbiological tests showed that global coliform and fecal coliform bacteria were found in 17% and 8% of the samples, respectively [23].

Recently, a study was conducted to determine the physicochemical parameters and bacteriological quality of drinking water from coolers in Makkah city (Saudi Arabia). Sixty-three samples were analyzed and tested from randomly selected water coolers [24]. It was found that the drinking water from coolers in Makkah city complied with international standards and were within the acceptable limits.

Recent research work was conducted on the groundwater’s suitability for drinking and irrigation purposes in Makkah city, Saudi Arabia [25]. Several water quality indices were used to examine the geochemical mechanisms influencing the chemistry of groundwater and assess groundwater resources. In fact, 59 groundwater wells were tested for different physical and chemical parameters using conventional analytical procedures. By using the drinking water quality index (DWQI), it was found that only 5% of the wells gave good drinking water, while 95% of the wells were unsuitable for drinking and required appropriate treatment. Also, the irrigation water quality index (IWQI) indicated that 45.5% of the wells were classified under high restriction for agriculture and can be utilized only for highly salt-tolerant plants. So, 54.5% of the wells presented no restriction for irrigation.

Another study on the water quality of 173 groundwater samples was carried out in Makkah Province, Saudi Arabia [26]. Physicochemical parameters, water quality indices (WQIs), and spectral reflectance indices (SRIs) were combined to investigate water quality and controlling factors using multivariate modeling techniques, such as partial least-square regression (PLSR) and principal component regression (PCR). The water quality test was carried out using the drinking water quality index (DWQI), and the dissolved solids (TDS), heavy metal index (HPI), contamination degree (Cd), and pollution index (PI) were calculated.

A novel hybrid treatment system has been developed for application in both conventional and advanced oxidation treatment processes [27]. In fact, an integrated system was designed for the effective treatment of recycled automobile service station wastewater (ASSWW), which comprised sedimentation (sed), catalytic ozonation, adsorption, and filtration. Two catalysts/adsorbents were investigated: granular activated carbon (GAC) and rice husk (RH) were employed individually and in combination for the first time in the studied hybrid process, and their performance was compared and evaluated.

A new approach for the removal of arsenic (As) from drinking water by developing a novel solution has been presented [28]. The level of As was investigated using drinking water samples in different areas of Lahore, Pakistan, and As removal was compared with and without using catalysts. It has been found that the catalytic ozonation process significantly removes arsenic compared to single ozonation and adsorption processes.

Another study investigated drinking water quality in Islamabad city (Pakistan) [29]. Thirty-two samples were tested, and it was found that twenty-six samples were unsafe for drinking and presented high arsenic, conductivity, and alkalinity values. Also, the microbiological situation was taken into account for health risk assessment. Another investigation on the suitability of groundwater for irrigation and drinking was elaborated in Haripur district, Pakistan [30]. In this study, thirty-four groundwater samples and eight surface water samples were analyzed to determine their physicochemical parameters. It was found that most of the samples were within the limit of the Pakistan Standard Quality Control Authority (PSQCA) and World Health Organization (WHO). Four samples were found unsuitable for irrigation. Sodium and magnesium have been used to improve water quality before using it.

A comparison was made between opinions on tap water quality and the habits of its use in Poland and Ukraine, taking into account different seasons of the year as periods of use of supplied water [31]. Tap water parameters are evaluated differently in Poland and Ukraine at different times of water supply. A model was developed to evaluate parameters of the tap water supplied on the territory of Poland and Ukraine and to learn the expectations of customers in these countries.

A study concerning seasonal effects on the contamination of tap water was conducted in the rural area around urban Beijing, China [32]. Multi-isotope analyses were applied to identify the specific hydro-chemical processes and major contamination sources and then evaluate the water quality problems in urban groundwater. The results showed that 30% of the analyzed tap water in the wet season and 23% in the dry season represent a serious health risk due to high nitrate concentrations. Moreover, half of the tap water could not be drinking due to pollution by ammonium in the wet season.

An investigation on the seasonal variations in the chemical and biological quality of water was conducted after overnight stagnation for a period of one year [33]. It has been found that the tap water quality deteriorated with the increase in the total iron concentrations. The total bacterial cell concentrations increased by more than 60% after overnight stagnation. The bacterial structure changed significantly among different seasons, where the diversity of the community was much higher in spring.

Water pollution is a serious problem due to the potential for contracting diseases if the low-quality water is consumed untreated. So, for environmental protection, we must keep water coolers in good status and free from pollution through continuous disinfection and regular maintenance with frequent changes of the filters related to coolers.

The first part of the present work was devoted to studying the quality of the drinking water from coolers established by voluntary people or organizations in public areas to provide free water for the public. The aim of this study is to ensure that these coolers continuously supply clean and safe drinking water for public health protection. All water coolers in Saudi Arabia source water from desalination systems. So, in the second part of this work, we have focused on the water desalination process, which plays very important role in providing potable water for all locations in Saudi Arabia, especially for Madinah city. Different techniques are used for water desalination to provide the drinking water which is distributed in different water coolers in Madinah city.

The objectives of the present work are:

• Investigating the quality of drinking water from different water coolers in public places (this is the first investigation of its kind in Madinah city);
• Auto-detection of low-quality water (values outside the range of the SASO and WHO standards) and closing the concerned water cooler automatically;
• Activating dispensers to provide the best water cooler quality and replacing the contaminated ones;
• Recommending the frequent maintenance and cleaning of water coolers;
• Providing safe drinking water for public health protection in concordance with SASO and WHO standards;
• Choosing the best technique of water desalination to provide the best quality of water;
• Presenting the advantages and disadvantages of different processes used for water desalination techniques such as reverse osmosis, multi-stage flash distillation, multi-effect distillation, and electrodialysis.

The novelty of this work is to prevent the public, by using auto-detection process, if the quality of water is low. So, the proposed management system of water treatment allows the activation of dispensers to provide the best quality of water coolers.

2. Methodology

2.1. Study Area

Madinah city is considered to be an arid region which is characterized by hot temperature in summer months where the temperature reached the value of 55 °C [6]. The high temperature in Madinah city causes low humidity and makes the climate dry. In general, weather in Madinah is influenced by a subtropical dry arid (desert) climate. This makes people have a big need to drink water every day. For this reason, there are many water coolers installed in Madinah city. Also, the population of the studied area is almost around 1,700,000, and the number of visitors in the studied area annually ranges between 6 and 8 million from all over the world.

This study focused on public places in Madinah city, Saudi Arabia. Samples for analysis were chosen from places with high concentrations of people, such as near schools or university areas, gardens and mosques, farms, and marketing areas. All places are indicated in Figure 1.

2.2. Collection of Water Cooler Samples

In this work, 66 water samples were collected from 22 water coolers (3 samples from each cooler) and analyzed in accordance with standard methods of water analysis [7]. Average results for each water cooler sample were calculated. The sources of water cooler samples were divided into two:

• Local water for coolers 1–19 are the government’s desalinated water;
• Groundwater for coolers 20–22, after treatment using reverse osmosis (RO) filtering.

The samples were collected in prewashed (with de-ionized distilled water, diluted HNO₃, and doubly de-ionized distilled water), high-density polyethylene in (500 mL) bottles for physicochemical analyses. Some investigations were performed in the field within minutes of sample collection such as pH, TDS (total dissolved salts), and EC (electrical conductivity). Preservation in the field was achieved by refrigeration by putting samples in ice and keeping them there until they were submitted to the laboratory. Preservation by acidification with diluted HNO₃ was applied to heavy metals and trace element analyses after water samples were filtered. The water samples were collected in 200 mL sterilized borosilicate glass bottles for bacteriological analyses (fecal coliform and total coliform) and carried out within 4 h after sampling.

To provide clean, safe, and healthy drinking water for the general public from coolers in public places in Madinah, different analyses, tests, and water treatments should be performed following the steps below:

• Physicochemical analysis of water samples;
• Measurement of different concentrations of anions in water samples;
• Measurement of concentrations of heavy metals in water samples;
• Bacteriological tests of water samples.

Physicochemical analysis and bacteriological factors were analyzed for each sample. pH, TDS (total dissolved salts), and EC (electrical conductivity) were acquired by a conductivity meter with a pH meter (Hach ‘HQ40d’); total hardness (TH) was measured by titration with EDTA; and turbidity was investigated using a turbidity meter. Nitrates, nitrites, sulfates, fluoride, and free residual chlorine were measured by UV-Visible Spectrophotometer Hach DR/4000. Heavy metals and trace elements (Pb, Cd, Cr, Mn, Zn, Cu, and Fe) have been tested for all samples using inductively coupled plasma-optical emission spectroscopy (ICP—OES; optima 2100 DV Perkin Elemer).

Analytical-grade reagent chemicals were employed for the preparation of all solutions. Freshly prepared double de-ionized distilled water, from a quartz still, was used in all experiments. pH, TDS (total dissolved salts), and EC (electrical conductivity) were determined by using a multimeter (Model HQ 40d, HACH). First, the meter was calibrated using two buffer solutions at pH = 4.01 and pH = 7.0, respectively. After successful calibration, the electrode was rinsed thoroughly using distilled water. The electrode was placed into the sample, and the read button was then pressed. When the reading was stable, the pH was recorded. The meter was verified after measuring each of the five samples. For EC determinations, the meter was calibrated by using standard 1000 μS/cm NaCl solution and verified after five measurements. pH and electric conductivity (EC) of the samples were measured while collecting the samples. The chloride titration was analyzed using the standard titrimetric method. Here, silver nitrate solution (0.0141 N) was used as a titrant, and potassium chromate was used as an indicator. NaCl is used for the determination of the strength of silver nitrate. pH of the water was adjusted so that it would fall within 7 to 10 pH units, and 1 mL of K₂CrO₄ indicator solution was added. Then, the obtained solutions were titrated with standard AgNO₃ to a pinkish yellow end point. The titrant was standardized, and a reagent blank value was established. Hardness was analyzed using the standard EDTA (0.01 M) titration method. Erichrome Black T was used as an indicator. First, 25 mL of the sample was diluted to 50 mL with distilled water, and 1 mL of buffer solution was added, as well as two drops of indicator solution. Then, the solution was titrated with EDTA, until the last reddish tinge disappeared (the solution is normally blue). Nitrates, nitrites, sulfates, fluoride, and free residual chlorine were measured with a UV-Visible Spectrophotometer Hach DR/4000. The proposed management system is presented by the flowchart in Figure 2, which summarizes the general methodology used to perform different analyses and treatments starting from the water source until the water reaches the coolers. In Figure 2, it is indicated that to evaluate the drinking water from coolers, it is necessary to first analyze the water sources (make-up water) and perform water treatment in the case of any contamination. Then, the water coolers were analyzed based on the following 4 tests: physicochemical analysis, concentration of anions, concentration of heavy metals, and bacteriological test.

2.3. Method for Determining Bacteriological Contamination

Water pollution is a serious problem due to the potential for contracting disease if the low-quality water is consumed untreated. Coliform bacteria such as Escherichia coli and Enterococci are used as important indicators of contamination in water drinking. Different methods for determining bacteriological contamination have been presented in the literature [34]. In fact, the currently used methods of analysis for coliform bacteria have been recently developed and present advantages and limitations as presented in this work. These methods can be classified as follows:

• Standard methods use chromogenic substrates for β-D-glucuronidase to identify E. coli and β-D-galactosidase to detect Enterococci.
• Fast methods based on fluorometric procedures have been developed that can be used on-site.
• Advances in biochemical procedures have been made in developing genomic, proteomic, and metabolomics methods.
• Molecular methods are used to determine the total bacterial content of contaminated water.

Biosensors technology have been developed to be used in laboratory processes. In this work, we have used the standard method, which is recommended for drinking water by the WHO standard.

3. Results and Discussion

The recorded physicochemical parameters of the water cooler samples (pH, EC, TDS, and TH) were compared with the standard values from the WHO and SASO. The mean data of the collected parameters such as pH, EC, TDS, and TH of drinking water samples are presented in Figure 3 and Figure 4.

The results showed that the values of the pH, TDS, EC, and TH parameters for most of the water samples (95%) were within the range of the SASO limit values. It was found that values of TDS and TH for water cooler Number 20 were lower than the allowed limits. Also, the results showed that the pH value for water cooler Number 21 was lower than the standard SASO value.

The obtained results also indicate that all average concentrations of anions in the water cooler samples (100%) were in the suitable range for nitrates, nitrites, sulfates, and free residual chlorine. However, 68% of the analyzed samples contained fluoride values lower than the standard value of SASO, as indicated in

Table 1. Average concentration of anions of water cooler samples.

Cooler Number	NO2−	NO3−	Free Cl2	SO42−	F−
	Limit of SASO
	3 mg/L	50 mg/L	(0.2–0.5) mg/L	250 mg/L	(1.5–0.6) mg/L
1	0.0028	1.43	0.26	2.9	0.02
2	0.0067	0.19	0.41	1.4	0.63
3	0.0149	1.17	0.39	9.6	0.05
4	0.0127	0.97	0.41	10.4	0.04
5	0.0066	1.69	0.21	16.5	0.08
6	0.0056	1.15	0.32	9.1	0.01
7	0.0123	1.10	0.49	12.0	0.02
8	0.0039	1.40	0.47	11.2	0.64
9	0.0069	1.72	0.41	9.3	0.03
10	0.0063	0.48	0.43	10.7	0.02
11	0.0118	1.11	0.45	11.2	0.02
12	0.0070	0.34	0.25	32.7	0.01
13	0.0121	0.05	0.21	2.2	0.01
14	0.0084	1.25	0.24	4.9	0.88
15	0.0103	0.82	0.21	5.2	0.70
16	0.0072	0.49	0.34	7.3	0.73
17	0.0025	0.77	0.42	7.6	0.84
18	0.0079	0.70	0.34	8.1	0.04
19	0.0038	0.66	0.36	3.8	0.07
20	0.0051	1.07	0.20	0.2	0.01
21	0.0057	3.39	0.23	3.2	0.63
22	0.0252	3.55	0.37	39.4	0.06

.

Table 2. Concentration of heavy metals and trace elements (mg/L) in water cooler samples.

Cooler Number	Pb (mg/L)	Cd (mg/L)	Cr (mg/L)	Mn (mg/L)	Zn (mg/L)	Cu (mg/L)	Fe (mg/L)
			Limit of SASO
	0.05	0.003	0.05	0.1	5.0	1.0	0.3
1	LDL	LDL	LDL	LDL	LDL	0.002	0.046
2	LDL	LDL	LDL	LDL	LDL	0.003	0.148
3	LDL	LDL	LDL	LDL	LDL	0.001	0.038
4	LDL	LDL	LDL	LDL	LDL	0.003	0.056
5	LDL	LDL	LDL	LDL	LDL	0.004	0.057
6	LDL	LDL	LDL	LDL	LDL	0.001	0.065
7	LDL	LDL	LDL	LDL	LDL	0.002	0.458
8	LDL	LDL	LDL	LDL	LDL	0.003	0.029
9	LDL	LDL	LDL	LDL	LDL	0.003	0.125
10	LDL	LDL	LDL	LDL	LDL	0.006	0.023
11	LDL	LDL	LDL	LDL	LDL	0.003	0.014
12	LDL	LDL	LDL	LDL	LDL	0.001	0.091
13	LDL	LDL	LDL	LDL	LDL	0.004	0.029
14	LDL	LDL	LDL	LDL	LDL	0.000	0.055
15	LDL	LDL	LDL	LDL	LDL	0.006	0.016
16	LDL	LDL	LDL	LDL	LDL	0.001	0.019
17	LDL	LDL	LDL	LDL	LDL	0.003	0.033
18	LDL	LDL	LDL	LDL	LDL	0.003	0.089
19	LDL	LDL	LDL	LDL	0.019	0.003	0.038
20	LDL	LDL	LDL	LDL	0.015	0.000	0.031
21	LDL	LDL	LDL	LDL	0.018	0.001	0.010
22	LDL	LDL	LDL	0.043	1.96	0.001	0.704

Note(s): LDL (Less than Detection Limit). Bold (values greater than SASO limit).

presents the concentration of heavy metals and trace elements (mg/L) in water cooler samples. It is noted that metals (Pb, Cd, Cr, Mn, Zn, Cu, and Fe) were measured for all water samples. The values indicate that all water samples tested have a good concentration corresponding to the normal limit of SASO standards, except for iron (Fe) in water coolers Number 7 and Number 22, where the values were found to be higher than the permitted limits, which are equal to 0.458 mg/L and 0.704 mg/L, respectively. This elevation of values can be caused by rusting in the coolers’ storage tanks and plumbing. The tests for biological contamination show that almost 4.5% of the coolers (cooler Number 15) were contaminated with total coliform, and 95.5% of samples were safe regarding total coliforms. Previous investigations in this field suggest that contamination may be caused by the accumulation of a small quantity of microorganisms from tap water or from the faucet surface, which becomes concentrated in the filters.

Table 3. Bacteriological test of water cooler samples.

Cooler Number	Total Coliforms	Fecal Coliforms	Streptococci Fecal	Notes
1	<1	<1	<1	Safe
2	<1	<1	<1	Safe
3	<1	<1	<1	Safe
4	<1	<1	<1	Safe
5	<1	<1	<1	Safe
6	<1	<1	<1	Safe
7	<1	<1	<1	Safe
8	<1	<1	<1	Safe
9	<1	<1	<1	Safe
10	<1	<1	<1	Safe
11	<1	<1	<1	Safe
12	<1	<1	<1	Safe
13	<1	<1	<1	Safe
14	<1	<1	<1	Safe
15	* TNTC	<1	<1	Unsafe
16	<1	<1	<1	Safe
17	<1	<1	<1	Safe
18	<1	<1	<1	Safe
19	<1	<1	<1	Safe
20	<1	<1	<1	Safe
21	<1	<1	<1	Safe
22	<1	<1	<1	Safe

Note(s): * TNTC: (Too Numerous to Count).

shows the bacteriological test results of the water cooler samples.

The concentrations of heavy metals and trace elements (mg/L) in water sources (make-up water) samples agreed 100% with the SASO standard. As can be seen in Table 2, only the iron (Fe) of cooler no.7 is outside of the limit. This is due to corrosion found in the steel pipe connected between the water tank of the make-up water (source) and the cooler. We solved this problem by changing this pipe. We then performed the analysis again for the same cooler, and the result revealed that the iron level was within the SASO limit.

Figure 3 shows the evolution of the physicochemical parameters of water sources in Madinah city. Most water samples (95.5%) have been found acceptable in the range of the SASO and WHO standards. Figure 4 represents the pH values for different water sources in Madinah city. Almost all the pH data are within the normal range of the standard interval, which is [6.5, 8.5].

Figure 5, Figure 6 and Figure 7 represent the evolutions of the EC, TDS, and TH, respectively, for different water cooler sources in Madinah city.

As shown in Figure 5, Figure 6 and Figure 7, the values of TDS and TH for cooler Number 20 are lower than the permitted limits. This may be attributed to the use of an RO filter for water cooler Number 20, and these low TDS and TH values decrease the minerals required for healthy human growth. Also, the conductivity is lower for the same cooler.

Also, the results showed that the pH value for water cooler Number 21) is less than the standard value of the SASO and WHO. Water with a low pH can be acidic, naturally soft, and corrosive in nature.

Figure 8 shows the evolution of the concentration of iron (Fe) in different water coolers studied in this work. It was found that for the water coolers Number 7 and 22, the concentrations of Fe exceed the SASO limit.

Physicochemical analysis and bacteriological tests were performed for samples from 22 water sources (make-up water), using three samples from each source, and the average results for each sample were calculated. The results are presented in

Table 4. Physicochemical parameters of water sources (make-up water) samples (pH, EC, TDS, and TH).

Cooler Number	pH	Conductivity (S/Cm)	TDS (mg/L)	TH (mg/L)
	SASO Limit
	6.5–8.5	400	100–1000	500
1	7.13	251	137	57
2	7.60	306	238	64
3	7.85	317	239	63
4	7.87	331	247	77
5	7.66	355	199.4	75
6	7.6	381	218.5	67
7	7.48	344	243	81
8	7.57	353	255	79
9	8.03	347	248	54
10	7.52	341	252	82
11	7.57	259	259	87
12	7.88	202	202	71
13	7.29	193	106.7	40
14	7.51	239	129.9	56
15	7.76	232	124.7	62
16	7.82	394	218	64
17	7.75	380	225	69
18	7.87	337	204	62
19	7.48	363	184.8	57
20	6.74	582	3780	1710
21	6.52	612	3925	1775
22	6.87	1663	10,080	3480

Note(s): Bold: higher than the allowed limits.

and

Table 5. Average concentration of anions of water sources (make-up water) samples.

Cooler Number	NO2−	NO3−	Free Cl2	SO42−	F−
	SASO Limit
	3 mg/L	50 mg/L	(0.2–0.5) mg/L	250 mg/L	(1.5–0.6) mg/L
1	0.0028	1.43	0.26	2.9	0.62
2	0.0067	0.19	0.41	1.4	0.63
3	0.0149	1.17	0.39	9.6	0.75
4	0.0127	0.97	0.41	10.4	0.64
5	0.0066	1.69	0.21	16.5	0.88
6	0.0056	1.15	0.32	9.1	0.71
7	0.0123	1.10	0.49	12.0	0.62
8	0.0039	1.40	0.47	11.2	0.64
9	0.0069	1.72	0.41	9.3	0.83
10	0.0063	0.48	0.43	10.7	0.72
11	0.0118	1.11	0.45	11.2	0.92
12	0.0070	0.34	0.25	32.7	0.81
13	0.0121	0.05	0.21	2.2	0.71
14	0.0084	1.25	0.24	4.9	0.88
15	0.0103	0.82	0.21	5.2	0.70
16	0.0072	0.49	0.34	7.3	0.73
17	0.0025	0.77	0.42	7.6	0.84
18	0.0079	0.70	0.34	8.1	0.64
19	0.0038	0.66	0.36	3.8	0.87
20	0.0140	52.3	1.61	720	1.59
21	0.157	53.39	2.23	790	1.63
22	0.0718	56.85	3.46	1840	2.15

Note(s): Bold: higher than the allowed limits.

. The mean data of the collected parameters such as the pH, EC, TDS, and TH of make-up water samples are presented in Table 4. The obtained results indicate that all pH values of make-up water samples (100%) were in the suitable range values of the SASO standard. Also, Table 4 shows that the values of the EC, TDS, and TH for 86.4% of make-up water samples (1 to 19) were within the range of SASO limit values, but it was found that 13.6% of make-up water samples (20 to 22) were higher than the allowed limits.

The obtained results also indicate that the average concentrations of anions such as nitrates, sulfates, fluoride, and free residual chlorine of most of the make-up water samples (86.4%) were in the suitable range values of the SASO. But it was found that 13.6% of make-up water samples has concentrations higher than the allowed limits of the SASO, as indicated in Table 5.

The bacteriological tests of the water source (make-up water) samples were all found safe for the different samples.

Comparative Analysis of Regional Countries

A comparative analysis of regional countries is presented in

Table 6. A comparative analysis of regional countries.

City/Country	Analysis and Results	References
Riyadh (Saudi Arabia)	Four hundred water samples from public coolers have been analyzed—95.5% of samples are within the limit of standards values of the SASO.	[5]
Sheikhpura (India)	The metal used for water cooler devices could affect the drinking water’s quality, which can be determined by its odor, color, taste, and concentration of organic and inorganic matter.	[11]
Alexandria (Egypt)	A total of 85% of water cooler samples contained less than 0.5 mg/L free residual chlorine, 65% of samples contained lead concentrations higher than 0.01 mg/L, and about 15% were microbiologically contaminated.	[14]
Sharjah (UAE)	Biological and chemical analyses of public water coolers were conducted on selected streets. All water samples revealed a water quality in concordance with allowable levels.	[15]
Iran	It was found that 50% of the tested samples contain residues outside of the Iranian standards.	[17]
Iran	It was found that 62% of water cooler samples had a bacteria count higher than the standard limits.	[20]
Walailak University, Thailand	Sixty water dispensers were tested. Results show that the total hardness value in 13 samples was higher than the limit values, and the microbiological tests showed that global coliform and fecal coliform bacteria were found in 17% and 8% of total samples, respectively.	[23].
Makkah, Saudi Arabia	Sixty-three samples were analyzed and tested from randomly selected water coolers.	[24]
Islamabad city (Pakistan)	Thirty-two samples were tested, and it was found that twenty-sox samples were unsafe for drinking.	[25]

.

The comparison of our results with those obtained in other regional countries, as presented in Table 6, reveals that our results showed that most of the water samples (95.5%) are in accordance with the SASO and WHO values. However, 62% of water cooler samples were contaminated [20], and 85% of water coolers [14] were safe.

4. Water Desalination Techniques

All water cooler sources in Madinah city (Saudi Arabia) come from desalination systems. Most of the samples used in this study are provided from water desalination system using the reverse osmosis (RO) technique, and a few samples are provided from water desalination systems using the solar still distillation (SSD) technique.

The water desalination process plays a very important role in providing potable water for all locations in Saudi Arabia, especially for Madinah city. Different techniques are used for water desalination to provide the drinking water which is distributed in different water coolers in Madinah city.

4.1. Advantages and Disadvantages of Desalination Techniques

There are two kinds of desalination technologies which are the most used in practice: thermal and membrane desalination [35]. For large-scale applications, the thermal processes used are:

• Multi-stage flash (MSF) distillation;
• Multi-effect distillation (MED);
• Solar still distillation (SSD).
  The membranes processes used are:
• Reverse osmosis (RO);
• Electrodialysis (ED).

In thermal desalination, salted water is preheated until it produces water vapor, which can be condensed to produce fresh water [34]. In membrane desalination processes, water is compressed using a thin membrane with tiny holes. Only the water flows through the pores, leaving the salt on the same side while fresh water passes through to the other side.

A high amount energy is required for thermal distillation plants compared to the membrane distillation process [36]. Membrane processes require pretreatment of the feed water, but there are many advantages of using reverse osmosis (RO) for desalination, including the high quality of the water produced, a lower cost of water production, simple operation, fast startup, and lower energy consumption. Nowadays, reverse osmosis (RO) is the most used technology for desalination, followed by multi-stage flash distillation (MSF) and multi-effect distillation (MED) [37].

The second part of this paper is focused on the advantages and inconveniences of different processes used for water desalination which allow for producing the best quality of drinking water. Many investigations have been carried about desalination techniques to obtain a better compromise between production and cost. Some of these techniques present some advantages and some inconveniences, which are described in the following sub-sections.

4.1.1. Advantages of Desalination Techniques

To provide clean drinking water for a population using desalination techniques is considered as a big advantage. Thermal desalinization plants, which produce most of the desalinated water in the world, are considered the easiest system to build and are principally constituted by tightly packed tube networks. Desalination units produce a very high level of purification. Membrane processes of desalinization consume less energy than thermal ones. Membrane processes are cleaner and safer. Also, among their advantages, the membrane processes use lower operating temperatures and pressures compared to the thermal processes.

4.1.2. Inconveniences of Desalination Techniques

The inconveniences of such techniques are the high energy required for driving these processes and the pollution generated when using them at a large scale. Also, the high cost to build commercial desalinization plants, such as those using the membrane process, is considered a disadvantage. The excessive wetting of the membrane makes them degrade with time due to the exceedance of liquid input pressure and membrane fouling. The main causes of excessive wetting of the membrane are due to organic fouling and inorganic scaling, as reported in the literature. Complicated physicochemical interactions are caused by wet membrane pores.

Table 7. Comparison between different methods of desalination techniques.

Desalination Techniques	Advantages	Disadvantages	Ref.
Reverse osmosis (RO)	Simple operation and fast startup. Low energy consumption. Low initial cost. High space/production capacity. No cooling water flows. Modular structure of plants. Couplable with many renewable energy sources. Outlet salt concentration around 500 ppm.	Membrane life about 5–7 years. High costs for chemical and membrane replacement. Pretreatment necessary, such as pre-filtration and chemical pretreatments. High pressure can cause mechanical failures.	[37,38]
Electrodialysis (ED)	Produces high-purity water. Low energy consumption. Moderate and low pressure used. Life of the membrane is around 7–10 years.	Only for brackish water. Frequent cleaning of membranes. Leaks may occur in membrane stacks. For potable water, bacterial contaminants cannot be eliminated by this system.	[39,40,41]
Multi-stage flash distillation (MSF)	Produces high-quality water which contains TDS levels lower than 10 mg/L. High rated capacity. Long operating life. Simple pretreatment of feed water. Cost and plant process independent of salinity level. Heat energy can be produced using power generation.	High initial cost. High energy demand. Scaling problems. Maintenance needs to stop all processes. Technical knowledge required. Low recovery ratio.	[35,42]
Multi-effect distillation (MED)	High-quality product water. Simple pretreatment of feed water. Automatic process needs minimal operational staff. Allows normal levels of biological matter. Heat energy can be produced using power generation.	Water productivity needs cooling and blending prior to being used for potable water needs. Scaling and corrosion problems. High energy consumption. Considerable initial cost.	[34,37,42,43,44,45]
Solar still distillation (SSD)	Run by solar radiation. Cheaper and requires minimum maintenance. It can be used at home-level scale. Adaptation benefits with climate change. No energy cost required. No moving parts.	Usable only for small applications The rate of distillation is usually very slow. Not useful for large scales. It is used only during the day when solar energy is available.	[36,46,47,48,49,50]

presents a comparison between different desalination techniques by given their advantages and their inconveniences.

5. Practical Applications of Water Quality

Water testing results have many applications, such as drinking water, irrigation purposes, the survivability of fish for a specific water, etc. The assessment of water quality, usually carried out by determining its physicochemical and biological properties or parameters against a set of standards, is used to determine whether the water is suitable for consumption or safe for the environment.

Environmental water quality is highly important for the well-being of flora and fauna in oceans, rivers, lakes, swamps, and wetlands. It impacts people and higher-order species which depend on these ecosystems for food and the transfer of nutrients.

Water quality is investigated to assess waters for two specific applications: public water supply and irrigation. Also, water testing results allow the best course of action for a specific waterbody to be identified, i.e., whether a treatment is needed or an aeration system should be installed. The amount of dissolved oxygen helps to determine what species of fish, if any, can survive in the water.

6. Conclusions

This study is devoted to the investigation of the quality of drinking water from coolers in public places in Madinah and to providing clean, safe, and healthy drinking water for the general public. Water quality is highly dependent on physical, chemical, and microbiological conditions. From our physicochemical analyses, we concluded that 95.5% of the analyzed water samples (in terms of pH, EC, TDS, and TH) taken from different water sources are in accordance with SASO and WHO values. In addition, all of the analyzed water samples (100%) contained permissible levels of nitrates, sulfates, nitrites, and free residual chlorine, as indicated by the results. However, 68.2% of the samples studied had fluoride concentrations below the standard values. Furthermore, heavy metals such as lead, iron, and others were tested for all water coolers. The measured findings indicate that just one cooler exceeded the permissible limit of 0.3 mg/L for Fe, and the biological contamination testing revealed that 4.5% of the coolers were infected with total coliform.

Our contribution helps to prevent the public from using water coolers, by using an auto-detection process, if the quality of water is low. The proposed water treatment management system allows the activation of dispensers to provide the best quality of water cooler. A recommendation has been given to the appropriate authority which would allow for a continuous control and analysis of different sources of drinking water starting with the water desalination process and covering the water transportation, water dispensing system, and water coolers. The quality of drinking water from coolers in public places in Madinah must be investigated regularly to continuously provide healthy water for the population. Therefore, this study makes the following recommendations: Regular maintenance and cleaning measures for water coolers, and disinfection should be performed at the water purification plants using classic disinfection processes such as UV, chlorination, and ozone disinfection. Also, a continuous control of water quality is necessary for public health. The filters installed at the water coolers should be replaced according to their life cycle, and the coolers need to be tested frequently to maintain the best quality of water. Finally, a compromise must be found between renewable energy and desalination techniques that reaches the best water production with good quality and low system costs.

The recommendation for future work is to study the quality of water from different locations and in different seasons. It is also recommended to study the effect of other parameters such as temperature and the type of filter used in coolers, which affect the quality of drinking water.