1. Introduction
The decline in the quality of water from springs, boreholes, sealed wells, hand-dug wells, streams, rivers and lakes is caused by the presence of microbes, nutrients, heavy metals, organic chemicals and sediments. Boreholes, which are wells drilled using a drilling rig, draw water from isolated groundwater sources that are filtered through layers of soil and rock before reaching the surface. These sources may contain minerals and have an unpleasant colour or odour, but they are mostly free of contamination and do not require disinfection. Sealed wells are shallow wells that have been sealed, with cement around a pump, to prevent contamination. However, contamination is a possibility, and therefore, chlorine is frequently used to treat sealed wells.
This research paper discusses the methods used to disinfect the public water supply system, which includes submersible pump and related water distribution systems. Disinfection kills or reduces harmful microorganisms like viruses, bacteria and other microorganisms present in drinking water. Controlling microorganisms in a well and the distribution system is achieved via disinfection. From the earliest records to the twentieth century, the history of water purification can be broken down as follows: the pursuit of clean water [
1]. From 1902 to 1921, a mixture of iron chloride and lime chloride was used to chlorinate a highly-coloured water supply [
2]. Four WQIs and FL, based on in situ measurements at nine different wells along the study area in Jouamaa Hakama Region (North of Morocco), were used and compared, alongside twelve bacteriological and physical–chemical parameters [
3]. The use of chlorine gas largely replaced the use of lime chloride in disinfecting drinking water [
4].
The process of flushing the well and water system with a chlorine solution, to kill bacteria and other microorganisms, is known as chlorination or ‘shock chlorination’ [
5].
Free chlorine residual comprises two main compounds: hypochlorous acid (HOCl) and hypochlorite ion (OCl
−). Hypochlorous acid is more effective in killing pathogens than the hypochlorite ion [
6].
Calcium hypochlorite Ca (ClO)2, chloride (Cl), hypochlorous acid (HOCL) and water (H2O) are involved.
When chlorine is added to water, the following chemical reaction occurs:
Chlorine, when added to water, reacts with hypochlorous acid and hydrochloride acid to form a pH-dependent equilibrium mixture.
Hypochlorous acid partially dissociates into hydrogen and hypochlorite ions based on the pH:
Chlorinated water recirculation helps to distribute the chlorine, thoroughly mix the water column and wash down the well casing’s sidewalls [
7].
Groundwater is water that is found below the surface. It is the source of water for wells and springs and helps to sustain water flow in surface water bodies such as lakes and streams. It is a valuable resource because it supplies many residents and businesses with water and contributes to the health and integrity of our aquatic ecosystems [
8]. Many groundwater sources and water from lakes, rivers, or streams contain ‘germs’ that can spread diseases. Pathogens are germs that cause water-borne infections, which can result in serious reactions and complications, including death. They include parasites, viruses, and bacteria. These pathogens, which are present in human or animal faeces, increase in number when they enter drinking water sources [
9].
Well disinfection helps to get rid of or reduce harmful bacteria and viruses, as well as harmless bacteria that cause a bad taste and smell [
10].
Although shock chlorination is necessary for the maintenance of wells and disease prevention, it does not guarantee safe drinking water. Safe drinking water can be ensured by incorporating shock chlorination into a well management strategy that includes the responsible decommissioning of abandoned wells, adequate well protection and the maintenance of a water monitoring program. Groundwater from private wells supports 5 million people across Canada [
11].
The aims of this study are as follows:
To investigate the physicochemical parameters and bacterial microbes in groundwater.
To study the effect of the disinfection and sterilization of water wells, by calcium hypochlorite, on groundwater geochemical variables and microbes.
To calculate the volume of disinfection and sterilization using a pumping test.
To compare the quality of Jordanian water wells, using Jordanian Drinking Water Standards, before and after the disinfection.
The microbial population, in a well, is divided into “nuisance” and “pathogenic” bacteria. The most prevalent pathogens are iron bacteria and sulphate-reducing bacteria (SRB) [
12]. Although these bacteria are not harmful, they pose a health risk as they form biofilms that protect against pathogens and hinder faecal coliform testing [
13]. There are pathogenic microbes, protozoa, and infections that make up unsafe microorganisms. The majority of microorganisms reside in various aggregates called ‘biofilms’. Biofilms are commonplace and symbolize the most prosperous way of life. They carry the potential for self-cleaning in soils, sediments, and water, and are the active ingredient in biofiltration [
14]. About half of all drinking water wells in the US, tested in recent studies, have evidence of faecal contamination. Groundwater is significantly associated with outbreaks of waterborne diseases; many pathogens have been found in groundwater [
15,
16].
This study aims to compare the quality of Jordanian water wells before and after the chlorination treatment. The quality parameters were compared to the Jordanian Drinking Water Standards and WHO (2011) to ensure that they adhere to the guidelines of the Drinking Water Standard. The proper regulation of the water supply includes the completion of a water well, the cleaning of existing wells, the proper development of new wells by flushing the water supply, remediation with a properly prepared chlorine solution and the collection and analysis of water samples. The limitations of the study are due to constraints on research design, methodology and materials.
5. Discussion
The World Health Organization’s standards serve as the foundation for laboratory analyses of the Jordanian drinking water standards [
29]. The EU guidelines from 1998 [
30], which serve as a reference for the Jordanian standards, could not recode the threshold values for some parameters [
29,
30].
The impact of pH: pH is a proportion of the acidic or basic states of water. As the human body is made up of 50–60 percent water, the pH of drinking water can significantly impact body chemistry and health. The study found that the pH of the water samples ranged from 7.96 to 8.02, which indicates that the water from the aquifer was alkaline in nature, as shown in
Table 5 and
Table 6. The pH of the water was in the range of 6.5–8.5, which was in tune with the guidelines established by WHO [
31] for the quality of drinking water. According to WHO recommendations, the pH may range from 6.5 to 9.5.
As defined by Adegboyega et al., the temperature that defines the value of the chemical reaction in water ranges from 30 to 32.01 °C [
32].
The turbidity, which ranged from 0.5 to 1.51 NTU, was also within WHO’s [
31] permissible limits of 5 NTU, i.e., the drinking water supply was of high quality, according to Jordanian standards, as shown in
Table 6.
Dissolved oxygen (DO), the maximum oxygen concentration that can dissolve in water, is determined by the temperature of the water, and it can vary from location to location and from time to time. The DO, in the range of 2.26 to 2.31, thus falls within permissible limits given by WHO (2017) [
33].
This study’s findings demonstrate that low bacterial counts were correlated with low turbidity values. The reports by Oparaocha et al. [
34], as well as the findings of Agbabiaka et al. [
35], also support these findings.
The total concentration of dissolved substances in groundwater is measured by TDSs, which is an important parameter for evaluating the quality of groundwater and drinking water. According to Anbazhagan and Nair [
36], TDSs refers to fully dissolved minerals in groundwater, such as calcium, chlorides, carbonates, bicarbonates, magnesium, silica, and sodium. According to Adesoji and Ogunjobi [
37], who conducted a similar experiment in which the water also exceeded the [
38] permissible limits of 500 mg/L recommended by the WHO (2010), the TDS values were 207, 208 and 212 mg/L, respectively, thus within the Jordanian standards [
20,
31].
The samples had total hardness values of 123, 125 and 130 mg/L, respectively. The reports regarding the recommended permissible limits of 500 mg/L also support these findings. The electrical conductivity of the water samples ranged from 700 to 900 μS/cm, and the average rates were recorded. Water had a higher electrical conductivity due to the dissolved salts.
The EC can be measured indirectly to the determine TDSs. The treated water samples, which were taken after treatment, were found to have the lowest EC values of 372, 376 and 383 μS /cm, respectively, which is a sign of a decrease in the dissolved salts. The electrical conductivity fell within the WHO’s acceptable range of 0–1000 μS /cm [
38].
On the one hand, the measurement of pollution indicator parameters, like ammonia and nitrate, demonstrated that all readings were within acceptable ranges (
Table 2,
Table 3 and
Table 4). Additionally, Figure 7 shows that there was a strong correlation between ammonia and the iron concentration in various sampling methods.
The effect of nitrate nitrogen can over stimulate the growth of aquatic plants and algae and result in the eutrophication of surface waters. It can even ‘kill’ a lake by depriving it of oxygen, which can lead to anaerobic conditions in the water bodies and fish deaths. Extremely high levels of nitrate nitrogen can make it harder for fish and other aquatic invertebrates to breathe, which can reduce the diversity of animals and plants in the environment.
The water’s nitrate (NO
3−) contents, which were 7.83, 7.88 and 8.23 mg/L, respectively, were low enough to not pose any health hazard to the consumers. In the presence of microbial contamination, a high nitrate content can result in thaemoglobinaemia, or blue baby syndrome, in bottle-fed infants [
32]. Therefore, water with a nitrate standard greater than 100 mg/L is not suitable for use in infants. Nitrate is a significant plant nutrient and is a naturally occurring component in the environment. The nitrate standard, given in this study, indicates that the water is less exposed to inorganic components in the auriferous materials. As the nitrate level is within the standard for drinking water, there is no health risk to consumers.
The magnesium ion (Mg
2+) was monitored with values of 6.27, 6.34 and 6.12 mg/L for the minimum and maximum levels. These levels did not go above the recommended limit of 30 mg/L for use in drinking water. The overall goal is to use the water quality index (WQI), for drinking water, to evaluate the quality of the groundwater in the Al-Zaatari camp, in Jordan, using the major cations and anions that could be harmful to humans [
39]. The WHO-permitted limit for fluoride concentrations is 1.5 mg/L. Therefore, the groundwater can be used for drinking, as it has fluoride concentrations of 0.2 mg/L. The water samples also contain iron, a vital mineral, in its naturally occurring form.
The quartzite rocks of Sheikhpura are an geogenic source of iron in groundwater in India. The literature mentions a similar geogenic source of iron in groundwater [
40,
41]. According to WHO and BIS drinking-related standards [
42], the ideal level of iron is less than 0.1 mg/L and 0.3 mg/L [
43]. A comparison of the laboratory results, with the respective threshold values of the aforementioned standard, is shown in
Table 6. It also contains the results of the laboratory analyses of the samples. The concentration of manganese ranges from <0.01 to 0.01 mg/L, which is under the permissible limit of 0.1–0.05 mg/L, as recommended by [
29,
30,
32].
Table 6 demonstrates that all other elements are present at concentrations below the permissible limit. The iron concentration ranges from 0.11 to 0.18 mg/L, which is under the permissible limit of 1.0 mg/L, as recommended by WHO.
Table 6 shows a comparison of the laboratory results, with the respective threshold values of the aforementioned standards.
Table 6 shows that all other elements are present at concentrations below their particular threshold values. The turbidity, sand content, pH, temperature and electrical conductivity were all measured during airlifting and backwashing. The sand content, turbidity, pH, temperature and electrical conductivity were all measured in the well water, which has very low turbidity.
Figure 4 depicts the sand content in conjunction with the electrical conductivity. Each screen section met the acceptance criteria, with a sand content of fewer than 50 parts per million and an electrical conductivity of 900 μS/cm. Water with a high salt content and a high sand content, as shown in
Figure 4, will have a high electrical conductivity; it will show a high level of impurity in this phase.
The swabbing, airlifting and water jetting of the isolated screen sections were simultaneously carried out after the airlift pumping and backwashing procedures. The swabbing tool was moved up and down, in each screen section, until the EC of 700 μS/cm and the sand content of 10 ppm met the EU standards [
30].
Figure 5 depicts plots of the sand content and electrical conductivity, which were decreased during the disinfection treatment and the other operation, following the jetting of each screen section; these values were 372 μS/cm, 376 μS/cm, and 383 μS/cm, respectively. The swabbing tool was used in three consecutive steps, with the pressure of the injected water increasing from 7 bar to 14 bar to 20 bar during each step.
The second run of swabbing and airlifting followed in the same manner as the first. A high rate of pumping and backwashing occurred at discharge rates of 60.27, 80.22 and 99.83 L/s, respectively. Each step was carried out until the turbidity and sand content was below 5 NTU and 2 ppm, respectively. As depicted in
Figure 6, the turbidity and sand content of the discharged water continuously decreased throughout the third step. Proper well development makes it easier to remove turbidity and sand content, which increases the success rate of the disinfection. According to Lechevallier et al., the suspended particles in cloudy water hinder the chlorine’s efforts to kill microorganisms [
44].
The authors concluded that the low removal of turbidity was due to the presence of fine clay particles in raw water, which penetrated the filter [
45]. In a full-scale study, turbidity removal was between 0% and 63%, due to the fine particles present in the raw water and the large fraction (4% by weight) of fines in the new sand media used in the study [
46]. Turbidity may not be a suitable surrogate for evaluating the removal of pathogens via slow sand filtration because it can achieve the effective removal of microbial pathogens without necessarily reducing turbidity.
Table 6 shows that the effect of chlorine on the minerals in the water can cause water from a chlorine-treated water supply system to be turbid. After steady-rate pumping, bacteriological analyses revealed the presence of the aerobic bacteria
Acinetobacter haemoliticus and a matching total bacterial count [
47].
This higher bacterial count is a clear sign of bacterial regrowth and post-treatment failure or contamination. The total coliform counts did not meet the WHO’s requirement of zero coliform counts in a 100 mL sample. This was a clear indication of contamination and inadequate water infrastructure. Sulphate-reducing bacteria, aerobic bacteria like Sphingomonas pauciummobitis, and coliforms could be found in the treated water. After well sterilization, the total coliform bacteria content was 1.8 MPN/100 mL, which was higher than the threshold (0/100 mL).
The growth of bacteria and the occurrence of coliforms depend on a complex interaction of many factors including temperature, disinfectant type and residual, pipe material, corrosion and other engineering and operational parameters [
48,
49,
50,
51]. Recent research has indicated that various disinfectants differ in their ability to interact with biofilm bacteria.
Monochloramine, although a much less reactive disinfectant than free chlorine, is more specific in the type of compounds that it will react with [
52]. Therefore, monochloramine can be more effective than free chlorine at penetrating and inactivating certain types of biofilms, particularly those containing corrosion products [
53,
54].
A study of 30 distribution systems, using free chlorine and chloramines, showed a difference in the density and occurrence of coliform bacteria between systems [
51]. Modelling indicates that the penetration of free chlorine into a biofilm is limited by its fast reaction rate [
52]. Free chlorine is essentially consumed before it can react with the bacterial components of the film [
55]. Chloramines, on the other hand, are slow reacting; they diffuse into the biofilm and eventually inactivate attached bacteria. This is a mechanism that has been demonstrated using an alginate bead model [
55,
56]. The study showed that free chlorine did not effectively penetrate alginate beads containing bacterial cells, but chloramines penetrated the alginate material and reduced bacterial levels by nearly one million-fold over a 60 min interval (2.5 mg/L chloramines, pH 8.9) [
57]. It also reported that hospitals supplied with water containing a chloramine residual were 10 times less likely to experience water-associated legionella infections. Similarly [
58], in a study of 166 hospitals, it was found that nosocomial legionellosis was five times less likely to occur in hospitals served with chloraminated water. The authors attributed the effectiveness of chloramines, for legionella control, to the ability of the disinfectant to penetrate biofilms.
In addition to the type of disinfectant used, the residual maintained at the end of the distribution system was also related to coliform occurrences [
51]. Systems that maintained dead-end free chlorine levels of less than 0.2 mg/L or monochloramine levels of less than 0.5 mg/L had substantially more coliform occurrences than systems maintaining higher disinfectant residual systems with highly assimilable organic carbon (AOC) levels. Therefore, the maintenance of a disinfectant residual alone does not ensure that treated waters will be free of coliform bacteria.
After well sterilization, the total coliform bacteria content was 1.8, which is also above the threshold (0/100 mL). The authors attributed this effect to the rapid reaction rate of free chlorine and its limited ability to penetrate a biofilm [
55]. Free chlorine is consumed before reacting with the film’s bacterial components [
55]. On the other hand, chloramines react more slowly; they can diffuse into the biofilm and ultimately inactivate connected microorganisms; this is a system that has been shown utilizing an alginate dot model [
55,
56]. Free chlorine, according to the study, was unable to penetrate bacterial-filled alginate beads. The concentrations of all the other elements were below their respective thresholds.
The status of the borehole was checked through a closed-circuit television logging unit (CCTV) survey before the assembly of the lasting pump. After well A was completed, from a depth of 284 m to a depth of 545 m, wells B and C were completed, respectively. The first CCTV survey was used for the final check. Some areas, including the dislocate pattern shown in
Figure 7, had small biofouling. It was confirmed, via the final CCTV survey and bacteriological laboratory results of the collected water samples, that the ongoing processes of biofouling and corrosion in wells may not affect their productivity or safety. The test results for the water samples taken from sterilized and disinfected wells revealed that neither iron bacteria nor bacteria species/anaerobic bacteria were present in the wells [
59].
The content of total coliform bacteria after well sterilization was <1.8, which is also above the threshold value (0/100 mL). The authors attributed this effect to the fact that the penetration of free chlorine into a biofilm is limited by its fast reaction rate [
52]. Free chlorine is essentially consumed before it can react with the bacterial components of the film [
55]. Chloramines, on the other hand, react slowly; they can diffuse into the biofilm and eventually inactivate attached bacteria; this is a mechanism that has been demonstrated using an alginate bead model [
55,
56]. The study showed that free chlorine did not effectively penetrate alginate beads containing bacterial cells. The concentrations of all other elements were below their respective threshold values. According to
Table 5,
Table 6 and
Table 10, the permissible limits of physical–chemical and bacterio-logical parameters are confirmed by the Jordanian standards for drinking water and WHO [
20,
31].