Evaluation of Point-of-Use Drinking Water Treatment Systems Efficiency in Reducing or Removing Physicochemical Parameters and Heavy Metals
 
Raziyeh Pourjamali ¹, Elham Khalili Sadrabad ², Sayed Aliasghar Hashemi ⁴, Hosein Shekofteh ⁵, Mehdi Mokhtari ⁶, Ali Heydari ², Fateme Akrami Mohajeri ^{2, 3}*
 
¹ International Campus, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
² Zoonotic Diseases Research Center, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
³ Department of Food Hygiene and Safety, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
⁴ Irrigation and Drainage, Department of Water Engineering, College of Agriculture, Shahrekord University, Shahrekord, Iran.
⁵ College of Agriculture, University of Jiroft, Jiroft, Iran.
⁶ Environmental Science and Technology Research Center, Department of Environmental Health Engineering, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
 

Citation: Pourjamali R, Khalili Sadrabad E, Hashemi SA, et al. Evaluation of Point-of-Use Drinking Water Treatment Systems Efficiency in Reducing or Removing Physicochemical Parameters and Heavy Metals. J Environ Health Sustain Dev. 2019; 4(1): 717-26.
 

 
Table 1: Mean values of qualitative and chemical parameters in two water sources of Rafsanjan

* ND: not detected in studied samples.
LOD: 2-100 ppb
Different letters in each row show significant differences (p < 0.05).
 

Table 2: The mean values of chemical and qualitative parameters in the water at the inlet and outlet of home water treatment devices

* ND: not detected in studied samples.
LOD: 2-100 ppb
Different letters in each row show significant differences between inlet and outlet water (p < 0.05).
The Mean concentration of all parameters except for arsenic was significant in comparison to standard limits (p < 0.05).
 

Table 3: Efficiency of two brands of home water treatment device

 

Discussion
Due to the lack of selective removal system in the water treatment devices, all cations and anions are eliminated regardless of their usefulness or harm ²¹, therefore the balance of minerals in the outlet water can be disturbed and put the consumer health into danger. In recent years, reverse osmosis has been very frequently applied in water treatment systems, which is known as a 21st century technology ²².
The consumers have been encouraged to use reverse osmosis due to its easy installation in home to achieve optimal water quality. The results of this study showed that, except for arsenic, the levels of the parameters in the inlet water of Rafsanjan were lower than the Iran National Standards of drinking water. The home water treatment device significantly was reduced all physicochemical parameters in the outlet water in the standard range. The EC of water represents its dissolved anions and cations, which their increase can have direct effect on water salinity. According to the European Standards, the minimum EC, for drinking water ranges from 400 μmoh/cm to 1000 μmoh/cm. Our results showed that the removal efficiency of the device for the EC was 83.95%, and its average amount in the water samples at the outlet of the treatment devices was obtained 138.5 μmoh/cm. The low level of EC in the present study is attributed to the reduction of water ions in the reverse osmosis treatment process.  
The result of research carried out during 2003, on the water treatment systems in Qom, reported the EC of water treated by devices 83-588 μmoh/cm; and the EC was less than 400 μmoh/cm in 83% of the samples ²³. In a study in Shadegan on 12 home and industrial water treatment devices, the EC was reported 140-1990 μmoh/cm ²⁴. Tavangar et al., showed the average EC of inlet and outlet water of home water treatment system 911 μmoh/cm and 229 μmoh/cm, respectively, with a removal efficiency of 75% ²⁴.
In the present study, the pH of the water was reduced about 0.9%, which was statistically significant when compared to the pH of inlet water. The mean efficiency of pH in brand 1 and brand 2 were estimated 10.30 and 12.5, respectively. The reason for the decrease in pH can be due to high reduction of anions and cations in the reverse osmosis process. In the water samples of the home water treatment devices in Shadegan, pH was ranged from 6.8 to 7.5 ²⁵. In a study conducted on water treatment devices in Qom, the pH of the outlet water was reported from 5.53 to 6.89 ²³. In the outlet water of treatment devices in Kashan city, the pH was found to decrease slightly and reach a range of 6.8-6.9 ². Tavangar et al. indicated the pH of the inlet water of the treatment devices decreased from 8.21 to 7.68 ²⁴. The mentioned studies confirm the results of the current study.  Low hardness is not suitable for drinking, although it is very suitable for industrial uses, so the level of hardness in the outlet water of treatment devices should be above 100 mg/l and range between 100 to 150 mg/l ²¹. The results of current study showed that the removal efficiency of point-of-use drinking water treatment systems for total hardness, calcium and magnesium hardness were obtained 84.5%, 74% and 85.5%, respectively. In addition, the results showed that the total hardness, calcium and magnesium hardness of Rafsanjan water were 161.37, 61, and 101.8mg/l, respectively. The mean total hardness, calcium and magnesium hardness at the outlet of home water treatment devices reported 23.95, 13.28 and 12.83 mg/l, respectively. The drinking water of Rafsanjan, according to the WHO classification, is considered as hard water (150-300 mg/l) ²⁶, but after treatment by the point-of-use drinking water treatment, it could be classified as soft water (0-75mg/l). In a study conducted in Bojnourd city, the average total hardness at the inlet and outlet were measured at 568 mg/l and 136 mg/l, respectively, and the total hardness removal efficiency was reported 76% ²⁴. In a similar study in Kashan, the average total hardness at the inlet and outlet of water treatment devices were approximately 319.37 mg/l and 118.25 mg/l, respectively, with the total hardness removal efficiency of 62.9% ²⁴. In another study in Qeshm city, the total hardness removal efficiency of water treatment systems was measured 99.5% ²². The results of these studies are consistent with the present study. In current study, the average sodium removal efficiency of the studied devices was obtained 83.6%. The average sodium concentration at the outlet of the water treatment device decreased significantly, indicating the high sodium removal efficiency of the devices. Sadigh et al. reported that the sodium removal efficiency of the device was 95.05%, which is consistent with the present study ²¹. By considering the fact that sodium concentration of water (without treatment) was lower than the Iran national standard, home water treatment devices could reduce it to very low concentrations. Sodium and potassium are among the salts that are important for the taste of water. From the health point of view, the reduction of these two elements can be beneficial for renal and dialysis patients, but it is undesirable for other people due to changes in taste of water ²⁷.
To reduce nitrate from drinking water, various physicochemical and biological processes are used to remove it from drinking water. One of the most practical physicochemical processes to remove nitrate is reverse osmosis. As shown in Table 3, the average nitrate removal efficiency for brands 1 and 2 was obtained 56% and 58%, respectively. Besides that, the average concentration of nitrate in the inlet and outlet water treatment devices was lower than the Iran national standard and the WHO standard (45 mg/l) ^{26, 27}. Therefore, it can be concluded that domestic water treatment systems have good nitrate removal efficiencies. It is known that nitrate has numerous health effects and is suspected to be carcinogen; the use of these devices can be very useful to prevent the potential effects of nitrates, such as methemoglobinemia and nitrosamine ²⁸. Naimi et al. found that the average nitrate concentration in the inlet and outlet water of the devices was 5.36 mg/l and 1.85 mg/l, respectively, with a removal efficiency of 65.5% ²⁴. Sadigh et al. reported mean nitrate levels in the inlet and outlet water of treatment devices were 6.01 mg/l and 0.93 mg/l, respectively by removal efficiency of 79.16% ²¹. Dehghani in Qeshm and Sehn in Finland reported the nitrate removal efficiency 92.22% and 91.75%, respectively, which is consistent with the results of our study ^{22, 29}. According to the US Environmental Protection Agency, the permissible limit of arsenic is 5-10 μg/l ³⁰. In the guidelines of the WHO and the Iran national standard, the maximum permissible level of arsenic in drinking water is determined 10 and 50 µg/l, respectively ³⁰. There are several methods for water treatment systems that can reduce arsenic levels of drinking water to the permissible level set by the standard. These methods include membrane processes, coagulation, active alumina and ion exchange. Before choosing the appropriate method, certain issues such as treatment costs, treatment efficiency, and the complexity of the technology and knowledge necessary to use that technology and the disposal of the resulting waste must be taken into account. The advantage of the reverse osmosis process, compared to other methods, is high removal efficiency, lack of chemicals and less attention of expert and full-time operator ²². The results of this study showed that the concentration of arsenic in water of Rafsanjan was eight times higher than the global standard. The arsenic removal efficiency of the treatment device was 86.7%, and the concentration of arsenic in the outlet water was reduced to standard level, and the lead concentration, in addition to being lower than the permissible limit in the inlet water, was reduced by 99% in the outlet water. Lin et al. used two methods of reverse osmosis and distillation at the point-of-consumption to remove arsenic from groundwater. The results showed that both methods have been effective in removing arsenic from the actual groundwater as well as artificial methods. Arsenic levels in the outlet water samples reduced to the standard limits and the arsenic removal efficiency was up to 99%. Although the efficiency of both methods was enhanced by increasing concentration; although the relationship between efficiency and concentration was not significant ³¹.
Mozafarian et al. investigated the arsenic removal efficiency of reverse osmosis process from water with five different types of membranes, and found that the highest arsenic removal efficiency of the membrane was 95% ³². Walker et al. investigated the effectiveness of home reverse osmosis systems for groundwater containing high arsenic levels. They showed that arsenic removal efficiency was higher than 95% ³³. Mokhtari et al. reported that the reverse osmosis process was effective to remove arsenic from drinking water, and had good removal efficiency (more than 95%) in surface and ground waters with arsenic concentration up to 2 mg/l ³⁴. These results also confirmed our results. Malakootian et al. investigated the sources of drinking water in the Rafsanjan plain. The existence of volcanic rocks in the region and the presence of sulfide compounds and streaks in these rocks is one of the reasons for the release of heavy metals. Arsenic, lead, and cadmium have similar sulfur properties and replace them when they form sulfides ³⁴. By the adaptation of the metamorphic map of the area and the regions with the same arsenic concentrations, it could be clearly observed that more volcanic rocks (andesite) were found in places where the concentration of arsenic is higher than standard. Because of the use of pesticides and herbicides containing arsenic in agriculture in Rafsanjan, the lack of a wastewater treatment system for metallurgical industries, and the chemical and cellulose industries, metals enter into wells and then penetrate into groundwater ³⁴.
The results of studies have shown that Rafsanjan water pollution by arsenic is due to both natural and human activities, which is consistent with the results of the present research. The concentrations of copper in all studied samples were lower than the standard recommended by the National Iranian Water Organization and the WHO. Malakootian et al. studied the southern Rafsanjan plain. They showed that due to the potential presence of copper in Bardsir and Rafsanjan regions' soil as well as the presence of sulfide streaks in the region, the amount of copper was even lower than that recommended by the National Iranian Water Organization and the WHO ³⁴. The results of the assessment of groundwater pollution in the Kerman showed that the concentrations of lead and cadmium in the water samples were higher than the standard limits for drinking water and those of copper and zinc was lower than the standard ³⁴. Nitzsche et al. investigated the removal of arsenic from drinking water by using a sand filter system in Vietnam in 2015. Results showed the efficient and reliable performance of the system, with an arsenic removal efficiency of 95% ³⁵.
Conclusion
EC and pH values of inlet water were in the standard limits, although arsenic levels were ​​higher than the permissible limits and other parameters such as total hardness, calcium, magnesium,  sodium as well as metals copper, zinc and lead were lower than standard limits. All parameters in the outlet water samples were significantly lower compared to those in the inlet water samples. The results of current study showed that home water treatment devices were highly efficient to remove the physicochemical parameters of water; the devices could reduce the concentrations of the parameters up to those under the standard limits, which is not desirable for some elements. However, due to a significant decrease in the concentration of arsenic, it is suggested that specific filters can be used at the inlet municipal water to adsorb heavy metals, especially arsenic.
Acknowledgments
The authors would like to appreciate the department of Public Health, Shahid Sadoughi University of Medical Science, for their cooperation.
Funding
This study is a part of thesis which was funded by Shahid Sadoughi University of Medical Science.
Conflict of interest
There is no conflict of interest.
 

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