Physicochemical quality monitoring of groundwater for drinking purposes in rural Ujjain, Central India: findings of a 2-year longitudinal study

Rampant use of groundwater for drinking purposes in several parts of the world has raised the concern over its quality. Owing to increasing population, overuse, and pollution of surface water sources, the use of groundwater has increased to considerable extent. Despite this, little attention is paid towards the monitoring of groundwater resources to assess their suitability for drinking purposes. To assess the groundwater quality in rural areas of Ujjain District of Madhya Pradesh, India, in order to check its suitability for drinking purpose, water quality analysis was done at seven time points during the two study years in six villages of Ujjain District, Central India. A total of 868 groundwater samples from 124 households were collected, and standard analytical methods were employed for analysis. Overall groundwater quality of the area is good and qualified for drinking. However, occurrence of high amount of dissolved solids (> 800 mg/L) and hardness (> 400 mg/L) is the issue of concern, as long-term use of such water might result in variety of health ailments, such as kidney stones and atopic dermatitis in children. Regular monitoring and long-term surveillance of drinking water sources are necessary to keep track of the changes occurring in the system.


Introduction
Water is one of the most essential requirements for living beings. Out of the total water present over the earth's surface, only 3% is freshwater available for living beings [1]. Moreover, out of this 3%, much of the water is ice-locked and/or underground. Therefore, the remaining meagre amount of available freshwater needs to be used very judiciously. Nevertheless, an ever-increasing population, rapid industrialization, and pollution have led to the contamination of most of the water resources, be it surface water or groundwater [2][3][4]. Therefore, in order to have the accurate assessment for suitability of water resources, various methodologies and tools are being used across the globe [5][6][7][8]. It has been reported that in developing countries, around 90% of wastewater is directly discharged in surface water sources without any treatment [9,10]. This might be due to low awareness, lack of resources, and financial constraints. As far as India is concerned, approximately 70% of the country's water resources are polluted, indicating the seriousness of the issue [11]. Also, most of the groundwater resources are contaminated with various hazardous metals/metalloids, such as arsenic, cadmium, lead, and manganese [12][13][14][15][16] that make the water unfit for use.
Water quality in the Indian state of Madhya Pradesh has rarely been assessed. It has been reported that the water in the state suffers due to significant mining activities and agricultural nonpoint source pollution [17,18]. Moreover, heavy metal pollution has also been reported from drinking water sources in the state [19]. Various religious activities and associated mass bathing events further add to the pollution problem [20][21][22][23]. Emerging issues, such as the occurrence of antibiotic-resistant bacteria, have also been reported as being traced to illicit discharge of hospital waste in the city [24,25]. After recognizing water pollution as a public health problem, the government initiated various national-level programmes, such as the National Water Quality Monitoring Programme, to monitor and maintain water quality under its central-and state-governed institutions; however, satisfactory results could not be achieved. Various limitations of the existing monitoring system, especially in rural areas, have led to uncertainty regarding the quality of groundwater used for drinking purposes among rural households. Hence, in order to make an assessment of household drinking water quality, this study was conducted in the Ujjain District of Central India where water availability and quality are a concern [26,27].
There are a number of physicochemical parameters that are necessary to meet certain standards, in order to make water fit for use. In India, the Bureau of Indian Standards (BIS) provides limits for various parameters (Appendix 1). Therefore, water samples collected from Ujjain city in Central India were assessed for quality and compared with BIS standards. To make a comparative assessment, standards given by the World Health Organization (WHO) were also considered (Appendix 1). Statistical analysis was done, and based on the outcome; relevant preventive measures have been suggested.

Setting
This study was undertaken in the Ujjain District of the Indian state of Madhya Pradesh. Ujjain is one of 52 administrative districts and has a population of 0.52 million with approximately 60% living in rural areas [28]. The total literacy rate is 73.55% and female literacy is 60.7%. Of the total population, 21.3% live below the poverty line [28,29]. The population is mostly engaged in agriculture and related occupations. The infant mortality rate is 59 per thousand, while the maternal mortality ratio is 268 in the Ujjain District (Annual health survey 2010-11) [30], which is higher than the national average (viz. 30 per thousand and 130, respectively).
The present study is a part of an ongoing project that has been previously described in detail [31]. The data collection for this study occurred in parallel with data collected from children as described and presented elsewhere. In short, six out of the 60 villages were selected from the Demographic Surveillance Site of R.D. Gardi Medical College, Ujjain. A simple random method was used to select households with children from 1 to 3 years of age from a village that fulfilled the inclusion criteria of the previous study [31].

Design and sample collection
This study used a repeated cross-sectional design. Water samples were collected in seven rounds from the selected households of the six villages, as shown in Fig. 1. In each village, two drinking water samples from separate major sources were also collected.
The samples were collected during the pre-monsoon (May 2015, June 2016), monsoon (August 2014, August 2015, September 2016) and post-monsoon (January 2015, January 2016) seasons from 2014 to 2016 from various abstraction sources in clean polyethylene bottles and preserved by adding an appropriate reagent [15,32]. All the samples were stored in sampling kits maintained at 4 °C and brought to the laboratory for detailed physicochemical analysis. The sampling was done by trained research assistants.
All the chemicals used in the analysis were of analytical grade (Merck). Deionized water was used throughout the study. All glasswares and other containers used for the analysis were thoroughly cleaned by soaking them in detergent, followed by a soaking in 10% HNO 3 for 48 h and finally rinsed with deionized water several times prior to use.

Sample analysis
An analysis of various organoleptic and physicochemical parameters was carried out in order to evaluate groundwater quality. Temperature was measured using a thermometer with an accuracy of 0.1-0.2 °C. The pH was measured using a handheld digital pH meter (Thermo Fisher Scientific, Mumbai, India). Conductivity was measured using a digital conductivity meter (611-El, Electronic India, Parwanoo, India). A digital TDS meter (AM-TDS-01, Aquasol Digital, Rakiro Biotech Systems, India) was used for measuring the total dissolved solids.
Physicochemical parameters were analysed using standard methods [15,32]. Chloride, hardness (total, calcium, and magnesium), alkalinity, nitrate nitrogen, and Orthophosphate (OP) were measured through titration methods. The quantification of chemical constituents was based upon the calibration curves of standard solutions of respective constituents. These analyses were carried out in the Central Research Laboratory of R.D. Gardi Medical College, Ujjain.

Statistical analysis
Data were entered in Microsoft Excel and analysed using IBM SPSS Statistics 25.0 (IBM Corp. Armonk, NY, USA). Descriptive statistics were calculated. The observed values were compared with the standard reference values (BIS values). Differences in the mean values of the parameters across the study period (seven rounds over a 2-year period; i.e., temporal variation) and the differences in the values between the villages (viz. geographical variation) were studied. Factorial repeated measures ANOVA was used to test the existence of significant temporal and geographical variation among the measured parameters.

Ethical considerations
The study was approved by the institutional ethics committee of R.D. Gardi Medical College (No: 2013/07/17-311). Informed consent was obtained from concerned household heads for taking drinking water samples. Consent was also obtained from respective local village leaders for collecting water samples from drinking water sources.

Study samples
A total of 868 water samples from 124 households were collected and analysed, out of which only 29 households consistently used water from the same source. The most commonly used water source was the hand pump followed by well. It was also noted that many households frequently changed drinking water sources from one to another. The main reason for this seemed to be the  (Table 1).

Physicochemical properties of water
Among all the analysed parameters, total dissolved solids (TDS), total hardness, calcium hardness, and magnesium hardness were found to be exceeding the defined BIS limits (Appendix 1). These parameters were also beyond the limits in the source water itself, and therefore high values in the household water were evident ( Table 2).
The variations of these four parameters were plotted for each round (Fig. 2). It can be seen that in each round, the values are significantly higher than the BIS acceptable limits for these parameters. Moreover, variation in the water quality is also evident among different rounds or seasons. The ANOVA analysis showed that the above-mentioned four parameters are beyond acceptable limits (Appendix 2). There was a significant difference found among the water quality of the considered villages. A significant difference was found to be existing in the water quality during different seasons as well. No correlation was found in the water quality variation among the villages and seasons (Appendix 2).

Discussion
Long-term follow-up was undertaken in rural households of Ujjain for assessing the quality of drinking water. Organoleptic and physicochemical parameters in the collected water samples were evaluated and compared with drinking water quality standards [33,34]. Results showed that some of the parameters, viz. total dissolved solids (TDS), total hardness, calcium hardness, and magnesium hardness, exceeded the desired acceptable levels prescribed by BIS. Moreover, it was surprising that this phenomenon was common for all six villages. Other parameters were found well within the acceptable limits. It is noteworthy that there is no pattern in the increase of values over time for the particular parameters.
The acceptable limit for TDS is 500 mg/L for drinking purposes [33,34]. Levels of TDS were found to exceed the acceptable limit in all the villages in every season. Moreover, a sharp decline could be observed in TDS values for all villages in the samples collected in the third round (pre-monsoon: May 2015). This can be explained, as during the dry season there is no seepage of silt and/ or dissolved solids in the groundwater. Upon the arrival of the monsoon season, a large amount of water laden with silt seeps off the ground and mixes with the water beneath it, thus making it rich in dissolved solids. Hence, there is a dip in the curve in the pre-monsoon season   (Fig. 2). It is due to the fact that the monsoon season results in a rapid dissolution of carbonate and bicarbonate rocks, thus releasing the carbonate and bicarbonate ions in the surrounding water, which are responsible for hardness in the water. It is to be noted that values exceed not only the acceptable limits, but also permissible limits for calcium and magnesium hardness (200 mg/L and 100 mg/L, respectively). Water quality variation among seasons is found to be significant as rains in the monsoon season bring a high amount of dissolved and suspended solids, which are absent during pre-and post-monsoon seasons. Moreover, rains result in a faster dissolution of rocks, thus releasing    (Table 3) might be the outcome of local and geogenic factors. Such seasonal variations have also been reported in earlier studies of Ujjain [35]. High values of TDS and hardness (total, calcium, and magnesium) indicate the presence of various cations and salts, which is common in the case of groundwater. Bicarbonates, calcium, and magnesium are important elements for the high values of these parameters. It is known that calcium and magnesium are essential cations for health, as these are involved in many biochemical processes of the body [36,37]. It has also been reported that high levels of calcium in drinking water result in a low occurrence of dental caries [38], hypertension [39], and cardiovascular diseases [40,41]. However, there are other studies which indicate that excess calcium sometimes may result in an increased risk of myocardial infarction among postmenopausal women [42]. The consumption of water having high hardness levels might promote urinary health issues, such as formation of kidney stones [43][44][45]. Moreover, there are several studies which depict the positive correlation between hard water and atopic dermatitis (eczema), especially in children [46][47][48]. Therefore, consumption of such water is recommended only after undergoing sufficient treatment.
The hardness in water can be reduced by various methods, such as reverse osmosis, filtration, and ion exchange mechanisms [49][50][51]. Another common approach to reduce hardness is precipitation, which can be achieved through lime, lime soda, or sodium hydroxide softening. In this process, anions (e.g., carbonate and/or hydroxide ions), are used to bind with cations present in water (Ca and/or Mg), which leads to their precipitation and subsequent removal. In the reverse osmosis method, water is forced to pass through a semi-permeable membrane under pressure, which results in softer water. In the ion exchange mechanism, hard water is allowed to pass through sodium rich exchange material (also called zeolite). In this process, sodium ions get replaced by the cations present in water, viz. Ca and Mg, thus reducing the hardness of water.
Safe and clean drinking water is essential for all living beings. The present study is an attempt to realize the importance of long-term monitoring of drinking water sources for better health and quality of life. The study not only assessed the groundwater quality in rural households, but also followed the same households for two consecutive years to observe whether there was any change over time. The findings resulted in a comprehensive picture about the groundwater condition of the studied area. Therefore, emphasis needs to be on long-term surveillance for assessing changes in water quality over time. Longterm surveillance of drinking water parameters can further help in taking appropriate measures in time. The scope of the study can also be widened by including health-seeking data along with water quality, as it would help to build up cause-effect relationships, and various water-borne diseases can be prevented from occurrence. In order to facilitate this, local governments may also be engaged in water quality programmes, which can periodically examine water quality levels and take necessary action.

Conclusion
Drinking water quality in the rural areas of Ujjain, Madhya Pradesh in Central India, was monitored for the period of 2 years in different seasons. It was found that dissolved solids and hardness were exceeding recommended limits in the water samples, which might prove to be harmful for health in the long term. Thus, the present study emphasizes the importance of periodic water quality monitoring to witness changes in health and/or ecological outcomes. The authors recommend further studies to ascertain the health impact of long-term consumption of water with higher levels of dissolved solids and hardness. It is suggested that such water should be used for consumption only after applying necessary treatments. Moreover, it is established that long-term surveillance is necessary for maintaining the water quality, and hence this study might help upcoming researchers for planning and management of water quality programs.

Compliance with ethical standards
Conflict of interest The authors state that they have no conflict of interest.
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Parameters Units
Indian Standards (BIS) WHO Standards Acceptable limit Permissible limit Acceptable limit