Groundwater quality assessment in proximity to solid waste dumpsite at Uruli Devachi in Pune, Maharashtra

The management of groundwater resources is the leading factor for economic, domestic, industrial, agricultural, or any form of stability for any area (Masoud 2020) For the past several decades, to match the ever-rising need for drinking and agricultural water demand, the groundwater is extracted at a very fast rate. Research shows that about 33% of the population, globally is dependent on groundwater for its fresh water demand. However, if we consider the Indian scenario, groundwater is believed to be the chief water supply source in urban areas and in rural areas about 88% of the population is dependent on groundwater as their primary water supply source. (Stanly et al. 2021).

The groundwater quality is dependent on physical, chemical, and organic characteristics, which further regulate the groundwater usability for diverse utilities. The continual and augmented use and reuse of groundwater leads to the deterioration of groundwater quality (Kalita et al. 2021). The occurrence of several constituents such as arsenic, chromium, lead etc., beyond IS limits renders the groundwater source as not suitable for drinking, irrigation, or industrial use (Aher et al. 2019). The quality of groundwater quality is chiefly dependent on several natural factors such as geochemical characteristics and reactions, lithology, ion exchange, dissolved ions, wet and dry salt deposition in the atmosphere, solubility of salts, climate, and mineral weathering (Kumar et al. 2019). Groundwater quality can also be affected by several anthropogenic activities, such as mining, sewage disposal agriculture, and industrial use (Kumar et al. 2016). All over the globe, different aquifers are susceptible to rising threat of pollution due to urbanization, agriculture, mining, and industrial activities. Further, severe exploitation and reckless use of groundwater results in groundwater depletion and deterioration of its quality. The groundwater contamination may also present a severe effect on human health; hence, understanding the physical and chemical characteristics of ground water along with its quality is necessary (Selvam et al. 2018). This shall further help in suitable planning and groundwater resource management to regulate its thoughtful and sustainable use for different purposes such as domestic, agriculture, and industry (Sayyed & Wagh 2011; Mohindru & Garg 2017). Hence, for the existing study, the physico-chemical characterisation of the groundwater was performed for Uruli Devachi area. The main intent of this work is to determine the suitability of groundwater for domestic use by comparing it with Bureau of Indian Standards (BIS-2012; Jain & Vaid 2018).

Pune is considered to be the seventh-largest city of India, lying between latitudes 18° 22′ N & 18° 35′ N and longitudes 73° 44′ E & 73° 57′ E. It has mean sea elevation of about 559 m. About 1,600–1,700 tons per day of solid waste is generated in Pune municipality area and dumped at Mantarwadi dumpsite, located around 20 km away from Pune. The Mantarwadi dumpsite is located at Uruli Devachi in Haveli taluka. Pune city comprises mixed land use, which includes commercial, industrial, educational, institutional and, residential buildings. The solidwaste generated is heterogeneous in nature, which contains biodegradable waste in addition to plastic, paper, glass, and metal (Mane & Hingan 2012). It is anticipated that 45–50% of solid waste is organic in nature, 35–40% is inorganic in nature, which can be recycled, whereas 10–15% of solid waste is inert in nature. It is estimated that the solid waste would have calorific value exceeding 900 Kcal/kg.

During the initial period, there were no major problems in dumping the solid waste in low-lying areas at Mantarwadi disposal site. However, with urbanisation and population growth, the solid waste quantity increased and the land became scarce. In fact, the rapid population growth increases the stress on groundwater and leads to water shortage in several areas. The effluent discharged from the industries consists of solids and different impurities, which infiltrate through the soil and slowly mix with the groundwater bodies (open well) further degrading the groundwater quality. In addition, the leachate resulting from the dumpsite start percolating in the soil and causing pollution of groundwater in nearby areas (Niloufer et al. 2013; Das & Mahanta 2019). As a result, the quality of groundwater near Uruli Devachi village has further deteriorated, rendering it unsuitable for drinking, bathing, or any other domestic use, as well as for irrigation (Dhere & Jagnnath 2016). Research also shows that, people residing in this area are facing several health as well as environmental problems due to improper solid waste disposal.

The locations for sampling were choosen on the downstream side of the dumpsite, within a distance of about 3 km from the dumpsite. Representative samples of groundwater were taken from two bore wells and seven open wells, which were placed on the downstream side of the dumpsite (Raman & Sathiyanarayanan 2011). The collection of samples was carried out manually, and the water samples were stored in appropriate containers. The sampling locations details are mentioned in Table 1 and shown in Figure 1.

For determining, physico-chemical characterisation and quality evaluation, total 18 representative groundwater samples were collected before and after monsoon for the year 2014. The groundwater samples were taken in HDPE bottles. The HDPE bottles were first rinsed with the samples, then filled with respective ground water samples until the edge, and instantly closed to prevent contact with atmospheric air. The bottles were labelled properly and transported to the laboratory in an icebox. After reaching the laboratory, the samples were handled for preservation as per guidelines mentioned in APHA (2007). After that, the samples were analysed in the laboratory.

The standard procedures as per the recommendation of APHA (2007) were observed for sample collection, handling, and preservation to ensure quality system protocols. The physical parameters such as conductivity and pH were assessed on site and while other parameters such as HCO₃, Ca, NO₃Mg, K, Na, SO₄, Fl, and Cl, were analyzed as per the recommendation of APHA (2007). Flame photometer was used to find parameters like potassium and sodium, while volumetric methods were employed to determine parameters such as magnesium, calcium, hardness, and chlorides. UV/V is spectrophotometer was used for determination of nitrate, phosphate, zinc, chromium, and sulphate. To assess the groundwater suitability for drinking, the comparison of different groundwater quality parameters was done with BIS (2012) standard guidelines values for drinking water. In absence of BIS standards, WHO (2004) standards were used for comparison of physico-chemical characteristic to determine its suitability for drinking purpose.

The occurrence of the ions and impurities in the groundwater is mainly dependent upon the geologic formation at a particular area. The deccan trap basalt forms the main water-bearing formation in Pune district. The hydrogeology of the Pune district forms the basis of selection of the characteristics such as pH, colour, turbidity, temperature, electrical conductivity, hardness, alkalinity, TSS, TDS, BOD, COD, chlorides, nitrates, potassium, sulphate, sodium, phosphate, calcium, and magnesium for determination of water quality. Determination of physico-chemical characterisation of water is crucial in assessing the water suitability for different utilities such as domestic, irrigation, and industrial use (Tomar et al. 2012). The analysis of physico-chemical parameters in the groundwater samples was carried out as per the recommendations of APHA.

Representative samples of groundwater tube wells and open wells around the solid waste dumping site were analyzed for different physical and chemical parameters. These samples were analyzed during premonsoon as well as postmonsoon period for below mentioned water quality parameters. The statistical summary of groundwater quality in the study area including minimum, maximum, and mean of various physico-chemical parameters is given in Table 2.

For assessing the groundwater suitability, comparison was carried out between the physico-chemical characteristics of groundwater samples and Indian Standards (BIS 2012). The outcome of evaluation of groundwater quality with Indian standards is summarized herewith.

No colour was observed for all samples, which showed that organic matter was absent in the samples. Temperature increase in water reduces its potability due to release of gases such as carbon dioxide at higher temperatures, which shall impart taste to water. The desirable range of temperature for drinking water is around 15–18 °C. However, the lower temperatures shall increase the palatability of water due to coolness. For the current study, the temperature was found to be varying from 20 to 23 °C during premonsoon and 18 to 22 °C for postmonsoon samples; hence no major change was observed in temperature.

As per BIS the permissible range for pH is 6.5–8.5. pH shows a significant role in disinfection of water. It is suggested that the pH of water should be less than 8 for an effective disinfection process while using chlorine. However, if the pH of water falls below 7, it is expected to result in corrosion. If the corrosion process is not curtailed, it will impart taste and colour to water, and render it unsuitable for drinking. In the current study, pH for the premonsoon season was observed to be between 5.2 and 7.4 and for postmonsoon was 7.2–8.6. The increase in pH during the postmonsoon season can be attributed to an increase in mineral concentration during the rainy season.

As per research, there exists a relationship between gastro-intestinal problems and turbidity. According to BIS recommendations, acceptable limit for turbidity is 1 NTU and the permissible limit is 5 NTU. The samples for current study area showed turbidity ranging from 0 to 3.1 NTU for premonsoon season and 0 to 1.2 NTU for the postmonsoon season. After rainy season, the suspended impurities are expected to settle down naturally; therefore a reduction in turbidity is observed.

The property of electrical conductivity is usually linked with mineral contaminants or excessive hardness causing ions. Electrical conductivity can be linked to the presence of dissolved ions in water. Since organic compounds do not conduct electricity, their influence on electrical conductivity is considered to be very low. Therefore, higher values of electrical conductivity suggest percolation or dissolving of the soil material in the water samples (Ibraheem & Mazhar Nazeeb Khan 2017). The values of electrical conductivity for the samples in this study, are 0.24–6.2 μS/cm for the premonsoon season and between 1.23 and 2.3 μS/cm for the postmonsoon season. There is no limit prescribed for electrical conductivity as per BIS.

TSS are generally lower in groundwater, except in case of turbulent water flows with fine clay material or organic solids. There is no prescribed standard by BIS for TSS, but it may affect turbidity in water. The TSS for the current study ranged from 187 to 1,100 mg/L for premonsoon and 18–46 mg/L for postmonsoon, indicating dilution in concentration due to natural sedimentation process after monsoon.

Chlorides in one of the principal anions existing in natural waters. In natural water, chloride is usually present along with sodium, calcium, potassium, and magnesium. In the case of groundwater, excessive chloride can be attributed to natural processes such as soil erosion or rock weathering. Whereas artificial sources of higher chloride concentration can be related to mixing with sewage, seawater or saline residues in the soil. Excessive chloride can lead to taste a problems in water. The threshold for taste is a concentration ranging between 200 and 300 ppm for calcium, potassium, and sodium chloride. Based on threshold of taste, BIS has recommended the permissible limit as 1,000 mg/L and acceptable limit as 250 mg/L for chloride. As shown in Figure 2 for current study, the chlorides concentration was in the range of 189–623 mg/L for premonsoon season and 260–476 mg/L for post monsoon season. Research suggests that consuming water with high chloride concentration can result in renal stones, hypertension, stroke, asthma, osteoporosis, or laxative effects. Further, water with high chloride concentration can affect plants and wildlife and cause corrosion of metals.

Presence of hardness in freshwater can chiefly be attributed to occurrence of calcium or magnesium salts. Presence of carbonate ions is linked with temporary hardness whereas non-carbonate ions are linked with permanent hardness in water. Water having hardness less than 100 ppm results in corrosion of pipes and also has low buffering capacity. Whereas temporary hardness if greater than 200 ppm as CaCO₃ results in formation of scale in the pipes at distribution systems and tanks inside buildings (Singh et al. 2020). As recommended by BIS, 200 mg/L is the acceptable limit and 600 mg/L is the permissible limit for total hardness in drinking water. As shown in Figure 2 the values of total hardness, in existing study was ranging from 1,423 to 3,280 mg/L for premonsoon and 234–276 mg/L for postmonsoon, which shows the presence of calcium and magnesium ions. The total hardness in all the groundwater samples was observed to be exceeding acceptable limit for the premonsoon season.

The occurrence of dissolved solids is linked with its taste in water. The relation between palatability and taste of drinking water with respect to TDS can be expressed as follows: Water having TDS less than 300 ppm is termed as excellent; water with TDS in the range of 300–600 ppm is classified as good for taste; water with TDS 600–900 will be termed as fair in taste; water with TDS ranging between 900 and 1,200 ppm shall be classified as poor; while water having TDS higher than 1,200 ppm shall be termed as unacceptable. As per recommendations from BIS, 2,000 mg/L is the permissible limit while 500 mg/L is the acceptable limit for TDS. It is also suggested that water samples having TDS exceeding 500 ppm can result in gastrointestinal problems so are considered unsuitable for drinking purposes. For all premonsoon samples TDS was observed to be between 360 and 1,323 mg/L and for postmonsoon conditions it was observed to be between 315 and 934 mg/L, as shown in Figure 3. Thus, it can be concluded that for all the samples in the study area, TDS is well within the permissible limit of 2,000 mg/L prescribed by BIS.

The presence of alkalinity in groundwater is primarily linked with the amount of existing bicarbonates, carbonates, or hydroxides existing in it. The total alkalinity for existing study is principally owing to the occurrence of bicarbonates, whereas alkalinity caused due to presence of carbonates or hydroxides is nil. When carbon dioxide from atmosphere or soil, is dissolved in groundwater, it forms bicarbonates (Mahanta et al. 2020). Carbonate rocks can be considered as another natural source of bicarbonates in groundwater. The incidence of bicarbonate in groundwater typically imparts alkalinity to it. The acceptable limit for alkalinity as recommended by BIS is 200 mg/L and permissible limit is 600 mg/L. As shown in Figure 3, total alkalinity was observed to be between 145 mg/L and 960 mg/L for premonsoon samples whereas total alkalinity for post monsoon samples was observed to be between 28 mg/L and 96 mg/L. Excessive alkalinity when present imparts unpleasant taste and cloudiness to water.

BOD is defined as the amount of oxygen required by aerobic microorganisms for decomposition of biodegradable organic matter in aerobic conditions. The BOD value of water thus indicates the nature and magnitude of water pollution. As per CPCB guidelines, the BOD value for a drinking water source without conventional treatment should be less than 2 mg/L for Class A. As seen in Figure 4, the BOD values were found to be in the range of 28 mg/L to 58 mg/L for premonsoon and 38 mg/L to 68 mg/L for postmonsoon. Results imply that all the samples had BOD values in excess of the desired limit, probably, due to percolation of industrial or domestic wastewater into groundwater.

COD is defined as the measure of organic pollution in aquatic ecosystems. It indirectly estimates the amount of organic compounds in water. In BIS, there is no mention of COD, which suggests that COD is expected to be zero in drinking water. The COD values for the premonsoon season ranged from 310 to 980 mg/L and for the postmonsoon season ranged from 48 to 85 mg/L. The COD values were found to be higher than the BOD values for all the samples, which suggests the presence of non-biodegradable chemically oxidizable substances along with biodegradable substance.

Nitrate is the primary form of nitrogen existing in the environment and a vital plant nutrient. It is easily soluble in water and easily passes through the soil to ground water. Certain ground waters might show presence of nitrate due to leaching effect from vegetation. The artificial sources of nitrate in groundwater may be decaying organic matter, domestic wastes, and fertilizers. When nitrate is present in excessive concentration, it is a potential health hazard and may lead to health problems such as blue baby syndrome in infants and also cause gastro-intestinal cancer. The acceptable as well as permissible limit of nitrate is 45 mg/L as per BIS. As seen from Figure 4, the value of nitrates were observed to be between 10 mg/L and 34 mg/L for premonsoon and between 18.2 mg/L and 32.4 mg/L for postmonsoon, which was well below the acceptable limit of 45 mg/L.

According to the drinking water quality standards of the BIS, E. coli bacteria should not be detected in any 100 ml sample. In the existing study, E. coli was found to be absent in all the samples for both premonsoon and postmonsoon samples.

The presence of calcium ions is recommended in drinking water, as it is considered to be a vital element for bone growth. Also due to its higher solubility, calcium ion is generally found in abundance in the groundwater. As per the recommendations of BIS, the desirable limit for calcium is 75 mg/L and the permissible limit is 200 mg/L. As seen from Figure 5, the samples in current study had calcium values ranging from 178 to 420 mg/L for premonsoon and ranging from 152 to 320 mg/L for postmonsoon. For sampling locations, OW5, BW1, and BW2, the calcium values are higher even than the permissible limit.

Magnesium is added to groundwater on coming in contact with some rocks and minerals. After materials such as limestone or gypsum are dissolved in water, they release calcium and magnesium. Magnesium plays a vital role in enzyme activations, but a higher concentration of magnesium leads to laxative effects while a deficiency of magnesium causes functional changes (Keesari et al. 2016). Excessive magnesium when present in groundwater, renders the soil as alkaline, which shall highly influence the crop yield. The desirable limit for magnesium is 30 mg/L and the permissible limit as recommended by BIS is 100 mg/L. As per Figure 5, for the existing study, the premonsoon values ranged from 12 to 78 mg/L and postmonsoon values ranged from 14 to 65 mg/L. Certain samples in premonsoon condition exceeded the desirable limit of BIS.

Almost all soils and rocks include sodium that will easily dissolve in water. Therefore, all ground waters contain some levels of sodium. Hence, sodium-bearing rock minerals and erosion of salt deposits can be termed as the generic sources of sodium entering the groundwater. On chemical reaction of sodium with chloride ions, the result is saline soils, while on reaction with carbonate, it results in alkaline soils. When excessive concentration of sodium is present, it replaces the calcium and magnesium ions in the soil, and decreases its permeability, resulting in hard soils under dry conditions. There is no limit for sodium prescribed by BIS, while as per WHO, the acceptable limit is 200 mg/L for drinking water. As seen from Figure 5, the premonsoon values of sodium were within the range of 45–110 mg/L and postmonsoon values were found to be between 34 and 87 mg/L. The mean threshold for taste is around 200 mg/L in the case of sodium. Research shows that excessive intake of sodium can cause severe health effects in case of humans already having blood pressure problems.

Potassium when dissolved in water behaves similarly to sodium. Potassium is a necessary element for humans but if present in excessive concentration, it may lead to digestive or nervous disorders. The BIS does not prescribe any limit for potassium while as per the recommendation of WHO, the permissible value is 10 mg/L. As shown in Figure 5, for potassium, premonsoon values were within the range of 23–208 mg/L and postmonsoon values were found to be between 13 and 165 mg/L, higher than 10 mg/L. It can be inferred that excessive use of fertilizer or contamination with domestic sewage may be the cause for the increased concentration of potassium.

The most common form in which sulphur can be present in water is sodium sulphate or calcium sulphate. Generally, higher concentration of sulphates may result from contamination with agricultural runoff or industrial wastewater. When excessive sulphate is present in drinking water it can impart a noticeable taste and also lead to laxative effects. If sodium sulphate is present in a concentration greater than 250 mg/L, it will impart taste whereas the taste threshold for calcium sulphate is 1,000 mg/L. When concentration of sulphate is greater than 150 mg/L, it can lead to dehydration or gastrointestinal irritation in human beings. As recommended by the BIS acceptable value is 200 mg/L while the permissible value is 400 mg/L for sulphate. As seen in Figure 5, the values of sulphate for premonsoon samples ranged between 90 mg/L and 273 mg/L, while for postmonsoon sampling the values of sulphate ranged between 83 mg/L and 232 mg/L. For the existing study area, the sulphate concentration in all the samples is observed to be lower than the permissible limit recommended by the BIS.

Phosphorus is a vital element for organisms as well as plants. Phosphorus is present naturally in rocks and other mineral deposits. During the course of weathering of rock, phosphorus is gradually released as phosphate ions that are easily dissolved in water. In natural, uncontaminated waters, phosphate occurs in three main forms as organic phosphates, condensed phosphates or orthophosphate. A permissible limit for phosphate does not exist in BIS; however, the permissible limit as per WHO is s 0.1 mg/L. As seen in Figure 6, phosphate was found to be within 4.5 mg/L to 7 mg/L for the premonsoon and 2.4–6.1 mg/L for the postmonsoon season. For both the seasons, the concentration of phosphate is observed to greater than the permissible limit prescribed by WHO for drinking water. Percolation of agricultural runoff with fertilizer residue or weathering of phosphate-containing rocks can be probable reasons for high phosphate content.

Heavy metals such as lead and mercury were below detectable limits, whereas zinc and chromium were present in detectable concentration. As shown in Figure 6, the zinc values ranged from 7.8 to 9.3 mg/ L for premonsoon samples and from 6.32 to 8.72 mg/L for postmonsoon samples. Chromium was found range from 3.76 to 9.4 mg/L for the premonsoon and 2.1 to 6.86 mg/L for the postmonsoon season.

It can be inferred from the existing study that the solid waste disposal at Urali Devachi is posing severe health and environmental problems and in the surrounding areas. Various environmental concerns associated with solid waste dumping include breeding of flies and mosquitoes, odour issues, unaesthetic sight, contamination of surrounding soil and groundwater by leachate emanating from site, etc. The leachate arising from the dumpsite comprises several pollutants such as heavy metals, trace elements, organic compounds, etc, which mix with the surrounding groundwater or soil and contaminate it. Comparing the mean values, it can be concluded that temperature, pH, EC, turbidity, alkalinity, total hardness, dissolved and suspended solids, COD, Cl, SO4, PO3, Ca, Mg, Na, K, Cr, and Zn were higher in the groundwater samples during the premonsoon phase than in the postmonsoon phase and showed a clear-cut seasonal effect (Anwar & Aggarwal 2016). While BOD and nitrates showed an increase in the postmonsoon over the premonsoon season, owing to increased biological activity on availability of necessary moisture during the postmonsoon season. Zinc and chromium in the study area exceed the limits rendering it unsafe for drinking, commercial use, irrigation, and industrial purposes. Therefore, the study indicates an imperative requisite for improving the current practice of solid waste handling and management in Pune city, India. Immediate attempts should be made to control the haphazard growth of the landfill site. Natural and synthetic liners may be utilized for isolating leachate within the dumpsite to protect the soil and groundwater.

Not applicable.

The authors declare they have no competing interests.

All relevant data are included in the paper or its Supplementary Information.