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Water quality of both available surface and groundwater resources does not satisfy the criteria for potable water in most parts of the country. The Ministry of Jal Shakti report revealed that 70% of water resources in India are polluted by untreated sewage and industrial effluents. The monitoring report of the Central Pollution Control Board (CPCB 2011), based on biological oxygen demand (BOD) and coliform bacteria count, indicated that organic pollution is predominant in aquatic bodies. The groundwater of around 600 districts (i.e. almost one‐third of India) is nonpotable. On the other hand, the Central Groundwater Water Board (CGWB) has reported the presence of contaminants like fluoride, nitrate, arsenic, iron, and other heavy metals in the groundwater of many regions (Table 1.4). As and F⁻ contamination of groundwater is a significant public health risk concern for Indian people. As and F⁻ contamination of groundwater is a health threat for approximately 100 and 66 million Indian people, respectively (Bindal and Singh 2019; Kadam et al. 2020). Other major groundwater contaminants like U, NO₃⁻, Fe, HCO₃⁻, etc. have also been reported in several parts of India. High nitrate content in water is another grave concern in many states (Ministry of Water Resources 2014; Kaur et al. 2019). Apart from governmental organizations, various studies/reports on groundwater and surface water quality have confirmed the presence of other contaminants like uranium, cadmium, lead, copper, sulfate, pesticides, and organic pollutant in the water resources of India (Bacquart et al. 2012; Mittal et al. 2014; Chowdhury et al. 2016; Kumar et al. 2016; Bajwa et al. 2017).

Both the groundwater and surface water quality are not qualifying criteria for potable water in most parts of the country. Surface water is continuously facing quality issues due to the discharge of sewage and industrial and agricultural wastes. Groundwater in India is affected by heavy metals (As, Fe, Pb, U) and anions (F⁻, NO₃⁻, SO₄²⁻) in different parts of the country.

Table 1.4 Number of states and districts affected by geogenic contamination in groundwater.

Source: CGWB (2019).

Contaminants	No of affected states	No of affected districts
Arsenic (As)	10	68
Fluoride (F−)	20	276
Nitrate (NO3−)	21	387
Iron (Fe)	24	297