Water quality and standards

Water quality criteria

Source : Central Pollution Control Board

Drinking Water quality

Drinking water is water intended for human consumption for drinking and cooking purposes from any source. It includes water (treated or untreated) supplied by any means for human consumption. The quality standards for drinking water in India is prescribed by Bureau of Indian Standards laid down IS 10500 : 2012. To access the same, click here.

Ground water quality scenario in India

Indian Sub-Continent is endowed with diverse geological formations from oldest Achaeans to Recent alluviums and characterized by varying climatic conditions in different parts of the country. The natural chemical content of ground water is influenced by depth of the soils and sub-surface geological formations through which ground water remains in contact. In general, greater part of the country, ground water is of good quality and suitable for drinking, agricultural or industrial purposes. Ground water in shallow aquifers is generally suitable for use for different purposes and is mainly of Calcium Bicarbonate and Mixed type. However, other types of water are also available including Sodium-Chloride water. The quality in deeper aquifers also varies from place to place and is generally found suitable for common uses. There is salinity problem in the coastal tracts and high incidence of Fluoride, Arsenic, Iron and heavy metals etc in isolated pockets have also been reported. The distributions of various constituents present in ground water in different parts of the country is as follows.

Salinity

Salinity in ground water can be broadly categorised into two types, i.e. Inland Salinity and Coastal salinity

Inland Salinity

Inland salinity in ground water is prevalent mainly in the arid and semi arid regions of Rajasthan, Haryana, Punjab, Gujarat, Uttar Pradesh, Delhi, Andhra Pradesh, Maharashtra, Karnataka and Tamil Nadu. There are several places in Rajasthan and southern Haryana where EC values of ground water is greater than 10000 mS /cm at 25^oC making water non-potable. In some areas of Rajasthan and Gujarat, ground water salinity is so high that the well water is directly used for salt manufacturing by solar evaporation.

Inland salinity is also caused due to practice of surface water irrigation without consideration of ground water status. The gradual rise of ground water levels with time has resulted in water logging and heavy evaporation in semi arid regions lead to salinity problem in command areas.

Coastal Salinity

The Indian subcontinent has a dynamic coastline of about 7500 km length. It stretches from Rann of Kutch in Gujarat to Konkan and Malabar coast to Kanyakumari in the south to northwards along the Coromandal coast to Sunderbans in West Bengal. The western coast is characterized by wide continental shelf and is marked by backwaters and mud flats while the eastern coast has a narrow continental shelf and is characterized by deltaic and estuarine land forms. Ground water in coastal areas occurs under unconfined to confined conditions in a wide range of unconsolidated and consolidated formations.

Normally, saline water bodies owe their origin to entrapped sea water (connate water), sea water ingress, leachates from navigation canals constructed along the coast, leachates from salt pans etc. In general, the following situations are encountered in coastal areas

• Saline water overlying fresh water aquifer
• Fresh water overlying saline water
• Alternating sequence of fresh water and saline water aquifers

In India, salinity problems have been observed in a number of places in most of the coastal states of the country. Problem of salinity ingress has been conspicuously noticed in Minjur area of Tamil Nadu and Mangrol – Chorwad- Porbander belt along the Saurashtra coast.

Fluoride

85 % of rural population of the country use ground water for drinking and domestic purposes. High concentration of fluoride in ground water beyond the permissible limit of 1.5 mg/l poses the health problem. Nearly the occurrences of fluoride beyond permissible limit (> 1.5 mg /litre) has been observed based on the chemical analysis of water samples collected from the groundwater observation wells.

Arsenic

Arsenic occurs naturally in the environment as an element of the earth’s crust with an abundance of 1.8 ppm by weight.. Arsenic combines with other elements such as oxygen, chlorine and sulphur to form inorganic arsenic compounds. Arsenic and its compounds are widely used in agriculture, livestock feed, medicine, electronics, metallurgy, chemical warfare agents etc. Synthetic organic compounds have now replaced arsenic in most of the uses. Arsenic is an element of interest in terms of environmental issues and health impacts.

Transport and distribution of arsenic in environment is complex and there is continuous cycling of different forms of arsenic through air, soil and water. It is introduced in soil from parent rock during pedogenesis and further in ground water during weathering of rocks followed by leaching. It can also be introduced from anthropogenic sources such as arsenical pesticides, fertilizers, irrigation, dust from burning of fossil fuel and disposal of industrial and animal wastes. In ground water inorganic arsenic is present, commonly as arsenate (As V) and arsenite (As III), inter-conversion of which takes place by oxidation-reduction.

Arsenic as a contaminant is significant in terms of its toxic nature with exceedingly diverse manifestations of poisoning. Drinking water is the major pathway for ingestion of arsenic in human system. As per BIS (IS 10500:2012), the acceptable limit of Arsenic is 0.01 mg/l and the permissible limit in absence of alternate source is also 0.01 mg/l. Elevated concentrations of arsenic in ground water are reported from various parts of India but particularly  affecting the large parts of the Ganga- Brahmaputra Plains. The aquifers in the alluvial plains embedded within the Late Quarternary deposits are reported to be affected, with a few exceptions where the Hard rock aquifers are also affected as in Chhatttisgarh and Karnataka states. In India high concentration of arsenic beyond permissible limit of 0.01 mg/l in ground water has been reported from 18 States.

The arsenic concentration in ground water is marked by wide spatial variability.Depth wise the contaminated water is generally found to be confined within 100m in alluvial aquifers.

Iron

High concentration of Iron (>1.0 mg/l) in ground water has been observed in more than 1.1 lakh habitations in the country. Ground water contaminated by iron has been reported from the states of Andhra Pradesh, Assam, Bihar, Chhattisgarh, Goa, Gujarat, Haryana, J&K, Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Manipur, Meghalaya, Orissa, Punjab, Rajasthan, Tamil Nadu, Tripura, Uttar Pradesh, West Bengal & UT of Andaman & Nicobar.

Nitrate

Nitrate is a very common constituent in the ground water, especially in shallow aquifers. The source is mainly from anthropogenic activities. High concentration of Nitrate in water beyond the permissible limit of 45 mg/l causes health problems. High Nitrate concentration in ground water in India has been found in almost all hydrogeological formations.

To access the Water quality maps, click here

Source : Central Ground water Board