Arghyam has compiled a brief presentation which gives details of the permissible and desirable limits of various parameters in drinking water as per Bureau of Indian Standards (BIS) standard specifications for potable water (BIS-10500-1991). The BIS drinking water specification (IS 10500:1991) was drawn up in 1983 and its most recent revision dates back to July 2010 (Amendment No. 3).
The standard was adopted by the Bureau of Indian Standards with the following objectives -
- To assess the quality of water resources, and
- To check the effectiveness of water treatment and supply by the concerned authorities.
They apply to drinking water supplied by different Authorities/ Agencies/ Departments of State Governments and Central Government, wherever applicable in the country. They also apply to water supplied by Non Government or Private Agencies for human consumption in any place of the country.
The various parameters covered include color, odour, pH, total dissolved solids, hardness, alkalinity, elemental compounds such as iron, manganese, sulphate, nitrate, chloride, fluoride, arsenic, chromium, copper, cyanide, lead, mercury, zinc and coliform bacteria.
The standard categorises various characteristics as essential or desirable. It mentions the desirable limit and indicates its background so that the implementing authorities may exercise their discretion, keeping in view the health of the people, adequacy of treatment etc. All essential characteristics should be examined in routine. Besides, all desirable characteristics should be examined either when a doubt arises or the potability of water from a new source is to be established.
The standard has categorically made relaxation in the specification when no alternate resources are available and therefore, to enable the Water Supply Agencies to exercise their discretion a maximum permissible limit has also been given to certain parameters.
In formulation of the standard for drinking water BIS has taken into consideration the following publications:
- International Standards for Drinking Water issued by World Health Organization, 1984.
- Manual of Standards of Quality for Drinking Water Supplies. Indian Council of Medical Research 1971.
- Manual on Water Supply and Treatment (third revision) CPHEEO, Ministry of Urban Development, 1989.
The Central Water Commission has recently come up with a document to present the tolerance limits for inland surface waters for the various classes of water use. As per ISI-IS: 2296-1982, the tolerance limits of parameters are specified as per classified use of water depending on various uses of water. The following classifications have been adopted in India –
- Class A: Drinking water source without conventional treatment but after disinfection
- Class B: Outdoor bathing
- Class C: Drinking water source with conventional treatment followed by disinfection.
- Class D: Fish culture and wild life propagation
- Class E: Irrigation, industrial cooling or controlled waste disposal
The document also lists the test characteristics for drinking water as per IS - 10500:1991 (amended).
Download the presentation by Arghyam, edition 2.1 of the standard IS 10500 : 1991, IS 10500: 2004, a short write-up on the standard by BIS and the document on "Tolerance and Classification" by CWC here -