Dear Sameh

It depends on your specific case and what you are looking for. It is good to look at drinking water standards for both WHO, EPA, sometimes also the Dutch intervention values or the Australian / New Zealand standards. Different standards cover different special parameters in addition to the normal drinking water parameters, so you need to check other standards if you can not find a drinking water standard for a specific parameter. Also, different levels of stringency may be applied in setting standards for different countries, which is prescribed according to the specific country's legislation, so it is good to decide if you want to use the most stringent standard (with cost implications for compliance) or rather a generally accepted standard for a specific parameter.

To summarize, there is no silver bullet standard that can be used for all possible cases.

Thanks very much Surina.. That is really useful

Pleasure

Most of the countries followed World health Organization standards for water quality parameters.purpose.This is mostly reliable and acceptable.

If you are working in the USA, use the EPA site as a general guide. Your specific state may have stricter regulations though so be sure to check the state's health or environmental protection department as well as the EPA. If you are working outside the USA, then I am sure others here have more insight than I can offer.

Thanks, I am interest in water quality parameters for groundwater in Egypt or Kingdom of Saudi Arabia or similar areas.

The WHO is very comprehensive.

Switzerland uses one of the highest standards of drinking water in the world.

http://www.therichest.com/expensive-lifestyle/location/top-10-countries-with-the-best-tap-water/

http://www.who.int/water_sanitation_health/dwq/en/

The VSA standards fro Switzerland: https://www.google.com/search?q=highest+standards+of+drinking+water&rlz=1C1SKPL_enAW446&oq=highest+standards+of+drinking+water&aqs=chrome..69i57.21015j0j7&sourceid=chrome&espv=210&es_sm=93&ie=UTF-8#es_sm=93&q=swiss+standards+of+drinking+water+quality

Europe tends to mention all its members under one standards, however the differences between the different countries are significant. And every country tends to use its own standards and regulations.

Aruba (lower Antilles) of the caribbean has a new system of desalination. It still produces according the DWI (Dutch), but also obtains the third best water quality in the world. This is not because of the Dutch standard, but more because of the local conditions.

Resume: Switzerland appears to have the highest standard.. For any further information I highly recommand Berson-UV technologies, who produces and designs, UV disinfection reactors and systems, and is active all over the world.

http://www.bersonuv.com/frontend/scripts/index.php?groupId=100&setMainAreaTemplatePath=mainarea_productlist.html

Other links about the WHO standards and uropean standard, where you find some significant information:

The comarison between the two mentioned: http://www.lenntech.com/who-eu-water-standards.htm'

WHO standards on drinking water:

http://www.lenntech.com/applications/drinking/standards/who-s-drinking-water-standards.htm

EU standards on drinking water:

http://www.lenntech.com/applications/drinking/standards/eu-s-drinking-water-standards.htm

Somewhere in the Middle East (I'm sorry I forgot the country), but it must be Kuwait or Saudi Arabia, they use a similar desalination, purification and Berson-UV disinfection system. There water quality happens to be better than ours, eversince they have used stainless steel as tubings. They have less leakage or line breaks, so they have less contamination from the environment.

I would look to these countries, since your interest is in that area.

I am really delighted to receive all these valuable comments. Thanks to all

WHO gives drinking water quality 'Guidelines', not standards. Every country has its own standards. nto account this small difference. like US EPA gives standards for the USA. Take i

Agreed Sidra, every country has its own water permissible limit for drinking purposes. In india we follow our own.which differ from WHO or EPA. The permissible limit has been decided by using various parameters. However when we talk about standard water quality than we consider WHO or EPA or such equivalent..

This is difficult. Try the EU WFD .... But each country will be different. Also different standards for different waterbodies. Some for groundwater eg nitrate but no equivalent for surface water.

Though EPA and WHO provide standards and guidelines to ensure good water quality, sometimes it is also important to look at the standards of your neighboring countries because they might share the same issues as you and might have certain parameters which are better than WHO or EPA.

Other than the European directives that Murat Ay mentioned, there are also OECD guidelines applicable for Europe , e.g. http://www.oecd.org/env/resources/drinkingwatersupplyandsanitation.htm, but as far as I can tell , some of it will be covered by WHO. If by standards you mean methods to establish drinking water quality, i.e. normalization, then there are international = ISO, European = CEN, and national, e.g. French (AFNOR), German (DIN) standards that are usually more detailed and specific than the OECD guidelines, and thus more difficult to implement.

Maximum permissible limit of chemical constituents in drinking water depend upon various factors which varies one country to other. However availability of water, tolerance power, purification processes etc. In case of India we have our own standard limits. Globally concern WHO is widely accepted.

WHO is the must applied and most reported standards. It even preferred to most national standards.

insomuch is drinking water WHO guidelines are the most appropriate if what you are looking is to monitor the quality of water for human beings

There is no "best" site or "most reliable" site or source for DW standards/limits/guidelines. You have to understand that many jurisdictions and organisations are developing them for their purposes, most jurisdictions are national in scope, some are international. All try to achieve principally the same goal, but have to work with different available resources (man power and money) and priorities, therefore the inherent quality of their output may vary and the quantity of their products (i.e., for how many substances they can develop standards).

You best bet is to examine the various sources (e.g. WHO, US EPA, Canadian Department of Health [Health Canada], Europe, individual European countries,Australia, etc.), understand how they are derived, and compare their results. Keep in mind that many of these jurisdictions also work in parallel in their own jurisdiction as well as on the international level, i.e., contribute to the WHO. You will find that some jurisdictions have a limit for a specific substance, while others have not, this is a reflection of their priorities and resources.

In comparing the available limits for a specific substance, understand how they were derived (i.e., what information was used and how this information was incorporated, what safety factors were applied, etc.), and when they were derived (i.e., what information was available at the time of derivation). This explains to a large extend the differences between values.