Many times, we see an advertisement or people say that water is very pure or clean or shuddh. What does it really mean? In hotels, the waiter asks if you need bottled water or regular water? ( I always ask for bottled water because I don’t want to take a chance with poorly maintained or mal functioning filters. I have experienced that a number of times)
Our senses of odor and sight do tell us intuitively to avoid certain types of waters with color, suspended matter, turbidity or water which smells bad. These may be because of physical, chemical or biological contaminations. Perceiving water quality through our senses may work only on some occasions.
A robust and fool proof method is necessary to ascertain the quality of water.Quantitative measure of physical, chemical and biological properties tells us, if the physical, chemical or biological properties are in line or not. This is where the mental model of water helps
The measurement of properties also helps in developing a Water Quality Index (WQI) – a single number which tells us if water is clean or fit for a particular use. WQI aids in easy communication of water quality or Shuddhata
This leads to the second important point – the context for water. What qualities define pure water? It’s a question Alice asks the Cheshire Cat
“Alice: Would you tell me, please, which way I ought to go from here?
The Cheshire Cat: That depends a good deal on where you want to get to.
What this brings us to are the STANDARDS for quality of different types of water. Standards are a combination of physical, chemical and biological properties of water with a certain values with limits. Standards tell us that beyond the limits or below the limits the water may not be fit for a certain use.
Some types of water have different requirements than other types. For example, the requirements for drinking water and irrigation or construction water are vastly different. The construction water requiring easier standards to meet than drinking water.
For example, the Indian standard for drinking water is IS 10500 : (2012) Drinking Water Specification. It has parameters concerning chemical properties with limits, toxic materials with limits etc. For example, the standard stipulates that maximum allowable limit for dissolved iron is 0.5 mg/l, there is no relaxation, it needs to be measured as per IS 3025, part 15 and has a comment that ‘Total concentration of manganese (as Mn) and iron (as Fe) shall not exceed 0.3 mg/l’.
These limits have been evolved over a period of time through extensive research and experience and finally established through scientific discussions and practical considerations through a panel of experts with expertise in subjects like public health, chemistry, biology etc. The standards are periodically reviewed and updated.
The standards of water prevalent today are numerous, for example some of the standards are
The pollution Control Board has developed elaborate standards for discharge of effluents to protect environment and public health.
The private sector also sets its own standards for water use. The semiconductor industry has very stringent standards for water quality for use in chip washing to ensure quality of semiconductor chips.
The new standards which are being developed are for recycled water for potable use as new challenges are being encountered due to contaminations from manmade chemicals like pesticide residues, pharmaceutical residues and biological viruses like SARS.
The effort for development and revision of standards is a continuous effort to meet the emerging challenges.
If you have any questions about water, feel free to reach out. I would love to hear from you.