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Drinking-Water Standards refer to some quality parameters set for drinking water which must be met as per the International Standards for drinking water. Access to clean and safe drinking water is the right of every citizen. Unfortunately, this life-sustaining natural resource is dangerously contaminated because of human activities and certain environmental factors. It is estimated that water-borne diseases have an economic burden of approximately 600 million USD per year in India. A safe water supply is the backbone of a healthy economy, yet it is fully under prioritised in many parts of the world. Keeping in mind the detrimental effects of this situation on human health, certain parameters have been listed by several health organizations for drinking water.
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Key Terms: Safe Drinking Water, International Drinking Water Standards, WHO, Water-borne Diseases, Inorganic Elements, Ph, Turbidity, Taste, Clean Water
What are Drinking Water Standards?
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Drinking quality standards are a set of rules and regulations that the water supply authorities and the water quality maintenance authorities of various regions are supposed to follow before the supply of water is made in a particular area. These standards of drinking water are implemented to provide safe drinking water for public use in general, making sure that there are the least risks associated with the drinking water that is supplied. These set parameters of drinking water aim at the removal of disease-causing microorganisms.
The introduction of filtration and chlorine disinfection has resulted in a very rapid drop in the incidences of waterborne diseases in India. Drinking water supplies must also be safe in terms of the number of chemical constituents. The basic requirement of safe drinking water is to make sure that there is the absence of any harmful chemical element/ compound present in water as well as maintaining an appropriate/ standard quantity of the essential chemicals present in the supply of drinking water.
Water
Read More: Importance of Water
Drinking-Water Standards Adopted by Countries
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The guidelines of WHO for drinking-water quality are the International reference point for standard-setting and drinking-water safety. Many countries have devised certain standards regarding the safety of drinking water. These rules are followed throughout that particular country or continent.
In India, the Bureau of Indian Standard has specified drinking water quality standards which are made in reference to the guidelines issued by World Health Organisation (WHO) in India to provide safe drinking water to the people. The countries that have not adopted any specified standards for safe drinking water follow WHO’s guidelines for safe drinking water.
Need for Drinking Water Standards
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The need for drinking water standards can be explained with the help of the following points:
- Provides nourishment: Water is required for all the metabolic reactions in the body, maintaining a constant body temperature, helps in digestion and absorption of food. All these and many other such requirements are carried out properly if the water contains essential organic, inorganic compounds and dissolved gases in the right amount.
- Prevention of diseases: As more and more water bodies are getting polluted due to water pollution from various agencies there is a greater risk of water-borne infections in the sources of drinking water. Thus, proper treatment of water to remove all the harmful chemical elements and disease-causing microorganisms is essential to prevent water-borne diseases.
- For agriculture and food processing: If the agricultural products and the factory processed foods are contaminated because of the use of unsafe and unclean water then a public health issue can happen.
Contaminated Water
Read More: Water Pollution Control
Drinking-Water Specifications By WHO
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Guidelines developed by the World Health Organisation for safe drinking water are also referred to as the International Drinking Water Standards.
| Parameters | Standard Limits as per WHO guidelines in mg/l |
|---|---|
| Acrylamide | 0.0005 |
| Ammonia | 1.5 |
| Antimony | 0.02 |
| Arsenic | 0.01 |
| Barium | 0.7 |
| Benzene | 0.01 |
| Benzo | 0.0007 |
| Boron | 0.5 |
| Bromate | 0.01 |
| Bromoform | 0.1 |
| Cadmium | 0.003 |
| Chloride | 200-300 |
| Chlorate | 0.7 |
| Chlorine | 5 |
| Chromium | 0.05 |
| Copper | 2 |
| Dichlorobenzene | 0.03 |
| Dissolved oxygen | No health-based guideline value is recommended |
| Edetic acid | 0.6 |
| Flouride | 1.5 |
| Hexachlorobutadiene | 0.0006 |
| Iron | No health-based guideline value is recommended |
| Lead | 0.1 |
| Manganese | 0.04 |
| Mercury | 0.006 |
| Molynate | 0.006 |
| Molybdenum | 0.07 |
| Monochloroacetate | 0.02 |
| Nickel | 0.07 |
| Nitrate | 50 |
| Nitrilotriacetic acid (NTA) | 0.2 |
| Selenium | 0.01 |
| Sulphate | No health-based guideline value is recommended |
| Styrene | 0.02 |
| Trichloroethylene | 0.04 |
| Toluene | 0.7 |
| Total Dissolved Solids (TDS) | No health-based guideline value is recommended |
| Trichloroacetate | 0.02 |
| Uranium | 0.015 |
| Vinyl chloride | 0.0003 |
| Xylene | 0.5 |
| Zinc | No health-based guideline value is recommended |
Read More: Scarcity of Water
Important Elements and Compounds in Drinking Water and Their Standard Limits
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- Fluoride: The deficiency of fluorides in water leads to tooth decay. The maximum permissible limit of fluoride content in water is 1 PPM, above which it might lead to dental fluorosis and skeletal fluorosis.
- Lead: Lead enters the water supply system through lead faucets pipe, pipes and fixtures. Although it is impossible to remove lead from entering the water supply system, there is a great need to regulate the concentration of lead in the water below 1 PPM.
- Arsenic: Arsenic enters the human body by drinking contaminated water. The maximum level of arsenic in safe drinking water is 0.0 1 milligram per litre. Beyond this limit, it can cause arsenic poisoning. Long term arsenic consumption can cause cancer, liver disease, diabetes, and nervous system complications ( loss of sensation in the Limbs and hearing problems).
- Nitrates: Nitrate usually enters the water bodies through chemical fertilizers, acid rain, effluents discharged from factories etc. The maximum permissible limit of nitrate in water is 50 mg/l.
- Iron: High concentration of iron in the groundwater table is a common phenomenon in many states of India. Prolonged consumption of water with high concentrations of iron beyond 1 mg/ l can cause Hemochromatosis, stomach problems and nausea. Although low levels of iron in drinking water are essential to fulfil the micronutrient need of our body for normal functioning.
Physical Parameters of Safe Drinking Water
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Aesthetic quality of drinking water is also important as it serves as an indicator of impurities or contaminants in water.
- pH: The pH of normal drinking water should be between 6.5 and 8.5.
- Taste: Safe and clean drinking water is tasteless however presence of certain dissolved mineral salts (those which are safe) can impart a slide alkaline taste to water.
- Turbidity: Turbidity is a concern and many people prefer clean and clear drinking water.
- Colour: The colour of safe drinking water for most people is colourless and crystal clear. However, the presence of a minute amount of organic material can add a brownish tint to water
- Odour: Safe and clean drinking water should be devoid of any odour. Odour in drinking water serves as an indicator of the presence of certain organic matter.
Safe Drinking Water
Read More: Physical Properties of Water
Things to Remember
- The International Standards of drinking water are a set of guidelines issued by the World Health Organization (WHO) which aims to guide the water supply authorities in the elimination of harmful substances from water and inclusion of essential mineral elements in the right amounts.
- In India, the Bureau of Indian Standard has specified drinking water quality standards made in reference to the guidelines issued by World Health Organisation (WHO) in India to provide safe drinking water to the people.
- Safe and clean drinking water are colourless, odourless, tasteless and without any turbidity.
- Drinking water must be free from all kinds of disease-causing germs and harmful chemicals and should have essential elements in the right amount.
Read More: Forms of Water
Sample Questions
Ques. Which water contaminant is the most dangerous? (3 Marks)
Ans. Lead is the most dangerous contaminant of water as it causes lead poisoning. Prolonged consumption of water with high concentrations of lead can cause developmental delays, abdominal pain, and neurological changes (loss of control and coordination of the skeletal muscles and mental retardation). It causes death when present in high doses in the body.
Ques. What do you mean by TDS? How is it measured? (3 Marks)
Ans. TDS stands for Total Dissolved Solids. It is defined as the number of particles of solute present in 106 million particles of solvent. The formula for measuring TDS is–
(Mass of solute ÷ Mass of solvent ) ×106 = TDS
Ques. How do arsenic and other such elements enter water sources? (3 Marks)
Ans. Arsenic occurs in nature in both combined and free states. In the combined state it is present as oxide, sulphides, nitrites and other such compounds in the rocks. During the process of weathering rocks followed by leaching, arsenic and other such elements enter the deeper layers of soil and accumulate in the water table of the groundwater.
Ques. For which elements or compounds are present in the water, there are no strict guidelines set by WHO? (3 Marks)
Ans. For Iron, sulphate, zinc and dissolved oxygen, there are no strict guidelines by WHO as to how much quantity is safe. But the high concentrations of iron and zinc can cause a number of health problems.
Ques. List three main causes of Water pollution. (3 Marks)
Ans. The three main causes of Water pollution are-
- Discharge of effluents from the various factories and industries- Almost all the factories in our country discharge their wastes and toxic by-products into the river causing water pollution on a mass scale.
- Excessive use of fertilizers and pesticides- The high food supply-demand in our country puts pressure on the farmers to increase their yields three-fold. As outcome chemical fertilizers and pesticides are used extensively to grow more crops quickly. The excess fertilizers and pesticides that remain on the top soil get washed off as surface runoffs which then enter the rivers and lakes and contaminate the water bodies with harmful chemicals.
- Sewage- The city’s sewage system collects all the domestic water from the houses and disposes it into the river without proper removal of harmful substances. Sewage water contains a lot of chemicals from detergents and soaps and shampoos and organic matter. All these cause pollution of the river
Ques. International Drinking Water Standards is formed by which organization and when? (2 Marks)
Ans. The World Health Organisation WHO's Guidelines for Drinking-water Quality was set up in Geneva, in 1993. These are the international reference point for standard-setting and drinking-water safety.
Ques. What do mean by hard and soft water? (2 Marks)
Ans. Hard water is one which does not lather with soap, while soft water lathers with soap. Soft water can be used for washing and bathing purposes, while hard water cannot.
Ques. List the cause of the hardness of water. State one method to remove the hardness of the water. (3 Marks)
Ans. Hard water is caused due to the presence of excessive minerals in water which imparts a characteristic hardness to water due to which it cannot lather with soap. The minerals that impart hardness to water are generally salts of calcium and magnesium. The hardness of water can be removed by using ion exchange resins which work mainly to replace the magnesium and calcium ions with sodium ions, thus, softening water.
Ques. Why is there a need to implement International Drinking Water Standards? (3 Marks)
Ans. The following are the reasons to implement International Drinking Water Standards-
- For ensuring safe and clean drinking water for everyone. As a basic necessity, one has the right to access clean and safe drinking water.
- The guidelines for Drinking Water issued by World Health Organisation (WHO) are devised in a way that is suitable for almost every human being posing the least risks.
- To improve water quality, means to improve the standard of living of the citizens. Following the International Drinking Water Standards will not only prevent the occurrence of diseases but also help in maintaining good health.
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