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Water Quality
  Water Quality
1. What is water quality?
Water quality is the measure of suitability of water for a particular use based on its selected physical, chemical and biological characteristics. Various parameters of the water are measured which later compared with the standard guidelines and then decided on the suitability of the water for particular use.
Some of the parameters like temperature, pH, electrical conductivity and dissolved oxygen can be measured at the sampling site itself whereas other parameters measured in the laboratory.
The standard parameters of the water are decided based on its use. For example, the water quality standard for drinking water may be different that for the safety of aquatic life, irrigation etc.
2. How is water polluted?
Water is known as the universal solvent and is seldom found pure in nature. In fact, natural waters may contain hundreds or even thousands of chemicals, and in some cases, an equal number of biological life forms (such as microorganisms).
All forms of life depend on water. Sometimes harmful substances can dissolve in water. Substances that harm the quality of water are known as pollutants or contaminants. Most contaminants in water do not cause problems because they are not toxic and are at such low amounts. However, some substances which dissolve in water, even at very low levels, can be harmful. Pollutants and contaminants are generally referred as same. More specifically, pollutants are usually thought of as contaminants or impurities in water due to the activities of people and Contaminants are usually thought of as impurities in water caused by natural processes.
Nature and people are the two primary causes of water pollution. Natural events such as volcanic eruptions, landslides, floods and wild animal wastes, can produce polluting materials. These pollutants are then washed down to lakes, rivers and other streams along with runoff or other agents and damage water quality. Groundwater can become contaminated by the minerals it comes in contact with. A natural source of groundwater pollution is a gas called radon. Radon comes from certain types of rock which contain the element radium. Scientists believe radon is dangerous to people, so groundwater from wells where minerals contain radium should be tested for radon.
People are more responsible for water pollution. Carelessness, lack of knowledge are makes people pollute water. Houses, Farms, factories, automobiles are potential sources of pollutants.
The wastes from the hoses sometimes make the water polluted. Though fertilizer and pesticides are useful for the plants, its excessive use causes the nutrition to wash down the water bodies. Excessive nutrition produces more algae which make water green and nuisance and may also kill the fishes and aquatic lives due to lack of oxygen. Similarly the toxic pesticides if swept to water bodies make them toxic and unusable for any living beings. Likewise untreated water and chemicals from factories contaminates the water. Some gases released by internal combustion engines react with water and produces acid rain.
3. What are the types of pollution?
There are mainly two types of water pollution. Point source pollution and non-point water solution.
Point source: if the pollution enters a water body from any particular point, it is called Point source pollution. For example, effluent from sewage plant, city storm drain factory sewage outlet.
Non-Point source: this pollution refers to contamination which does not originate from a single discrete source of pollution. It is a cumulative effect of pollution gathered from several sources of pollution. For example, leaching out of nitrogen compounds from agriculture land, contaminants storm water washed from parking lots, highways, urban runoff (if these all are not diverted to city storm drain), runoff from forest etc.
4. Some general tips for controlling water pollution
If you want to help keep our waters clean, there are many things you can do to help. You can prevent water pollution of nearby rivers and lakes as well as groundwater and drinking water by following some simple guidelines in your everyday life.
  • Conserve water by turning off the tap when running water is not necessary. This helps prevent water shortages and reduces the amount of contaminated water that needs treatment.
  • Be careful about what you throw down your sink or toilet. Don't throw paints, oils or other forms of litter down the drain.
  • Use environmentally household products, such as washing powder, household cleaning agents and toiletries. Take great care not to overuse pesticides and fertilizers. This will prevent runoffs of the material into nearby water sources.
  • By having more plants in your garden you are preventing fertilizer, pesticides and contaminated water from running off into nearby water sources.
  • Don't throw litter into rivers, lakes or oceans. Help clean up any litter you see on beaches or in rivers and lakes, make sure it is safe to collect the litter and put it in a nearby dustbin.
5. Some common water pollution treatment methods
Industrial Water Treatment:
The treatment basically passes different phases. In a water treatment plant, sewage goes through a number of chambers and chemical processes to reduce the amount and toxicity of the waste.
  • The suspended solids and inorganic materials are removed using filter in the first stage.
  • Organics matters are reduced in the next phase using biological filters and processes that naturally degrade organic waste and materials.
  • And the final phase treatment must be done in order to make it reusable. All solid particles and chemicals are removed using some additives.
Septic Tank:
Septic tanks are used to treat water from individual house. It treats the water at the same place where it is located. All the untreated sewage from the individual property is made to flow into the septic tank where the solids are separated from the liquid.
  • Heavier particles settle at the bottom of the tank whereas lighter particles, such as soap scum, will form a layer at the top of the tank.
  • Biological processes are used to help degrade the solid materials.
  • The liquid then flows out of the tank into a land drainage system and the remaining solids are filtered out.
Ozone waste water treatment:
This method of treatment is gaining high popularity these days. The method requires the use of an ozone generator, which decontaminates the water as Ozone bubbles percolate through the tank. Ozone, a highly reactive form of oxygen is capable of converting organic molecules to water and carbon dioxide. This is called mineralization. Ozone can also convert the heavy metals like irons and manganese in to flocks which are easily filterable. The treatment also removes nasty odour and also leaves no trace of its use because it quickly converts back to oxygen after use.
There are some disadvantages also in using this treatment method. The treatment is expensive as it consumes high energy and can't be used when power is lost. It can't remove dissolved minerals and salts and also some times the byproducts of the process like Bromate is harmful for health.
Under the Advance Oxidation Process (AOP), Ozone is converted to hydroxyl radicals which are even more powerful oxidizers than ozone itself. Ozone and Ozone AOP is used to treat a wide variety of wastewater including:
  • Textile
  • Meat processing
  • Animal waste treatment
  • Septic
  • Cutting fluids recycling
  • Chicken egg processing effluent
  • Laundry water recycling
Dentrification is a part of nitrogen cycle which helps is controlling the leaching of nitrates into ground water and helps in protecting the GW contamination. Some bacteria in the soil convert the nitrogen in the fertilizer to nitrates which is easy for plant to absorb. When oxygen level is low another form of bacteria converts the nitrates back to nitrogen gas, nitrous oxide or nitrous dioxide. The conversion of these nitrates into gas is called denitrification. This prevents nitrates from leaching into the soil and contaminating groundwater.
6. Effect of polluted water
The effect of polluted water is far reaching and not only bounded to environment but to human and animal also. The water pollution has now become a global concern. Numerous diseases, health problem even fatalities have been associated with water pollution. Some effects are pointed below:
  • Heavy metals like lead, mercury, iron, cadmium, aluminum and magnesium reach the food chain through plants and aquatic animals. This causes heavy metal poisoning in case the level in the water is very high. These are toxic to marine life such as fish and shellfish, and subsequently to the humans who eat them. Heavy metals can slow development; result in birth defects and some are carcinogenic.
  • Toxic compounds in industrial waste damages the aquatic life and those who eat them. Some toxins in such waste may even lead to death. They can cause immune suppression, reproductive failure or acute poisoning.
  • Microbial pollutants spread infectious disease through drinking water. This problem is of major concern in developing countries. Cholera and typhoid fever are primarily the result of microbial pollutants.
  • Excessive organic matters and nutrition produces more algae on water. Algae consume more oxygen. Lack of oxygen may suffocate the aquatic lives which at critical stage may lead to death of such animals.
  • Nitrates in drinking water leads to diseases of infants that may lead to their death. Cadmium is a metal in sludge-derived fertilizer. This can be absorbed by crops. When people ingest this, they may cause diarrheal disorders, liver and kidney damage. The inorganic substances like mercury, arsenic and lead are the causes of pollution. Other chemicals can also lead to problems concerning the taste, smell and color of water.
  • One of the most powerful pollutants of water is oil. Oil spilt on water may be consumed by the aquatic animals. Many animals can be annihilated in case they ingest oil. Similarly if the oil coats the feather of bird, they may die. The dirt and silt carried by the water may prevent sunlight entering the water body. If the sun can't reach plant, they perish. Suspended particles in fresh water also reduce the quality of drinking water for human. Such sediments may also clog the fish gill.
  • Acid rain contains sulfate particles, which can harm fish or plant life in lakes and rivers.
7. Drinking Water Quality Standard
Standard developed by Government of India
Water Quality Standard from WHO
WHO standard of Drinking Water
8. Ground water quality scenario in India
9. What is naturally present in water?
The most common dissolved substances in water are minerals or salts that, as a group, are referred to as dissolved solids. Dissolved solids include common constituents such as calcium, sodium, bicarbonate, and chloride; plant nutrients such as nitrogen and phosphorus; and trace elements such as selenium, chromium, and arsenic.
In general, the common constituents are not considered harmful to human health, although some constituents can affect the taste, smell, or clarity of water. Plant nutrients and trace elements in water can be harmful to human health and aquatic life if they exceed standards or guidelines.
Dissolved gases such as oxygen and radon are common in natural waters. Adequate oxygen levels in water are a necessity for fish and other aquatic life. Radon gas can be a threat to human health when it exceeds drinking-water standards.
10. How do human activities affect water quality?
Urban and industrial development, farming, mining, combustion of fossil fuels, stream-channel alteration, animal-feeding operations, and other human activities can change the quality of natural waters. As an example of the effects of human activities on water quality, consider nitrogen and phosphorus fertilizers that are applied to crops and lawns. These plant nutrients can be dissolved easily in rainwater or snowmelt runoff. Excess nutrients carried to streams and lakes encourage abundant growth of algae, which leads to low oxygen in the water and the possibility of fish kills.
Chemicals such as pharmaceutical drugs, dry-cleaning solvents, and gasoline that are used in urban and industrial activities have been found in streams and ground water. After decades of use, pesticides are now widespread in streams and ground water, though they rarely exceed the existing standards and guidelines established to protect human health. Some pesticides have not been used for 20 to 30 years, but they are still detected in fish and streambed sediment at levels that pose a potential risk to human health, aquatic life, and fish-eating wildlife. There are so many chemicals in use today that determining the risk to human health and aquatic life is a complex task.
Water Quality/ Pollution
11. Water Quality Criteria
Designated-Best-User Class of water Criteria
Drinking Water Source without conventional treatment but after disinfection A
  • Total Coliforms Organism MPN/100ml shall be 50 or less
  • pH between 6.5 and 8.5
  • Dissolved Oxygen 6mg/l or more
  • Biochemical Oxygen Demand 5 days 20°C 2mg/l or less
Outdoor bathing (Organized) B
  • Total Coliforms Organism MPN/100ml shall be 500 or less pH between 6.5 and 8.5 Dissolved Oxygen 5mg/l or more
  • Biochemical Oxygen Demand 5 days 20°C 3mg/l or less
Drinking water source after conventional treatment and disinfection C
  • Total Coliforms Organism MPN/100ml shall be 5000 or less pH between 6 to 9 Dissolved Oxygen 4mg/l or more
  • Biochemical Oxygen Demand 5 days 20°C 3mg/l or less
Propagation of Wild life and Fisheries D
  • pH between 6.5 to 8.5 Dissolved Oxygen 4mg/l or more
  • Free Ammonia (as N) 1.2 mg/l or less
Irrigation, Industrial Cooling, Controlled Waste disposal E
  • pH between 6.0 to 8.5
  • Electrical Conductivity at 25°C micro mhos/cm Max.2250
  • Sodium absorption Ratio Max. 26
  • Boron Max. 2mg/l
Below-E Not Meeting A, B, C, D & E Criteria
12. General standards for discharge of environmental pollutants
13. Environmental Data Bank
14. Real Time Air Quality Status
15. Highlights of CPCB
16. Publications from CPCB
17. CPCB annual report