Water Quality Standards in India | WHO Guidelines

In this article, we will discuss water quality standards in India.

  1. Introduction  

Water available in the source may contain many harmful constituents i.e. various impurities at various concentrations. The presence of a higher concentration of impurities in drinking water cause diseases but the presence of some minerals in the water may be beneficial to human beings which should be within a limit. The maximum concentration limit of impurities in water at which it is not harmful to human health is termed as water quality standard. Drinking water quality standards describe the quality parameters set for drinking water.

Every human on this planet needs drinking water to survive and that water may contain many harmful constituents, there are no universally recognized and adopted international standards for drinking water. Where drinking water quality standards do exist, most are expressed as guidelines or targets rather than requirements, and very few water standards have any legal basis or are subjected to enforcement.

The water quality should be good enough to drink after water treatment from the source. Due to impure water quality, there is a high chance of getting suffer from water-borne diseases.

The water should be well treated. The water source should be protected from contamination and much care should be given during the rainy season because at the rainy there is a high chance of water getting contaminated.

The chlorination should be done by the calculation, disinfection process should be done well to kill the presence of the pathogenic chemicals.

  2. Water Quality Standards in India  

Following are some important drinking water quality standards in India.

  a. Turbidity  

Turbidity is a measure of the extent to which light is either absorbed or scattered by suspended material in water. Absorption and scattering are influenced by both size and surface characteristics of the suspended material; turbidity is not a direct quantitative measurement of suspended solids. For example, one small pebble in a glass of water would produce virtually no turbidity.

If this pebble gets crushed into thousands of particles of colloidal size, measurable turbidity would result. Turbidity is measured photometrically by determining the percentage of light of a given intensity that is either absorbed or scattered.

The original measuring apparatus called a Jackson turbidity meter was based on light absorption and employed a long tube and standardized candle. The glass tube was calibrated with readings of one JTU being equal to the turbidity produced by 1 mg SiO₂, in 1 liter of distilled water. Turbidity of 5[ppm is accepted and rejected if it is greater than 10 NTU.

Turbidity measurements made using proprietary nephelometric devices are Expressed as Nephelometric Turbidity Units (NTU).

  b. Colour  

Pure water is colorless, but water in nature is often a closed foreign substance. It is measured by the ability of the solution to absorb light. Water having partly color due to suspended matter is said to have apparent color.

Colour contributed by dissolved solids that remain after removal of suspended matter is known as true color. While the true color in water is due to dissolved materials only. The organic compounds casing true color may exert a chlorine demand thereby seriously reducing the effectiveness of chlorine as a disinfectant. Color is measured by a tonometer. The intensity of the color is measured on a platinum cobalt scale. One milligram of potassium plus half a milligram of metallic cobalt is dissolved in 1 liter of distilled water is one true color unit. Colored water is aesthetically objectionable for drinking purposes.

  c. pH  

It is the symbol for the logarithm of the reciprocal of hydrogen ion concentration in gram atoms per liter, used to express the acidity or alkalinity of a solution on a scale of 0 to 1, where less than 7 represents acidity, 7 neutrality, and more than 7 alkalinities. It is determined by electrometric and colorimetric methods. The value of pH drinking water is 6.5 to 8.5.

  d. Taste and odour  

If every water tap on the property has a taste or smell, it is likely the main water supply. If it occurs only in a few taps, the problem is with the fixtures or pipes that supply those specifics.

  e. Hardness  

Hardness is defined as a measure of resistance to localized plastic deformation induced by mechanical indentation or friction.

  f. Total Suspended Solids (TSS)  

Total Suspended Solids (TSS) is defined as a dry-weight of suspended particles that do not dissolve, in a sample of water that can be analyzed by a filter trapped by a filter.

  g. Total Dissolved Solids (TDS)  

The solids present in water may be either dissolved or suspended solids and some of these suspended and dissolved solids is total solids. The solids present in water is generally expressed in ppm or mg/lit.

The water sample when ket into the oven for evaporation at 103 ºC -105 ºC for 24 hrs obtained residue is total solids. Further obtained if ignited in a muffle furnace at 600 ºCfor 15-20 minutes, volatile solids escape out and obtained Is fixed or inorganic solid.

  h. Alkalinity  

Alkalinity refers to measuring the ability of water to neutralize acids. The alkalinity of water can be caused by the presence of one or more ions. These include hydroxide, carbonate, and bicarbonate.

  i. Chlorine  

Chlorine levels of up to 4 mg per liter (mg / L) or 4 parts per million (ppm) in drinking water are considered safe. At this stage, harmful health effects are unlikely to occur.

  j. Nitrate  

Nitrate is a compound that is formed naturally when nitrogen combines with oxygen or ozone.

  k. Sulphate  

Sulfates are a combination of sulfur and oxygen and are part of the minerals found naturally in some soil and rock formations that include groundwater.

  l. Fluoride  

The Department of Health and Human Services (DHHS) sets the optimal level of fluoride for preventing tooth decay at 0.7 ppm, or 0.7 milligrams (mg) in every litre of water. The previously this numbers in force from 1962 to 2015, was 0.7 to 1.2 ppm. In 2015, it was revised to the lower limit.

  m. Zinc  

Zinc is naturally present in water. The average zinc concentration in seawater is 0.6–5 ppb. Rivers typically contain between 5 and 10 ppb zinc. Algae contain 20-700 ppm, marine fish and shells have 3-25 ppm, oysters have 100-900 ppm and shrimp fish have 7-50 ppm.

  n. Temperature  

The temperature of the water is determined by ordinary thermometers. The temperature of surface water is equivalent to the atmosphere whereas that of groundwater may be slightly more or less than that of atmospheric temperature.

The temperature of the water has an effect on the physical properties of water such as density, viscosity, surface tension, saturation value of gases dissolved in water, biological activity. For public water supply, it should be between 10 °C to 15.6 °C. Temperature greater than 25 t is undesirable and above 35 °C is unfit for public water supply.