Physio-chemical Parameters of Water Quality

Water is one of the most important compounds and found in abundant in the ecosystem. All living organisms on the earth need water for their survival and growth. As of now, the earth is the only planet having about 70 % of water. But due to the increased human population, industrialization,globalization, use of fertilizers in the agriculture and man-made activity, it has become polluted with different harmful products. That's why it is necessary to check the quality of drinking water time and again, because due to the use of contaminated drinking water, human population, and animals can suffer from various water-borne diseases.

Physiochemical Parameters of Water Quality

It is necessary and important to test the water before it is used for drinking, domestic, agricultural or industrial purposes. Water must be tested with different physicochemical parameters. Selection of the parameters for testing of water solely depends on for what purpose we are going to use that water and to what extent its quality and purity is needed. Water contains different types of floating, dissolved, suspended and microbiological as well as bacteriological impurities. Some physical test should be performed for testing of the physical appearance such as temperature, color, odor, pH, turbidity, etc, while the chemical tests should be performed for its BOD, COD, dissolved oxygen, alkalinity, hardness. To obtain more and more quality and pure water, it should be tested for its trace metal, heavy metal contents, and organic i.e. pesticide residue.Following different physiochemical parameters are tested for the monitoring of quality of water.

Temperature

The water temperature controls the rate of all chemical reactions and affects the growth of fish and other water organisms, reproduction, and immunity, in an established system. Drastic temperature changes can be fatal to fish.

P^H

pH is the most important in determining the corrosive nature of the water. Lower the pH value higher is the corrosive nature of water. pH was positively correlated with electrical conductance and total alkalinity. The reduced rate of photosynthetic activity, the assimilation of carbon dioxide and bicarbonates which are ultimately responsible for the increase in pH, the low oxygen values coincided with high temperature during the summer month. Various factors bring about changes the pH of water. The higher pH values observed suggests that carbon dioxide, carbonate-bicarbonate equilibrium is affected more due to change in physicochemical condition.

Electrical Conductivity (EC)

Conductivity shows a significant correlation to various parameters such as temperature , pH value , alkalinity , total hardness , calcium , total solids, total dissolved solids , chemical oxygen demand , chloride and iron concentration of water. The underground drinking water quality of can be checked effectively by controlling theconductivity of water and this may also be applied to water quality management of other areas. It is measured with the help of EC meter. EC meter measures the resistance offered by the water between two platinized electrodes. The instrument is standardized with known values of conductance observed with standard KCl solution.

Alkalinity

Alkalinity is defined as the quality of ions in water that will read to neutralize the hydrogen ions. Alkalinity is thus a measure of ability to neutralizeacids. Alkalinity acts as a stabilizer for pH. Alkalinity, pH and hardness affect the toxicity of many substances in the water. Constituents of alkalinity in the natural water system includeCO^-_3,,HCO^-_3,HPO^--₄ and NH₂ along with CO₂.

Dissolved Oxygen

DO is one of the most important parameters.Its correlation with water body gives direct and indirect information e.g. bacterial activity, photosynthesis, availability of nutrients, stratification etc. Dissolved Oxygen of water is of paramount important to all living organisms. Potable water should have DO higher.

Carbonate

Whenever the pH touches the range 8.3, the presence of the carbonates is indicated. It is measured by the titration with standardized hydrochloric acid using phenolphthalein as an indicator. Below pH range 8.3, the carbonates are converted into an equivalent amount of the bicarbonates. The titration can also be done pH-metrically or potentiometrically.

Bicarbonate

It is also measured by the titration with standardized hydrochloric acid using methyl orange as indicator. Methyl orange turns yellow below pH 4.0. At this pH, the carbonic acid decomposes to give carbon dioxide and water.

Calcium

It is measured by a complexometric titration with astandard solution of ETDA using Patton’s and Reeder’s indicator under the pH ranges of more than 12.0. These conditions are achieved by adding a fixed volume of 4N Sodium Hydroxide. The volume of titer (EDTA solution) against the known volume of thesample gives the concentration of calcium in the sample.

Biochemical Oxygen Demand (BOD)

Biochemical oxygen demand (BOD) is one of the widely used measures to detect the water quality. BOD is defined as the amount of oxygen required for the microbial decomposition of the organic matter in the water. So, the BOD measures the amount of degradable organic materials present in the water. If the amount of organic matter in waste water is more, more oxygen will be utilized by bacteria to degrade it. Higher the requirement of oxygen, higher is the amount of organic matter in water and poorer is the quality of water.

Chemical Oxygen Deman (COD)

Chemical oxygen demand (COD) is the oxygen required by the organic substances in the water to oxidize them by a strong chemical oxidant.COD is another measure of organic material contamination in water specified in mg/L.Both BOD and COD are key indicators of the environmental health of a surface water supply. They are commonly used in waste water treatment but rarely in general water treatment.

Chloride

It is measured by titrating a known volume of sample with standardized silver nitrate solution using potassium chromate solution in water or eosin/fluorescein solution in alcohol as anindicator. The latter indicator is an adsorption indicator while the former makes a red colored compound with silver as soon as the chlorides are precipitated from solution.

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