Chetan Singh Pundeer (12 CE 036) 1

D.O & C.O.D( DISSOLVED OXYGEN DEMAND)

ANDCHEMICAL OXYGEN DEMAND )

CHETAN SINGH PUNDEER

(12 CE 036 )

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WHAT IS D.O ?

Dissolved oxygen refers to the level of free, non-compound oxygen present in water or other liquids. It is an important parameter in assessing water quality because of its influence on the organisms living within a body of water. In limnology (the study of lakes), dissolved oxygen is an essential factor second only to water itself .  A dissolved oxygen level that is too high or too low can harm aquatic life and affect water quality.Non-compound oxygen, or free oxygen (O2), is oxygen that is not bonded to any other element. Dissolved oxygen is the presence of these free O2 molecules within water.The bonded oxygen molecule in water (H2O) is in a compound and does not count toward dissolved oxygen levels. One can imagine that free oxygen molecules dissolve in water much the way salt or sugar does when it is stirred .

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WHAT IS C.O.D ?COD (Chemical Oxygen Demand) is the amount of oxygen required to degenerate all poution in a chemical way (by adding oxidising agents and heating). In general with chemical destruction you can remove more polution than with the biological way.. It is expressed in milligrams per liter (mg/L) also referred to as ppm (parts per million), which indicates the mass of oxygen consumed per liter of solution.

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WHERE DOES D.O COMES FROM ?

Dissolved oxygen enters water through the air or as a plant byproduct. From the air, oxygen can slowly diffuse across the water’s surface from the surrounding atmosphere, or be mixed in quickly through aeration, whether natural or man-made 7. The aeration of water can be caused by wind (creating waves), rapids, waterfalls, ground water discharge or other forms of running water. Man-made causes of aeration vary from an aquarium air pump to a hand-turned waterwheel to a large dam.Dissolved oxygen is also produced as a waste product of photosynthesis from phytoplankton, algae, seaweed and other aquatic plants.

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METHOD FOR D.OThere are three methods available for measuring dissolved oxygen concentrations. Modern techniques involve either an electrochemical or optical sensor. The dissolved oxygen sensor is attached to a meter for spot sampling and laboratory applications or to a data logger, process monitor or transmitter for deployed measurements and process control.The colorimetric method offers a basic approximation of dissolved oxygen concentrations in a sample. There are two methods designed for high-range and low-range dissolved oxygen concentrations. These methods are quick and inexpensive for basic projects, but limited in scope and subject to error due to other redoxing agents that may be present in the water .

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METHOD FOR CODPotassium dichromate is a strong oxidizing agent under acidic conditions. (Acidity is usually achieved by the addition of sulfuric acid.)

In the process of oxidizing the organic substances found in the water sample, potassium dichromate is reduced (since in all redox reactions, one reagent is oxidized and the other is reduced), forming Cr3+. The amount of Cr3+ is determined after oxidization is complete, and is used as an indirect measure of the organic contents of the water sample.

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THANK YOU

Submitted To:- Ms. Himadri Rajput

Submitted By:- Chetan Singh Pundeer (12 CE 036)