BY :Darshit Hapaliya –

130570137017Akash Kanani – 130570137025

Jaykishan Nariya – 130570137031

Subbimated to : Dr. A.S.ARORA

(ES-2,ES)-MEFGI

Introduction :

The amount of oxygen dissolved in water is important to aquatic life. Decaying matter in sewage, industrial discharge, agriculture and urban runoff uses up the dissolved oxygen in water.

The Chemical Oxygen Demand (COD) is measure of the amount of chemicals (usually organic) that consume Dissolved Oxygen.

COD is the measurement of the amount of the oxygen in water consumed for chemical oxidation of pollutant.

COD determine the quantity of oxygen required to oxidize the organic matter in water or waste water sample, under specific condition of oxidizing agent, temperature and time.

What is COD ?

Chemical Oxygen Demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water . Most applications of COD determine the amount of organic pollutants found in surface water.

How is COD measured?

It is expressed in milligrams per liter (mg/l) . Which indicates the mass of oxygen consumed per liter of solution . Older references may express the as parts per million (ppm) .

COD measurement instrument

Why measure COD?

COD often measured as rapid indicator of organic pollutant in water . It is normally measured in both municipal and industrial wastewater treatment plants and gives an indication of the efficiency of the treatment process . The efficiency of the treatment process is normally expressed as COD removal., measured as a percentage of the organic matter purified during cycle.

Procedure for Cod measurement

Two types method for COD measurement

Open Reflux Method Closed Reflux Method

Open Reflux MethodThe sample and a blank are

refluxed in strongly acidic solution in the presence of standard potassium dichromate solution for 2 hours using a reflux apparatus comprising of an Erlenmeyer flask, a vertical condenser and heating mantle.

The remaining unreduced dichromate of the digested sample and blank are measured by titrating against standard ferrous ammonium sulfate (FAS) solution using ferroin indicator.

Closed Reflux Method Closed reflux method has the

cost advantage and it generates minimum of hazardous waste.

In cases of turbid or highly colored samples, prefer titrimetric method, rather than colorimetric method but titrimetric method is time consuming and require high degree of skill.

Which Apparatus/Equipment Required for COD measurement?

Culture tubes

standard ampules

Block heater

Titration Apparatus

Application of COD DATA

The COD test is used extensively in the analysis of industrial wastes. It is particularly valuable in surveys designed to determine and control losses to sewer system. Results may be obtained within a relatively short time and measures taken a correct errors on the day they occur. In conjunction with the BOD test , the COD test is helpful in indicating toxic condition and the presence of biologically resistance organic substance . The test is widely used in the operation of treatment facilities because of the speed with which result can be obtained.