chemical oxygen demand ppt with full concept

1. BY :
Darshit Hapaliya – 130570137017
Akash Kanani – 130570137025
Jaykishan Nariya – 130570137031
Subbimated to : Dr. A.S.ARORA
(ES-2,ES)-MEFGI

2.  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.

3.  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.

4.  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.

5.  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) .

6.  COD measurement instrument

7.  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.

8.  Procedure for Cod measurement
 Two types method for COD measurement
 Open Reflux Method
 Closed Reflux Method

9. Open Reflux Method
The 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.

10.  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.

11.  Which Apparatus/Equipment Required
for COD measurement?
 Culture tubes
 standard ampules
 Block heater
 Titration Apparatus

12.  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.