8/19/2019 What is the Purpose of Using Blank Sample in the Experiment

1/2

1. What is the purpose of using blank sample in the experiment?

- The main reason for using the blank sample is to control the volume of organic

material in the sample. COD was carried out to measure the oxygen demand of 

organic compounds in a sample of water, and we have to ensure there were no

accidentally outside organic materials added to the sample to be measured. blank 

sample is created by adding the reagents to a volume of distilled water. !oth water 

and blank sample will be compared. The oxygen demand for the blank sample is

subtracted from the COD for the original sample to ensure the true measurement of 

organic matter.

2. What is the objective of COD test and hat is the different beteen COD and

!OD test?

- The chemical oxygen demand "COD# is the amount of oxygen consumed to

completely chemically oxidi$e the organic water constituents to inorganic end

 products. %t was carrying out to determine the organic oxidi$e able matters content of 

water samples. &hile, !iochemical Oxygen Demand is a common, environmental

 procedure for determining the extent to which oxygen within a sample can support

microbial life.

- &hile !OD describes the biological oxidation capacity of a wastewater, it is not a

measure of the total potential oxidation of the organic compounds present in the

wastewater. number of chemical tests are used to measure this parameter, either in

terms of the oxygen re'uired for virtually complete oxidation, or in terms of the

element carbon. (robably the most common test for estimating industrial wastewater 

strength is the Chemical Oxygen Demand "COD# Test. This test essentially measures

the chemical oxidation of the wastewater by a strong oxidi$ing agent in an acid

solution. The value for the COD test is always greater than the !OD test and is not

always a good indication of !OD values for the same waste.

- !ecause the COD test oxidi$es both biologically degradable and unbiodegradable

organic materials, the energy available for biological action is usually overestimated.

8/19/2019 What is the Purpose of Using Blank Sample in the Experiment

2/2

)owever, this does not reduce the usefulness of the test. %f it is assumed that the

fraction of organic material that is not oxidi$ed in the COD test remains constant,

then any change in COD between two points in the process provides an assessment

"in terms of oxygen# of corresponding energy change. The change in COD then can

 be used to establish the kinetics of energy conversion in the process, i.e., the energy

removal can be directly linked to the COD change. !y contrast, !OD* values re'uire

a correction factor to correspond the energy changes, because the test values do not

reflect the total oxygen demand.

". Wh# the COD$s value needs to be monitor for the polluted surface ater such as

in lakes and rivers as ell as for aste ater?

- %n environmental, the chemical oxygen demand "COD# test is commonly used to

indirectly measure the amount of  organic compounds in water . +ost applications of COD

determine the amount of organic  pollutants found in surface water  such as lakes and rivers,

making COD a useful measure of water 'uality. The amount of organic mater in the lake or river

will show the index of the water 'uality and we also can categori$e whether the lake or river

extremely polluted or not.

http://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Pollutanthttp://en.wikipedia.org/wiki/Pollutanthttp://en.wikipedia.org/wiki/Surface_waterhttp://en.wikipedia.org/wiki/Lakehttp://en.wikipedia.org/wiki/Riverhttp://en.wikipedia.org/wiki/Riverhttp://en.wikipedia.org/wiki/Water_qualityhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Pollutanthttp://en.wikipedia.org/wiki/Surface_waterhttp://en.wikipedia.org/wiki/Lakehttp://en.wikipedia.org/wiki/Riverhttp://en.wikipedia.org/wiki/Water_qualityhttp://en.wikipedia.org/wiki/Organic_compound