Biological Oxygen
Demand and Chemical Oxygen Demand
Difference Between BOD and COD
BOD
versus COD
Quality of a given
water sample depends on a number of variable factors.
In addition, it can be categorized in several
ways such as biological, physical and chemical.
Oxygen demand is one of the most common ways
of measuring the quality of water. Both BOD and COD are coming under that
phenomenon.
The main intention of this article is to give
a clear idea about both of the concepts, similarities, differences, and
practical usage of them.
What
is BOD?
BOD is the
abbreviation of biological oxygen demand in water.
It is also called as biochemical oxygen
demand. Before moving in to a deep discussion about the topic, it is better
going through some of the important concepts regarding water quality.
There are some key factors taken into
consideration in order to determine water quality. They are namely pH,
turbidity, microorganisms, dissolved-oxygen content, and dissolved-nutrients.
The main parameter, which can affect the
water quality, is the composition of water.
Normally water contains gases, inorganicions, organic compounds, living organisms and some of the other trace chemicalcompounds.
The composition is varying depending on the
different factors such as temperature, source and level of pollution.
Particularly the microbial population and the
dissolved oxygen concentration are changed with the alterations of the
above-mentioned factors.
There is a significant relationship among
organic matter, microbial population and finally with the dissolved oxygen
content in water.
It can be nicely explained like this. Aerobic
microbes need oxygen for their metabolism. They use dissolved oxygen and
convert organic matter into energy. They utilize the provided energy from
organic food, for their further metabolic reactions and especially for their
reproduction.
The population density is increasing with
respect to the gained energy, but it depends on the available food content.
This metabolic requirement for the newly
created population, again creates a demand for the dissolved oxygen, which is
proportional to the available food.
Therefore, the biological oxygen demand can
be defined as the amount of dissolved oxygen required by aerobic organisms, to
breakdown organic materials, in order to obtain energy for their metabolism.
This value should be tested under given
temperature for a given period of time, and it will depend on the nutrient
concentration and enzymatic reactions too.
BOD value in polluted water is normally
higher than the fresh water. Increased BOD can be resulted due to domestic sewage, petroleum residues and wastes of animals and crops.
What
is COD?
Chemical oxygen
demand, which is commonly abbreviated as COD, is an indirect method of
determining organic compounds in water.
Not only COD is engaged with decomposition of
organic matter, but also, it relates with the oxidation of inorganic chemicals
(ammonia and nitrite).
It is explained as the capacity of water, to
consume dissolved oxygen during both of the cases.
COD and BOD both can be indicated as mg/L or ppm (parts per million)
What is the difference between BOD and COD?
• BOD
is only a measurement of consumed oxygen by aquatic microorganisms to decompose
or oxidize organic matter. However, COD refers to the requirement of dissolved
oxygen for the oxidation of organic and inorganic constituents both.
•
Although, some of the organic compounds, which can be broken down by
microorganisms, are countable for the biological oxygen demand, they may not be
encountered in measuring chemical oxygen demand.
.
http://www.differencebetween.com/difference-between-bod-and-vs-cod/
.
http://www.differencebetween.com/difference-between-bod-and-vs-cod/
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