Dilution BOD5 concentration is 198 mg/l ±

Dilution method

This standard method is recognized by the United State of
America and widely used around the globe, the standard method used for the
examination of water, waste water and also estimating the level of
biodegradation . In order to obtain BOD5, dissolved
oxygen (DO) concentrations in a sample must be measured before and after the
incubation period, and appropriately adjusted by the sample corresponding
dilution factor. This analysis is performed using 300 ml incubation bottles in
which buffered dilution water is dosed with seed microorganisms and stored
for 5 days in the dark room at 20 °C to prevent DO production via
photosynthesis. In addition to the various dilutions of BOD samples, this
procedure requires dilution water blanks, glucose glutamic acid (GGA)
controls, and seed controls. The dilution water blank is used to confirm the
quality of the dilution water that is used to dilute the other samples. This is
necessary because impurities in the dilution water may cause significant
alterations in the results. The GGA control is a standardized solution to
determine the quality of the seed, where its recommended BOD5 concentration
is 198 mg/l ± 30.5 mg/l. For measurement of carbonaceous BOD (cBOD), a
nitrification inhibitor is added after the dilution water has been added to the
sample. The inhibitor hinders the oxidation
of ammonia nitrogen, which supplies the nitrogenous BOD (nBOD). When performing
the BOD5 test, it is conventional practice to measure
only cBOD because nitrogenous demand does not reflect the oxygen demand from
organic matter. This is because nBOD is generated by the breakdown of proteins,
whereas cBOD is produced by the breakdown of organic molecules.

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The manometric method

The method developed by Caldwell
and Langelier (1948) is based on the measurement of pressure decrease
due to the oxygen consumption by microorganisms oxidizing the organic matter.
In practice, the sample bottles are filled with a measured volume of sample.
The microorganisms degrade organic substances using the gaseous oxygen trapped
in the closed bottle. The carbon
dioxide formed by this process is absorbed, generally with sodium hydroxide
pellets. The pressure changes are measured by a manometer and converted to
oxygen consumption by the device to estimate the BOD value, if the BOD value is
high definitely the biodegradation level is high (the consumption level of the
organic material present in the water body is high by microorganism). The
measurement heads close the analysis bottles hermetically, and the pressure
changes are measured with pressure sensors and converted to BOD. These
alternative methods are very widespread in the industrial sector because they
are simple to use. Indeed, these methods allow the measurement of the BOD in
samples contaminated by high levels of carbon compounds without making
dilutions because of the large pool of oxygen trapped in the bottle.

 

 

Principle of the BOD measurement by the manometric method

 

 

 

 

 

 

 

 

The photometric method

To reduce the working are a required to perform a BOD test, Hach
Lange and Macherey  Nagel (BOD5 Nanocolor_) proposed cuvette tests. The tests
follow the same protocol as the standard method (dilution of samples with high organic loads, incubation at 20 _C in a dark room,
variability of the microbial population, and required analysis time) and are
based on the dissolved oxygen consumption by the microorganisms present in the
samples analysed during this period. The dissolved oxygen is analysed before
and after the analysis period directly in the cuvettes. In the Hach Lange
tests, the dissolved oxygen, after the addition of several reagents to the test
cuvettes, forms a red dye proportional to the dissolved oxygen concentration. The measurement of this red dye by
spectrophotometry allows the estimation of the oxygen consumption and,
therefore, the BOD. The measurement of the dissolved oxygen in the Macherey
Nagel test is based on Winkler’s method (the iodometric method). These methods
provide indirect estimates of the BOD.

Dilution method

This standard method is recognized by the United State of
America and widely used around the globe, the standard method used for the
examination of water, waste water and also estimating the level of
biodegradation . In order to obtain BOD5, dissolved
oxygen (DO) concentrations in a sample must be measured before and after the
incubation period, and appropriately adjusted by the sample corresponding
dilution factor. This analysis is performed using 300 ml incubation bottles in
which buffered dilution water is dosed with seed microorganisms and stored
for 5 days in the dark room at 20 °C to prevent DO production via
photosynthesis. In addition to the various dilutions of BOD samples, this
procedure requires dilution water blanks, glucose glutamic acid (GGA)
controls, and seed controls. The dilution water blank is used to confirm the
quality of the dilution water that is used to dilute the other samples. This is
necessary because impurities in the dilution water may cause significant
alterations in the results. The GGA control is a standardized solution to
determine the quality of the seed, where its recommended BOD5 concentration
is 198 mg/l ± 30.5 mg/l. For measurement of carbonaceous BOD (cBOD), a
nitrification inhibitor is added after the dilution water has been added to the
sample. The inhibitor hinders the oxidation
of ammonia nitrogen, which supplies the nitrogenous BOD (nBOD). When performing
the BOD5 test, it is conventional practice to measure
only cBOD because nitrogenous demand does not reflect the oxygen demand from
organic matter. This is because nBOD is generated by the breakdown of proteins,
whereas cBOD is produced by the breakdown of organic molecules.

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The manometric method

The method developed by Caldwell
and Langelier (1948) is based on the measurement of pressure decrease
due to the oxygen consumption by microorganisms oxidizing the organic matter.
In practice, the sample bottles are filled with a measured volume of sample.
The microorganisms degrade organic substances using the gaseous oxygen trapped
in the closed bottle. The carbon
dioxide formed by this process is absorbed, generally with sodium hydroxide
pellets. The pressure changes are measured by a manometer and converted to
oxygen consumption by the device to estimate the BOD value, if the BOD value is
high definitely the biodegradation level is high (the consumption level of the
organic material present in the water body is high by microorganism). The
measurement heads close the analysis bottles hermetically, and the pressure
changes are measured with pressure sensors and converted to BOD. These
alternative methods are very widespread in the industrial sector because they
are simple to use. Indeed, these methods allow the measurement of the BOD in
samples contaminated by high levels of carbon compounds without making
dilutions because of the large pool of oxygen trapped in the bottle.

 

 

Principle of the BOD measurement by the manometric method

 

 

 

 

 

 

 

 

The photometric method

To reduce the working are a required to perform a BOD test, Hach
Lange and Macherey  Nagel (BOD5 Nanocolor_) proposed cuvette tests. The tests
follow the same protocol as the standard method (dilution of samples with high organic loads, incubation at 20 _C in a dark room,
variability of the microbial population, and required analysis time) and are
based on the dissolved oxygen consumption by the microorganisms present in the
samples analysed during this period. The dissolved oxygen is analysed before
and after the analysis period directly in the cuvettes. In the Hach Lange
tests, the dissolved oxygen, after the addition of several reagents to the test
cuvettes, forms a red dye proportional to the dissolved oxygen concentration. The measurement of this red dye by
spectrophotometry allows the estimation of the oxygen consumption and,
therefore, the BOD. The measurement of the dissolved oxygen in the Macherey
Nagel test is based on Winkler’s method (the iodometric method). These methods
provide indirect estimates of the BOD.

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