BOD

Biological Oxygen Demand / Biochemical oxygen demand


Biochemical Oxygen Demand (BOD) or sometimes Biochemical oxygen demand is a measurement of water quality. This is used in water monitoring and provides an estimate of the oxygen used by microorganisms during the breakdown of organic material present in the water. The BOD parameter is normally quoted in mg/L (milligrams per litre) and sometimes as PPM (Parts per million). The value for BOD will always be lower than that of COD.

It is usually measured in the laboratory under controlled conditions over a 5-day period (e.g. BOD5) and oxygen depletion compared to a control. The reason for the five days is to give the Biological effects the opportunity to grow to a detectable level.

The BOD parameter (Biological Oxygen Demand) in waste water and sewage treatment is an important parameter as well as in rivers, canals and lakes. 

If the BOD parameter in the final effluent is too high and this is discharged the receiving water will have oxygen removed by the newly added biological pollution.  In the case of high levels of BOD and the associated low levels of oxygen in water can cause the aquatic fauna such as water beetles, crustaceans, and fish to die. This can have a cascading effect on the whole ecosystem causing long term damage!


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How is BOD measured?

ISO 5815:1989 - The BOD5 process 

The standard test for Biological oxygen demand (BOD) is to determine the amount of oxygen which algae, bacteria and other micro organisms consume while in a water sample over a five day period. These consume the water's oxygen aerobically replacing the oxygen with carbon dioxide. The sample temperature is regulated at 20 Celsius (68 Fahrenheit) in laboratory conditions. 

BOD5 is an indirect measure of all the biodegradable organic substances in the water sample. The BOD5 indicates how much dissolved oxygen (mg/l) is needed in a given time for the biological degradation of the organic wastewater constituents.

This Biological oxygen demand is a key parameter when determining the degree of pollution that wastewater represents  in the receiving water. It is also a huge factor in the ecology and high Biological oxygen demand can  destroy local ecosystems.

Can you wait five days before you know there is a problem with your BOD discharge?



How do I get a rapid Biological Oxygen Demand value?

UV254 is a simple quick chemical free surrogate measurement for the BOD parameter

What is UV254? Ultraviolet transmittance refers to the amount of light that passes through a sample at the wavelength of 254 nm. UV254 absorption can be used as a surrogate measurement of BOD (Biological oxygen demand or Biochemical oxygen demand ) and uses only UV light to measure,  and can give results in 10 seconds.

UV254 is absorbed and scattered by the organics, colloids, and suspended solids. UV Absorbance often expressed as A254 or ABS is the light absorbed by a sample.

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UV254 a proven modern alternative to slow BOD5  

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• Results every 10 seconds

• Valuable trend data 

• Results in seconds not minutes

• All data stored in excel compatible format

• 10 hours use without recharging

• Modern icon-driven touch screen

• All results come with time and date stamps

•Devices will store calibration for 16 different locations

• Stores over 10 years of results


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