The interpretation of BOD

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Hi Dear All:

I have a very basic question. Which one does the BOD show in the wastewater?

1. The amount of microorganisms?

or

2. The amount of organic matter?

 

Taxonomy

20 Answers

  1. Hey Iman Dorri , 

    BOD stands for the amount of oxygen needed to decompose organic waste in wastewater. As more oxygen is needed as higher is the grade of pollution = BOD level. 

    The most common test method used to determine the BOD level is called BOD5 test. In this test the oxygen consumption after 5 days of incubation time is measured. 

    You can find more details and explanations in our 3 minute video tutorial here:  BOD tutorial

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  2. BOD is the indirect measurement of organic pollution a wastewater stream contains in it when discharged into the aquatic resources. 

    As any wastewater stream contains diverse range of Organic pollutants, quantifying them individually might not help a lot in terms of the impact it makes on the receiving water. While when the waste stream containing organic pollutants are discharged in to the aquatic body, it imposes an oxygen demand on the aquatic resources consuming the DO present in the aquatic body due to reductive nature of the organic pollutants present in the stream. As DO was considered as one of the most significant parameter to measure the health of aquatic bodies due to its impact on the aquatic life present in the aquatic bodies, tests were developed to measure the amount of OXYGEN a stream could consume when discharged into the aquatic body. The BOD test is the measure of this organic pollution using Bacteria as the basic process "workers" which consumes the Organic pollution in the presence of Oxygen. Thus by measuring the DO level at a period of interval , one can estimate how much oxygen demand the pollution event could make on the receiving water. So BOD test is indirect measurement of organic pollution present in the stream containing organic pollutants.          

     

  3. BOD is Biochemical Oxygen Demand which signifies the amount of Oxygen needed by the micro organisms like bacteria and virus to digest the organic matter in the waste water (or used water) measured after 5 days when the used water sample is incubated at 20 degree celsius. It was infact developed as a measure of microbial contamination of the River Thames in London about a century ago when the river was heavily contaminated with faecal matter and the citizens were bearing a severe disease burden due to this contamination. It took about 5 days for the contaminated water to travel its entire distance to the sea and thus the 5 day BOD.

    BOD is widely used for assessing the usabliity of used water for different purposes. It also indicates indirectly the amount of dissolved oxygen present in the used water  for the aquatic organisms to sustain and indicates the quality of surface waters, although DO directly indicates the quality of surface waters. Hope this gives an idea my friend.

  4. Here are a few FAQ's related to this as it is often an industry and Academic question by students.

    What is BOD?: https://mantech-inc.com/analysis-systems/biochemical-oxygen-demand/#1527777885794-d64aac38-1a98

    What is COD?:   https://mantech-inc.com/analysis-systems/chemical-oxygen-demand/#1527776540240-b46f8151-8476

    What is the difference between BOD and COD?:  https://mantech-inc.com/analysis-systems/chemical-oxygen-demand/#1527776540490-440adc81-12c4

    What is a faster and green way to measure BOD5 vs 5 days?  PeCOD:   https://mantech-inc.com/analysis-systems/chemical-oxygen-demand/ 

    Good luck! Robert

  5. It appears that there is a substantial misunderstanding of the BOD.  It is a measure of the oxygen consumed (respiration) by bacterial acclimated to a particular waste stream.  The word acclimated in one of the most important parts of the definition.  In order to get a correct measure, one needs a seed bacteria acclimated to the waste stream.  I would suggest that you may want to look up the definition in Standard Methods by AWWA, WEF, etc. It may also be in SW846 but I'm less sure of that location.

     

  6. I think it is  meant as a  measure of the organic matter content in wastewater. In any case microorganisms(bacteria) can be added to improve digestion of organic matter if need be.

  7. The following link may assist  https://www.linkedin.com/pulse/what-difference-between-bod-cod-ben-ohlmeyer/

  9. Organic matter... If you compare COD and BOD numbers... you will learn how much is Organic and how much are inorganic. These are important numbers to evaluate if waste is suitable for Biological Treatment or not, or what pre-treatment required. www.eecusa.com

     

  11. Hi,

    the analogy to car fuel consumption in order to get from A to B might be a good one. This is not only a function of the geographic position and height differences, as one could assume. Additionally, this is a function of car condition, driver's style, air quality, weather, traffic jams, etc.

    The same way BOD reflects the amount of oxygen needed to get the sludge treated as desired (A to B). 

    I hope approach was quite poetical  :) 

  12. BOD Measures the pollutant load due to biochemically degradable substances by analyzing the oxygen consumed by aerobic bacteria.

     

    Definition : BOD is a measure of the oxygen required by micro-organisms whilst breaking down biologically degradable organic matter.

    1 Comment

    1. The measure of BOD and COD is an indicator of how healthy your water is.  It is used as a test of water quality.

  13. The BOD is the parameter for the concentration of easily biodegradable organic compounds in the sample. It is expressed as the amount of oxygen that is consumed by aerobic microorganism to degrade these compounds.

    It can be measured as total, which means no filtration or cetrifugation of the sample - or as disssolved proportion of the total amount, then you have to filtrate the sample before measuring.

    The corresponding parameter for all (total) amount of organic (or oxidizable) compounds in the sample is the COD. In general the BOD is around 50% of the COD in case of pure domestic wastewater samples.

  15. Hello,Very good question.Indirectly BOD means both 1 &2 and oxygen content,

    Five-Day Biochemical Oxygen Demand (BOD5): BOD5 is defined as the amount of oxygen required by bacteria to decompose organic matter for a specified time (usually5 days) under aerobic conditions. The amount of oxygen reported with this method represents only the carbonaceous oxygen demand (CBOD) or the easily decomposed organic matter. BOD5 is commonly used to measure natural organic pollution

    Chemical Oxygen Demand (COD): COD is defined as the oxygen equivalent of the organic portion of the sample that is susceptible to oxidation by a strong chemical oxidant potassium dichromate K2Cr2O7,

    2 Comments

    1. So, can we conclude that high BOD shows High concentration of microorganisms and organic matter, both

      ?

    2. Not quite correct.  BOD5 is the amount of oxygen consumed by bacteria over exactly a 5-day incubation period at 20 deg C in the dark.  It represents both carbonaceous and nitrogenous (due to ammonia present) oxygen demand.  CBOD5 is the "Carbonaceous" component of BOD5.  Letting the test run for 20-days results in a greater oxygen demand and is referred to as Ultimate BOD; however, depending on the biodegradability of the organic matter present, aerobic biological decomposition may continue past 20 days.  It is an estimate of the amount of biodegradable organic matter and is used to determine the oxygen supply requirements for aerobic treatment, as well as the oxygen sag due to treated effluent discharged into a receiving water body. 

  19. This is a great question.  My understanding is that BOD is a measure of the organic material in a wastewater that can be digested or degraded by micro-organisms such as bacteria, fungi and the like.  The organic material can be dissolved in the wastewater, like sugar in coffee or it can be in particulate form.

    1 Comment

    1. Spot on Andrew. BOD measures the amount of oxygen used by microorganisms in metabolizing the organic matter. It is an indirect way of measuring the organic matter in the water.

      Commented on by

  20. BOD measures amount of oxygen needed by microorganisms to break down the organic matter in wastewater sample.

     

    2 Comments

    1. Ben: The link is not working

    2. I've read it in Metcalf, but still it's vague to me.