Talk:Biochemical oxygen demand

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The beginning isn't clear[edit]

I am reading this as an environmental advocate working to better crack down on water polluters, and am trying to understand what BOD is, but the beginning of this doesn't quite get me there. What is it measuring? Is it a thing? A rate of consumption? Is it better to have a higher number or a lower number?

So is the article telling me that if you have a BOD of 5 mg/L, that means the water consumers approximately 5 mg/L of OXYGEN in a five day period? You want this to be as low as possible, right, because you want more oxygen in the water so fish and other aquatic life can use it, yes? No? BradyDale (talk) 19:45, 22 February 2011 (UTC)

Yes, lower BOD indicates better water quality. BOD is an indicator of oxygen-demanding substances in the water body, i.e. pollution. If the substances suck up a lot of oxygen, there's less oxygen available for fish and other critters. Here's a good overview: "Dissolved Oxygen and Biochemical Oxygen Demand" (US EPA). I agree that the beginning of this Wiki article is a bit technical. A bit of "plain English" editing would help. Moreau1 (talk) 06:03, 23 February 2011 (UTC)

Environmental athourities set BOD limits on dicharge water into receiving waters,based on the recieving waters ability to aborb the oxygen uptake. It is a bit more complicated than just saying the discharge water has a BOD of 5 mg/L. You have to know the concetration of reagent water vs water sample that was used, as well as the flow of the discharge water in order to calculate the oxygen demand. — Preceding unsigned comment added by (talk) 23:29, 30 July 2011 (UTC)

It is easy to misunderstand the importance of total mass when focusing on concentrations. Ten gallons of water with 10 mg/L BOD has just as much impact on a stream as one gallon with 100 mg/L BOD. Multiplying waste flow by concentration clarifies impact on the stream receiving the waste. The ultimate oxygen demand of waste is not typically considered by USEPA unless the stream receiving that waste is already demonstrating evidence of low oxygen problems. A BOD limit of 30 mg/L will typically be required for streams without demonstrated oxygen deficits -- even if the stream could re-aerate a greater oxygen demand. When lower BOD limits are set for streams, those limits are usually set by mass rather than concentration. That BOD limit will often be set as a 5-day BOD (hopefully based on correlation with ultimate BOD) because the 5-day test protocol is so widely practiced.Thewellman (talk) 01:42, 31 July 2011 (UTC)
But please also bear in mind that comments applicable to the USA are not necessarily applicable elsewhere. European standards are not based purely on available dilution and are expressed as concentrations . The standards also incorporate maximum permissible limits for BOD in waste irrespective of pollution.
As an aside, I note also your edit regarding the choice of temperature for the BOD test and the reference quoted for that. I don't have access to the source quoted but my recollection was that the Royal commission on sewage disposal chose the BOD 5 test in 1908 and selected the temperature of 68oF as the maximum likely temperature of a British river. It would be worth investigating your source and seeing whether they quote an original reference for their assertion - it wouldn't be the first time that authors of a text book have made assumptions rather than checked out all the references.  Velella  Velella Talk   12:12, 31 July 2011 (UTC)
My response to an earlier comment regarding regulatory procedures was not meant to imply USEPA procedures were any more widely utilized that the previously stated procedure. My reference was silent as to the time and location of the initial laboratory work, but indicated the temperature approximated "...a median value as far as natural bodies of water are concerned." I have little doubt the safety factor of using the temperature of greatest concern would have been a good rationalization for temperature selection; but I haven't been able to verify that from my references.Thewellman (talk) 17:59, 31 July 2011 (UTC)

BOD30 in Australia?[edit]

UK uses BOD5, Am I right in thinking that Austrailia uses a BOD30 to reflect the residence time in Austrailian rivers?

I don't know about Australia, but in the US, BOD30 is frequently used to gather more information on the wastewater being analyzed, often with dissolved oxygen (DO) graphed against time. It becomes burdensome for routine use because of needing 5 or 6 times as much incubator space for a month's daily samples than BOD5. -- WCFrancis 18:26, 6 May 2005 (UTC)

these 2 paragraphs don't fit[edit]

The following 2 paragraphs used to be in the article, but they were so poorly intregrated into the article that it made the article very confusing to read. These paragraphs are preserved here so that someone can re-integrate the worthwhile bits of them:

However, the act itself without proper technical measures could not stop and prevent further pollution of the rivers. From this point of view, the formation of the Royal Commission on Sewage Disposal in 1898 can be understood as the milestone in the development of wastewater treatment technology. This commission co-ordinated the activities leading to better understanding of factors affecting the water quality in receiving waters and to evaluation of new treatment procedures. One of the best known outputs of the commission is the BOD5 test recommended in 1908. The famous "30:20 + full nitrification" effluent standard was adopted in 1912 which was a great challenge for the development of wastewater treatment processes capable of meeting this standard.

The Royal Commission on River Pollution which was established in 1865 and the formation of the Royal Commission on Sewage Disposal in 1898 led to the selection in 1908 of BOD5 as the definitive test for organic pollution of rivers. Five days was chosen as an appropriate test period because this is supposedly the longest time that river water takes to travel from source to estuary in the UK. In 1912 the commission also set a standard of 30 ppm BOD5 as the maximum concentration of permitted in sewage works discharging to rivers provided that there was at least an 8:1 dilution available at dry weather flow. This was contained in the famous 30:20 +full nitrification standard which was used as a yardstick in the UK up to the 1970s for sewage works efluent standard.

ike9898 13:39, Apr 27, 2005 (UTC)

This is good historical information and should not be lost. I'll give it some thought. Maybe a subheading on the historical perspective. -- WCFrancis 18:30, 6 May 2005 (UTC)
Done - only one year late ! Velela 14:26, 29 June 2006 (UTC)
Yes, I thought this was good historical information, too, and was somehow helpful in getting this whole page, which is rather hard. BradyDale (talk) 19:53, 22 February 2011 (UTC)

Other info[edit]

Additional info on Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) being used as substitutes should also be included. -- WCFrancis 18:30, 6 May 2005 (UTC)


There should be some discussion of standards used in BOD. That is the glucose-glutamic acid standard used to check DI water quality.

On a related noted... I couldn't follow the part about UK versus US standards. Mainly, which is more rigid? Which goes farther? I can't tell. BradyDale (talk) 19:55, 22 February 2011 (UTC)

Please correct pristine water reference[edit]

How can modern pristine waters have a BOD of 1 or less when the Limit of Detection is 2 mg/L???

Because the limit of detection relates to conventional run-of-the-mill analysis. By using larger volumes, more precise methodologies and more replicates it is possible to extend the limit of detection to below the 1 mg/l level. It is always worth bearing in mind the statistical as well as the biological and chemical limitations of tests such as BOD. Velela 14:17, 29 June 2006 (UTC)


I revert a copyvio of this page. Mateus Hidalgo 02:15, 7 August 2007 (UTC)

BOD bottle[edit]

There is no information about which bottle should be used when a standard test is held. 300ml BOD bottle, right? Raymond "Giggs" Ko 07:01, 2 November 2008 (UTC)

The BOD test is not bottle dependent, many labs use a 500ml bottle for the samples under test if using a titration method for determination or as small as 50ml if using an electronic DO probe, but the size of the bottle is only a function of practicality and space. Use of a too small bottle might lead to more variable results and a too large bottle might not fit in the incubator. Velela (talk) 10:04, 2 November 2008 (UTC)

Calculation of BOD[edit]

Could the BOD of a diluted sample be calculated by (Initial DO-Final DO)/Decimal fraction of the sample? Raymond "Giggs" Ko 07:08, 2 November 2008 (UTC)

No. Sample size is not relevant. E.g. if original sample is diluted 1:10 with de-ionized water and has a concentration of 9 mg/l at the start and has a concentration of 5 mg/l at the end of 5 days and the control shows a drop of 1 mg/l over the same period , then the BOD of the water in the original sample = (9-(5-1)) *10 = 50 mg/l. Velela (talk) 10:09, 2 November 2008 (UTC)

(9-5-1) = 5? —Preceding unsigned comment added by (talk) 13:24, 23 April 2009 (UTC)

Yes you are right - one set of parentheses missing (now corrected above) - the result is still the same!  Velela  Velela Talk   17:19, 23 April 2009 (UTC)

Typical BOD5 values[edit]

This section is misleading and vague. First, it doesn't claim what these typical BOD5 values are for (though it would seem that we are discussing municipal sewage), nor does it note that we are discussing BOD5. It neglects whether these are carbonaceous or total BOD values, nor does it source the typical BOD5 values (they aren't from the Standard Methods 21st Edition, anyway). Moreover, it would be quite a pristine river to have 1mg/L BOD5; there are natural waters with 15mg/L mean BOD5 values. There is far too much variance for this even to be considered. It would be like claiming a specific sodium content for water: the dead sea and a freshwater lake will not be even remotely comparable.

Worse yet, the BOD5 is a qualitative test -- a fact neglected in the article. This is an essential detail if any value can be assigned to these "typical" BOD5 values. I'm going to get around to cleaning this article up a bit, but I'd like some kind of sourcing on these and a reason not to just outright remove the section. (talk) 20:00, 22 June 2009 (UTC)

BOD is a quantitative test. You end up with a number as a result which is indicative of the biodegradable organic matter in the sample. Do not edit if you do not know what you are doing.Cross Reference (talk) 17:54, 28 January 2010 (UTC)

I signed out the Sawyer, McCarty & Parkin textbook that was the reference for that section and I could not find any of the cited information in it. Did the author cite the wrong source? Erinboberin (talk) 18:59, 10 May 2010 (UTC)

I wrote the original text based on 30 experience managing the quality of the aquatic environment. Somebody else appended the reference, but it is a reference I don't have access to. I am sure that I can find a valid reference for these figures - it may take a while though...  Velella  Velella Talk   13:20, 31 July 2011 (UTC)

Focused too much on analytical methods[edit]

This article is very well written in terms of the scientific methodology for testing BOD (similar to the CBOD) but I think there are some issues with nuance, and a lack of general info on BOD.

While those of us in water quality often refer to BOD/CBOD(5) as tests or methods, what we really are referring to are the methods for assessing BOD/CBOD. BOD is a measure of the demand for oxygen resulting from biochemical processes. There are test to measure it, but it is not the tests. This shoudl be made clear. The way the lead/content is written, it states that BOD is the method/test. We should really start out with a basic description of what BOD is, why it's an important measure, etc, and then spend some time talking about how it's measured.

The EPA gives a good example here (3/4 of the way down page)

The page currently reads as if you were talking about eggs, but only talked about how to cook them. There's a lot more to the subject:) I will try to get back and add detail, but please, in the mean time, I hope someone else will do so as well. Jbower47 (talk) 22:10, 6 June 2011 (UTC)

Language Sidebar of Article Missing[edit]

Why is the language sidebar of the article missing? There are quite a few languages that have an article about BOD (العربية, Català, Čeština, Español, Eesti, Euskara, فارسی, Français, Galego, Bahasa Indonesia, Italiano, 日本語, 한국어, Nederlands, Norsk nynorsk, Norsk bokmål, Polski, Português, Русский, Srpskohrvatski / српскохрватски, Српски / srpski, Svenska, தமிழ், Türkçe, Tiếng Việt, 中文). In those articles the english article does also miss in the sidebar.--Nix schlecht (talk) 10:22, 4 January 2014 (UTC)

Is biological oxygen demand the same as biochemical oxygen demand?[edit]

I think the use of BOD to mean Biological Oxygen Demand [as in Elisabeth v. Munch's excellent powerpoint presentation: Characteristics of Urine, Faeces and Grey Water] and Biochemical Oxygen Demand [which is how BOD is defined here] needs tidying up. My understanding is that Biochemical OD is the sum of Biological OD and Chemical OD. Biological OD is due to the action of bacteria whilst Chemical OD is due to the oxidation of chemicals without the involvement of living organisms. AndrewJohnWarren (talk) 09:49, 17 March 2016 (UTC)

No "Biochemical " is correct and it does not refer to the sum of biological and chemical ODs. Please do the mathematical addition for results from any sample of water to demonstrate the fallacy of that belief. COD typically includes the whole of BOD plus the oxygen demand of materials incapable of biochemical oxidation. Summing them would make no sense.  Velella  Velella Talk   09:59, 17 March 2016 (UTC)

OK, thanks for that. It seems to remain the case that BOD stands for two different things with different values....?AndrewJohnWarren (talk) 11:21, 17 March 2016 (UTC)

No, it's just two different terms used for the same thing: biological oxygen demand is the same as biochemical oxygen demand. I actually would always call it biological oxygen demand. EvMsmile (talk) 13:30, 17 March 2016 (UTC)
The term was coined by the Royal Commission on Sewage Disposal in setting out the 30:20 standard. Whilst we may all agree that the word "biological" better conveys the meaning, "biochemical" is the word used in the historical precedent. Regards (talk) 20:31, 17 March 2016 (UTC)

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