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The BIG Problem with Analyzing for Chemical Oxygen Demand

When a project manager asks that a Chemical Oxygen Demand analysis be performed at Manchester lab, the response is usually, "Do you really need it or can you get by with some other test to give you the information you need?" The current EPA-approved method (410.4) used to analyze for Chemical Oxygen Demand (COD) is a fairly simple and reliable test so why would the COD analyst wish to discourage requests for this analysis? The answer lies not in the test but in what is left behind as waste. Reagents containing sulfuric acid, silver, chromium, and mercury are added to each sample before COD analysis. The waste from the analysis is viscous and extremely acidic because of the sulfuric acid. To be safe enough to ship, the acid in the waste must be neutralized. In order to neutralize the sulfuric acid in the waste effectively, the waste must be diluted 5 to 10 fold producing 5 to 10 times more hazardous waste than originally collected.

Incinerating companies that dispose of hazardous waste charge by the drum - the more the volume to be disposed of, the more the cost. Furthermore, waste which contains more than 200 parts per million mercury, which COD waste does, cannot go to an ordinary incinerator but must be taken to one of the few (and more expensive) retorting incinerators. This type of incinerator captures mercury rather than releasing it to the atmosphere.

The "simple and reliable" COD test is actually a time-consuming, hazardous, and expensive analysis when the disposal of the waste produced by the analysis is considered. An alternative COD method has recently come on the market which uses manganese as the catalyst and produces no hazardous waste. Unfortunately, it is not an EPA-approved method. If use of an EPA approved method is not essential, then this alternative may just fit your needs while preventing pollution at the source.

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URL: http://yosemite.epa.gov/R10/LAB.NSF/Programs/COD