Tools of the Trade: COD Testing Equipment

Chemical Oxygen Demand (COD) is an important parameter for determining the amount of organic pollution in wastewater. Frequent monitoring of oxygen demand within any type of wastewater treatment system is beneficial to detect problem areas, efficiencies, or overloading. COD testing has an advantage over Biochemical Oxygen Demand (BOD) testing in that it is quicker than the five-day standard BOD test, and COD can be directly correlated to BOD.

Unfortunately, when samples need to be sent to an outside laboratory for testing with a substantial turnaround time, immediate adjustments to a treatment system cannot be made. In addition, frequent outside laboratory testing can become costly over time. Wouldn’t it be more convenient if COD tests could be performed onsite with immediate results?

Fortunately, COD is a parameter that can easily be tested in-house with the correct equipment and use of a small laboratory area. Hach Company produces a COD testing system that consists of reagent vials, a reactor (heating), and a spectrophotometer. A sample is mixed with the premeasured reagent in a vial and then heated in the reactor to oxidize and digest. The spectrophotometer is then used to determine the COD value colorimetrically. The testing process takes 1½ to 3 hours to complete and multiple vials can be heated at one time, saving on the processing time. In addition, the spectrophotometer can be used for testing a variety of other parameters with the use of different reagent vials.