Chemical Oxygen Demand (COD)

Chemical Oxygen Demand (COD), and its cousins Biochemical Oxygen Demand (BOD) and Carbonaceous BOD (cBOD), are essentially measurements of energy. They are the energy contained in the molecular bonds of the carbonaceous and nitrogenous organic substances in a wastewater stream.

Organic material is food for microbes; these microbes break the bonds and consume the energy released in the process. In an aerobic environment, the breaking of bonds consumes oxygen. Thus, the profile of types and quantities of molecular bonds in the molecules in the wastewater stream determine its “oxygen demand.” The classic BOD5 test is one way to estimate the potential of waste to consume oxygen. It involves seeding a sample with live microbes, incubating and waiting for five days, then reading the oxygen depletion to gauge the result. This method is time-tested, being in use for over 100 years, but it’s messy, imprecise, and most importantly, slow. The time delay from sample to results means that test results are useless for detecting transient problems or engaging in real-time process control.  Fortunately, ZAPS Technologies has an alternative to this slow process.

Hybrid Multispectral Analysis (HMA) provides a rapid and precise technique for characterizing the driving force behind oxygen demand in a real-time basis. In the HMA approach, high intensity light is used to identify molecular bonds and particles in the sample stream characterizing the potential demand of the oxidants and oxidizers present. The HMA method’s use of light allows for a very rapid and precise characterization of the sample stream without the need of surrogate microbial seeds or other sample disruptions. The end result is a more continuous, direct, and efficient form of monitoring.

  • Parameter Detection Range/Sensitivity Accuracy
    Chemical Oxygen Demand (COD) 0.7 to 1400 mg/L ±6%

  • To learn more about the optical approach used by the LiquID to measure COD please read the How It Works – COD located in the Library and Resources section of our website.
  • Please Contact Us if you have additional questions about measuring COD or general inquires into the LiquID Station.