Attention:

Certain features of Sigma-Aldrich.com will be down for maintenance the evening of Friday August 18th starting at 8:00 pm CDT until Saturday August 19th at 12:01 pm CDT.   Please note that you still have telephone and email access to our local offices. We apologize for any inconvenience.

COD Measurement in Waste Water (Rapid-Digestion Method)

Prove InstrumentsPhotometric determination of chromate consumption subsequent to digestion in 20 min

COD Rapid-Digestion Method

According to the relevant standard (ISO 15705), the COD determination with cell tests is performed at 148 °C, since the COD/water mixture in the cell already boils at this temperature. Higher digestion temperatures are thus not appropriate in this case. The conventional boiling time is 120 minutes: However, as practical experiments have shown, most wastewater samples are already adequately digested within the space of just 20 minutes. Besides the standard method we therefore offer a COD rapid-digestion method that has the following advantages:

  • Standard-compliant digestion temperature (148 °C)
  • No additional investments are necessary, since standard thermoreactors can be used
  • Depending on the number of samples, the user can choose between thermoreactors with twelve or 24
    wells, meaning that a large number of samples can be processed simultaneously.

Sample Preparation

Both types of the thermoreactors allow entering of up to seven customised methods. Refer to the instructions in chapter 5.6.1 how to enter customised method in the instrument's manual.

Select and enter 148 °C digestion temperature as well as 20 min total heating time. Switch the thermoreactor to manual start in setup menu. Start preheating. If the final temperature 148 °C has been reached, the symbol S will be displayed indicating that the thermoreactor is in standby mode. Insert the prepared tubes and wait until the temperature has been equilibrated to 148 °C again. Then press run/enter key again to start the timer and heating cycle. If the 20 min heating time is over, take the hot tubes out of the thermoreactor and put it into a stand. Let cool down to approx. > 40 °C and swirl to mix the tube content. Let suspended solids settle and measure the value as per instruction of the photometer manual for the test used.

We know from our practical experience and from customers' response, that most of the wastewater samples will show identical results when using the 20 minutes digestion time instead of the 120 minutes digestion time.

Analysis

Determine with the below mentioned test kits.

Materials

     

Product 114560 is not compatible with Move 100.