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SOP for Operation and Cleaning of COD Digester

To provide a procedure for the operation of the COD Digester.

This procedure is applicable to COD Digester at XYZ Ltd.

Quality Control Chemist and above

Quality Control Head

  • Ensure that the instrument is clean and free from dust.
  • Keep the instrument 1 foot away from the wall.
  • Keep the instrument away from the washbasin or any water source.
  • Ensure that any solvent/chemical does not fall on the aluminum block when it is hot.
  • Use asbestos gloves while handling the hot tubes.
  • Do not try to remove the tubes from the COD block and keep it in the tube stand.
  • Do not try to remove the condenser tube when it is hot.
  • Switch OFF the instrument when not in use.
  • Calibrate the digital timer controller and heating sensor of the COD Digester once a year by the approved outside agency.

  • Disconnect the instrument from the electrical connection.
  • Clean the instrument with a soft cloth.
  • Clean the tubes as per SOP of Cleaning of Laboratory Glassware.

  • Connect the instrument to the main supply. Switch on the main supply.
  • The red-colored bulb will glow indicating the power supply is connected.
  • The orange-colored bulb will glow indicating the heater is on.
  • The orange-colored bulb remains on till the temperature is attained and will get switched off when the desired temperature is attained.
  • Adjust the required temperature and time with the help of keys given on the digital control panel.
  • Press the SET key.
  • The display will show SP for temperature.
  • Set 150°C temperature with the help of the up and down key.
  • Again press the SET key.
  • Display will show soak time.
  • Set 2.0 Hours time with the help of up and down key.
  • In soak time parameter the digits before decimal are hours & after decimal it is minutes. i.e, (hh:mm)
  • Fill 30 ml of the content of sample in each tube and tightly close with condenser tube.
  • Place 30 ml filled tubes in the aluminum COD block of COD Digester for 2 hours.
  • After completing the cycle, digital alarm for 10 seconds will produce and heating will get automatically stopped.
  • Allow to cool at room temperature.
  • Perform further analysis as per Specification of Chemical Oxygen Demand.

COD: Chemical oxygen demand
SPSet point
°CDegree Celsius
hh: mm
Hours: Minutes



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