Measuring dissolved oxygen in water and why it’s important.

Posted in: Applications, Electrodes

Author: Amy Measor

Date Posted: 25/03/2021

Dissolved oxygen (DO) is a measure of how much oxygen is dissolved in water. It has important chemical and biological implications across a large range of applications that are vital for everyday life. We can study water sources to get an idea of the water quality and if it is suitable for the intended purpose.

Why is measuring dissolved oxygen in water important?

Dissolved oxygen comes from either the atmosphere or from photosynthesis by aquatic plants or algae. Higher levels of DO in a water source are more likely to support aquatic life, therefore monitoring levels is important across a range of settings.

Electrochemical DO sensors can be used for a range of research and regulation purposes including;

  • Laboratory testing
  • Ecological studies
  • Biochemical oxygen demand (BOD) testing
  • Long-term monitoring
  • Sample and spot testing
  • Process control

The data obtained can give vital information about safety, quality, waste, environment and ecosystems.

How to measure dissolved oxygen

One way to measure dissolved oxygen is by using electrochemical sensors.

Galvanic and polarographic are two examples of electrochemical dissolved oxygen sensors. In each sensor type the sensor is placed into the sample, and attached to a dissolved oxygen meter, instrument or datalogger. The calibration and measurement information will be displayed in ppm, mg/l or percentage saturation, depending on the instrument used.

Polarographic dissolved oxygen electrodes have a replaceable membrane and require some set-up and maintenance from the operator. They require some time to warm up when plugged into the meter, in order for the cell to polarise.

Galvanic dissolved oxygen electrodes are easy to use and require very little maintenance. They have a fixed membrane and do not require refilling.

Both sensors can have temperature sensors fitted, to provide automatic temperature compensation and give more accurate measurements.

To view our range of dissolved oxygen probes and other products visit our online store or contact one of our friendly team.

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