Measuring Dissolved Oxygen (DO) with IoT

Dissolved Oxygen (DO) is perhaps one of the most critical indicators of water quality. IoT (Internet of Things) dissolved oxygen sensors are used to accurately measure the oxygen content in water and transmit the results in real-time back to a central database, cloud or water monitoring platform.

Dissolved oxygen refers to the level of free oxygen present in the body of water; oxygen is vital for the survival of fish and other aquatic lifeforms. The ability to automatically and accurately measure DO in a body of water using IoT equipment offers several advantages over traditional methods.

How does oxygen get into the water?

Oxygen can enter a water system in several ways, but these methods are generally categorised as surface-aeration and sub-surface aeration.

  • Oxygen from the atmosphere can dissolve and mix into the water’s surface. Examples of atmospheric surface aeration could include the wind disturbing the surface of the water, movement from streams, waterfalls or similar flows of water.
  • Algae and other underwater grasses create oxygen through photosynthesis and will release this into the water.  Oxygen is then used by fish and also important aerobic bacteria that can break down excess nutrients in the water.

What is the right level of Dissolved Oxygen?

As previously mentioned, Dissolved Oxygen is a critical component of any healthy aquatic system or watercourse. Therefore it is essential to ensure DO levels are optimal. Dissolved oxygen in water can range from 0-18ppm (parts per million), while a healthy aquatic system should have DO levels of around 5-6ppm.

Local authorities, environment agencies and utilities all have a responsibility to measure DO levels regularly. Fishing pond operators and fish farms are similarly interested in maintaining healthy levels of dissolved oxygen.

IoT Dissolved Oxygen Sensors (Libelium)

The Libelium Plug & Sense Smart Water and Smart Water Xtreme support two types of IoT sensors that can be used to measure dissolved oxygen in the water.

  • Smart Water – Dissolved Oxygen Sensor. This is a galvanic cell sensor that can measure DO in the range 0-20mg/L with an accuracy of ±2%. The sensor produces a voltage proportional to the dissolved oxygen in the solution. The sensors include a 5m cable.
  • Smart Water Xtreme – Optical dissolved oxygen and temperature sensor probe. The OPTOD probe uses luminescent optical technology that is better suited to long-term or remote IoT monitoring of dissolved oxygen. The OPTOD probe is highly accurate, even in low-flow water systems or with low concentrations of dissolved oxygen