Dissolved Oxygen Sensing in a Flow Stream using Molybdenum Chloride Optical Indicators

Dissolved oxygen concentration is considered the most important water quality variable in fish culture. Reliable and continuous (24/7) oxygen monitoring of dissolved oxygen (DO) in the 1-11 mg/L range would be of great benefit to the aquaculture industry. We briefly review selected DO sensors from both the Clark and optical sensor categories as well a comparing their differences, both advantages and disadvantages. We introduce our fiber optic technique for continuous monitoring of DO levels in a flowing aqueous stream. An inorganic molybdenum chloride compound was used as the optical indicator in the oxygen sensitive material. The reflection mode fiber sensor is based on the ability of oxygen to quench the red luminescence of the molybdenum chloride indicator. The advantage of our broad-band, optical dissolved oxygen sensor is shown and discussed.