Processing Magazine

DO Probe with Luminescence Technology

July 3, 2012

The newest model of Hach Company''s LDO® Probe aims to eliminate industry traditions by making testing more efficient. Measuring dissolved oxygen (DO) in wastewater applications is critical to optimizing the nitrification and denitrification processes, establishing stable waste degradation and monitoring plant effluent. Until 2003, operators could only measure DO using amperometric measurement techniques that were expensive to maintain and yielded low confidence. In 2003, Hach introduced the first probe that used luminescence technology to measure DO. This technology has recently been approved and added to the official federal register by the EPA for reporting DO in NPDES permitted outfalls. The Hach LDO probe uses a luminescent sensor to measure the concentration of dissolved oxygen in a solution. Molecules within the senor are excited by a blue LED and the oxygen in a sample causes them to relax. The higher the concentration of oxygen in a sample, the faster the luminescent molecules will return to their normal state.The sensor also takes into account the temperature of a sample, which has significant bearing on an accurate DO measurement. Each sensor cap is calibrated in the factory prior to shipping, so it can determine the relationship of life span, temperature and oxygen concentration resulting in a complete picture of what is happening in the facility.