Iron (Fe) and manganese (Mn) are often found in groundwater. High levels can create aesthetic issues with drinking water including taste and odor problems as well as staining of water fixtures. A common method of removing these contaminants is to oxidize them and then remove the precipitates via filtration. Ozone is one of the oxidants employed in this application.
To measure the oxidation process, Oxidation-Reduction Potential measurements are taken using ORP sensors instead of direct measurement of the ozone residual. Hach Company (Loveland, CO), is developing a technique of measuring ozone in the Fe/Mn application using differential turbidity measurements, i.e. the amount fo turbidity before and after ozonation. This method take advantage of the formation of the Fe/Mn precipitates after oxidation to measure the amount of ozone present. The amount of precipitate formed should be proportional to the ozone in solution.
Hach’s research reported in Ozone Science and Engineering July-August 2010 shows that differential turbidity measurements are indeed proportional to ozone dose. In addition, testing also indicated that differential turbidity had lower maintenance requirements than ORP.