AWWA WQTC64092

This presentation describes an innovative bench-scale method for determining ozone demand in test waters in the field along with three case studies to demonstrate the effectiveness of the method. Current industry practice for determining ozone demand is often calculated by comparing water quality data with demand values from literature, a method that can underestimate demand if unknown or unquantified contaminants are present. The method described in this paper is an effective and efficient way of accurately ascertaining ozone demand for properly sizing ozone treatment equipment. The method described in this paper uses an onsite ozone generator and distilled water to quantify gas transfer relationships. The ozone is sparged into the distilled water in multiple trials of varying duration with the ozone concentration being measured at the end of the sparging using the standard indigo method. A curve of measured ozone versus time is used to develop transfer equations relating ozone transfer to ozone concentration. These relationships are then used to ascertain gas transfer into the test water during ozone sparging tests and subsequent ozone residual testing. The results of these tests allow a calculation of ozone demand in the test water. Three case studies are presented to demonstrate the method. Includes tables, figures.