After a decade of development: A profile of municipal drinking water plants utilizing a sidestream injection process

The technology of rapid ozone mass transfer followed by degasification, the GDT(TM) Process, was first introduced in 1995 by Mazzei et al. At the time of introduction, municipal ozone installations utilized a low concentration, air-fed ozone gas as a disinfectant in atmospheric contact basins fitted with fine bubble diffusers (FBD). Over the past decade, air-fied ozone has given way to highly concentrated, oxygen-fied ozone. The change to concentrated oxygen feed gas has increased concerns about the corrosive affects of high finished water dissolved oxygen (DO). Water treat- ment plants using oxygen fed ozone have reported finished water DO levels in excess of 20 mg/L, with some plants resorting to air sparging at the back end of the contact basin to restore finished water to atmospheric gas levels. However, the evolution to oxygen feed gas has also produced significant cost benefits. Operating an ozone generator oil oxygen increases its ozone production; reducing the size and capital cost of the generator needed to meet ozone output requirements. The use of a concentrated gas stream has also led to the development of side stream injection systems, which move the gas mixing out of the atmospheric basin and into the upstream pipeline (Neemann, 2002), resulting in a more compact contact basin design. Municipal water plants not having a CT requirement have streamlined one step further, by eliminating the ozone contact basin in favor of a sidestream injection Process. This paper reviews the technology of the GDT sidestream injection process and introduces 2 municipal water treatments plant (WTP) installations utilizing this process to remediate taste and odor compounds and as a method to reduce finished water dissolved oxygen concentrations.