Oxygen transfer in clean and process water for draft tube turbine aerators in total barrier oxidation ditches

Total barrier oxidation ditches (TBODs) have been installed over the past 5 years in the U. S. under the inno vative provisions of the U. S. Environmental Protection Agency (EPA) Innovative and Alternative (1/A) Technology Construction Grants Program. One I/A feature of this system is the claimed energy savings due to high oxygen transfer efficiency of draft tube submerged turbine aerators (DTTAs). In an effort to evaluate the oxygen transfer performance of DTTAs in the TBOD con figuration (with J-tube extenders to transfer aerated mixed liquor to the downstream side of the barrier wall), full-scale testing pro grams were conducted at two locations using a variety of clean and process water testing techniques. In clean water, the American Society of Civil Engineers (ASCE) sanctioned testing procedure was used and compared to the radioactive tracer (radiotracer) procedure and a dissolved oxygen (DO) mass balance across the DTTA/J-tube assembly. The radiotracer procedure was also used in process water testing and compared to the off-gas procedure and a long-term mass balance on oxygen demanding material. All test methods agreed very closely, indicating that the ASCE procedure can be used in noncomplete mixing geometries, such as oxidation ditches. The precision of the various methods was different. Specific recommendations are made to better adapt the ASCE procedure to this geometry. J. Water Pollut. Control Fed., 61, 1449(1989).