ADVANCED OXIDATION DITCH DESIGN MEETS STRICT EFFLUENT REQUIREMENTS

The Ripon, Wisconsin wastewater treatment facilities needed upgrading to comply with new effluent requirements for BOD and TSS, and to provide reliable nitrification. An oxidation ditch system was selected from the several process alternatives evaluated based on ease of operation and capital costs. The proposed oxidation ditch system included separate basins for biological phosphorus removal, automatic dissolved oxygen control system utilizing oxidation-reduction potential (ORP) probes, and deep final clarifiers with energy dissipating inlets. ORP monitoring and set points were used to control the speed of the aerators for matching oxygen demand. These same probes were used to identify periods of high organic loadings and automatically control urea feed rate.The oxidation ditch system was started up in May 2003 and has been reliably achieving the stringent effluent requirements, as well as producing an effluent low in total nitrogen. The oxidation ditch process provides for automatic control of dissolved oxygen, denitrification, supplemental nitrogen feed, and improved biological phosphorus removal.