Design Considerations for a Nitrification-Denitrification Process Using Two Fixed-Bed Reactors in Series

This paper concerns design considerations (kinetics and hydraulic criteria) for a biological nitrification-denitrification attached culture process for sewage treatment. The treatment system is composed of two submerged filters. The first one, an anoxic reactor, denitrifies and retains wastewater suspended solids. The second one oxidizes organic carbon and ammonia nitrogen. It was found that the main parameter for the system is the recycle ratio since it sets the real hydraulic detention time in reactors and determines the quantity of nitrogen available to the denitrification process.