Experience from Start-up and Operation of Deammonification MBBR Plants, and Testing of a New Deammonification IFAS Configuration

A single-stage deammonification process utilizing biofilms on moving carriers in a mixed reactor (ANITA™ Mox) is studied. Partial nitritation and autotrophic N-removal occur simultaneously within the biofilm. Ammonium Oxidizing Bacteria (AOB) oxidize NH4 to NO2 in the aerobic zone of the biofilm (i.e. external biofilm) while Anammox bacteria (AnAOB) located in the anoxic zone of the biofilm (i.e. internal biofilm) consume NO2 produced by AOB together with the excess NH4. The process is implemented at full-scale as a Moving Bed Biofilm Reactor (MBBR) to treat reject water from dewatering of digested sludge. Biological startup was accelerated using a seeding strategy. N-removal rates up to 1.2 kgN/m3react.d were observed. The achievable rate is influenced by substrate transport inside the biofilm. One possible strategy to increase the N-removal is to use Integrated Fixed-Film Activate Sludge (IFAS) to separate the nitritation and anammox reactions spatially, allowing the AOB to grow in suspended phase to better utilize DO, while allowing the biofilm to specialize in AnAOB reaction to achieve higher rates. A lower bulk DO can be used in this mode. Results from full-scale ANITA Mox MBBR treating sidestream effluent are presented together with preliminary ANITA Mox IFAS results from a full-scale prototype showing an increase in N-removal rate of up to 3 times that usually achieved in pure MBBR configuration.