Effective nitrogen removal in a two-stage partial nitritation-anammox reactor treating municipal wastewater - Piloting PN-MBBR/AMX-IFAS configuration

A novel partial nitritation-anammox (PNA) reactor configuration was piloted for 250 days. Primary effluent from full-scale municipal wastewater treatment plant was treated in a two-stage biofilm system incorporating innovative process control for cold partial nitritation. Partial nitritation was combined with carbon removal in a moving bed biofilm reactor (MBBR) to achieve high-rate treatment and nitritation was obtained with dissolved oxygen to total ammonium nitrogen (DO/TAN) ratio control and free ammonia (FA) for inhibition of nitratation. Effluent from MBBR was directed to an integrated fixed-film activated sludge (IFAS) reactor where nitrogen was removed via anammox. MBBR achieved partial nitritation at 2.0 ± 0.3 g-N m^-2 d^-1 and nitrogen removal in the IFAS reactor reached 0.45 ± 0.1 g-N m^-2 d^-1 (55 g-N m^-3 d^-1). The process performed well at 19 ± 3 °C with an average effluent total inorganic nitrogen (TIN) concentration of 11 ± 4 mg L^-1.