Evaluating the potential of a hybrid baffled reactor for simultaneous organic matter and nitrogen removal of dairy wastewater

Abstract This work designed and assessed the performance of a structured-bed hybrid baffled reactor (SBHBR) with anaerobic/anoxic chambers, treating different dairy wastewater. The anoxic chambers in SBHBR were exposed to intermittent aeration for the simultaneous removal of organic matter and total nitrogen (TN) under a low COD/TN ratio. The hydraulic retention time (HRT) in SBHBR was 48h, with 16.3h in the anoxic zone, where intermittent aeration was implemented, consisting of 60 minutes of aeration and 30 minutes without aeration. The COD/TN ratios tasted were 2.1 ± 0.6, 0.84 ± 0.5, and 0.35 ± 0.1 in the inlet of the anoxic chambers. The SBHBR provided COD removal efficiencies above 90% in all experimental stages. The relevant results achieved in this research regarding carbon and nitrogen removal efficiencies were obtained in stage III. The SBHBR achieved a TN removal efficiency of 82.3 ± 11.4% during this stage. The nitrification and denitrification efficiencies were 85.9 ± 17% and 85.2 ± 9%, respectively, resulting in the anoxic zone TN removal efficiency of 74.6 ± 14.7% with a C/N ratio of 0.35 ± 0.1. Stoichiometric calculations based on nitrogen removal and the C/N ratio required by the denitrification process were used to corroborate the activity of bacteria that perform the anammox pathways as their main mechanism.