High-throughput nitritation of reject water with a novel ammonium control loop: Stable effluent generation for anammox or heterotrophic denitritation

Abstract

This work presents a new control system for the nitritation of high-strength ammonium wastewater as reject water from sludge dewatering. It is based on three independent feedback control loops: (i) DO control by manipulating the aeration flow-rate, (ii) pH control with the addition of solid Na2CO3 and (iii) control of NH4+–N concentration in the reactor using the influent flow-rate as the manipulated variable. Its application in an activated sludge configuration with one reactor and a settler, demonstrated: (i) capability to achieve stable effluent composition with proper NO2-–N/NH4+–N ratio for anammox treatment and ii) possibility to obtain an effluent with full nitritation suitable for heterotrophic denitrification only modifying the ammonium setpoint. A nitrogen loading rate (NLR) up to 5.0±1.0gNL−1d−1 was stably treated using real reject water (T=30°C, pH=7.5) with a NO2-–N/(NO2-–N+NO3-–N) ratio of 99%. NLR reached up to 9.3±0.5gNL−1d−1 with synthetic wastewater.