Optimized design of a stable, long term and robust attached growth mainstream partial nitritation system

Design strategy and mechanism of nitrite oxidation suppression of elevated loading rate partial nitritation system

“…Two-reactors in series partial nitritation MBBR system configuration were identified in the preliminary work of this study based on findings from Ikem et al (2023) to optimize the effluent concentration from the partial nitritation MBBR system for subsequent downstream anammox treatment. The experimental set-up consisted of two identical lab-scale MBBR reactors (2L each) operated in series ( Figure 1 ).…”

“…P N1 and P N2 were both equipped with a coarse bubble aeration system, with diffusers positioned at the base of the reactors to provide adequate DO in the bulk solution and allow sufficient mixing of the carriers. The airflow rates were maintained at 1.5 and 1L/min for P N1 and P N2 , respectively, as previous findings demonstrated that adjusting airflow above 1.5 L/min resulted in increased nitrite oxidation to nitrate ( Ikem et al, 2023 ). Moreover, P N2 had lower influent TAN concentration and fewer carriers than P N1 ; as such would necessitate a reduced airflow rate to limit nitrite oxidation.…”

“…The AnoxK™5 were seeded carriers harvested from a biological oxygen demand (BOD) removal municipal IFAS wastewater treatment system located in Hawkesbury, Ontario, Canada, and were operated in a single bench lab partial nitritation MBBR system operated at elevated TAN concentrations prior to this study. The reactors were designed at a target TAN SALR of 5 g TAN/ m 2. d, recommended as the optimum for the partial nitritation MBBR system based on the previous findings, as it demonstrated stable and steady performance as well as high partial nitritation rate (Schopf et al, 2019;Ikem et al, 2023). The TAN SALR in the nitrifying MBBR systems at ambient temperature are conventionally designed typically between 0.45 to 1.0 g TAN/m 2. d with respect to target effluent TAN concentrations (Hem et al, 1994;Odegaard, 1999;Young et al, 2017b); thus, the TAN SALR present in this study was significantly elevated (referred to as elevated TAN SALR) than conventional TAN SALR which would potentially allow operating high-rate partial nitritation and small land footprint system.…”

“…In recent studies, an elevated TAN loading rate, as a means of a passive and low operational design strategy, has been shown to achieve stable partial nitritation rates within a two-stage configured MBBR system (Schopf et al, 2019(Schopf et al, , 2021Ikem et al, 2023). Schopf et al (2019Schopf et al ( , 2021 achieved stable and robust partial nitritation at an elevated TAN loading rate of 6.5 g TAN/m 2. d in an MBBR system fed with TAN concentration of 125mg TAN/L, simulating TAN concentrations observed in industrial wastewaters.…”

“…In this system, stable partial nitritation was attributed to the morphological impacts resulting from operating at an elevated TAN loading rate that could allow for NOB activity to be effectively suppressed ( Schopf et al, 2021 ). Consequently, the feasibility of using this design strategy to achieve stable partial nitritation has been evaluated at conditions and TAN concentrations between 25 to 44 mg TAN/L typical for mainstream municipal wastewater ( Ikem et al, 2023 ). Ikem et al identified critical design parameters, a TAN surface area loading rate (SALR), a hydraulic retention time (HRT), and an airflow rate optimized for stable partial nitritation of a mainstream elevated loaded MBBR system.…”