Valorization of Dishwashing Scrubber as Biocarrier for the Enrichment of Anammox Bacteria Under Realistic Conditions

The hypersensitivity of anammox bacteria toward fluctuating temperature (seasonal) conditions significantly limits its real-world application. Biomass immobilization alleviates the impact of environmental shocks on the anammox process. In this study (291 d), a sequencing batch reactor engaging dishwashing scrubbers as model waste biocarriers and an amalgamation of activated, anaerobic, and anammox sludge (1:1:0.5 ratio) as inoculum (at influent pH 8.0) were deployed for the startup of the anammox process. Intriguingly, the SBR was run at ambient temperature (6–37 °C) at varying nitrogen loading rates (g N m−3 d−1) of 20, 30, 40, 46.4, 58, 60, 81.2, 92.8, and 116. Notably, anammox activation took place at ⁓247 d wherein the reactor performance improved and exhibited stable nitrogen removal (NH4+–N, NO2−–N and total nitrogen removals were 100, 99, and 72.04%, respectively). Additionally, post 279 days of reactor operation (280 – 291 d), the reactor demonstrated an average total nitrogen removal rate (g N m−3 d−1) of 88.2 at a maximum nitrogen loading rate (g N m−3 d−1) of 116. The 16S rRNA gene sequencing results revealed that Anammox bacteria predominated in the reactor, highlighting the fact that the reported increase in the percentage abundance of Candidatus Kuenenia at 266 d was exorbitantly higher (41.69%) than inoculum sludge (0.18%). Nitrospira (23.9%) and Nitrosomonas (4.32%), in addition to anammox, were found in high concentrations, suggesting presence of dissolved oxygen in the system.