Effective inhibition prevention strategy for the enrichment of anammox bacteria with low concentrations of substrates at 25 °C

Abstract

This work aimed to enrich anaerobic ammonia oxidation (anammox) bacteria, which can be potentially used in mainstream wastewater treatment systems for enhancing economical autotrophic nitrogen removal. Anammox bacteria were enriched in a sequencing batch reactor (SBR) with continuous feeding of ammonia and nitrite at 25 ± 2 °C. The results indicated that the concentrations of ammonia and nitrite at each moment ranged from 0 mg/L to 30 mg/L and 0 mg/L to 10 mg/L respectively, by adjusting the feed stream supply rate based on the reaction rate. Furthermore, the free ammonia (FA) and free nitrous acid (FNA) concentrations were controlled systematically at desired low levels of 0–1.96 mg/L and 0–2.94 μg/L respectively, to prevent substrate inhibition on anammox bacteria. Candidatus Kuenenia-anammox bacteria were highly enriched for approximately 4 months, as demonstrated by the proportion increased from a negligible value to 17.60 %. This promising operational mode proposed an available choice to enrich various microorganisms of expected functions, to accelerate reactor start-up and enhance biological efficiency.