Morphological, kinetic, and microbial community characterization of anammox bacteria with different inoculations and biofilm types for low-ammonium wastewater treatment

Abstract

Granular anammox sludge treating high-ammonium wastewater and biofilm anammox sludge treating low-ammonium wastewater were inoculated in two identical reactors to treat low-ammonium wastewater. The morphological and microbial community characterizations were investigated. Kinetic models were applied to understand kinetic characterizations and predict reactor performances. Both types of sludge adapted well in 10 and 5 days with the average total inorganic nitrogen removal efficiencies >85%. The average particle size of the granular sludge decreased from 843 μm to 515 μm. The biomass and thickness of the biofilm sludge increased by 17% and 66% when NH4+-N, NO2−-N and temperature increased from 10 mg/L to 33 mg/L, <0.5 mg/L to 41 mg/L, and circa 13 °C to 35 °C, respectively. The granular sludge had higher maximum utilization rate constant and saturation value constant (16.393 and 12.934 mg/(L·h)) than biofilm sludge (1.017 and 0.080 mg/(L·h)), indicating the inherent difference of inoculations. The granular sludge inoculated from high nitrogen loading rate (NLR) (0.36 g-N/(g-VSS·d)) condition had the potential to withstand a higher NLR than that in present reactor (0.14 g-N/(g-VSS·d)). The results of Grau second-order model indicated that both reactors performed good nitrogen removal efficiency despite inoculations and types differences, and can predict the nitrogen removal efficiency well. Microbial community diversities deceased, but granular bacteria richness increased due to the lower free ammonium and free nitrous acid. The dominant anammox bacteria in the granular sludge shifted from Candidatus Kuenenia to Candidatus Brocadia. Candidatus Kuenenia was always the dominant anammox bacteria in the biofilm sludge.