Insights into the spatial effects of carbon source type on oxygen mass transfer mechanism and microbial community characteristics

The dissolved oxygen (DO) concentrations in wastewater and biofilm under four types of carbon sources were explored to further reveal the mechanism of oxygen mass transfer (OMT). In aerobic fluidized bed biofilm reactor (AFBBR) system, microbial community composition and functional microorganisms were analysed to characterize the influence of OMT on microbial metabolism. The DO concentrations with sodium acetate, sodium propionate, glucose, and starch reached to 6.43 ± 0.36 mg/L, 5.92 ± 0.21 mg/L, 6.91 ± 0.50 mg/L, and 7.20 ± 0.43 mg/L, respectively. Differences in carbon source led to significant differences in wastewater and biofilms OMT efficiency. The oxygen transfer rate (OTR) under four types of carbon sources was in the order starch>glucose>sodium acetate>sodium propionate, but the parameters for diffusion dynamics [Db = (3.68 ± 0.09) × 10−6 cm2/s, Di = (3.26 ± 0.99) × 10−4 cm2/s, ki = (5.94 ± 0.16) × 10−3 cm/s, and LF = (2174 ± 72 μm)] in the biofilms were highest with sodium propionate. With sodium propionate and glucose, Actinobacteria was the dominant bacteria (60.3 % and 78.5 %). However, with sodium acetate and starch, the dominant bacteria was Proteobacteria (88.9 % and 45.0 %). Sodium propionate improved wastewater treatment efficiency by altering microbial community composition and metabolic functions. The average removal of CODcr, NH4+-N, TN, and TP reached to 93.1 %, 86.9 %, 81.3 %, and 57.2 %, respectively.