Carbon to nitrogen ratios influence the removal performance of calcium, fluoride, and nitrate by Acinetobacter H12 in a quartz sand-filled biofilm reactor

Abstract

This study investigated the influence of different carbon to nitrogen (C/N) ratios on the bio-removal efficiency of aquatic pollutants like calcium (Ca2+), fluoride (F−), and nitrate (NO3-N) in a quartz sand-filled biofilm reactor (QSBR) to treat the low C/N wastewater using Acinetobacter sp. H12 at pH 6.50. The simultaneous bio-removal rate of Ca2+, F−, and NO3− reached 56.31%, 96.33, and 96.95 respectively. Nitrogen gas (N2) was produced with no evidence of N2O emission. Moreover, the morphological study of strain H12 and biological precipitates through SEM revealed that strain H12 provides the nucleation sites for microbially induced calcium precipitation to remove Ca2+ and F−. Besides, XPS and XRD peak spectra implicated that Ca2+ and F− were removed as CaF2 and Ca5(PO4)3F co-precipitates. The 16S rRNA sequencing analyses revealed that H12 belongs to Acinetobacter and has stronger MICP and denitrification potential as compared with other strains under low C/N conditions.