A new technology for simultaneous calcium-nitrate and fluoride removal in the biofilm reactor

In this study, a biofilm reactor containing Acinetobacter sp.H12 was established to investigate the simultaneous denitrification, the removal of calcium and fluoride performance. The main precipitation components in the reactor were determined by SEM, XPS and XRD. The effects of HRT (6 h, 9 h and 12 h), pH (6.0, 7.0, 8.0), influent F^- concentration (3 mg/L, 5 mg/L, 10 mg/L) on synchronously removal of nitrate and F^- and Ca²⁺ during reactor operation were studied. Optimum operating conditions were achieved with a nitrate removal ratio of 100%, F^- removal ratio of 81.91% and Ca²⁺ removal ratio of 67.66%. Nitrogen was the main gaseous product analyzed by gas chromatography. Extracellular polymers (proteins) were also identified as sites for biological precipitation nucleation by fluorescence spectroscopy. Moreover, microbial distribution and community structure analysis showed that strain H12 was the dominat strain in the biofilm reactor. And combined with the performance prediction of the reactor, strain H12 played a major role in the process of simultaneous denitrification, F^- and Ca²⁺ removal.