[Bioregeneration of Anion Exchange Resin Used in Nitrate Removal]

Anion exchange resin is a feasible adsorbent for nitrate removal because of its high efficiency and cost-effectiveness, but brine regeneration complicates subsequent wastewater procedures. Bioregeneration degrades the nitrate from the nitrate-laden resin, which can decrease brine solution usage and waste discharge. In this study, based on investigation of the effect of carbon source, for example, glucose, sodium acetate, sodium lactate, and methanol, on bioregeneration, nitrate-laden resin was employed to investigate the effects of inoculum amount and salt concentration on bioregeneration with sodium acetate as the carbon source. The results showed that the bioregeneration process comprised chemical desorption and biological denitrification and was limited by the biological process. With increasing inoculum amount, the bioregeneration time was remarkably reduced. Nitrate on the resin could be completely biodegraded within 10 h when the inoculum amount (measured as VSS) was higher than 0.6 g·L^-1. Furthermore, higher NaCl concentrations improved the chemical desorption of nitrate, resulting in a sharp increase in soluble nitrate. However, the denitrification process of bioregeneration was also eventually limited by the biological process. When the concentration of NaCl was higher than 20 g·L^-1, bioactivity of the denitrifying bacteria was limited and the bioregeneration time increased to more than 10 h. The result of multi-cycle adsorption-bioregeneration experiment showed that the NO₃^--N adsorption capacity of bioregenerated resin was stable at 30-35 mg·g^-1.