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Reuse of spent resin for aqueous nitrate removal through bio-regeneration

Ye, Ting, Wang, Ke, Shuang, Chendong, Zhang, Guang, Li, Aimin
Journal of cleaner production 2019 v.224 pp. 566-572
adsorption, anion exchange resins, biomass, denitrification, denitrifying bacteria, inoculum, ion exchange, nitrates, wastewater
Some commercial products of anion exchange resins have been used in removing aqueous nitrate, but their application has been limited by the spent resins and the brine-waste. In this work, the regeneration of nitrate-laden resin using denitrifying bacteria was investigated for the reuse of the spent resin without brine-waste discharge. The results indicate that the bio-regeneration contains two mainly processes of chemical regeneration (ion exchange) and bio-degradation (denitrification), in which the denitrification related to the inoculum amount was the limiting factor of bio-regeneration. The bio-regeneration time was reduced to about 4.0 h with increasing inoculum amount to 2.2 g VSS/L. It also reduced from more than 50.0 h–4.0 h with the decreasing resin amount from 5.0 g to 0.2 g in the saturation of 35.5 mg/g, and reduced from 12.0 h to 3.0 h with the resin saturation from 27.4 mg/g to 2.70 mg/g in the resin amount of 0.2 g under the inoculum amount of 2.8 g VSS/L. The comparation of bio-degradation rate between data with different resin amount and data with different resin saturation suggested that the spent resin with a high degree of saturation is favorable to bio-regeneration. The bio-regenerated resin can be reused with 11.6% of capacity loss in the initial 5 cycles and gradually reach a stable reusability. This decrease was attributed to the adsorption of protein-like substances onto resin rather than biomass attachment onto resin. This study proposes the reuse of spent resin by bio-regeneration in a reuse mode for the aqueous nitrate removal, with at least 87.5% reduction on the production of waste water from bio-regeneration process.