To address the challenge of deep denitrification in wastewater treatment plants, this study innovatively constructed an integrated closed-loop process combining “biological-ion exchange-electrocatalysis-biological” to achieve efficient removal of nitrate. The nitrate removal rate using the Gandu composite bacterial agent reached 86%, with the effluent reduced to 14.0 mg·L −1 . After 180 min of adsorption on trimethylamine-loaded D301 resin, the treated effluent (14.0 mg·L −1 NO 3 − ) achieved a removal rate exceeding 94%, with the effluent concentration as low as 0.84 mg·L −1 , below the threshold for causing water eutrophication (1.0 mg·L −1 ) and regulatory standards (WHO < 10 mg·L −1 NO 3 − ), and consistent with the Langmuir model and the pseudo-second-order kinetic model. For high-salt regenerated solution (5000 mg·L −1 NO 3 − , 10% NaCl), the phosphate-modified foam iron-nickel electrode (P-FeNi-foam) achieved a nitrate removal rate of 97.61% within 6 h, with a small amount of byproduct NH 4 + , significantly outperforming microbial methods (15.3%) and Pd-Cu bimetallic catalysts (44.67%). This advantage stems from the O–H…OPO 3 structure on the electrode surface, which reduces the adsorption potential and dissociation potential of H 2 O, promoting the generation of hydrogen radicals from a kinetic perspective, inhibiting Fe corrosion, and thereby facilitating nitrate reduction. Additionally, the consumption of Cl − during the electrocatalytic process suppresses the formation of byproduct NH 4 + . This process achieves a total nitrate removal rate of 99.16% and creates favorable conditions for biological reuse by electrocatalytically consuming Cl − , forming a closed-loop treatment system. The integrated “biological-ion exchange-electrocatalytic-biological” process holds broad application prospects in the treatment of nitrate wastewater.
Zheng et al. (Sat,) studied this question.
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