Construction of continuous-flow electrodialysis ion-exchange membrane bioreactor for effective removal of nitrate and perchlorate: Modelling and impact analysis of environmental variables

A novel continuous-flow electrodialysis ion-exchange membrane bioreactor (EDIMB) was firstly established for the simultaneous and effective removal of nitrate (NO3-) and perchlorate (ClO4-) in water. The optimum operation conditions predicted by response surface method (RSM) were water-compartment HRT of 20 h, bio-compartment HRT of 15.5 h, voltage of 10 V and acetate dosage of 444.88 mg/L, contributing to NO3- and ClO4- removal of 93.13% and 92.81%, acetate utilization efficiency of 98.49% and total current efficiency of 60.93%, without secondary pollution caused by the residual carbon (the total organic carbon TOC in effluent < 2.4 mg/L). Herein, the removal of pollutants was positively correlated with water-compartment HRT and operation voltage, acetate utilization was negatively related with acetate dosage, and the total current efficiency was negatively with water-compartment HRT and operating voltage. The final effluent pH of system decreased with the increase of voltage, and basically remained neutral. Meanwhile, the biological reduction in bio-compartment could reduce the resistance of pollutant transmembrane migration, and thus enhance ion migration. Microorganisms were the key elements for pollutant migration, and water-compartment HRT and acetate dosage were the significant factors for succession of microbial community structures. Thauera, Azospir, Meso-rhizobium and Curvibacte were the main denitrifying bacteria/ perchlorate reducing bacteria.