Installation of a bioelectrochemical system as a pre-cleaner in a constructed wetland with higher pollutant loading under continuous mode

Abstract

In this study, two-phase continuous vertical flow constructed wetlands were installed with a pre-cleaner bioelectrochemical system for the removal of NH₄⁺-N (60.41–85.78%), NO₃⁻-N (25.55–35.18%), TN (57.80–84.65%), TKN (37.24–70.08%), PO₄³⁻-P (38.89–63.40%), SO₄²⁻ (49.53–76.06%), and COD (25.83–74.70%) from municipal wastewater. The non-attainment of breakthrough points for PO₄³⁻-P shows its efficient removal by the matrix as insoluble PO₄³⁻-P. The flux of the electron acceptor species was inverse to each other in the pre-cleaner bioelectrochemical system (ME-I) and the constructed wetland bioelectrochemical system (ME-II-CWs). The functionalities and the change in the morphology of the matrix were evaluated using FTIR and SEM-EDX analysis. Fine globular structures were observed in cavities and the smooth surface of the fresh iron scraps (ISs) changed to a rough surface. The peeling was evenly distributed on ISs' surface after wastewater treatment. The iron contents decreased in iron scraps' surface by 47.33%, while it was deposited in the activated carbon layer, as inferred from the increase in its level by 5.99%. The application of a higher applied potential enhanced the COD reduction efficiency of the ME-I system. The surface incorporation of O contents to 48.08% from 18.93% in the granular activated carbon improved its pollutant-capturing behavior. The results of the present study showing the combination of CWs with the bioelectrochemical system is a promising technological approach in terms of wastewater treatment.