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[Display omitted] • Heavy metals and microplastics were treated through interpenetrating bipolar plate electrocoagulation (IBPE). • Changes of current density and initial pH value were proved to affect the experimental results. • Reaction mechanism of IBPE reactor for removing heavy metals and microplastics was analyzed. • IBPE reactor could effectively remove heavy metals and microplastics in secondary effluent of WWTP. In this study, the mixed pollutants of microplastics and heavy metals from secondary effluent of wastewater treatment plant (WWTP) were removed by interpenetrating bipolar plate electrocoagulation (IBPE) reactor. Heavy metals and microplastics in the wastewater were simultaneously removed during the experimental process with high removal efficiency. The influences of current density, initial pH and reaction time on the removal rate were analyzed. When the current density was 12 mA / cm2, the initial pH was 6 and the reaction time was 20 min, the optimal removal efficiency of heavy metals and microplastics were obtained with removal rates of 95.16% and 97.5%, respectively. Under the condition of different current densities, the change of removal rate with time was fitted through mathematical model. The complexation forms of heavy metals and surface groups of microplastics were analyzed through pseudo-voltammetry curve. The operation cost of removing microplastics and heavy metals through IBPE reactor was 0.91 $·L−1 under the optimal experimental conditions. The experimental results suggested that this process reduced the potential harm of microplastics and heavy metals to aquatic organisms and human beings. The IBPE could be applied as a clean technology for simultaneous removal of microplastics and heavy metals from secondary effluent of WWTP. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) in water pose a great threat to the ecological environment, but the impact of MPs on constructed wetland microbial fuel cells (CW-MFCs) has not been studied, so in order to fill the research gap and enrich the research in the field of microplastics, a 360-day experiment was designed to determine the operating status of CW-MFCs at different concentrations (0, 10, 100 and 1000 μg/L) polyethylene microplastics (PE-MPs) at different times, focusing on the changes of the CW-MFCs' ability to handle pollutants, power production performance and microbial composition. The results showed that with the accumulation of PE-MPs, the removal effect of COD and TP did not change significantly, and that the removal rate was maintained at around 90% and 77.9% respectively, within 120 d of operation. What's more, the denitrification efficiency increased (from 4.1% to 19.6%), but with the passage of time, it decreased significantly (from 7.16% to 31.9%) at the end of the experiment, while oxygen mass transfer rate was significantly increased. Further analysis showed that the accumulation of PE-MPs did not affect the current power density significantly with the changes of time and concentration, but the accumulation of PE-MPs would inhibit the exogenous electrical biofilm and increase the internal resistance, thereby affecting the electrochemical performance of the system. In addition, the results of microbial PCA showed that the composition and the activity of the microorganisms were changed under the action of PE-MPs, that the microbial community in CW-MFC showed a dose effect on the input of PE-MPs, and that the relative abundance of nitrifying bacteria with time was significantly affected by PE-MPs concentration. The relative abundance of denitrifying bacteria decreased over time, but PE-MPs promoted the reproduction of denitrifying bacteria, which was consistent with the changes in nitrification and denitrification rates. The removal modes of EP-MPs by CW-MFC include the adsorption and the electrochemical degradation, with two isothermal adsorption models of Langmuir and Freundlich being constructed in the experiment, and the electrochemical degradation process of EP-MPs being simulated. In summary, the results show that the accumulation of PE-MPs can induce a series of changes in substrate, microbial species and activity of CW-MFCs, which in turn affects the pollutant removal efficiency and power generation performance during its operation. [Display omitted] • The effect of EP-MPs on CW-MFCs was studied for the first time. • CW-MFCs realized the effective removal of EP-MPs. • EP-MPs' high level inhibited denitrification efficiency, promoting OUR. • EP-MPs concentration change hardly affects CW-MFCs power generation efficiency. • EP-MPs change the composition of microorganisms in CW-MFC. [ABSTRACT FROM AUTHOR]