Simultaneous organic carbon, nitrogen removal, and electricity generation in a novel A4-MFC system for the treatment of leachate from a composting site: performance and modeling

Abstract

In this study, a novel microbial fuel cell (A4-MFC) was designed and operated to treat and recover the energy from a compost leachate. Central composite design (CCD) through response surface methodology (RSM) was used for the optimization of MFC performance as a function of two main operational factors (chemical oxygen demand (COD) concentration of 1000–5000 mg L⁻¹ and hydraulic retention time (HRT) of 2–4 days) to achieve the finest response of simultaneous COD, total Kjeldahl nitrogen (TKN), ammonium (NH₄⁺) removal, and bioenergy generation. Statistical analysis showed that the performance of the MFC was obviously influenced by the independent variables (initial COD and HRT). Moreover, based on the ANOVA results using multiple regression analysis, it was found that the most fitted model for this reactor was the quadratic model. Under the initial COD (10 000 mg L⁻¹) and HRT (4 days), the highest removal efficiency of COD, TKN, and NH₄⁺ were 92.3%, 95%, and 96%, respectively. Indeed, the maximum current, voltage, current density, and coulombic efficiency (CE) were 2 mA, 41.76 mV, 803.6 mA m⁻³, and 62.3%, respectively. The results indicate that the A4-MFC system has a great efficiency in treating the leachate with high initial COD concentration, and it can be offered as a promising bio-electrochemical reactor for the treatment of strength wastewaters.