The construction of large microbial fuel cells (MFCs) and their long-term reliability are current challenges. MFCs generate power while purifying wastewater, save electricity, avoid pollutant stripping into the air and are a source of CO2. To understand larger MFCs, a 1000-L MFC was designed. It was built from transparent polyester and electrodes were from reticulated vitreous carbon. Four power management devices were connected to an ensemble of 64 MFC units and assembled as a 12 m long MFC. Two Raspberry and a personal computer with Python programmed software automatized power management. The MFC was run for one year under maximum power point tracking (MPPT). Temperatures between 11.5 °C and 21 °C corresponded to WWTP conditions. The reactor shared electrolytes within 12 m long half-cells and 80–95% COD was removed generating 0.015 to 0.060 kWh/m3 with an energy efficiency of 5.8–12.1%. Voltage reversal were seen as potential imbalances among MFC units and all self-healing. Ammonium removal reached 48%, phosphorous was reduced to 0.59 mg/L, and micropollutants degraded by 67%. Biofilm mapping by 16S rRNA metagenomics indicated bi-sectorial metabolic properties. 10 Major genera were essential in the elongated scale up MFC generating electricity, reduced energy needed, and purified wastewater.