Phosphorus recovery directly from sewage sludge as vivianite and simultaneous electricity production in a dual chamber microbial fuel cell

Abstract

Phosphorus (P) recovery from waste streams is a crucial option for the looming global P crisis, and P recovery from sewage sludge, as the final effluent of P from wastewater treatment plant (WWTP), is even more significant. In this study, a dual chamber microbial fuel cell (MFC) was constructed in order to directly recover P from sewage sludge utilizing cathodic Fe reduction to produce a more valuable product of vivianite for the first time, avoiding the pre-treatment of sludge and simultaneously producing energy. The results showed that a recovery efficiency of 99.08% for dissolved P from sludge was reached, while the production of newly formed vivianite was approximately 2.33 mg/g calculated by P fractionation and demonstrated using X-ray diffraction and X-ray photoelectron spectroscopy. The best P recovery efficiency was obtained at an initial catholyte pH of 7 and Fe/P molar ratio of 1, while the concentration of anolyte initial dissolved chemical oxygen demand (COD) affected the rate of electricity production. The electrical energy output of MFC had a highly positive relationship with the anolyte total COD degradation efficiency (R2 = 0.9716). This research opens up a new possibility for MFC systems to directly recover phosphorus from sewage sludge.