Phosphorus removal and recovery from anaerobic bioreactor effluent using a batch electrocoagulation process

Abstract

A batch monopolar electrocoagulation system was developed and studied for the removal of phosphorus from anaerobic bioreactor effluent using iron as an electrode material. The study focused on the optimization of the independent variables, such as initial pH, retention time (RT), current density (CD) and inter-electrode distance (IED) using the response surface methodology (RSM) to maximize the removal of total phosphorus (TP). A quadratic model was fitted to the experimental data for TP removal. The optimal parameters were found to be pH of 6.75, RT of 11.06 min, CD of 300 A/m2, and inter-electrode distance of 1.5 cm resulting in 98.05% TP removal and energy consumption of 1.28 kWh/m3. A kinetic study for TP removal revealed that at optimal conditions, removal followed first-order kinetics (K = 0.185 m/min). Phosphorus was recovered from the post-precipitated sludge through combustion at 900 °C followed by acid leaching with sulfuric acid. Acid leaching tests were carried out with sulfuric acid for the post-precipitated sludge obtained at the optimum conditions. It resulted in around 91% of phosphorus recovery at a liquid-to-solid ratio of 100 mL/g.