Phosphorus recovery from low phosphate-containing solution by electrodialysis

The use of electrodialysis to treat a low phosphorus-containing solution (0.011 g L-1 HxPO43-x) was evaluated aiming at the recovery of phosphorus from municipal wastewater. The study was held in galvanostatic mode using a five-compartment electrodialysis cell with two pairs of cation- and anion-exchange heterogeneous membrane. A two-stage electrodialysis setup was proposed to recover phosphorus from a low phosphate-containing municipal wastewater. At underlimiting current density conditions, a solution with a phosphate concentration higher than 0.100 g L-1 was obtained by consecutively changing the solution in the diluted reservoir after reaching a demineralization rate of 50.0%. A concentration factor of 9.7 was obtained and no significant changes that could compromise the efficiency of the process were observed. The phosphate ions of the concentrated solution could be then separated from coexisting ions, such as sulfate, by the employment of over-limiting current density conditions, with its feasibility dependent on the use of alkali resistance anion-exchange membranes.