Recovery of Nutrients from Wastewater via Electrodialysis

Abstract

The need to treat wastewater in a sustainable way to minimalize contamination and maximize the recovery of nutrients is widelyrecognized. The focus is mainly on the removal and recovery of nutrients because of eutrophication problems in receiving waters,limitations of mining resources and high costs affiliated with nutrient production. Removal of nutrients is also a growing problemfor water authorities, as authorities often tighten standards of discharged waters to avoid unnecessary discharge of nutrients intowater bodies.The universally used technologies for nitrogen and phosphorus removal involve biological nitrification and denitrification and metalsalt precipitation. However, applying these technologies nutrients are made unrecoverable for fertilizing. Electrodialysis (ED) isa membrane process capable of concentrating and separating ions from wastewater. Thanks to the applied current, the migration ofions occurs, and ions are concentrated in the concentrate solution. Laboratory scale ED showed the potential of nutrient recoveryfrom wastewater sources.In this study, nutrients were recovered in concentrate solution from wastewater sludge liquid discharge by using electrodialysis.Calcium and sodium values in concentrated solution increased 10 times, values of potassium and chloride 5 times. The amount ofammonia nitrogen raised from 60 mg/l to 1700 mg/l. The concentrate enriched by nutrients may be used in further processes, e.g.phosphorus and ammonia nitrogen can be precipitated into the form of struvite.