Recovery of Nutrients from Wastewater via Electrodialysis

The need to treat wastewater in a sustainable way to minimalize contamination and maximize the recovery of nutrients is widely recognized. 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 problem for water authorities, as authorities often tighten standards of discharged waters to avoid unnecessary discharge of nutrients into water bodies. The universally used technologies for nitrogen and phosphorus removal involve biological nitrification and denitrification and metal salt precipitation. However, applying these technologies nutrients are made unrecoverable for fertilizing. Electrodialysis (ED) is a membrane process capable of concentrating and separating ions from wastewater. Thanks to the applied current, the migration of ions occurs, and ions are concentrated in the concentrate solution. Laboratory scale ED showed the potential of nutrient recovery from 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 of ammonia 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.