Water resource recovery facilities (WRRFs) are striving to maintain highly sustainable operations while minimizing impacts to rate payers. Recovering nutrients from wastewater solids can help WRRFs achieve this balance. This project aims to optimize acid gas (AG) digestion of wastewater biosolids and build on existing AG processes to develop a novel advanced digestion process: Acid+ Digestion. Acid+ Digestion would offer WRRFs an option to increase digester capacity; enhance nutrient resource recovery as struvite; protect digestion, dewatering, and centrate handling from struvite fouling; and reduce biosolids phosphorus. Research partners: City of Columbus, Metropolitan Sewer District of Greater Cincinnati, and The Water Tower.