Phosphorus Removal in CAFO Wastewater: Impacts of Seeding and Mixing Strength

Struvite crystallization is a potential technology for removing, recovering and reusing phosphorus from municipal, industrial and agricultural wastewater streams. Many aspects of this process has been studied, however, research on Concentrated Animal Feeding Operation (CAFO) wastewater is limited. This study explored the potential applications of struvite crystallization on CAFO wastewater streams. The specific objective was to determine the impact of seeding materials and mixing strength on struvite crystal sizes and P removal efficiency.

Research results revealed that seeding materials led to increased crystal size and precipitation in synthetic wastewater. Among the seeding materials evaluated, struvite crystals had the best performance. Mixing strength also affected crystal growth; mixing strength of 75S -1 provided the optimum condition for crystal growth. Reaction time beyond one hour had no apparent effect on enhancing P removal. Experimental results showed that calcium was the major competing ion in struvite formation and struvite purity was greatly reduced when Ca/Mg molar ratio was higher than 1. Based on experimental results, struvite crystallization process does have the potential to be used in treating CAFO wastewater.