Sonication-Assisted Struvite Fertilizer Production From Anaerobic Granular Sludge Effluent of Seafood Processing...

The burgeoning seafood processing industry generates nutrient-rich effluents that necessitate sustainable management to prevent environmental degradation. This study investigates, for the first time, the intensification of struvite fertilizer (MgNH₄PO₄·6H₂O) crystallization from anaerobic granular sludge effluent of a seafood processing plant using ultrasonic irradiation. The process was systematically optimized to enhance nutrient recovery and crystal quality. Experimental results demonstrated that high-purity struvite with a well-defined prismatic morphology was successfully synthesized. Optimal precipitation conditions were identified at a Mg²⁺:NH₄ ⁺:PO₄ ^3- molar ratio of 1:1:1, a stirring speed of 200 rpm, and a temperature of 25°C, with a combined reaction and settling time of 2.5 h. Notably, the integration of sonication-specifically in degas mode-significantly accelerated nucleation kinetics and facilitated uniform crystal growth. Compared to conventional mechanical agitation, the sonication-assisted approach yielded higher recovery efficiencies and improved crystal size distribution by mitigating localized supersaturation and enhancing mass transfer via acoustic cavitation. These findings underscore the potential of sonochemical intensification as a green, efficient strategy for transforming wastewater pollutants into high-value fertilizers, thereby advancing the circular economy in the seafood sector.