Phosphorus recovery from recirculating aquaculture systems: Adsorption kinetics and mechanism

Recirculating aquaculture systems (RAS) have grown in popularity in recent years due to their potential to provide a high-quality protein source in a contained environment. With increased production comes the need for RAS wastewater treatment to remove waste products such as phosphorus, which can harm other aquatic life in the area by causing algae blooms. Additionally, there is potential to harvest the wasted phosphorus for use as a fertilizer and to combat nutrient scarcity. This study investigates a phosphorus adsorbent, RhizoSorb (R) (base material of aluminum oxide), for its applicability in RAS use under fresh water, simulated seawater, and real RAS water conditions. Film diffusion and intraparticle diffusion were both rate-controlling steps in the adsorption process, and the good fit of the Elovich model indicated that chemisorption is likely the dominating adsorption mechanism. Phosphate removal decreased with increasing salinity in all tests, which can be attributed to both anion competition and increasing pH. The Freundlich isotherm fit the equilibrium data better than the Langmuir isotherm, showing that adsorption is a multi-layer process and that the adsorbent is highly heterogeneous. The Clark model was better suited than the Thomas model for predicting the performance of the adsorbent in a flow -through system. The adsorbent showed high removal efficiencies and good selectivity for phosphate in all tests.

Automated summary

Recirculating aquaculture systems (RAS) are popular for their potential to provide high-quality protein and this study investigates the applicability of a phosphorus adsorbent in RAS wastewater treatment. The results show that the adsorbent has high removal efficiencies and good selectivity for phosphate under different water conditions.