Recovery phosphorus and water resources from corn deep-processing wastewater using a combined process of forward osmosis and hydroxyapatite

Abstract

The global scarcity of phosphorus and water resources has become a pressing environmental issue, prompting extensive research into resource recovery strategies. Wastewater generated from corn starch processing exhibits high chemical oxygen demand (COD) and elevated concentrations of nitrogen and phosphorus, and is typically treated using combined anaerobic-aerobic processes. However, effluent from secondary biological treatment still contains considerable phosphorus, with PO₄^3--P concentrations exceeding 70 mg/L. Consequently, implementing water and phosphorus recovery processes as an alternative to conventional chemical removal methods aligns with circular economy principles and supports sustainable development goals. This study investigated the feasibility of recovering phosphorus and water from the effluent of secondary sedimentation tanks in corn starch processing wastewater using a forward osmosis-hydroxyapatite (FO-HAP) combined process and optimized the operational parameters. In the FO unit, the phosphorus concentration increased 5.9-fold compared to the feed water, reaching a PO₄^3--P level of 210.2 mg/L, with a water recovery rate of 80 %. In the HAP-induced crystallization unit, phosphorus removal efficiency reached 98 %, and the purity of the synthesized HAP was 75 % under optimal conditions (stirring intensity of 200 rpm, pH of 10, Ca/P molar ratio of 3). Overall, the FO-HAP combined process provides an effective approach for recovering phosphorus and water from secondary effluent in corn starch processing, offering both a practical technical solution and a theoretical basis for wastewater treatment and resource utilization in the industry.