Optimizing phosphate removal by manipulating manganese and cobalt levels in soil aquifer treatment system

Abstract

Manganese (Mn²⁺) and cobalt (Co²⁺) metals have been reported to exhibit complex interactions with phosphate (PO₄^3-) ions, which can influence their mobility, reactivity, and removal behavior in soil aquifer treatment system (SAT). This study aimed to investigate the role of manganese (Mn²⁺) and cobalt (Co²⁺) in phosphate (PO₄^3-) removal within a soil aquifer treatment system. A lab-scale column experiment was conducted using sand as the filtration media, and a synthetic wastewater containing 20 mg/L PO₄^3-, 60 mg/L Mn²⁺, and 40 mg/L Co²⁺ was used. The breakthrough curves showed efficient removal of PO₄^3- during the infiltration process, with concentrations reaching as low as 1 mg/L. The regression analysis revealed that Mn²⁺ had a strong negative correlation effect on PO₄^3- concentration, indicating its stimulatory role in PO₄^3- removal. Conversely, Co²⁺ showed a strong positive correlation effect, suggesting its promoting effect on PO₄^3- concentration. Optimization analysis identified optimal concentrations of 57.4 mg/L for Mn²⁺ and 4.8 mg/L for Co²⁺ that interacted with lower PO₄^3- concentrations, achieving the desired outcome of reducing PO₄^3- levels. These findings highlight the importance of considering Mn²⁺ and Co²⁺ concentrations in soil aquifer treatment systems for effective phosphate removal.