Effects of potassium and magnesium in the enhanced biological phosphorus removal process using a membrane bioreactor

This study assessed the role of potassium (K⁺), magnesium (Mg²⁺), and calcium (Ca²⁺) ions in the enhanced biological phosphorus removal (EBPR) from wastewaters using a membrane bioreactor (MBR). A linear relationship in the anaerobic and aerobic/anoxic phases for P _uptake versus P_release was obtained using the known equation ΔP_uptake a X ΔP_release+ b, where the constants "a" and "b" were found to be 0.44 and 8.40, respectively. Both potassium and magnesium were soluble with phosphate in the anaerobic phase, but they accumulated again during the successive aerobic/anoxic phase. The linear correlation coefficients (R²) of K ⁺/PO₄-P and Mg²⁺/PO₄-P were calculated as 0.6682 and 0.8884, respectively. The molar ratio of C _K/P during anaerobic phosphorus release was observed to be 0.20 mol/mol, whereas C_Mg/P was 0.21 mol/mol. Furthermore, unlike potassium and magnesium, calcium was not co-transported with phosphorus during the release and uptake processes.