Removal of phosphorus from a municipal wastewater by simultaneous precipitation of iron- hydroxy-phosphate (IHP) was investigated. The addition of Fe3+ was performed to supplement biological excess phosphorus removal by a completely mixed alternating aerobic–anoxic (AAA) activated sludge process. The cycles of 3-h anoxic time and 3-h aerobic digestion were set to controlling a single-sludge nitrification–denitrification. In this study, attempt has been made to analyse the effects of initial dis- solved Fe/P molar ratio and pH on IHP precipitation. The AAA treatment process to remove soluble reac- tive and total phosphorus from domestic wastewater had a moderate efficiency. The empirical formula of IHP that differs from different pH ranges was verified. Two types of Fe4(OH)9PO4 and Fe5(OH)6(PO4)3 pre- cipitate may occur in different conditions of the AAA process. The efficiency of phosphorus removal from domestic wastewater by an AAA process was verified to contribute to a working methodology for the application of technologies in the field of domestic wastewater treatment.
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