Systems and methods for removing phosphorous (P) from P-containing wastewater are disclosed. The system includes a main filter unit (MFU) comprising P-adsorbing material. The MFU receives the P-containing wastewater and forms therefrom MFU-filtered wastewater having a first pH. A pH adjusting unit (AU) that contains pH-reducing material receives the MFU-filtered wastewater and forms therefrom AU-filtered wastewater having a second pH lower than the first pH. A replaceable filter unit (RFU) similar to the MFU but smaller may be arranged upstream of the MFU to pre-filter the P-containing wastewater. Some or all of the RFU may be replaced when maintaining the system.