Sludge water was recycled using an ultrafiltration (UF) system. In order to control membrane fouling, three typical Fe(II)-activated peroxymonosulfate (PMS) processes: Fe(II)/PMS-UF (FPUF), 1/4Fe(II) × 4/PMS-UF (F4PUF) (adding Fe(II) in small increments four times), and