Simultaneous removal of organic and nitrogen compounds in intermittently aerated activated sludge process using magnetic separation

Magnetic separation was introduced to an activated sludge process to improve the solid-liquid separation characteristics of the sludge. The process was operated with the intermittent aeration method and applied for the removal of organic matter and nitrogen in wastewater. The activated sludge supplemented with magnetite (Fe3O4) powder (magnetic sludge) exhibits a ferromagnetic property and deposited on the surface of magnetic disks due to magnetic force. The magnetic separation apparatus (composed of rotary magnetic disks and scrapers) separated treated water from the sludge suspension of 13-22 g VSS 1(-1) within 5 min. Compared with the sedimentational separation process, the magnetic separation technique showed better performance. Simultaneous removal of about 89% of TKN and about 92% of soluble CODct in influent was performed under loading rates of 0.92 g CODcr 1(-1) d(-1) and 0.10 g TKN 1(-1) d(-1), respectively, with a non-aeration/aeration cycle of 40/20 min. (C) 1997 Elsevier Science Ltd.