A new generation of high gradient magnetic separation (HGMS) has recently received attention again, especially for its applications in the field of water and wastewater treatment. The reason for this attention is that a newly developed superconducting magnet can be used to easily generate a high magnetic field, under which even weakly paramagnetic materials can be separated at high efficiency. We have developed a new wastewater treatment process using magnetic gel particles containing immobilized microorganisms and magnetic particles. The magnetic gel particles are separated and recovered from the effluent in water and wastewater treatment processes, and are then recycled to a bioreactor directly or reused after storing. In this research, a novel type of magnetic separator without a filter matrix was designed for the separation and recovery of magnetic gel particles with different magnetic characteristics. No backwashing is required for this new type of separator. By using the separator, polyethylene glycol (PEG) gel particles with 2% magnetite were continuously separated and recovered from the PEG gel particles with 0.04% magnetite at an efficiency of around 90%. The PEG gel particles containing nitrifying bacteria and magnetic particles were available for the oxidation of ammonia solution at a slightly lower nitrification rate than the PEG gel particles with nitrifying bacteria but without magnetite.

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