Demonstration of Magnetic activated sludge process for water treatment with zero emission of excess sludge

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Magnetic activated sludge (MAS) process was developed for the efficient treatment of wastewater. Magnetic activated sludge was prepared simply by seeding magnetite (Fe_3O_4) to the activated sludge. High affinity of attraction of magnetite by the sludge was observed. The developed magnetic activated sludge was attracted by the magnetic drum/disk and was separated by the scraper of the magnetic apparatus. The separated sludge returned again to the aeration tank for their active participation. Therefore, the MAS process could maintain high concentration of microorganisms in the reactor tank for biodegradation of organic pollutants. This process might be efficiently operated by the cell growth and decay of the microorganisms in the reactor tank. Therefore, the MAS process could cut excess sludge emission during wastewater purification. Bench-scale experiment was carried on various kinds of organic pollutants viz. phenol, polyvinyl alcohol, detergent, and endocrine disruptor. The bench-scale experiment was found to be successful for the biodegradation of those pollutants without excess sludge production. The pilot scale application of MAS process is under experiment using municipal sewage. In the pilot plant, the MAS process was also found to be successful for the purification of municipal sewage about 500 days of experiment without withdrawal of excess sludge. During this period, about 16 m^3 of sewage was continuously treated in about 8 m^3 of aeration tank. About 90% COD_<Cr>, removal was achieved by this process. The performance is compared to conventional activated sludge process. In addition, the MAS process could remove 70% of total nitrogen in the sewage by sequential nitrification and denitrification through intermittent aeration. Suspended magnetite and dissolved iron ions were not observed in the effluent from the process.