High Gradient Magnetic Separation Technique for Wastewater Treatment

Abstract

Smit Nymegen Magnetic Water treatment Systems (MWS), a business group of Smit Transformatoren BV, has recently developed a very efficient magnet for wastewater treatment. The magnet is the core element of a complete system to eliminate phosphates, heavy metals and other pollutants from wastewater. The system is based on the attachment of wastewater pollutants to a magnetic carrier material (magnetite) and a subsequent magnetic separation of the magnetite-pollutant conglomerates. After separation, the magnetite is recovered and re-used in the process. Main advantages of the magnetic separation process are:▸high elimination performance▸low power input for magnet operation▸compact process▸low space requirements▸no clogging because of open matrix structure. The development of the magnetic system has been focused on the phosphate-removal from effluents of sewage treatment plants. Being a tertiary treatment, magnetic phosphate removal can be applied after any type of sewage treatment and it does not interfere with the biological process. Pilot plant tests at various sewage works showed that magnetic separation reduces the total-phosphate concentration to values as low as 0.1-0.5 mg/l. The system will be demonstrated in two full-scale plants with a capacity of 300 m3/h and 600 m3/h, respectively. The costs of magnetic phosphate removal (Dfl. 12,- to 18,-) are competitive with those of other phosphate removal techniques. The development of the magnetic phosphate removal system is granted by the Dutch Ministries of Housing, Physical Planning and Environment, Economic Affairs and Transport and Public Works.