Osaka University researchers said Wednesday they had developed a system to purify waste water from paper recycling plants at lower cost by using superconducting magnets.

A team led by Prof. Shigehiro Nishijima and instructor Shinichi Takeda developed the system in which pollutants in waste water are combined with ferric oxide particles and then absorbed by magnets.

The researchers said the system can halve the cost and the space needed for waste water processing facilities at paper recycling plants.

Futaba Shoji, an Osaka-based company that jointly developed the system, will start sales of the system in spring.

Currently, waste water from paper-recycling plants is preprocessed by pressure flotation and then by the activated sludge method.

As many recycled paper companies are small and midsize firms, costs of waste water purification and sewage fees are heavy burdens on them.

Under the new system, microparticles of ferric oxide and flocculating agents to bring particles together are put into waste water that has been preprocessed by pressure flotation.

Ferric oxide particles are combined with colorants, chemical agents and other organic constituents that then settle after combining.

After removing the settled substances, waste water is sent into a magnetic separator using superconducting magnets.

A set of 50 filters shaped like wire nets inside the separator absorb the remaining pollutants using extremely strong magnetic force.

The newly developed system has already been tested in a paper recycling plant in Osaka Prefecture.

The result showed that the chemical oxygen demand of waste water could be reduced from about 200 to 300 milligrams per liter to 20 to 40 milligrams, which means the water after purification is clean enough to be discharged into a river.

The system also can be used for processing waste water from plants processing foodstuffs, textiles and chemical agents, the researchers said.

A single unit of the system that can process 2,000 tons of waste water a day, needs 36 square meters of space and would be priced at 100 million yen to 150 million yen.

Though an average-sized paper recycling plant requires two or three units, there are substantial benefits to replacing the activated sludge method, which needs hundreds of square meters of space and 600 million yen to 1 billion yen to purchase a unit, the researchers said.