Water filtration with mineral-based byproducts as a sustainable treatment technology

Agnieszka Renman et al.

The aim of the project was to investigate whether the 200 000 ton slag, that is not used optimally or deposited every year, can be alternatively applied as water treatment materials, ensuring future outlets and providing added value for the steel industry and society. Five goals had been set and could be met: test of filter material for purification in small sewage plants, testing of mineral filters for industrial wastewater and stormwater, new technology to build road shoulders on busy roads with slag that simultaneously cleans stormwater, laboratory-tested filter products, and two graduated doctors.

Slag's properties can be modified in the furnace to contain minerals that have properties to bind phosphorus or metals from water. Slags can separate both cations and anions from contaminated water, anions even at pH value 10. Furthermore, slag and bark in combined filters are able to remove PFAS and also fluorine by modifying of AOD slag. Some types of slag are recommended to replace sand in soil beds for sewage treatment. Stormwater wells in cities and industry can be equipped with slag filters. Storm water from traffic-intensive roads can be cleaned in the road shoulder with certain types of slag.

R&D has been conducted in clear collaboration between industry and academia. The research has been conducted in the laboratory, at the companies and in the field. Implementation has been possible through researchers and companies starting pilot facilities and studying their function and utility to achieve sustainability goals. The analysis made is that different types of Swedish-produced slag are useful by-products, after simple reprocessing or after modifications, in water purification applications. These applications can be of several different types and be interesting for several end users.