Sawdust suitable for purification of industrial wastewaters

Chemically modified pine sawdust can be used for removing nitrates and metals from industrial and mining wastewaters. In her dissertation, M.Sc. Anni Keränen developed water purification materials from Finnish wood-based waste materials, and studied their use in wastewater treatment.

The biomaterials selected for the research (sawdust, bark and peat) were chemically modified so that their surface properties became favorable for attachment of harmful substances. It was discovered in laboratory tests with synthetic watery solutions that attachment of nitrate was very quick and that the material functioned on a wide pH and temperature range. This is favorable for practical applications. Modified sawdust was successfully used also in purification of actual industry and mining wastewaters.

The purification method is primarily based on ion exchange. Metals attached to the purification material can be salvaged by regenerating the material with saline.

Mining projects have been in the public eye in recent years because they produce wastewater discharges. Sulfate causes waters to become salty, nitrate and phosphate increase nutrient load, and metals accumulate in the ecosystem.

Results from the dissertation study can be used in development of new water purification technologies. Development of bio-based water treatment materials from local raw materials decreases dependency of fossil raw materials, and offers forestry by-products new applications. It is possible to re-use purification material several times.

Anni Keränen: Water treatment by quaternized lignocellulose to be presented for public defence in the University of Oulu on 31. March 2017

Last updated: 30.10.2017