The EU has been putting more and more money into generating power from renewable sources like sun, air, and water, with the aim of reducing CO₂ emissions and a gradual shift away from consuming fossil fuels. However, coal remains an important raw material in Europe. Unlike brown coal, hard coal is also used in other industries besides power production and is therefore traded and consumed by all EU countries except Malta (https://ec.europa.eu/eurostat/web/products-eurostat-news/w/ddn-20230622-2).

Countries of Northern Europe, with Poland being dominant in this field, extract hard coal even 1000 meters below the earth surface.

The extraction of coal from the earth is accompanied by the pumping of substantial quantities of wastewater that contains a significant salt content of up to 10%,. If these waste streams, also known as brines, end up in the environment, they will cause salinization of surface waters and the pollution of underground aquifers. The process of salinization has an influence on aquatic ecosystems, while contamination of groundwater may reduce in the future potential sources of potable water.

The LIFE Brine Mining Project, which is co-funded by the EU LIFE Programme, was initiated in 2019 with the objective of eliminating the discharge of coal mine brines into the environment, through the direct extraction of valuable materials contained within them. Under the coordination of NTUA, Greece, the project opens the perspective for the coal mining industry to improve its wastewater management by applying the developed solution, thus contributing to the implementation of the Circular Economy Strategy in the coal mining sector, throughout Europe. The LIFE Brine-Mining team consists of 10 partners, including two universities, one research institution, and seven small and medium enterprises from three EU countries: Greece, the Netherlands, and Poland.

An innovative demonstration system was developed to treat coal mine brines for the project implementation. The system is a combination of membrane technologies (ultrafiltration, nanofiltration, electrodialysis, reverse osmosis), precipitation reactors, evaporation, and crystallization units.

The demonstration system operated for 19 months in the Ziemowit mine area, in the Upper Silesian region, Poland, achieving very high standards. The system treated coal mine brine with a salt content of 8% and produced:

1. High purity water that is suitable for irrigating crops, watering parks, cleaning public buildings, and also useful for the mine itself for cleaning or other industrial purposes.
2. Magnesium hydroxide (Mg(OH)₂), calcium carbonate (CaCO₃), calcium sulfate (CaSO₄) and sodium chloride (NaCl), all of high purity (above 91%). By exploiting these valuable salts for commercial purposes, the coal mine can augment its revenue, while the buyers can derive advantage from the lower prices compared to the current market rate.

The demonstration system has been designed so that its 24h system operation potentially allowed the prevention of the discharge of 7,000 cubic meters brine per year into surface water, and the recovery of 5,800 tons of clean water and 432 tons of salts per year. The demonstration system was also tested for the treatment of brine from other mines, such as potassium mines, showing the same efficiency as in the coal mine sector. During the entire demonstration period, about 150 cubic meters of mine water was treated.

For more information about the LIFE Brine-Mining Project, please visit our website: brinemining.eu.