#07 | Zero liquid discharge application in coal mining – a case study

By Wojciech Mikołajczak (IMN)

Intending to attain the EU target of net-zero carbon emissions by 2050, the EU production of hard coal in 2021 was reduced to 57 million tonnes; 79 % less than the 277 million tonnes in 1990. Nevertheless, coal still accounts for about 20% of total electricity production in the EU. It also provides jobs to around 230,000 people in mines and power plants across 31 regions and 11 EU countries.

Poland, as by far the largest coal producer delivers added value to the EU, but this comes with a high environmental cost at a national level. In 2018, an estimated 182.4 million m³ of saline waters drained directly into rivers causing substantial damage to Polish water resources[i]. The salination of the Vistula River is the cause of losses in industry, agriculture and water transport which were estimated to be $100-$250 million In 2018 [ii].

The first plant globally to apply a Zero Liquid Discharge system to treat coal mine brine effluent and recover water and saleable salts was Debiensko Desalination Plant[iii]. Construction began in 1988 and the total cost of the equipment was  $60 million. The installation consists of an evaporation plant – operational since 1993, and reverse osmosis (RO) with pretreatment – completed in July 1995. The main drawback of this installation is high energy consumption – ca. 970 kWh/t of salt recovered.

The RO pretreatment includes algicide dosing in a storage tank, disinfection, flocculation/sedimentation and dual media filtration. After a two-stage microfilter system (50 μ and 5 μ, respectively), the pretreated water is desalinated at 6–7 MPa in a RO system with spiral wound RO membranes. The RO permeate is decarbonated and disinfected before distribution in the drinking water net.

The first section of the thermal plant is composed of two brine concentrators, designed by Resources Conservation Company (RCC, Since 2005 part of GE’s Water & Process Technologies). By using the seed crystal recycling technique developed in the early 70s, it is possible to concentrate the feed near the precipitation point for NaCl. The second section of the thermal plant includes one crystallizer for the production of NaCl, two pusher centrifuges for salt removal from supersaturated brine and one fluidized bed dryer. The crystallizer is a forced circulation submerged-tube evaporator equipped with a mechanical vapor compressor.


[i] Spatial and Environmental Surveys Department, ‘Statistical analyses. Environment 2019, Statistics Poland’, Warsaw, Nov. 2019

[ii] P. Jasinski and H. Lawton-Smith, Environmental Regulation in Transforming Economies: The Case of Poland. Routledge, 2018

[iii] B. Ericsson and B. Hallmans, ‘Treatment of saline wastewater for zero discharge at the Debiensko coal mines in Poland’, Desalination, vol. 105, no. 1–2, pp. 115–123, Jun. 1996, doi: 10.1016/0011-9164(96)00065-3.

‘EURACOAL Market Report’, EUROCOAL, 1, May 2019. [Online]. Available: https://euracoal.eu/library/coal-market-reports/

European Commission, ‘Critical Raw Materials Resilience: Charting a Path towards greater Security and Sustainability’, Brussels, COM (2020) 474 final, Mar. 2020.

Eurostat, ‘Coal production and consumption statistics’, 2022. [Online]. Available: https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Coal_production_and_consumption_statistics

Eurostat, ‘Production of lignite in the EU – statistics’, 2021. [Online]. Available: https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Production_of_lignite_in_the_EU_-_statistics