The hydrochemical studies assessed the area affected by one of the largest mineral pro-cessing facilities of the Kola Peninsula (Russia), the Olcon Mining and Processing Plant. Based on the results of the laboratory analyzes, nitrate ion was found to be the major contaminant of the quarry waters. Discharge of untreated waste water leads to nitrogen pollution of the natural waters of the region and, as a consequence, disruption of the functioning of hydroecosystems. To address the environmental issue, the authors proposed an effective method for the biological treatment of nitrogencontaining mine drainage. The key point is the implementation of the Chlorella kessleri microalgae into the existing treatment system. The research describes in vitro studies of the purification process on model solutions and presents the major findings. Besides, a technological solution is proposed for the application of the treatment technique for the studied pit waters. The higher efficiency of waste water purification will not only prevent further pollution of natural waters but also raise the living standards of local communities by improving the environmental situation in the area. The outcomes of theoretical studies and laboratory experiments open up the prospect of using the biological treatment technique for nitrogen removal from wastewater in the polar mining regions.