Effect of Water Treatment on the Chemical Composition of Drinking Water: A Case of Lovozero, Murmansk Region, Russia

Abstract

The surface waters in Russia’s Murmansk Region used for public water supply are exposed to the negative impact of dust particles carried from the storage facilities for mining waste. For example, lanthanides and other rare metals enter the surface waters in Lovozero District from the tailings storage facilities (TSFs) of the Lovozero Concentrator, which requires thorough water treatment of drinking water. Using the monitoring data of the natural water of the Virma River and of the tap water in the residential community of Lovozero, Murmansk Region, and with the help of physical and chemical modeling (in the software suite Selector), we examined the effect of reagents used in water treatment on water chemistry. It was shown that the use of aluminum polyoxydichloride coagulant can lead to an increase in the concentration of aluminum and chlorine in water, a change in pH and Eh values. The use of liquid chlorine leads to a decrease in pH values and a change in the concentration of HCO3−, which entails a change in the forms of migration of calcium and lanthanides in solution. The composition of the precipitated phases changed, which indicates a change in the water chemistry, demonstrating that the applied water treatment technology adopted in Lovozero fails to improve water quality. It was shown that replacing liquid chlorine (a hazardous reagent) with NaOCl optimized the water treatment process, eliminating the need to stabilize the pH by adding sodium. Physical and chemical modeling was found to be useful for studying and optimizing water treatment processes.