Retrospective Hygienic Assessment of the Color of Water in Centralized Water Supply Systems of Populated Areas of the Russian Federation

Introduction: The color of water in Russian water bodies is associated with the presence of colored organic substances, iron compounds, and other metals as natural impurities. Water color is affected by climate change, seasonality, floods, and anthropogenic impact. Currently, methods for decolorization of highly colored natural waters are being actively developed.

Objective: To compile a list of water bodies with very high water color values based on the results of laboratory testing of water from centralized water supply systems in populated areas of the Russian Federation.

Materials and Methods: We used laboratory results of testing water sampled from centralized water supply systems in 2022–2025 to evaluate water color values for compliance with the standard and categorize them according to the Hazen color scale.

Results: In 2022–2024, water color exceedance was detected in all samples while in 2025, 4.2 % of the samples were noncompliant. In 2022–2024, the maximum color value detected was 458.0 and in 2025 – 535.0. In 2025, very high water color values were established in 0.3 % of water from water sources and pipelines and 0.1 % of water from the distribution network. Very high color values were also determined for 41 of 167 surface water bodies with water intakes.

Discussion: The decrease in the maximum water color values in water sources and pipelines and in the proportion of exceedances in 2025 was associated with a reduction in wastewater discharge, construction and reconstruction of water treatment facilities, and changes in drinking water treatment technologies. Future plans include public health risk assessment of exposure to highly colored drinking water, the study of high-color treatment methods, and evaluation of their effectiveness.

Conclusion: Highly colored waters are used for drinking water supply in the Russian Federation. Our findings formed the basis for a list of highly colored surface water bodies.

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