Detection of unauthorized wastewater discharge into a surface water body using infrared thermography

Introduction. The relevance of this study is due to sanitary and hygienic risks associated with anthropogenic pollution of surface waters, especially in sanitary protection zones (SPZ) of drinking water sources. Disruption of the thermal regime of water bodies promotes the growth of pathogenic microflora. The use of infrared thermography as a remote monitoring method can significantly improve the efficiency of sanitary and hygienic water monitoring.

Objective. To substantiate and test a method for detecting unauthorized wastewater discharge into surface watercourses using thermal imaging equipment with subsequent bacteriological verification.

Materials and methods. The study used thermograms and water samples from the coastal zone of the Don River within sanitary protection zones (SPZ) boundaries. Thermal imaging was conducted using portable and remote devices, including the Doogee V20 Pro (InfiRay) and DJI Mavic 3 Thermal. Bacteriological analysis (total coliforms, Escherichia coli, Enterococcus faecalis) was carried out in accordance with MU 4.2.3690–21, while sample transport and storage followed GOST R 59024–2020. Statistical analysis was performed using Student’s t-test (p < 0.05).

Results. Thermal inspection of the Don River delta revealed coastal areas where water temperature exceeded background levels by ≥3 °C. These locations showed more than fivefold exceedances of total coliforms, E. coli, and E. faecalis concentrations. The calculated expanded uncertainty (±0.85 °C, p = 95%) confirmed the reliability of these differences. A correlation was found between thermal anomalies and microbiological indicators, indicating two likely sources of unauthorized discharge.

Limitations. The developed approach allows identifying potential sources of unauthorized wastewater discharge into surface waters associated with sanitary and bacteriological exceeds.

Conclusion. The practical value of infrared thermography has been confirmed by field studies. The method proved effective as an auxiliary tool for the rapid detection of unauthorized discharges and enhancing the effectiveness of sanitary and hygienic water monitoring.

Compliance with ethical standards. The study did not require approval from a biomedical ethics committee or other documentation.

Contributions:
Kalyuzhin A.S. – study design, data analysis, manuscript writing, manuscript editing;
Morozova M.A. – study design, manuscript editing;
Zamaraev V.S. – manuscript editing;
Sinitsyna O.O. – data analysis, manuscript writing, manuscript editing.
All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version.

Conflict of interest. The authors declare no conflict of interest.

Funding. The study had no sponsorship.

Received: June 17, 2025 / Revised: July 22, 2025 / Accepted: October 15, 2025 / Published: November 14, 2025

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