Assessment of Small-Settlement Wastewater Discharges on the Irtysh River Using Tracer-Based Mixing Diagnostics and Regularized Predictive Models
Anapyanova S. Kolpakova V. Kulisz M. Nabiollina M. Yeremeyeva Y. Nurbayeva N. Sherov A.
January 2026Multidisciplinary Digital Publishing Institute (MDPI)
Water (Switzerland)
2026#18Issue 2
An integrated field–analytical framework was applied to quantify the impact of two small-settlement treatment facilities (TF1 and TF2) on the Irtysh River (East Kazakhstan). The main objective of this study is to quantify effluent-driven dilution and non-conservative changes in key water-quality indicators downstream of TF1 and TF2 and to evaluate parsimonious models for predicting effluent-outlet BOD and COD from upstream measurements. Paired upstream–downstream control sections are sampled in 2024–2025 for 22 indicators, and plant influent–effluent records are compiled for key wastewater variables. Chloride-based conservative mixing indicated very strong dilution (approximately (Formula presented.) for TF1 and (Formula presented.) for TF2). Deviations from the mixing line were summarized using a transformation diagnostic (Formula presented.). At TF1, several constituents exceeded mixing expectations ((Formula presented.) for COD, (Formula presented.) for ammonium, and (Formula presented.) for phosphates), while nitrate shows net attenuation (Formula presented.). At TF2, (Formula presented.) values cluster near unity, indicating modest deviations. Under a small-sample regime (Formula presented.) and leave-one-out validation, regularized regression provided accurate forecasts of effluent-outlet BOD and COD. Lasso under LOOCV performed best (BOD_after: RMSE = 0.626, MAE = 0.459, and (Formula presented.) ; COD_after: RMSE = 0.795, MAE = 0.634, and (Formula presented.)). The results reconcile strong reach-scale dilution with constituent-specific local departures and support targeted modernization and operational forecasting for water-quality management in small facilities.
anthropogenic load , domestic wastewater , Irtysh river , small sewage treatment facilities , water quality
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Department of Water Resources and Melioration, Faculty of Water Resources and Information Technology, Non-Profit Joint Stock Company Kazakh National Agrarian Research University, Almaty, 050010, Kazakhstan
Center for Competence and Technology Transfer in Water Management and Water Use, School of Architecture, Construction and Energy, Non-Profit Joint Stock Company “D. Serikbayev East Kazakhstan Technical University”, Ust-Kamenogorsk, 070004, Kazakhstan
Department of Organization of Enterprise, Faculty of Management, Lublin University of Technology, Lublin, 20-618, Poland
Department of Ecology, Institute of Forestry and Environment, Non-Profit Joint Stock Company “S. Seifullin Kazakh Agro Technical Research University”, Astana, 010011, Kazakhstan
Department of Use of Hydromelioration Systems, Faculty of Hydromelioration, Tashkent Institute of Irrigation and Agricultural Mechanization Engineers, National Research University, Tashkent, 100000, Uzbekistan
Department of Water Resources and Melioration
Center for Competence and Technology Transfer in Water Management and Water Use
Department of Organization of Enterprise
Department of Ecology
Department of Use of Hydromelioration Systems
10 лет помогаем публиковать статьи Международный издатель
Книга Публикация научной статьи Волощук 2026 Book Publication of a scientific article 2026