Considerable changes have been observed in surface waters’ quality in recent years. They include an increase in dissolved organic carbon (DOC) concentrations, as well as a shift of natural organic matter (NOM) composition in favor of low molecular weight (LMW), and they are expected to occur on a wider scale in the future. Those predictions are particularly worrying given the importance of surface water as the main potable water source for numerous communities across the globe. Conventional methods of surface water treatment for drinking purposes mostly focus on the process of coagulation. The progressing changes in the quality of surface waters, however, render the conventional treatment via coagulation inefficient. The issue of the presence of natural organic matter in drinking water sources, its anticipated changes, and the related treatment problems are all complex and pressing matters that need addressing. This paper aims to provide a critical review of recent findings regarding NOM removal via coagulation in reference to the current NOM-related issues and their potential solutions. The paper discusses the application of different types of coagulants, and their respective advantages and disadvantages. Coagulation-integrated processes including adsorption, membrane filtration, biological processes, and oxidation are also addressed. Lastly, insights on the future approach to the discussed issues and conclusions are presented.

Treated wastewater (TW) is a valuable source of water for plant irrigation, helping to protect water resources. However, to use it, a preliminary treatment is necessary, typically involving coagulation to reduce turbidity and then disinfection to ensure microbiological safety. The aim of this research was to determine changes in the concentrations of basic fertilizer components (N, P, and K) in TW after the coagulation process. The tests were carried out in three measurement series for volumetric and surface coagulation using three coagulants: Al₂(SO₄)₃, PAX-XL 19F, and PAX-XL 1911. Four doses of aluminum were used for each coagulation method (volumetric coagulation: 1, 2, 4, and 8 mg Al/L; surface coagulation: 0.25, 0.5, 1, and 2 mg Al/L). Studies have shown that despite the reduction in the concentration of nutrients during the coagulation process, the reclaimed water used for grass irrigation would cover the entire K requirement of this plant. In the case of N and P, the demand would be covered by 14.34% and 8.55%, depending on the coagulant used and its dose. It was also documented that the type of coagulant significantly influences the reduction of fertilizing properties during wastewater treatment. PAX-XL19F was found to cause the least reduction in P and K concentrations, while Al₂(SO₄)₃ had the least negative impact on N regardless of coagulation method or dose.

This study evaluated inorganic-organic coagulant blends for surface water treatment, focusing on purification performance, chemical stability, environmental impact, and potential practical applications. The blends consisted of poly(diallyldimethylammonium chloride) (polyDADMAC) combined with either aluminum sulfate (ALS) or polyaluminum chloride (PAX-XL 19 F). Laboratory-scale coagulation tests were conducted using two dosing strategies: a fixed dose of one coagulant combined with increasing doses of the other. Treatment performance was assessed based on color, turbidity, permanganate index (PI), and ultraviolet absorbance at 254 nm (UV ₂₅₄ ). Chemical stability was evaluated using the Langelier Saturation Index (LSI), Ryznar Stability Index (RSI), Puckorius Scaling Index (PSI), Larson Ratio (LR), and saturation indices. The production-related Global Warming Potential (GWP) of the inorganic coagulant components was also estimated. The most effective treatment configurations were achieved when polyDADMAC was applied at a fixed dose of 2.5 mg/L while the dose of the inorganic coagulant was increased. The polyDADMAC/ALS blend at 2.5/22.0 mg/L and the polyDADMAC/PAX-XL 19 F blend at 2.5/19.3 mg/L achieved comparable color removal (66.67 ± 12.47% and 66.67 ± 4.71%, respectively) and turbidity removal (85.20 ± 4.58% and 84.64 ± 5.93%, respectively). The PAX-XL 19 F/polyDADMAC blend demonstrated greater PI removal efficiency and a less pronounced impact on water chemical stability. However, replacing ALS with PAX-XL 19 F resulted in a higher estimated production-related GWP. Overall, the results indicate that coagulation using selected coagulant blends can effectively support the preliminary treatment of surface water for drinking water production as well as selected non-potable applications.

Przedstawiono problematykę oceniania skłonności wody do wykazywania właściwości korozyjnych bądź do wytrącania osadu węglanu wapnia, na podstawie analizy różnych wskaźników stosowanych do wyznaczania stabilności wody, z uwzględnieniem ich metod obliczania, interpretacji oraz znanych ograniczeń w stosowaniu. W artykule opisano również praktyczne przykłady zastosowania wybranych wskaźników stabilności wody do oceny jej właściwości korozyjnych.