Organic matter present in natural water is a serious problem during water treatment in terms of the possibility of creating disinfection by-products (DBP). The new materials and processes are still analyzed in order to improve the efficient removal of organic matter as well as other pollutants from water intended for human consumption. The aim of the presented study was to evaluate the efficiency of using various combined processes: (a) coagulation and adsorption, (b) oxidation with ozone and coagulation, (c) oxidation with ozone, coagulation and adsorption, and (d) oxidation with ozone, UV irradiation, coagulation and adsorption for treatment of the modified surface water. In the presented study, the changes in pH, turbidity, color, organic matter content (evaluated as oxidizability, total and dissolved organic carbon content, UV 254 and 272 absorbances), and Ni²⁺, Cd^2+, and Pb²⁺ ions content were determined during modified surface water purification. Supporting the coagulation process by adsorption with additional ozonation and UV irradiation of the water sample improved the treatment processes of modified surface water. Processes associated with coagulation increased the efficiency of removing color by 4–16% and reduced the value of UV₂₅₄ and UV₂₇₂ absorbance by 10–20%. Using ozonation did not significantly change the content of total organic matter. Heavy metal ions were mostly removed by coagulation and adsorption processes (40–60%). Including ozone, oxidation resulted in insignificant changes in the concentration of metal ions in the purified water (less than 5%). During the treatment of the tested, modified surface water, the best efficiency was observed after the use of coagulation and adsorption processes enhanced with ozone oxidation. The additional involvement of UV irradiation did not have a significant effect on the removal of the analyzed pollutants.

The aim of the research work was to evaluate the capability of pre-hydrolysed aluminium salts to reduce turbidity, colour and organic matter from surface water. The coagulants used in the study were Al₂(SO₄)₃ and hydrolysed polyaluminium chlorides: PAX18, PAX-XL3, PAX-XL10, PAX-XL 19F, PAX-XL1905, PAX-XL61 and PAX-XL69. Using pre-hydrolysed salts—polyaluminium chlorides—made it possible to obtain better effects of surface water treatment compared with the results accomplished with non-hydrolysed aluminium salt (aluminium sulphate). At a dose of 3 mg Al L⁻¹ the best effects of turbidity, colour and organic matter removal were obtained using PAX-XL1905, which is polyaluminium chloride of high alkalinity. Under these conditions, 89% reduction in turbidity and 50% in colour was achieved. Moreover, the total organic carbon (TOC) value decreased by 26%. When pH was decreased from 8.2 to 6.2 the effectiveness of TOC removal increased (upto 37%). The addition of powdered activated carbon to water during coagulation did not significantly affect the effectiveness of organic compounds removal.

The requirements for water intended for domestic and economic purposes prompt the search for new solutions in surface water treatment technologies. In this study, the enhancement of coagulation processes by connections with adsorption and/or ozonation for surface water treatment was studied. The possibility of a reduction in natural organic matter (NOM) content in modified surface water was analysed regarding changes in colour, turbidity, oxidisability (OXI), total and dissolved organic carbon (TOC, DOC) and absorbance at 254 nm (UV₂₅₄). Additionally, the changes in copper and zinc ion content during the modified surface water treatments studied were analysed for initial metal concentrations of 0.5 or 1.0 mg/L. Studies of modified surface water were carried out with doses of medium-basicity PAX coagulant (C2) 5 mg/L and PAC 100 mg/L. During the coagulation process, the colour decreased by 86–90%, turbidity by 85–90%, OXI by 65–77%, TOC by 65–76% and UV₂₅₄ absorbance by 73–84%. The enhancement of coagulation with adsorption and/or ozonation resulted in an increased efficiency of colour and turbidity removal by 2 and 4%, respectively. The highest increase in efficiencies of OXI, TOC, DOC and UV₂₅₄ removal, by 12, 12, 11 and 11%, was observed for the connection of ozonation with coagulation and adsorption. The efficiency of metal ion removal from modified water observed for the single coagulation process was 58 and 55% for copper and 46 and 43% for zinc, respectively, for initial concentrations of 0.5 and 1.0 mg/L. The intensification of coagulation with ozonation and adsorption resulted in metal removal on the level of 66 and 62% for copper and 62 and 54% for zinc.

In recent years, conventional water treatment systems have been supported by ozonation or UV irradiation processes. The efficiency of four hybrid processes: (1) coagulation and adsorption, (2) ozonation and coagulation, (3) ozonation, coagulation and adsorption, (4) ozonation, UV irradiation, coagulation and adsorption of inorganic and organic pollutants removal was analysed. In the presented study, the content of organic matter in natural water was evaluated as colour, oxidisability (OXI), total and dissolved organic carbon (TOC and DOC) content and UV absorbance at the wavelength of 254 nm for natural and modified water. Additionally, removal of Ni²⁺, Cd²⁺and Pb²⁺ ions during the treatment processes was analysed. The coagulation process with the use of polyaluminium chloride removed 45% of colour and 39, 26% and 45% of OXI, TOC and UV absorbance, respectively. Using the ozonation before coagulation increased efficiency of colour and UV₂₅₄ absorbance reduction by 33% and 25%, respectively. Coagulation with both UV irradiation and adsorption had insignificant results on the analysed factors value. The coagulation process was the most efficient for metal ions removal (40–78%). The ozonation process before coagulation increased removal up to 55–85%. Additional irradiation with UV or using of the adsorbent during coagulation of initially ozonated water had an insignificant impact on metal ions concentration in water.

The application of oxidation processes, including advanced oxidation, in water treatment is one of the effective methods for eliminating risks associated with the presence of organic substances in water and those formed during chlorination. This article presents the impact of advanced oxidation in the UV + O₃ process on the content and structure of organic substances present in three natural waters with different levels of total organic carbon (TOC). The process was carried out using low-pressure and medium-pressure lamps with an irradiation time of 40 min and ozone doses of 1.5 gO₃/m³ and 5 gO₃/m³. Advanced oxidation, regardless of the type of lamp used or the ozone dose, had the greatest effect on the content of humic acids, which underwent both transformation and mineralization. The use of a low-pressure lamp resulted in an increase in the content of organic substances with the lowest molecular weight (1.3 kDa. Regardless of the ozone dose and the type of lamp used, the transformation of organic substances dominated over mineralization, whose efficiency reached a maximum of 44.9% and 38.4% for the low-pressure and medium-pressure lamps, respectively. The degree of organic substance transformation and the efficiency of their removal were directly proportional to the TOC content in the raw water. The use of a low-pressure UV lamp ensured higher process efficiency, which is also associated with lower energy costs.