The design of a water treatment plant requires thorough analysis of water quality, capacity, location, and reliable technologies. Groundwater sources with elevated levels of organic matter, color, arsenic, and dissolved gases represent a particular challenge for treatment. In this study, the application of dissolved air flotation (DAF) was systematically investigated as a pretreatment method for groundwater purification. Jar test experiments were conducted to evaluate the removal of total organic carbon (TOC), color, and arsenic under various coagulant dosages. The results demonstrated that DAF achieved up to 65% TOC removal and significant arsenic reduction, while also improving water color. Compared with conventional pretreatment, optimized DAF conditions provided higher efficiency and practical applicability for real-world water treatment plant design. The findings highlight the potential of DAF as an effective technology for addressing complex groundwater contamination and contribute to expanding its use beyond conventional surface water treatment.

In this paper, based on the data of the Ribnica accumulation (Serbia), and the required quality of raw and treated water, an optimal solution for improving and optimization of the technology of water purification to drinking quality at a water treatment plant (WTP) in Zlatibor, Serbia, was proposed to ensure maximum efficiency and flexibility in system operation. Analysis of water quality has shown that after the treatment at the plant, all parameters were within the respective maximum available concentrations (MAC) stipulated by the Rulebook on the hygienic suitability of potable water of the Republic of Serbia, except for the nickel content. The paper presents the results of the nickel removal using multiple laboratory tests as well as at the WTP to achieve the best procedure for water treatment. In accordance with the results obtained the water quality problem in terms of the nickel removal was solved and the required effects are obtained (nickel content below the MAC, i.e. <0.02 mg dm-3)

Zrenjanin's water supply is from the spring "Mihajlovacki road", where groundwater is collected from 34 wells at depths of 50 to 137 m. The quality of the water, which is characterized by an increased color, content of organic matter, ammonia, dissolved gases (methane) and metals (arsenic, sodium and boron), requires complex treatment. Many domestic and foreign experts have been involved in researching firstly the efficient and then the optimal process of processing this water. more or less successful. This paper presents the application of purification technology at the water factory in Zrenjanin as a result of cooperation between companies Metito Utilities Limited (Pannonian Water Ltd Belgrade) and "Jaroslav Cerni" Water Institute Ltd.

Dissolved-air flotation (DAF) is widely used for surface-water pretreatment but remains insufficiently explored for chemically complex groundwater. This study develops a thermodynamic and bubble-dynamics modeling framework to evaluate the feasibility of DAF pretreatment for groundwater containing elevated arsenic, natural organic matter (NOM), and color. The study is theoretical and model-based; no experimental dissolved-air flotation tests were performed. Air solubility was calculated at pressures of 4–6 bar and temperatures of 13–17 °C, while microbubble size, rise velocity, and bubble–floc interaction efficiencies were estimated using established physical models. Laboratory coagulation–flocculation jar tests with FeCl₃ and FeCl₃/PAC were used to define realistic floc properties prior to flotation modeling. No experimental dissolved-air flotation tests were conducted; all flotation-related results presented in this study are derived from thermodynamic and hydrodynamic modeling. Results show that a temperature decrease from 17 to 13 °C increases effective gas supersaturation by ~15% and shifts predicted microbubble diameters from ~60–90 µm to ~35–60 µm under identical operating conditions. The qualitative consistency between modeled flotation-relevant parameters and previously observed coagulation–flocculation trends for color, total organic carbon, and arsenic removal supports the proposed mechanistic framework. The study demonstrates how coupling coagulation chemistry with thermodynamically optimized air dissolution can enhance DAF applicability for arsenic- and NOM-rich groundwater.

The ratio of concentrations of total nitrogen and five-day biochemical oxygen demand in the sanitary wastewater of an energy infrastructure facility in Serbia is many times higher than usual, resulting in only half of the total nitrogen being eliminated in wastewater treatment plants (membrane bioreactor with anoxic and aerobic reactors) by denitrification. The first step of analysis was mathematical modelling of the composition and origins of the input wastewater. The model was developed based on the scientific literature data on composition of human excrement and the data on composition of water used for sanitary purposes. Next, it was successfully verified by comparisons to the experimental data of the wastewater composition. In the next step, a model for wastewater treatment simulation was created by using the BioWin software (Envirosim Associates, USA) in order to examine functioning of the plant and test the effects of several possible modifications of the process. A good agreement with the qualities of the influent and effluent determined by laboratory analyses was achieved after model calibration. The results of simulations showed a tenfold decrease in the total nitrogen concentration and a fortyfold decrease in the total phosphorous concentration in the effluent after introducing the following modifications to the simulated process: ferric chloride dosing, increasing dosing of acetate in the anoxic reactor by a factor of seven, increasing of the waste activated sludge rate by a factor of four and increasing the recirculation flow rate by a factor of three.

The results of two flow, sampling and laboratory analysis campaigns of wastewater indicated their high dilution by the intensive inflow of foreign water into the fecal sewage system, which is a major problem for the functioning of the future wastewater treatment plant, which would have to be significantly oversized. A two-day field testing campaign was carried out, which included inspection of manholes, Measurements of flow, electrical conductivity and temperature of water to determine whether there is an inflow of surface water or infiltration of groundwater, and to find the points and/or zones of the most intense inflow of foreign water. The site of the inflow of the previously unregistered stream was found and possible solutions to the problem were defined.