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.

The condition of the existing sewerage system, the mean value and extremes of hydraulic loads for dry and rainy weather, organic load and key parameters of wastewater quality are determined based on the analysis of the collected technical documentation related to the existing sewerage system, statistical data on the number of inhabitants connected to the sewerage system, questionnaires filled out by the public utility company and industrial enterprises, the results of flow measurements and sampling of wastewater and testing of its physico-chemical characteristics. The algorithm for calculating the input parameters relevant for the dimensioning of the future plant is then selected depending on the condition of the sewerage system and the planned reconstructions and extensions, demographic, as well as projections of economic development.

An analysis of the dynamics of the process of biochemical colmation of laterals of radial wells at the Belgrade groundwater source is presented. A very good correlation between the rate of forming of the colmations and the concentration of bivalent iron was obtained, on the basis of which the maximum recommended flows and velocities were defined, which are in good agreement with the values from previous articles and studies. The effects of regenerations on yield and the total volume of extracted water (up to 2 times higher than in the case of no regeneration) were investigated using a mathematical and software model. A correlation was developed linking the ratio of the amounts of water extracted with and without regeneration, to the aquifer hydraulic resistance, the coefficient of local hydraulic losses reduction due to regeneration, and the number of regenerations. The factor equal to the square root of the number of regenerations increased by one was added to the expressions for the maximum recommended values of inlet velocities and flows per lateral. The differences in flows and extracted volumes between operating modes with constant flow between regenerations and a constant, minimal water level were also examined using the model. The ratio between the total extracted volumes when the drawdown is kept equal to maximum and when the flow between the regenerations is kept constant reaches up to 1.25.

This work presents a review of mechanical centrifugation and pyrolysis, two prominent techniques used for the efficient management of oil refinery sludge. The petrochemical industry produces large quantities of hazardous oily sludge, which demands complex and costly treatment methods due to its diverse composition. However, a major component of this sludge is crude oil, which holds significant recycling potential. As a result, various technologies, including combined processes, have been developed to recover crude oil from sludge. This study evaluates the effectiveness of combining mechanical centrifugation and pyrolysis, specifically focusing on their oil recovery capabilities. The primary objective is to explore the development of these recycling technologies while summarizing and comparing their mechanisms, advantages, and limitations.

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.