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a b s t r a c tOne of the main operational problems when using reverse osmosis (RO) technology is membrane scaling. Scaling directly affects membrane service life, the efficiency of the desalination process and operating costs, therefore predicting and preventing sediment precipitation in membrane systems is a key aspect of their operation. This process also plays an important role during the desalination of geothermal waters. Geothermal waters often exhibit high levels of carbonate hardness and elevated concentrations of silica, sulphates, strontium, barium and other elements. The elevated temperature of geothermal water during its desalination is particularly conducive to the formation of sediments, especially carbonates, but also silica, barite, alumino-silicates and in some cases copper sulphates. The work presents the results of research designed to optimise the selection of antiscalants which permit the reduction of deposits precipitating on the membranes used in the process of water treatment. They included modelling studies, laboratory tests and microscopic analysis of sediments formed on the membranes. The study used brackish geothermal water extracted from the geothermal intake. The geochemical modelling that was carried out (using the program PhreeqC) has allowed a detailed assessment of the tendency of mineral deposits to precipitate from the water being tested. It demonstrated what should be expected as regards the precipitation of different geochemical characteristics. It was all the more necessary to propose an appropriate antiscalant for a broad spectrum of action. Several commercially available antiscalants were used for tests in the RO process. The study was carried out using DOW FILMTEC membranes.

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In this article, particle image velocimetry studies were conducted in a low-speed wind tunnel to investigate the effects of blowing ratio and blade span in terms of the characteristics of the flow field around a film-cooled blade leading edge. The measurements were performed at 20%, 40%, 60%, and 80% of blade span and blowing ratios of M = 0.5, M = 0.75, M = 1, M = 1.5, and M = 2. Velocity, turbulence intensity, and structure of vortices during the interaction between cooling flow and mainstream were analyzed in detail. The analysis shows a significant increase in mainstream velocity at low blowing ratios, M \ 1. Peaks of turbulence were observed at low-and high-span locations. Aerodynamical losses are expected at higher blowing ratios due to the formation of secondary vortices near the outgoing jet. These vortices were a consequence of velocity gradients at this zone.