Airlift pumps are the simplest devices used for lifting and transporting of liquid in water and wastewater systems. They constitute the subject of interest in numerous studies, focusing on their two-phase flow. The knowledge of two-phase flow parameters is necessary for the correct design of an airlift pump. In the available literature on the subject, one will find numerous models describing the two-phase gas-liquid flow. One of the most popular is the Zuber-Findlay model, also called the slip model. The subject of the present research consisted in a vertical bubble column, with the diameters of 50 and 75 mm, used to transport the water-air mixture. Based on the results obtained, hydraulic characteristics were developed: liquid flow depending on the depth H s and the air flow Q p. For the mathematical description, second-degree polynomial model was applied, as well as and assessment of the determination coefficient was performed. Efficiency factors of the airlift pump and other parameters for two-phase mixture during the airlift pump's operation were determined using the slip model. Based on the experiment, it has been found for both of the analysed diameters that the efficiency of the airlift pump increased along with the depth H s and the air flow Q p. The airlift pump achieves maximum liquid efficiency within a specified range of the immersion depth. In a small diameter airlift pump (50 mm), slug and plug flow regimes are predominant.

The efficiency of the aeration process in airlift reactors with moving beds Efektywność procesu napowietrzania w reaktorach barbotażowych ze złożem ruchomym AbstractThe current work consisted of performing tests on the prototype airlift reactor, examining the efficiency of oxygenation in an airlift reactor equipped with an airlift pump and an additional nozzle to aerate and mix water in the tank. In particular, the objective was to find the optimal submergence of the nozzle which would allow achieving the best possible oxygenation of water with adequate lift efficiency. The testing was performed in two series: with a tank fully filled with water; with a tank filled with 80% water and 20% moving bed. The use of a moving bed with a high specific surface area significantly improved aeration conditions and decreased mixture flow velocity thus causing an increase of gas and liquid contact time. The research has shown the effect of nozzle position on the aeration and circulation conditions in the reactor. Keywords: airlift reactor, aeration, moving bedStreszczenie Praca polegała na wykonaniu serii doświadczeń na modelu fizycznym prototypowego reaktora barbotażo-wego. Badano skuteczność natleniania wody w reaktorze barbotażowym wyposażonym w podnośnik powietrzny, zaopatrzony w dodatkowy króciec napowietrzający i powodujący cyrkulację cieczy w zbiorniku. Celem było znalezienie optymalnego zagłębienia króćca, które pozwoliłoby na osiągnięcie jak najlepszego natlenienia cieczy przy odpowiedniej wydajności podnośnika. Badania wykonano w dwóch seriach: dla zbiornika napełnionego wyłącznie wodą i dla zbiornika wypełnionego w 20% objętości złożem ruchomym. Zastosowanie złoża o dużej powierzchni właściwej znacznie poprawiło warunki napowietrzania, zmniejszyło prędkość cyrkulacji mieszaniny, co pozwoliło zwiększyć czas kontaktu cieczy i gazu. Badania wykazały wpływ położenia króćca na warunki tlenowe i cyrkulację mieszaniny w reaktorze.Słowa kluczowe: reaktor barbotażowy, napowietrzanie, złoże ruchome 168

Barbotage reactors such as airlift reactors (ALR) and bubble column reactors (BCR), due to their two-phase flow systems, were investigated in many research papers. In their basic design variants, they are typically used to lift, mix, and aerate liquids, while, when equipped with additional elements in hybrid variants, their individual properties, i.e., lifting, mixing, and aeration of liquids, can significantly change with the same reactor geometry. The object of this study was to develop a hybrid barbotage reactor in various structural design variants. The structure consisted of a barbotage column of 50 mm in diameter, used to transport a water–air mixture outside the reactor (so-called external loop). The installation was additionally equipped with a nozzle in order to improve mixture aeration and circulation efficiency. The nozzle was mounted at various heights of the column pump segment. Additionally, the reactor was equipped with s moving bed in two variants (20% and 40% reactor capacity) in order to determine its effect on the mixture aeration and circulation conditions. Based on the measurement results, aeration curves were prepared for various structural design and column packing variants of the reactor. Properties of the two-phase mixture were determined for both parts—ALR and BCR. Technological and energy parameters of the aeration process were calculated, and the results obtained for the individual structural design variants were compared. It was found that, for the most advantageous design, in terms of aeration efficiency, the aeration nozzle should be placed in the mid-length of the pump segment of the barbotage column, irrespective of the hybrid reactor packing rate with the moving bed. The reactor packing with the moving bed resulted in a decreased mean water velocity in the reactor. For most analyzed structural design variants, the respective packing with the moving bed had no significant effect on aeration efficiency. Only for one structural design variant did the lack of packing significantly improve oxygen levels by as much as approximately 41%.

Especially in non-urbanized areas there is a need to use various waste products, e.g. from agriculture, households, etc. New products that are created in a simple way should be able to be used many times without the use of complicated and expensive technology. This article presents the potential of biochar used in wastewater treatment processes and sludge management in small installations - for the maximum maintained number of users equal to 50. The possibilities of two substances used in sewage management processes, such as char and biochar will be presented. These substances, produced from pyrolysis, are stable carbon-rich compounds which have various beneficial applications like soil conditioning, remediation and wastewater treatment. In particular, biochar originating from wastewater sludge pyrolysis, possible to be generated at the place of formation, was taken into account. In addition, ways to increase the reliability of the treatment plant with biochar based filters are described.

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