MOSCOW, 18 Apr. Scientists of the Samara Polytechnic University as part of a research team have developed a scheme for efficient wastewater treatment from oils, petroleum products and other non-wettable pollutants. According to the developers, the new technology makes it possible to increase the specific productivity of the process by 10% without increasing the cost. The results of the study are published in Chemical Engineering and Processing: Process Intensification.
Scientists from the Samara State Technical University (SamSTU), together with colleagues from the Penza State University of Architecture and Civil Engineering, have developed a new pressure flotation technology.
Flotation is a method that is used to enrich minerals. It is based on the fact that substances are held differently at the liquid/gas or oil/liquid interface. Hydrophobic (non-wettable) particles are fixed on it, while those with a high affinity for water do not. The method allows you to separate particles according to this principle.
The developers proposed to improve the use of pressure flotation in wastewater treatment plants. In this case, air is supplied to the saturator tank, and a pressure of 4–6 atm is injected into it. Air dissolves in water, and when this mixture is splashed into the flotator, the pressure drops sharply to atmospheric pressure and gas bubbles form.
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» The essence of this method is most easily explained by opening a bottle of sparkling wine. While the bottle is closed, there are no bubbles in it, but after opening the liquid «boils». Dissolved gas is released from it under high pressure in the form of bubbles, «explained Sergey Stepanov, Professor of the Department of Water Supply and Sanitation of ASA SamSTU.
Stepanov added that the bubbles capture hydrophobic contaminants – oils, oil products and suspension – into the foam layer. In this way, wastewater is purified. width=»600″ data-crop-height=»338″ data-source-sid=»not_rian_photo» class=»» />
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According to the scientists, most of the flotation cleaning plants now use a fine fraction of bubbles, the size of which does not exceed 0.07 mm. They proposed to additionally use medium-sized bubbles.
Researchers have developed a new saturator circuit — a device that will allow obtaining and separating bubbles of 0.2–0.3 mm in size. It is these bubble sizes that are a compromise between the amount of impurities captured from the water and their ascent rate, the scientists explained. https://ria.ru/20220101/voda-1766344871.html» data->
«Small bubbles will capture more contaminants, but will float more slowly. And then you will need a large surface of the skimmer. And too large bubbles will not provide effective wastewater treatment, because they can retain fewer contaminants. Bubbles 0.2–0.3 mm do not create additional flow turbulence, which protects them from premature separation from the trapped particles,» Sergey Stepanov said.
The scientists specified that the proposed design consists of two chambers. In the first, small bubbles capture particles of pollution and form primary complexes with it. In the second, these complexes pick up faster medium bubbles and, like on an elevator, are lifted to the surface for subsequent foaming and removal.
In the future, scientists plan to introduce their developments at existing treatment facilities.