Cleaning and disinfecting water: the ultrasound prospects

One of the research directions of Hilsonic, an innovative UK-based ultrasonic cleaner appliances manufacturer, is studying the effect of plasma on the chemical and bioactive properties in liquid-phase media. The development of methods aimed controlled elimination of biological and chemical micro-objects in aqueous environments for the purpose of disinfection, the establishment of cleaning sonochemical systems to purify water from oil, heavy metals and other organic pollution, and an analysis of the technological parameters of the process water treatment and the prospects of creation of the necessary pilot equipment are on the agenda.

Currently, due to the worsening shortage of drinking water throughout the world, the need to develop new scientific and technological solutions aimed at sterilisation and domestic sewage, and industrial process water is growing. The The needs for food and medicine define the development of methods for fine cleaning and disinfection of water. A number of industrial sterilisation technologies that exist today, and based mainly on the thermal effect on the treated environment, have one drawback – high energy consumption, fast wear and the formation of by-products – precipitation of metal salts.

Therefore, communities are facing is an urgent task to create new methods of targeting a hydrophilic chemical and biological properties in the aqueous phase. Using powerful ultrasonic processes can reduce the cost of processing, increase the efficiency of current products, or creating new products to intensify traditional processes or to encourage the implementation of new approaches taking into account the current environmental situation.

To solve the problem of selective exposure to the plasma on biological objects in the aqueous phase a technique of driving a plasma discharge in a stream of fluid is considered. The stream of liquid that must be subjected to plasmachemical processing via conduit is directed into a hydrodynamic transducer disposed at the inlet of the reactor, in which the liquid due to pressure drop and lowering of the enthalpy flow is forming vapor-liquid two-phase supersonic flow at reduced pressure. In the reactor, the electrodes between which an external power source an electric field (DC, AC, high-frequency, microwave, or a combination thereof), the intensity of which exceeds the breakdown threshold of the two-phase medium, leading to excitation of the quasi-stationary low-temperature glow plasma discharge. After exposure to the plasma chemical fluid enters the tapering portion of the duct and is collected in the storage, or fed to the unit through the membrane treatment for further separation and processing.

During the preliminary sonoplasmic and biological researches in the water a sonoplasmic discharge of directional influence on biological objects is considered, in particular, the various strains of microorganisms to disinfection and sterilisation of water.

A series of experiments is carried out in aqueous solutions of rod Escherichia coli cells and Micrococcus luteus cell groups. The increase in the discharge current up to 5 ampere has stopped the growth of bacteria after the passage of through the discharge zone. Parallel produced crops showed a significant reduction in CFU (colony forming units) after 5 minutes of exposure, which is consistent with the direct microscopic observation. After 10 and 15 minutes of exposure Escherichia coli and Micrococcus luteus were not detected. The sterility of the treated solution in the latter case was maintained during subsequent storage at room temperature for at least 10 days.

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