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USE OF AN EJECTOR-CAVITATOR FOR EFFICIENT TREATMENT OF SHIP BALLAST WATER

Dmitry Mizgiryov

Abstract

The article discusses an urgent problem of designing systems for ship ballast water (BW) treatment ensuring high efficiency at low power consumption and small mass and size. Transportation of invasive organisms with ballast water presents a serious danger for the world ocean. According to the International Marine Organization (IMO), the BW global turnover reaches 12 billion tons annually. A number of species of aquatic organisms transferred daily with ballast water exceeds 7,000. Many of them not only survive in ballast water, but also after the ballast water discharge in ports and adjacent water areas adapt successfully to new environments affecting existing ecosystems. Thus, the current practice of BW changeover should be replaced by efficient on-board treatment so that to prevent further expansion of invasive organisms all over the world with ballast water. For this purpose a system the main element of which is an ejector-cavitator combining functions of a hydrodynamic cavitator, a water-gas ejector, and a mixer may be offered. Cavitation is a rupture of dropping liquid under tensile stresses due to the change of characteristics of the velocity and pressure fields occurring at rarefaction in the considered point of the liquid. During the rupture of dripping liquid cavitation bubbles (cavities) form filled with steam, gas or their mixture. Due to intensive vibration and high temperature at a single point, cavitation destroys actively organic compounds and cell membranes of microorganisms. Therefore, cavitation treatment may be an effective instrument for disinfection of ballast water and extermination of harmful macro- and microorganisms. This unit is installed on a pump pressure line, it does not contain moving parts, has relatively low hydraulic resistance and small weight and size parameters. Based on the results of the conducted experiments, optimal characteristics ensuring efficient operation of the ejector-cavitator were found.

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DOI resolver: doi.org/10.5593/sgem2019/5.1/s20.097

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