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Disinfection of ballast water using ozone nanobubble technology

Katris Konstantinos

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Year 2021
Type of Item Diploma Work
Bibliographic Citation Konstantinos Katris, "Disinfection of ballast water using ozone nanobubble technology ", Diploma Work, School of Chemical and Environmental Engineering, Technical University of Crete, Chania, Greece, 2021
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The majority of freight transportation internationally is carried by vessels. For a very long time, maritime remains the top choice in the ways of global transportation. Nevertheless, since maritime is so widespread across the world, it certainly has an impact in sea ecosystems, leaving an ecological footprint. Two most important factors of sea environment pollution are: the toxic gas emissions from internal combustion ship engines, and the uncontrolled discharge of ballast water. Each vessel has its own ballast water tanks that are occasionally filled with sea water in order to regulate the freight weight loss when travelling with less cargo. Therefore, very large amount of sea water, possibly contaminated from foreign sea shores may be illegally discharged at a totally different coastal area without any local authority control. In 2018, International Maritime Organization (comm. IMO) established a regulation framework (D2 regulation) concerning restrictions on discharged sea water quality standards. Many shipyard companies have developed ballast water disinfection systems that manage to treat and discharge ballast sea water completely cleaned. In this thesis a new way of sea water disinfection is being examined. More specifically, sea water is treated by using ozone nanobubbles which are expected to maintain the ozone in a more stable way than ordinary macrobubbles. Apart from the significance of the bubbles size, bacteria inactivation analysis is also a very important aspect that shows whether this water treatment method has capabilities or not. Moreover, the effect of salinity and initial ozone concentration on the ozonation process was studied.During the experimental process of sea water disinfection, bacteria was added to the saline water with an initial bacterial concentration of 10^7 CFU/mL of Escherichia coli and Enterococci. The ultimate disinfection effect (CFU(Inactivated)/mg ozone) was increased by the increase of salinity.

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