Advanced oxidation processes in ships' ballast water treatment

Brodske balastne vode općenito se smatraju glavnim vektorom za prenošenje alohtonih morskih organizama. Iako je primjenjivost priličnog broja tehnologija utemeljenih na poznatim postupcima pripreme pitke i obrade otpadne vode ispitana na balastnim vodama, vrlo malo njih oslanjalo se na postupke napredne oksidacije. Glavni cilj ovog rada bio je istražiti primjenjivost nekih naprednih oksidacijskih postupaka u obradi brodskog vodenog balasta. Ove tehnologije počivaju na generiranju vrlo reaktivnih OH radikala u dovoljnoj količini da mogu učinkovito utjecati na uklanjanje mnoštva visoko otpornih spojeva u vodi. Ispitana je mogućnost primjene ultrazvuka velike snage u obradi brodskih balastnih voda. Djelovanje ultrazvuka u vodenim otopinama očituje se kroz fenomen akustične kavitacije u kojoj pri implozivnom urušavanju kavitacijskog mjehurića nastaju izvanredne okolnosti koje pogoduju nastajanju hidroksilnih radikala. Ispitan je utjecaj amplitude ultrazvuka i zasićenje otopine pojedinim plinovima na nastajanje OH radikala. Rezultati istraživanja upućuju na mogućnost primjene ultrazvuka velike snage u obradi balastnih voda. Primjenu ozona u obradi balastnih voda prati nastajanje ukupnih rezidualnih oksidanata koji posjeduju izvjesno dezinfekcijsko svojstvo te se ponekad i nazivaju sekundarnim oksidantima. Ispitivanje raspada ukupnih rezidualnih oksidanata u tami pokazalo je da neki parametri vode poput temperature, saliniteta i sadržaja prirodnih organskih tvari u vodi bitno utječu na brzinu raspada te se njihov uglavnom nepoznati i nepredvidivi utjecaj na kinetiku raspada ukupnih rezidualnih oksidanata mora uzeti u obzir prilikom obrade balastne vode ozonom. S ciljem ispitivanja primjenjivosti UV/O3 postupka u obradi vodenog balasta, konstruiran je i izveden pilot uređaj u Dubrovniku koji se sastoji od hidrociklona, višeslojnog filtra, ozon generatora i UV reaktora. Rezultati preliminarnih ispitivanja ove tehnologije pokazali su da postoji veliki potencijal za njenu primjenu, međutim za postizanje učinkovitije inaktivacije vrlo otpornih vrsta kao što je Artemia salina potrebne su više doze ozona od onih primijenjenih u eksperimentu.Ships' ballast water is generally considered to be a major contributor to the introduction of non-indigenous species because of the large volumes and frequency of possible inoculations. While there has been a considerable amount of research done on the ballast water treatment in the last 15 years, there have been very few that have dealt with the application of Advanced Oxidation Processes (AOPs) for the prevention of transference of aquatic invasive species. The main goal of this work was to investigate the applicability of AOPs for treating ballast water. In the treatment of drinking water, these AOPs utilize generated OH radicals (hydroxyl radicals), highly reactive oxidizing agents, to oxidize and destroy a wide variety of pollutants. Since the oxidation in these processes is accomplished by the hydroxyl radicals, any AOP which has the capability to produce high concentrations of dissolved hydroxyl radicals could be of interest and potentially used for the treatment of ballast water. Ultrasonic irradiation is one treatment option being considered for eliminating non-indigenous species in ballast water. Ultrasonic irradiation of aqueous solutions induces acoustic cavitation that lead to enhanced chemical reactivity and OH radical production. The optimization of ultrasonic irradiation as an advanced oxidation technology can be accomplished by adjusting the ultrasonic amplitude and saturating gas during sonolysis. The production rate of the hydroxyl radical was investigated in terephthalic acid solution during sonolysis as a function of the horn amplitude and the nature of the dissolved gases. Results indicated that there is a great potential for the application of high power ultrasound in ballast water treatment. When ozone is applied to seawater, secondary disinfectants are formed, commonly measured and expressed as total residual oxidant (TRO). The goal of this study was to determine those variables most likely to affect the rate of TRO decay in dark that occurs over time in ballast tanks. Results indicated that seawater characteristics such as temperature, salinity and organic content strongly affect the rate of TRO decay, and therefore need to be thoroughly considered in determining ozone requirements for ballast water treatment. In order to examine the applicability of UV/O3 process, a pilot plant was designed. It consisted of a hydrocyclone, multimedia filter, ozone generator and UV reactor. The pilot study showed that UV/O3 process can offer advantages over individual use of ozone and UV irradiation in terms of inactivation efficiency, but for removal of extremely resistant cysts, such as Artemia salina sp., higher ozone doses need to be applie