Is ozonation an efficient method for the treatment of marine waters?

Abstract

Event Abstract Back to Event Is ozonation an efficient method for the treatment of marine waters? Joana F. Leal1*, Valdemar I. Esteves1 and Eduarda B. Santos1 1 University of Aveiro, Department of Chemistry, Portugal Ozonation contributes to water disinfection (eliminating most target pathogens) and improves the water quality by reduction of biochemical oxygen demand. It promotes the oxidation and degradation of organic compounds by formation of reactive oxygen species which may react with the organic molecules [1]. But, will this method be efficient in all matrices? What are the problems associated with the ozonation process in marine waters? This work intends to answer these questions, not only based on the chemical reactions that occur between ozone and the natural components of the waters, but also through a set of experiments carried out in natural marine waters [2]. For that, natural water samples from two different aquaculture companies of Portugal (designated as company A and company B) were collected twice. These two companies have distinct water circuits, but have some common steps of water treatment. In the two companies, water samples were collected before entering in the production tanks (blank control, L0 – water intake), at the output of tanks (L1), after mechanical filter (L2) and after ozonation (L3). Additionally, in company B, water samples were collected after the biological filter (L2b). For each sampling site, three to six replicates were collected in each sampling. All water samples collected were characterized regarding to the following parameters: pH, salinity, total suspended solids (TSS), dissolved organic carbon (DOC), total and inorganic carbon of suspended particles (TCpart and ICpart). In addition, spectroscopic characteristics of water samples were analysed by UV-Vis and 3D molecular fluorescence spectroscopies [3]. Throughout the water treatment circuit (L2, L2b and L3 sampling sites), the analyzed parameters did not show a large variation. The most obvious example is the absence of significant degradation or mineralization of dissolved organic carbon after the ozonation process. Using UV-Vis and 3D molecular fluorescence spectroscopies, one also concluded that very significant changes on the structure of the organic matter after ozonation did not occur, namely in company B (figure 1), where DOC before treatment is higher and the ozone dose is lower than in company A [3]. The results obtained in this work corroborate the low efficiency of ozonation to degrade organic matter, in saltwater, putting into evidence the need to combine it with another treatment process, in order to improve the efficiency of water treatment. Figure 1 and 2 – Excitation-emission spectra (n ≥ 2) of filtered aquaculture’s water samples (contour maps) collected before (above) and after (below) ozonation, in company B. Figure 1 Figure 2 Acknowledgements Authors would like to acknowledge funding from National Foundation for Science and Technology – FCT (POPH/FSE) to Centre for Environmental and Marine Studies (CESAM) (UID/AMB/50017/2013). Authors are also grateful to the University of Aveiro. Joana F. Leal thanks FCT for her PhD grant (SFRH/BD/88572/2012).