Use of fluorescence spectroscopy to control ozone dosage in recirculating aquaculture systems

Abstract

The aim of this study was to investigate the potential of fluorescence spectroscopy to be used as an ozone dosage determination tool in recirculating aquaculture systems (RASs), by studying the relationship between fluorescence intensities and dissolved organic matter (DOM) degradation by ozone, in order to optimise ozonation treatment. Water samples from six different Danish facilities (two rearing units from a commercial trout RAS, a commercial eel RAS, a pilot RAS and two marine water aquariums) were treated with different O dosages (1.0-20.0 mg/L ozone) in bench-scale experiments, following which fluorescence intensity degradation was eventually determined. Ozonation kinetic experiments showed that RAS water contains fluorescent organic matter, which is easily oxidised upon ozonation in relatively low concentrations (0-5 mg O/L). Fluorescence spectroscopy has a high level of sensitivity and selectivity in relation to associated fluorophores, and it is able to determine accurately the ozone demand of each system. The findings can potentially be used to design offline or online sensors based on the reduction by ozone of natural fluorescent-dissolved organic matter in RAS. The suggested indirect determination of ozone delivered into water can potentially contribute to a safer and more adequate ozone-based treatment to improve water quality.

Removal of Pharmaceuticals, Toxicity and Natural Fluorescence by Ozonation in Biologically Pre-Treated Municipal Wastewater, in Comparison to Subsequent Polishing Biofilm Reactors

“…This could be because humic-like fluorescence was the hardest degradable organic matter in the wastewater [39]. Similar results have also been observed in a previous study, where generally humic-like fluorescence intensity was difficult to remove compared with protein-like fluorescence intensity in water from recirculating aquaculture systems when treated with various ozone doses [26].…”

Controlling of geosmin and 2‐methylisoborneol induced off‐flavours in recirculating aquaculture system farmed fish—A review

“…A wide variety of ozone dosages (3–24 g/kg feed) have been reported in RAS (Bullock et al, ; Summerfelt, Sharrer, Tsukuda, & Gearheart, ) or an ORP value up to 300 mV in freshwater and 400 mV in marine systems (Bullock et al, ; Gonçalves & Gagnon, ; Li, Blancheton, Liu, Triplet, & Michaud, ). Ozone is considered toxic to a wide range of marine and freshwater organisms at above 0.01–0.1 mg/L concentrations (Gonçalves & Gagnon, ; Spiliotopoulou, Martin, Pedersen, & Andersen, ). If overdosed, ozone might reach culture tanks and harm the cultured species, for example the gills and tissues of fish by leaving them more susceptible to microbial infections or severe gill damage leading to osmolality imbalances or even death (Bullock et al, ).…”

Ozonation control and effects of ozone on water quality in recirculating aquaculture systems

“…Fluorescence spectroscopy was used to determine indirectly the dosage of ozone delivered into water, as described by Spiliotopoulou et al (2017) utilising a fluorimeter (Cary Eclipse, Varian).…”

“…The ozone gas was monitored daily with a spectrophotometer (Section 2.3.1.1). Dissolved ozone was measured in the pump sump and rearing tank (Section 2.3.1.2) by the indigo method (Antoniou et al, 2013) and the fluorescence intensity removal method (Spiliotopoulou et al, 2017). Water samples were collected daily from the rearing tank and the pump sumps of the four running units for further analysis.…”

“…set the basis for a highly sensitive and accurate method to control ozone, based on the natural fluorescence removal of organic matter upon ozonation in an RAS (Spiliotopoulou et al, 2017).…”