The Science

There are a number of Advanced Oxidation Processes (AOP) that can degrade MIB and GSM including Ozonation and Photocatalysis: 

Ozonation

Ozonation seems useful but this method is not very effective for the degradation of GSM and MIB. Ozone is a strong oxidant, which also has disinfectant properties. It is commonly used for the disinfection of drinking water and for the degradation of organic pollutants. A peculiar advantage of ozonation is that it helps flocculation of suspended solids, thus reducing the load on the filtration systems which is particularly useful in aquaculture. Since O₃ spontaneously decays into O₂, it must be generated on-site. Ozonation induces the oxidation of bromide to bromate ions and whilst Bromide is harmless and is often present in fresh water it is always present in relevant amounts in seawater. Bromate, on the other hand, is a suspected carcinogen and is lethal to fish. For the application of RAS, low ozone concentrations (less than 1μg L^-1) have been shown to improve water quality but do not significantly reduce the concentration of off-flavour compounds. High ozone concentrations, instead, are effective, but lethal to the farmed species and can produce high concentrations of bromate.

Photocatalysis

The most studied photocatalytic system is Titanium Dioxide (TiO₂) irradiated with UV light, which is effective in the degradation of GSM and MIB. TiO₂ has the advantages of low cost, photochemical stability and non-toxicity. The photocatalytic degradation of GSM and MIB follows pseudo-first order kinetics, with hydroxyl radicals as the main active species. Unlike other UV-based methods, which require shorter wavelengths, UVA radiation is sufficient to photo-excite TiO₂. Moreover, in TiO₂ photocatalysis the bromide concentration is generally stable, and no bromates are formed. One problem that hinders the industrial application of TiO₂photocatalysis is the low quantum yield, which results in slow kinetics and lower energy efficiency than other AOPs. However, our proprietary technology is based on applying both these processes simultaneously and creating.

Photocatalytic Ozonation

The coupling of photocatalysis and ozonation – photocatalytic ozonation – (PO) allows removal of the specific weaknesses of the single technologies, namely the slow kinetics for photocatalysis and the low reactivity with some organic species (GSM and MIB among others) and unwanted by-products for ozonation.

When the two techniques are coupled, a synergy is observed whereby the extent of degradation is greater than that determined by the sum of the two processes taken alone. The synergy in PO depends on the relative weight of the rates of the two processes if performed individually under the same experimental conditions. It was found that the synergy is maximized at a fixed relative weight of the two processes. The specific value for this weight is reaction specific, but generally a smaller fraction of the photocatalysis allows maximum synergy