1.4.3. Photocatalysis
Photocatalysis is a form of advanced oxidation process involving the production of hydroxyl radials (OH-) that
attack oxidizable contaminants. Photocatalysis has been shown to oxidize almost any organic contaminant, typically
used for treatment of organic pollutants, and is highly effective in the disinfection of microbial contaminants [26].
The hydroxyl radicals are formed through a light-induced reaction requiring O2, water and a semiconductor catalyst.
The semiconductor Titanium dioxide (TiO2) is demonstrated to be the most active catalyst [26]. Additionally, TiO2
is resistant to chemical breakdown, low cost, safe and readily available (in the developed world). Using TiO2 the
oxidation reaction can be induced by solar UV spectrum (up to 390nm). Photocatalysis has been shown as a
successful system by numerous authors [27-30].
Although photocatalysis has been shown to deactivate organic compounds, the process is dependent on a number
of factors including UV radiation, mass of catalysis, pH, temperature and oxygen concentration of the water.
Additionally the TiO2 must be held in suspension during treatment and recovered after treatment. For the current
system, the requirement of a low maintenance and low complexity system invalidates the use of photocatalyic
methods.