Elimination at Source of Biocidal Agents from Fresh Water Environments by TiO2 Photocatalysis

Herbicides and pesticides (i.e. biocides) are widely used world-wide. Many biocidal agents are persistent in the freshwater environment and are on the EU watchlist for priority and priority hazardous substances, as well as the Scottish Environmental Protection Agencies risk matrix for contaminants in surface waters. Several biocidal agents have been shown to have adverse health effects in humans including carcinogenic properties, birth defects, and disruption of the endocrine system. Therefore, the development of a system for the source management of these compounds is timely and pressing. Photocatalytic degradation of biocidal agents is well established in the scientific literature, mostly by the application of titanium dioxide (TiO2) photocatalysis. TiO2 is a non-toxic, abundant chemical that has many applications including in the food and cosmetics industries. Photocatalytic activity results in the creation of short-lived high energy hydroxyl radicals upon the input of UV irradiation resulting in the subsequent oxidation of pollutants. To date, TiO2 photocatalytic treatment has not been not widely employed due to limitations such as catalyst removal and energy costs. The requirement of energy input in the form of near UV light has been a barrier to deployment until the recent advent of water submersible UV-light emitting diodes (UV-LEDs ; 367 nm).
Aims/Objectives:
This project aims to develop a pilot scale modular photocatalytic treatment unit that can be deployed for source management of biocide discharge, i.e. in drainage channels, waste gutters, rural SuDS, or waste water ponds. This aim will be achieved by:
• evaluating the performance of different treatment unit designs at bench scale in the removal of 10 commonly encountered biocidal agents (table 1)
• Selecting the most suitable treatment unit design then develop and construct pilot scale units
• determine a suitable test site(s) for deployment
• evaluation the pilot scale unit in situ through LC-MS and ecotoxicological testing
Methods/Approach:
For photocatalytic removal of pollutants, the photocatalyst must be immobilized on a suitable matrix to eliminate the requirement for post treatment catalyst removal. Initially different matrices for immobilization and their performance in the oxidation of 10 commonly occurring biocidal agents (table 1) will be evaluated in bench scale reactors (already constructed at RGU) in pure water and environmental samples. Following this, a bench scale modular treatment unit will be designed and constructed to prove the functionality of the design, followed by a pilot scale treatment unit, including fluid modelling via Ansys CFD for optimisation.

The project will be hosted at the Robert Gordon University in Aberdeen.