Solar-Enhanced Advanced Oxidation Processes for Water Treatment: Simultaneous Removal of Pathogens and Chemical Pollutants

Abstract

The review explores the feasibility of simultaneous removal of pathogens and chemical pollutants by solar-enhanced advanced oxidation processes (AOPs). The AOPs are based on in-situ generation of reactive oxygen species (ROS), most notably hydroxyl radicals •OH, that are capable of destroying both pollutant molecules and pathogen cells. The review presents evidence of simultaneous removal of pathogens and chemical pollutants by photocatalytic processes, namely TiO2 photocatalysis and photo-Fenton. Complex water matrices with high loads of pathogens and chemical pollutants negatively affect the efficiency of disinfection and pollutant removal. This is due to competition between chemical substances and pathogens for generated ROS. Other possible negative effects include light screening, competitive photon absorption, adsorption on the catalyst surface (thereby inhibiting its photocatalytic activity), etc. Besides, some matrix components may serve as nutrients for pathogens, thus hindering the disinfection process. Each type of water/wastewater would require a tailor-made approach and the variables that were shown to influence the processes—catalyst/oxidant concentrations, incident radiation flux, and pH—need to be adjusted in order to achieve the required degree of pollutant and pathogen removal. Overall, the solar-enhanced AOPs hold promise as an environmentally-friendly way to substitute or supplement conventional water/wastewater treatment, particularly in areas without access to centralized drinking water or sewage/wastewater treatment facilities.

Magnetic carbon xerogels for the catalytic wet peroxide oxidation of sulfamethoxazole in environmentally relevant water matrices

“…Nevertheless, the decrease of SMX removal may be ascribed to the presence of (i) dissolved organic matter and/or (ii) radical scavengers in the more complex water matrices, especially in the secondary treated wastewater. Since HO • radicals are nonselective oxidants [17], the presence of organic matter is expected to limit the SMX removal; while, at the same time, ion species (e.g., bicarbonates, chlorides and sulphates) may act as HO • scavengers, as previously shown for photocatalytic applications [62]. In order to better understand how the CWPO process is influenced by each of these components, additional experiments were performed using humic acid (HA) to mimic the presence of dissolved organic matter, and sodium bicarbonate (500 mg L −1 bicarbonates), sodium chloride (200 mg L −1 chlorides) and sodium sulphate (60 mg L −1 sulphates) to mimic the presence of the typical inorganic constituents of conventionally treated wastewater and drinking water.…”

Removal of Crotamiton from Reverse Osmosis Concentrate by a TiO2/Zeolite Composite Sheet

“…Based on the Beer-Lambert law and the distance from the reactor surface to the sheet, the light transmittance was 82.1%. Therefore, after passing through the RO concentrate in the batch reactor, the light intensity at the sheet surface decreased by 17.9%, which is called the screening effect [36]. This effect contributed to the decrease in the photocatalytic degradation efficiency.…”

Overview of the Main Disinfection Processes for Wastewater and Drinking Water Treatment Plants

“…AOPs are a very effective treatment technology since they can simultaneously degrade recalcitrant organic compounds and biological contaminants [66].…”