Advanced Oxidation Processes for Tertiary and Quaternary Wastewater Treatments: Trends, Future Prospects and Engineering Issues

In light of Global water scarcity, produced by population growth, climate change and excessive freshwater usage, there is a growing need for more efficient water management practices, including the utilization of reclaimed water. Noteworthy, the required water quality standards for such purposes still represent a serious challenge to deal with in current urban wastewater treatment plants. Besides the considerable microbiological content, an urban wastewater effluent also presents anthropogenic chemicals (e.g., micropollutants such as pharmaceuticals, personal care products, pesticides, flame retardants…), the latter collectively referred to as Contaminants of Emerging Concern (CECs). These substances pose challenges due to their limited biodegradability and their persistence in conventional wastewater treatment processes, ultimately finding their way into natural ecosystems upon discharge. In this sense, it is widely recognized that the integration of Advanced Oxidation Processes (AOPs) with the existing infrastructures can make wastewater effluents in compliance with new quality standards. Within this chapter, urban wastewater tertiary (disinfection) and quaternary (CECs removal) treatments by AOPs (with a particular focus on UV and solar driven ones) are discussed and compared to consolidated processes. Trends, future prospects and engineering issues are also discussed in view of new regulations at European level.