Consolidated and Innovative Disinfection Strategies for Wastewater: A European Vision

Reclaimed wastewater (RWW) is a non-seasonal source of freshwater highly valuable for agriculture. Nevertheless, it may represent a significant human health risk as it is a vehicle for many microbial pathogens that need to be efficiently inactivated before its use. Traditionally, all wastewater treatment plants (WWTPs) are designed to treat high volumes of water in a sequence of treatments able to remove inorganic and organic contents by primary and secondary treatments. To reach RWW criteria, which require a disinfection process, a tertiary treatment is added to this sequence. Among the conventional tertiary treatments commonly implemented in WWTPs, chlorination, ultraviolet light (UV-C treatment) and ozonation are highlighted. These treatments present a high and efficient capability for the inactivation of pathogens in water, but they have important drawbacks and limitations, such as the generation of harmful and toxic disinfection by-products, eventually microbial post-treatment reactivation, and cost, especially for UV-C and ozonation. Therefore, in the last decades, other treatments have been investigated to increase the water disinfection capability of these conventional tertiary treatments to overcome the limitations mentioned earlier and at the same time, try to reduce treatment costs and environmental impacts. Among the different technological approaches, advanced oxidation processes (including those driven by solar radiation) and nature-based solutions could be good candidates, as they have demonstrated high efficiency for water disinfection, relatively low cost and low environmental impact. This chapter aims to describe the fundamental aspects of all these tertiary wastewater (WW) disinfection processes with emphasis on pathogens' inactivation mechanisms, implementation, limitations and future challenges.