Perspective Chapter: Role of Nanobubbles Technology in Wastewater Treatments

Bulk nanobubble technologies, developed over the last decade, represent an environmentally friendly innovation in water treatment. Nanobubbles (< 200 nm) exhibit unique properties due to their colloidal behavior and negative surface charge. They are affected by Brownian motion, which enables them to remain stable in aqueous systems for several days, leading to a new approach for liquid-gas and solid-gas contact systems. Their main characteristics include exceptional stability, long residence times, large specific surface area, high gas transfer efficiency, strong interfacial potential, enhanced adhesion, and the ability to generate free radicals. These features make nanobubbles highly promising for enhancing conventional water and wastewater treatments, improving the overall efficiency of wastewater treatment plants. Main applications include flotation processes, aerobic biological technologies such as activated sludge, biological activated carbon, or membrane bioreactors, and ozone-based oxidation treatments. The generation of active free radicals that oxidize organic compounds facilitates pollutant degradation. Nanobubbles improve the efficiency of individual treatment processes, reduce operating costs and chemical consumption, and, in summary, may extend the limits of existing wastewater treatment plants. This chapter explores the fundamental properties and technological applications of nanobubbles in wastewater treatment, highlighting their potential to remove macro- and micro pollutants while improving overall process sustainability.