Nano-ozone bubbles for drinking water treatment

Abstract

Safe drinking water is a key necessity, and ozonation is one of the common processes in drinking water preparation. The main drawbacks of using conventional ozone methods are the high-buoyancy-related low retention time and rapid decomposition of ozone eradicating residual ozone in water, which do not support prevention of regrowth of microorganisms in treated water. When ozone is delivered as nanobubbles, it increases the retention time due to the low-rising-velocity-related low buoyancy and increased higher specific area of nanobubbles compared to those of ordinary bubbles. The diffusion and concentration of ozone in the water are very important in the treatment process. Experimental results and theoretical calculations show that using nanobubbles leads to lower diffusion and higher ozone concentration compared to using ordinary bubbles. Decomposition of ozone in water generates oxygen where higher oxygen concentrations are obtained using nanobubbles. The oxygen formed during decomposition of ozone generates radicals that can oxidise pollutants. This paper summarises the methods of generating nanobubbles for drinking water treatment at the commercial scale and proposes a method of using ceramic diffusers in a treatment plant with increased efficiency. Moreover, the cost–benefit analysis presented highlights the benefits of using ozone as nanobubbles.