The use of ozone processes in domestic drinking water treatment has been significant in Europe since the early 1900s and in North America for the past three decades. Here in New Zealand Timaru, Wanganui and Oamaru are leading the way forward, and with the upcoming NZDW standards changing, more councils are giving serious consideration to this outstanding performer. The many advantages of ozone as a multi-platform treatment technology are well documented, but often overlooked are cost savings in the long term of ozone over other systemss. Some examples are below:
As a flocculant ozone results in rapid and enhanced microflocculation of raw waters. The net result can be an increase in plant filtration rates, decrease in size of filtration beds and lower chemical costs.
As a pure disinfectant, the higher oxidation potential of ozone versus chlorine results in reduced contact time, which can mean smaller contact chambers (footprint). In cities where the cost of land is at a premium, the reduced space requirement is a tremendous savings, not to mention the savings cost in construction materials.
Some pollutants and bacteria are oxidized only by ozone. Cryptosporidium parvum, for example, are very resistant to most chemical disinfectants but are swiftly destroyed by ozonation. Most other applicable methods act as barriers or inhibitors to cysts but do not actually destroy them. UV inactivates organisms by disrupting the reproductive cycle, without killing the organism. Microfiltration strips water of all minerals, some of which are essential to human health. The ecological impact of the waste removed from the filters must also be dealt with as a seperate issue for pollutants of wastewater.
Ozone has a positive effect on COD removal by breaking down refractory compounds and making them biodegradable, and also prolongs the service life of GAC. This feature alone makes ozone economically feasible when GAC is needed. Ozone can totally replace chlorine, chloramines or chlorine dioxide in the preoxidation and main oxidation stages. Although some form of chlorine residual is required by regulations in the distribution networks, ozone can dramatically reduce its need, enhance the quality of the water without forming THM's and still be more economical than other oxidants.
With recent advancements in system
monitoring the cost of ozone from both capital and operating investment
is less than half of what it was several years ago. As the cost
of installation is reduced and application methods are refined,
ozone will continue to be a clear leader for desirable and economical
drinking water treatment.