More About Ozone

Chlorination has traditionally been used in the disinfection of municipal water. Ozone has many advantages over chlorine in this application:

1. Safety problems of chlorine storage, handling, and transportation are eliminated. Ozone is produced on-site.
2. Ozone destroys both bacteria and viruses, while chlorine is not very effective against viruses.
3. Shorter treatment times (1 - 10 min for ozone vs. 30 - 45 min for chlorine).
4. Lesser pH and temperature effects with ozone.
5. High dissolved oxygen concentration from ozonation improves receiving stream quality.
6. No toxicity to aquatic life has been found in studies of ozone disinfection.
7. No buildup of bioaccumulatable residuals has been observed in ozone-treated effluents.
8. There is no increase in total dissolved solids in ozone-treated water.
9. Wastewater quality improvements such as turbidity reduction and effluent decolorization accompany ozone treatment.

As many advantages as there are to using ozone to treat water, there are also disadvantages:
1) It is costly to produce ozone, both for equipment and power requirements.
2) Ozone is toxic - the Public Health Department has set the maximum safe working concentration at 0.1 ppm.
3) There is great difficulty in accurately determining the concentration of ozone in water. The best method thus far has an error of ± 1% .

Ozone Chemistry
Production of Ozone

Usually ozone is part of the treatment of drinking water, but there are other applications. Where in a wastewater treatment plant can ozone be used?

1)Disinfection of treatment plant effluents.

2) Tertiary treatment processes

3) Sludge treatment

4) Combined treatment with activated carbon, filtration, ultrasonics, or other chemicals.

5) Odor control

You may conclude with a short quiz.

REFERENCES Evans, Francis L.; Ozone in Water and Wastewater Treatment Forum on Ozone Disinfection: Proceedings Sponsored by The International Ozone Institute