Posted by poolplantcourses.org on Wednesday, January 4, 2012 Under: Disinfection
Ozone is a disinfection method that uses ozone to oxidise contamination in the pool water. It is a more powerful oxidiser than chlorine and will actually oxidise (and therefore, remove) chlorine from the pool water when it passes through the ozone dosing system. It is a non-residual disinfectant, which means that no ozone remains in the pool water once it has passed through the ozone dosing system in the plant room. This is different to chlorine because under normal circumstances, there will always be some chlorine in all areas of the swimming pool water circulation system, including the swimming pool itself. Because of this, where an ozone disinfection system is installed, there must also be an additional disinfection dosing system (such as chlorine). Without this secondary system, the swimming pool water would be re-polluted as soon as it circulated back into the swimming pool and this pollution would only be removed when the water goes through the pool plant system again. This is not sufficient to control the cross-contamination risk in swimming pools. Bacteria needs to be killed within seconds in order to minimise the risk. Having said that, the use of ozone will allow pool operators to use substantially lower levels of chlorine (as low as 0.5 mg/l). Another advantage is that ozone will kill cryptosporidium, whereas chlorine does not.

Ozone is not delivered to site, it is generated on-site. This means that there are no handling and storage issues. Ozone is a very toxic substance though and the on-site generation method means that extra training is required for pool plant operators. It is generated by passing an electrical discharge through dried air in an ozone generator, then it goes to a mixing vessel where it is mixed with the pool water, once the pool water and ozone have been mixed together it goes into a contact vessel because ozone needs about 2 minutes of contact time with the pool water in order to be effective, then it goes through a filter to remove all of the ozone from the pool water. The purified pool water then carries on its journey through the pool plant system and the air and any undissolved ozone goes through an ozone removal system before being vented externally. As you can see, ozone disinfection requires quite a lot of equipment, which can be an issue, as can the high levels of expertise required to operate and maintain the system safety.

In : Disinfection 

Tags: ozone "non-residual disinfection" oxidation