UV-OZONE SYSTEMS

Description

A UV-ozone system is a very powerful treatment process that may be used to oxidise toxic micropolluants and residual COD, to remove colour or to disinfect.

A UV-ozone system goes further than the simple addition of the oxidative properties of ultraviolet light and ozone. When ozone is mixed with the liquid effluent and exposed to ultraviolet light, powerful free radicals are created photochemically. These hydroxyl radicals (OH3) are very reactive and are able to break down the organic compounds in the effluent to carbon dioxide and water.

The short half-life of the hydroxyl radicals means that UV-ozone units have to be designed carefully to maximise the mixing of the effluent and ozone, and to optimise the transmission of the ultraviolet light.

Application

The UV-ozone system has applications in treating landfill leachate, landfill gas condensate, and effluents containing hazardous compounds such as aromatics, chlorinated aromatics, phenols and ketones. Many long-chain halogenated aliphatic and aromatic compounds can be oxidised to the point where they are biodegradable. UV-ozone systems have potential applications for colour removal from effluents from the dyeing and chemical industries.

Chlorinated hydrocarbons can be reduced by UV-ozone to carbon dioxide, water and chloride ions. Toxic intermediates are not normally produced.

UV-ozone can also oxidise the resistant aldehydes or organic acids that are sometimes produced when ozone oxidises organic material.

Sizing

A UV-ozone system sized to treat a typical effluent flow of about 10 m3/hour would require ultraviolet lamps rated at about 250 W, and either a 300 W oxygen-fed ozone generator or a 600 W air-fed ozone generator. The typical energy consumption for a UV-ozone system could be almost 01 kWh/m3 of effluent treated.