Civil Engineering Reference
In-Depth Information
A corona discharge, also known as silent electrical discharge, is commonly used to
generate ozone. In this process, an oxygen-containing gas passes through two elec-
trodes separated by a dielectric and an air gap. A voltage is applied to the electrodes,
causing an electron flow across the air gap. These electrons provide the energy to
disassociate the oxygen molecules, leading to the formation of ozone.
Ozone Disinfection Facilities
Ozone systems have four basic components, as
shown in Figure 19-12: a gas feed system, an ozone generator, an ozone contactor,
and an off-gas destruction system. The gas feed system provides a clean, dry source
of oxygen to the generator. The ozone contactor transfers the ozone-rich gas into the
water to be treated, and provides contact time for disinfection (or other reactions). The
final process, off-gas destruction, is required as ozone is toxic in the concentrations
present in the off-gas. Some plants include an off-gas recycle system that returns off-
gas to the first contact chamber to reduce the ozone demand in the subsequent cham-
bers. Some systems also include a quench chamber to remove ozone residual in
solution.
Gas Feed Systems.
Two types of gas feed systems are used. One uses pure oxygen
and the other air.
PURE OXYGEN SYSTEMS
. Pure oxygen systems are used to produce ozone at high con-
centration. The gas feed is either pure oxygen or oxygen-enriched air, or purchased as
liquid oxygen. The commonly used gas systems are as follows:
Atmosphere
Off Gas
Ozone Destruction
I
nfluent
Effluent
Ozone
Quench
(Option)
Ozone Gas
Gas Feed
System
Ozone
Generator
Fig. 19-12.
Simplified ozone facilities schematic
