Ozone has also been used for the control of microbial contamination in the aquaculture, aquaria, and power-plant cooling systems industries since the 1970's. Ozone is unstable at atmospheric pressure and therefore must be generated at the point of use. It is also a greenhouse gas and is toxic at high concentrations. These environmental and safety characteristics are strong negatives relative to shipboard treatment of ballast. However, the technology is relatively simple, effective, capital and operational costs are comparable to the three technologies evaluated in this report, and safety and environmental concerns are manageable.
Ozone is generated using UV light, electrolysis, or the cornea-discharge process.
Electrolysis generation is not commercially available. The three modules of an ozone treatment system are a generator, ozone contact chamber, and ozone destructor. The contact chamber is where the ozone is introduced to the water stream. The more ozone in the water, the higher is the microorganism mortality. The longer the ozone-contact time, the higher is mortality.