During the course of this study, two other technologies were encountered that could potentially be used to treat ballast water. As detailed investigation of these other technologies was beyond the scope of this project, only general descriptive information is provided below.

Electro-Ionization/Magnetic Separation (EIMS) technology is currently in use in several industrial applications, including metal finishing, food processing, electronics, wastewater treatment, textiles, and drinking water treatment. This technology uses a process of coagulation and filtration to remove and disinfect water of various contaminants. The following description by WSI (1998) is an overview of the sequential processes with EIMS.

1. A continuous flow of ionized oxygen/nitrogen plasma gas is introduced into the water subjected to treatment.
2. Air is passed through strong concurrent ultraviolet and magnetic field energies creating a "cold plasma" of magnetic oxygen and positive nitrogen ions. The injected gas plasma ions function a coagulating/oxidizing agents and generate oxidizing ozone-derivative ions
3. The ionized gas plasma stream is injected into the water stream, causing a coagulation process referred to as "electro-ionization." At this stage, positive nitrogen ions and negative oxygen ions act as flocculating agents, which gather and enhance colloids and particles that are electrically clustered.
4. The clusters of solids are flocculated out of suspension and separated by "magnetic separation" (MAG-SEP) filtration

This process removes virtually all particles larger than 1F m. In some industrial applications, EIMS-treated water is then filtered and treated with UV radiation to further disinfect the water.

Feasibility of Ballast Water Treatment. The current EIMS equipment supplied by WSI has a relative large footprint (approx. 20 ´ 20 feet) and complex instrumentation. These aspects alone would probably preclude its use for shipboard ballast- water treatment. Furthermore, the cost of the treatment system is expensive relative to the three technologies evaluated in this study. A single 100-gpm system from WSI costs approximately $200,000 and uses approximately 30 K/hr. Scale-up potential and associated cost economies of scale are unproven. On the plus side, however, the EIMS system and filtration modules are self-contained apparatuses and there are no known environmental effects or significant operational safety concerns.

Ozone (O₃) is the triatomic form of oxygen, and has been used for the disinfection of water supplies since 1886. 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. In industrial applications, ozone is not used to eliminate microbial populations, but rather to limit population growth (Oemcke and van Leeuwen 1998).

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. Like with other ballast treatment systems, biological effectiveness is a function concentration (equates to energy) and exposure period. The more ozone in the water, the higher is the microorganism mortality. The longer the ozone-contact time, the higher is mortality. For this reason, low-flow ozone treatment systems often use venturi-type contact chambers, while industrial systems use a "bubble contractor" chamber that maximizes ozone exposure.

Once introduced into water, ozone is lost through three main processes (Litved et al., 1995):

1. Reaction with water impurities. Low concentration of organics matter can cause rapid dissipation. When used to treat seawater or brackish water, various organic and inorganic oxidants are formed (Crecelius, 1979). Bromide ion in seawater can oxidize to hypobromous acid, bromate, and bromine. Hypobromous acid can react with aquatic organics to produce bromoform, and iodide and chloride can be oxidized by ozone.
2. Decomposition. After generation, ozone will decompose to oxygen through a cyclic set of reactions. Intermediaries include OH, O₃^-, and O₂^-. Terminators such as carbonate and bicarbonate react with OH radicals to stop the reactions.
3. Stripping of ozone to the atmosphere.

The primary purpose of the ozone destructor unit in the treatment system is to limit the amount of ozone that is stripped to the atmosphere, where, as previously discussed, it is a greenhouse gas and toxic at high concentrations.

Feasibility of Ballast Water Treatment. Oemcke and van Leeuwen (1998) conclude that the use of ozone for shipboard treatment is hindered by the relatively long exposure periods required and the variable pumping rates of ballast systems on large bulk carriers. Oemcke and van Leeuwen state that a shipboard ozonation plant would probably need to have variable-speed pump or gearbox so that could adjust the ozonation process to the flow rate of the ballast water. They also discuss that dinoflagellate cysts appear to be resistant to ozonation treatment, and that filtration will enhance effectiveness for other microorganisms.