The pulsed-wave UV delivery system provides radiation doses through a flashing of the source lamp. The effect of this pulsing technique is to provide short ‘bursts’ of higher energy into the system. The speed of the pulsing and the intensity of the UV radiation are specific to the design of the system and the available power supply (refer to Figure 2-3).

Research conducted in the field of UV radiation treatment focuses on the treatment of human and aquatic pathogens. The most intense research has been done for the aquaculture and water treatment industries (drinking and disposal). The target organisms for these industries are usually concerned with bacterial and viral infections of either human or fish populations. The target organisms for the treatment of ballast water include the same bacterial and viral components, but also the larval stages of many estuarine or marine organisms and live organisms such as fish, crabs, worms, and algae.

The use of filtration at more that one level may need to be considered in order to achieve the removal of larger animals and the removal of sediment and larval stage organisms. As previously discussed, the ability of UV radiation to treat unfiltered water is highly dependent of water clarity/turbidity. Most estuarine waters contain significant organic and inorganic suspended particles, which will reduce the transmissivity of the water and the effectiveness of UV treatment. To achieve kill ratios equivalent to treatment plants receiving filtered water, UV equipment receiving unfiltered water must increase energy and/or exposure period to achieve treatment criteria (i.e., radiation at a preset level at all points in the treatment chamber).

Based on data and interview information provided by several vendors, water that is filtered to a range of 25-50F m is optimal for removing particulate interferences and organisms larger than bacteria and viruses. Filtering intake water to 25-50F m also excludes target organisms such as zebra mussel veligers and toxic dinoflagellate cysts. The majority of the vendors responding to Battelle’s survey grouped their responses for 100F m, 250F m, and unfiltered water together, indicating similar biological effectiveness occur across these higher filtration levels.

The power and control modules associated with the UV chamber consists of high and low voltage power units with microchips that control the majority of the units’ functions. The units are enclosed in steel cabinets that provide protection from physical damage. According to several of the vendors, the power module does not need to be located adjacent to the UV chambers; however the electrical resistance over the distance traveled for the electricity would need to investigated on an individual basis. The control units are generally lower voltage than the power modules and contain the majority of the computerized control modules. These may be located at further distances from the UV chamber and generally require more protection from fluctuations in heat, humidity, water, and physical damage.

The UV radiation systems that were investigated during the study appeared to be relatively easy to operate. As described in Section 2.2, most UV systems are composed of three separate machines in sequence that produce the desired outcome of UV radiation. The control modules themselves are microchip based and will require some input from trained personal; this may be as simple as learning to input on and off sequences. The power modules are self-contained units that will require little attention when functioning. The UV chambers are also self-contained and require little attention.

Maintenance procedures will need to be acquired by some members of the crew. Maintenance procedures include

• Cleaning the quartz sleeves
• Changing of lamps,
• Ensuring proper power module function
• Overall system upkeep

An estimate of man-hours required for operation and maintenance of onboard UV systems could not be made from the data collected from this survey. Although, it appears that each vessel and system will vary depending on design, it appears that the complexity of operating a UV treatment plant is similarly to other shipboard systems. Whether specific ships have available man-hours to maintain the equipment is undetermined. Many commercial vessels operate with minimum crews, and the additional responsibility to maintain a UV plant may require that ship operators add crew, and thereby add significant costs to their business operations.

There are several UV system-specific safety concerns that should be addressed relative to shipboard application of this technology. The first issue is the use of high voltage electricity (220/440 V) to power the system. Considering that other shipboard machinery runs on high voltage electricity this should not be a major factor assuming that shipboard safety requirements for high voltage electricity will to be adhered to during the installation process. The operation of the UV radiation systems should raise no additional concerns if the system is installed and maintained properly. If the system is improperly installed or poorly maintained, there is risk of electrical accident comparable to other shipboard systems.

The second issue is the use of mercury-containing lamps to generate the UV radiation. The lamps’ source of the UV radiation may come from several sources including zeon (inert gas) or mercury. The systems that use mercury containing lamps (~ 20mg/lamp) keep them protected within the treatment chamber by the use of a quartz sleeve. The use of mercury containing lamps could be a concern onboard a ship given the relatively high potential for physical damage during storage and installation.

Mercury. The major environmental concern with UV treatment is accidental release of low-level mercury if mercury-containing lamps are broken or improperly disposed. Mercury is a well-known environmental toxicant, the release of which is regulated by numerous laws and agency programs.

Genetic mutation risk. Another environmental concern, which has postulated but not investigated by others (e.g., Lloyd’s Register, 1995), is genetic mutation. Aquatic microorganisms that survive the UV treatment process could be genetically mutated (by damage caused to their DNA from action of UV photons). It is expected that most or all of the surviving organisms with damaged genetic material will fail to procreate. However, a slim possibility exists that genetically altered DNA will benefit the surviving organisms, and that they will thrive in discharged environment. Although the risk of thriving mutants is considered remote, the possibility cannot be quantified until laboratory research is conducted using monocultures of test organisms exposed to UV radiation under a range of conditions.

In evaluating potential for genetic mutation among microorganisms that survive UV-treatment, one must weigh the low possibility of a mutation being passed to subsequent generations of the organism plus the low possibility that the mutation will give the organism a competitive advantage in the receiving ecosystem. Additionally, one must understand that shipboard ballast water treatment is unlike other biocide applications where there is significant risk of genetic mutation among surviving microorganisms. For example, in a biomedical laboratory setting, technicians apply chemical , radiation, and heat treatments to various instruments and containers. The materials are repeatedly treated and usually the treated materials remain in a confined area. Microbes that are able to resist the first treatment find that their competitors are dead, and they can now exploit the newly vacated habitat and available food to their maximum advantage (i.e., population growth). When the instruments and containers are then treated a second time, the resistant microbes comprise a much larger fraction of the population. For these reasons, most biomedical facilities and laboratories, use different biocides at different times to limit chances of developing resistant strains of microbes.