MERC The Biology of Garveia franciscana and Potential Options to Limit Impacts of Cooling System Fouling - page 11

9 Peracetic acid (liquid injection, experimental)
Peracetic acid, a derivative of hydrogen peroxide, has been considered for fouling control for
organisms such as zebra mussels. Peracetic acid has been explored or applied in a variety of
water treatment applications or as a disinfectant and has potentially fewer hazardous by-
products. However, effective dosage levels are relatively high, which require large storage
volumes and results in increased costs. As with all chemical treatments, peracetic acid
requires safe handling practices.
4.1.2. Non-Oxidizing
Non-oxidizing agents disrupt cell functions such as metabolism or reproduction. Like oxidizing
biocides, the time needed to impact organisms and for chemical degradationmay in some cases
be dependent on species being treated and affected by local water quality. A few specific
biocides have been considered for industrial scale water treatment, including the injection of
liquid menadione, alkylamines, gluteraldehyde, and acrolein. However, all of these non-
oxidizing biocides are still in the experimental stages, and are therefore not being considered at
this time.
4.2. PhysicalDisinfection
Physical disinfection systems use non-chemicalmeans to inactivate, disrupt, or kill organisms.
4.2.1. Ultraviolet Radiation (commercially available for fouling prevention)
Ultraviolet (UV) light destroys cellmembranes and either kills outright or alters cell structures to
inhibit organismal functions such as reproduction. UV is effective against many organisms from
viruses to the larvae of marine invertebrates. This method is frequently employed in municipal
and industrial water treatment where the percent UV transmittance (%UVT) of thewater is high
at the time of treatment. In these environments, UV treatment is generally low-power, and
therefore cost-effective.
UV treatments are unlikely to be effective in turbid coastal waters with a low %UVT. The
%UVT can be negatively affected by various typical environmental factors in estuarine systems,
such as high dissolved organic carbon concentrations, high turbidity, increased sediment load
caused by storms or large plankton blooms. These conditions likely require either a higher UV
dose/power per lamp or more UV tubes, resulting in higher power usage; or by reducing the
water flow rate, whichmay not be possible.
It is also important to note that UV is only able to treat organisms that are exposed to the UV
radiation, so all water entering the cooling systemsmust be treated continuously. Given the large
flow rates and volumes of coolingwater used by power plants, UV treatment is likely to be cost
prohibitive and not feasible.
4.2.2. Deoxygenation (experimental)
Producing lethal levels of oxygen (hypoxia or anoxia) can be an effective approach at controlling
or killing aerobic and higher organisms. Deoxgenation can be achieved through the addition of
oxygen-stripping chemicals (e.g., sodium bisulfite and ammonium bisulfite), injection of inert
gas (typically nitrogen and carbon dioxide), or inducing a vacuum to remove the oxygen in the
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