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8.2.3. List ofControl StrategiesReviewed
Satpathy et al. (2010) discuss the following control strategies and provide a few conclusions:
A.
Physicalmethods –Physicalmethods are screens and sieves that can be used to prevent entry
of macro-organisms or larger, but will not prevent micro-organisms or larvae from entering
coolingwater systems.
B.
High flow velocity –Using a high flow velocity onlyworks if velocity remains constant and
hydrodynamic conditions prevent the settlement and/or attachment of fouling organisms.
However, once organisms are attached, high flow often does not prevent their growth.
C.
Heat –Highwater temperatures can prevent orminimize fouling. For example, temperatures
of 40°C for one hour can kill many bivalves, but heatingwater in the coolingwater system is
energy intensive andwill interrupt normal flow.
D.
Mechanicalmethods –Thesemethods have not been popular because they are only useful for
microfouling control in the condenser section, interrupt normal cooling water flow, and can
be cost prohibitive.
E.
Osmotic control – Osmotic control by varying salinity can work on marine or freshwater
organisms if it is possible to greatlymanipulate salinity.
F.
Bromine-based compounds – Bromine chloride has been used to control fouling because the
biocide: (a) has rapid residual decay and lower potential for condenser corrosion rates, (b)
has high solubility, (c) has a high density that permits a large mass of liquid BrCl to be
supplied in a small container, (d) works under broad temperature and pH ranges, and (e)may
bemore economical when the cost of maintaining EPA regulation of discharge limit is taken
into account.
G.
Ozone – Ozone is a common fouling prevention approach but limitations include: (a)
difficulty to achieve uniform distribution, (b) ozonizer occupying large space and necessity
for on-site generation, and (c) high costs typically restrict the use of ozone largely for
treatment of potablewater and sewage.Moreover, there is very little information available on
the possible corrosion of condenser tubes. Like chlorine, ozone is also is affected by pH,
temperature, and organics.
H.
Bioactive compounds – A variety of other compounds have been considered and discussed
(e.g., iodine, hydrogen peroxide, potassium permanganate, and chlorine dioxide) but
Satpathy et al. (2010) concluded that they are still experimental and that extensive additional
research is needed.
I.
Antifouling coatings – Various coating options are available utilizing organometallic
compounds and copper oxide. Copper has not been popular due to high cost, operational
difficulty and short life span. Acrolein is an effective antifouling agent, but it is expensive,
highly toxic and also highly flammable. Non-stick or silicon based coating were discussed
briefly.
