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8.2. Biofouling and itsControl inPower Plant CoolingWater System–Satpathy et al. (2010).
8.2.1. Overview
Satpathy et al. (2010) provides the most recent and comprehensive overview of biofouling and
its control in power plant coolingwater systems as a chapter of the book entitled
Nuclear Power
(2010). An introduction/overview of biofouling in power plant cooling systems and how
biofouling growth affects the intake water needs of power plants is provided. Satpathy et al.
(2010) describes the economic impacts of biofouling, bio-growth in different sections of a
cooling water system, biofouling and safety consequences of nuclear power plants, and events
that could exacerbate fouling.
8.2.2. FoulingCaseStudy
An in-depth study at theMadras Atomic Power Station (MAPS) was chosen as a case study to
understand the biofouling problems in a typical seawater cooled power plant whose systems have
been studied in great detail. MAPS is located on the Kalpakkam coast (Bay of Bengal) and has
significant seasonal biofouling challenges, including two hydroid species
(Obelia biontata and
Obelia dichotoma
) thatwere second only to barnacles in abundance.
Selection of a suitable biofouling control strategy, particularly the chemical control methods, for
a coolingwater system depends upon the physicochemical properties of the coolingwater itself.
Biofouling control methods can become inefficient due to the ability of the fouling organisms to
alter the chemistry of the coolingwater themselves. Thus, continuous monitoring of the cooling
water at the outfall discharge is as important as that of the intakewater to find out the efficiency
of the control method. This is true for biocides in particular. For example, an increase in pH and
turbidity and a decrease in DO levels was noted in the MAPS forebay samples as compared to
that of the intake. Using hydrography and biofouling data, a studywas designed and carried out
to assess the impact of the activities of the fouling community on the physicochemical properties
of the cooling water at MAPS to assess any possible interference in the operation and
maintenance of the coolingwater system.
Satpathy et al. (2010) concluded that although methods like Amertap, spongeball, screens of
various sizes, heat treatment and different biocides are in use for prevention and control of
biofouling, chlorination stands out as the most widely used and efficient method owing to its
proven effectiveness, easy availability and relatively low cost for the chlorination of cooling
water. The authors estimated that electrochlorination (on-site/in-line production of sodium
hypochlorite) is one of themost cost-effective approaches to the use of a biocide in power plant
anti-fouling. Electrochlorination is about half the cost of the injection of liquid sodium
hypochlorite, and far less expensive than other common oxidants such as ozone. However,
recently implementedEPA and state limitations described abovemust also be taken into account.
MAPS is similar to the majority of power plants in that the fundamental biofouling control
strategy
selected for use is based on chlorination, with MAPS specifically using sodium
hypochlorite. However, chlorine demand values vary with location and season and should be
quantified to help optimize the process and to ensure that under- and over-dosing are prevented.
