RESPONSE OF THE GREEN MUSSEL PERNA-VIRIDIS (L) TO HEAT-TREATMENT IN RELATION TO POWER-PLANT BIOFOULING CONTROL

Biofouling in the cooling water circuits of coastal power stations pre sents considerable problems for their normal operation. Although chlor ination is commonly practised, operational problems, safety concerns a nd environmental issues have made it necessary to look for alternative methods of control. Heat treatment is considered as a viable alternat ive and is being practised by a few utilities in the USA and The Nethe rlands. This paper presents data on the lethal and sublethal effects o f temperature on the green mussel Perna viridis, a species causing fou ling problems for the Madras Atomic Power Station, located on the east coast of India. The mortality pattern and the physiological behaviour (byssus thread production, filtration rare and foot activity index) o f the green mussel were studied at temperatures varying from 10 degree s C to 46 degrees C. Synergistic effects of salinity and temperature o n mortality were also studied. Exposure of 2 mm size group mussels to a temperature of 39 degrees C showed 50% mortality in 58 min and 100% mortality in 73 min. Mortality was strongly dependent on age (size) of the mussels, young ones being more susceptible than older ones. The s tudy indicated that hear treatment has distinct advantages as an alter native to control mussel fouling in tropical power stations.