Studies on the Settlement and Control of Marine Organisms in Cooling Systems of Coastal Installations

Abstract

The project was sectioned to conduct investigation on the settlement of marine fouling organisms in the seawater cooling system of Karachi Nuclear Power Plant (KANUPP). For the past few years, a considerable damage has been reported to the seawater cooling system of the KANUPP. Many organisms, such as the larvae of barnacles and molluscs tend to settle and grow during the circulating sea water through the tubing of the coolant tubes affect the smooth flow of seawater through the cooling system and finally leads to increased corrosion and subsequent leaking of tubes. the periodic damages caused to the system and to the replaced tubing and accessories, cost heavily. The present investigation were carried out to study biological aspects of the fouling problem and to determine ways and means to control settlement of fouling organisms in the cooling system at a minimum cost. The result obtained from the study of the composition distribution and abundance of fouling organisms show that the dominant foulers in the cooling system are barnacles, serpulids, oysters and hydroids. The main fouling centres in the cooling system of KANUPP are ducts, pipes, intake tunnels, bay-walls and heat-exchange tubings.it was also found that dense populations of fouling organisms along the coast of Karachi are located in the backwaters, creeks and rocky shores. Results collected from the studies of seasonal distribution of planktonic larval stages of major fouling fouling groups and the seasonal settlement patterns of the larvae of fouling organisms occurring an exposure panels suggest that majority of the foulers breed round the year with the peak increased in the breeding activity confined to September-November and January-March. Minimum breeding was observed in the south west monsoon period (June through September). Similar trends were noticed in the settlement of algal spores and diatoms on the exposure panels. The fouling communities developing on the substrate for long periods were usually composed of a diverse fauna to be least affected by seasonal changes in larval settlement of various fouling organisms. Observations regarding chlorination and heat treatment of the fouling organisms indicate that a low level of chlorination on the continuous basis is useful in controlling larval settlement in the cooling system. It was found that the use of hot water (by recirculation of hot water discharge from the condensers trough the intake) to attain a temperature of 45oC for one hour also case mortalities of adult foulers. It is recommended that in order too achieve good results, low level continuous chlorination and hot water recirculation be pracriced. however, in case of non-availability of chlorine the frequency of hot water recirculation may be increased for the effective control of fouling n the cooling system of the power plant.