Chlorination and mussel control in the cooling conduits of a tropical coastal power station

The rationale for the present study has been the continued problem of biofouling in the cooling conduits of Madras Atomic Power Station (Kalpakkam), in spite of intermittent chlorination used as a fouling control measure. A diver-assisted inspection of the tunnel proved that the green mussel, Perna viridis (L.) was the major component of the fouling community inside the cooling conduits. Maximum biomass value recorded was 211 kg/m 2, observed inside the forebay shaft at a depth of 22.5 m. The total biomass of fouling in the entire tunnel system was estimated to be 578 tonnes, of which the contribution by P.viridis alone was 411 tonnes. High-level chlorination, followed by continuous low-level chlorination brought large quantities of sessile biomass from the tunnel to travelling water screens (TWS). A total biomass of about 187 tonnes of fouling debris was collected from TWS during February 1988 to January 1990. Of these, P.viridis accounted for 164 tonnes. The sizefrequency distribution of P.viridis collected on the TWS clearly showed that the appearance of young mussels (0–2 cm shell length) was correlated with the breeding pattern of green mussels in the adjacent coastal waters. The present study showed that intermittent chlorination is an ineffective method for mussel control in the power station cooling conduits. Continuous high-level chlorination is useful for dislodging established mussel communities from intake tunnels.