Use of coastal waters as condenser coolant in electric power plants: Impact on phytoplankton and primary productivity

(1) Studies on phytoplankton entrained in cooling system of a power plant revealed a reduction in biomass and gross primary productivity (GPP) at outfall, compared to intake.(2) GPP at outfall showed 50% reduction even when steam condenser was inoperative and indicated that chemical stress caused more reduction as compared to thermal stress.(3) Field studies carried out during low-dose, shock-dose and off-chlorination periods and short-term laboratory studies further confirmed that chlorination caused greater reduction than temperature.(4) Shannon diversity indices of phytoplankton were similar at intake and outfall. However, species differences were observed.(5) The study emphasises that chlorine is a major stress factor to entrained phytoplankton in cooling water systems.(6) The results are discussed highlighting the point that the relative importance of thermal and chlorine stresses needs to be factored in the development of effluent discharge criteria.