Cultivation of algae and nutrient removal in a waste heat utilization process

A process providing a beneficial use for waste heat and excess nutrients in the cooling waters of nuclear reactors and fossil-fueled power generating plants has been developed. The process involves the cultivation of selected strains of thermotolerant microalgae in heated discharge waters and the subsequent harvesting of the algal biomass for nutrient removal, recovery of energy and fertilizer, and extraction of high value products. The design of such a process is presented for a large cooling reservoir receiving a discharge of 10⁹1^?1 d^?1 of secondary cooling water containing 100 μg 1^?1 of available P and 400 μg 1^?1 of available N. Based on this nutrient load, with a 1% P content in the algal biomass and a productivity of 10 g m^?2 d ^?1, a 100 ha region would be needed for the process. Hydraulic barriers (submerged plastic curtains) would isolate the 100 ha algal production area “cultivation zone” in the influent end of the reservoir to create a hydraulic and thermal environment conductive to the selective growth of filamentous, thermotolerant, nitrogen-fixing, blue-green algae. The algal culture would be inoculated into the thermal plume and harvested near the distal barrier of the cultivation zone with rotating, backwashed, fine mesh screens (“microstrainers”). A portion of the harvested biomass would be recycled to the inoculation site to maintain a dense culture. This process could mitigate both thermal and nutrient loadings on receiving bodies of water.