GROWTH AND PRODUCTION OF THERMOPHILIC CYANOBACTERIA IN A SIMULATED THERMAL MITIGATION PROCESS

A cyanobacterial cultivation process, designed to mitigate impacts of thermal effluents by reducing their nutrient content, was simulated in bench-scale rests using semicontinuous cultures of the nitrogen fixin g thermophile Fischerella (formerly Mastigocladus laminosus). The cyan obacterial strains were isolated from and grown in water from nuclear reactor cooling reservoirs at the Savannah River Site near.Aiken, Sout h Carolina. Major limiting factors for biomass production under variou s scenarios included temperature, light, carbon and phosphorus. The am ount of biomass recycling needed to maintain a stable biomass in the m itigation (nutrient removal) zone of the mock reservoir varied with di fferent light and temperature scenarios that were tested. In the worst case scenario, when biomass was repeatedly recycled into heated water at the end of the light cycle rather than at the beginning, stable da ily production could be maintained only when 75% of the biomass was re cycled. Otherwise, the inoculated biomass was able to maintain one dou bling per day allowing a daily recycle of 50% of the biomass. Overall, the growth rates and primary production capabilities needed for succe ssful operation of a proposed process for nutrient removal from therma l effluents were demonstrated in these laboratory simulations. (C) 199 8 Published by Elsevier Science Ltd. All rights reserved.