(597h) A Novel Patented Open Cultivation System for Microalgae Using Recycled Water

In order to make production of algal biofuels a reality, it is necessary to recycle water and nutrients. Furthermore, large scale cultivation systems must have temperature, nutrient addition, pH, and agitation control to enhance productivity. A novel reactor system has been developed, patented, and tested at the pilot scale to achieve better systems control, minimize operational cost, and allow for year round cultivation even when evening temperatures are below freezing. The overall systems design will be presented as well as cultivation results that are compared to traditional raceways. Finally, results using recycled water will be discussed. There are two recycle strategies: one is to recycle the water or spent media only after harvesting the algae via centrifugation  or filtration or other more cost effective technologies, and the other is to harvest a part of the culture, recycle the water, add more nutrients, and operate the system as a fed-batch reactor.  This presentation will show the benefits and consequences of batch versus fedbatch operation with recycled water. Data suggests that after 3 to 5 fed batch operations, organics and nitrogen build up in the spent media and inhibit growth and productivity. Recycling the water or spent media when fresh inoculum is supplied is feasible for extended  recycle periods, however fed batch operation is more limited.  Growth rates, productivities, and the effects of recycled media will be presented. Nitrogen and phosphorous as well as total organic content is monitored as a function of recycle period. Although the results are dependent on algal species, overall it is feasible to recycle the water routinely, but the algal inoculum must be “refreshed” after a few fed batch cycles.