Effects of mixing rate and carbon d ioxide feeding on productivity of Spirulina platensis in flat plate photobioreactor

One of the major green house gases ( GHGs) leading to global warming is carbon diox ide. CO2 makes up 68% ofthe estimated total g reenhouse gas emissions. Microalgal biofixation o f carbon dioxide hasrecently gained renewed interest as a promising strategy for CO2 mitigation. PHOTOBIOREACTOR (PBRS) ARE COMPLEX SYSTEMS THAT COMPOSED OF S EVERAL SUBSYSTEMS SUCH AS LIGHT, NUTRIENT, AIR HANDLING GAS EXCHANGE SYSTEMS. THE EFFECTS OF CO2 FEEDING AND RATE OF MIXING ON BIOMASS PRODUCTIVI TY WAS EVALUATED IN CULTURES OF SPIR ULINA PLATENSIS GROWN IN A DESIGNED FL ATPLATE (PANEL) PHOTOBIOREACTORTHAT FEATURE IMPORTANT ADVANTAGES FORMASS PRODUCTION OF MANY PHOTOAUTOTROPHIC MICROORGANISMS AND MAYBE COME A STANDARD REACTOR TYPE FOR TH E MASS PRODUCTION OF SEVERALALGAL SPEC IES.THE PHOTOBIOREACTOR WAS CONSTRUC TED FROM TRANSPARENT ACRYLIC PLASTIC PLATE WITH THE DIMENSIONS OF 1M HIGHT, 0.6M LENGTH, 0.1M WIDE AND 15L WORKING V OLUME. THE REACTOR WAS SIDE ILLUMINA TED WITH COLD FLUORESCENT LAMPS AND AIR WAS PROVIDED FROM THE BOTTOM OF TH E REACTOR BY AN AIR PUMP. SPIRULINA PLATENSIS WAS BATCH CULTIVATED IN DIFFERENT TYPES OF GAS-S PARGED METHODS INCLUDING CONTINUOUS AND PERIODICAL INJECTIONS WITH AIR AND CARBON DIOXIDE. TOTAL MASS OF CARBON FED INTO THE SYSTEMS WAS COMPARED TO BIOMASS PRODUCTION. BIOMASS PRODUCTIVITY AND CO2 FIXATION RATE WERE INVESTIGA TED AND THE ABILITY OF CULTURE IN PHOTOBIOREACTOR TO USE AND FIX CO2 WAS EVALUA TED. THE RESULTS SHOWED THAT THE RATE OF MIXING REQUIRED DELICATE OPTIMIZATION: MAXIMAL PRODUCTIVITY COULD NO T BE OBTAINED IN VERY LOW MIXING RATE A ND HIGH RATE OF MIXING RESULTED IN CELL DAMAGE AND REDUCED OUTPUT RATE. TH E TOTAL MASS OF CARBON FED INTO THE SY STEM WAS COMPARED TO BIOMASS PRODUCTI ON. THIS STUDY SHOWS THAT IN THE SYSTEM S WITH GAS-SPARGING AND CO2 FEEDING, E FFICIENT RESOURCE UTILIZATION AND CARBON RECYCLING REQUIRES PRECISE DESIGN OF PHOTOBIOREACTORS. IT ALSO CONFIRMED THAT THE RANGE OF CO2 CONCENTRATI ON USED IN THE EXPERIMENTS WAS COST-EFFECTIVE FOR MASS CULTURE.