Thermosynechococcus sp. CL-1 cultivation for Zn removal in swine wastewater with simultaneous CO2 fixation and macromolecules accumulation

Abstract

Treatment of swine wastewater via cultivation of photosynthetic microorganism is highly promising due to the benefits in nutrient utilization, cost reduction, high efficiency, and production of various bioproducts. Besides, photosynthetic microorganisms are also acknowledged for their high tolerance toward extreme growth conditions, including the presence of heavy metals. This study assessed the tolerance of Thermosynechococcus sp. CL-1 (TCL-1) in the cultivation using swine wastewater for CO2 fixation, Zn removal, and production of lipid, protein, and carbohydrate. Addition of 113.2 mM dissolved inorganic carbon was also set for simulation of almost saturated CO2 content in a chemical scrubbing wastewater after CO2 absorption process. Experiment was conducted in a 1 L flat panel photobioreactor for 12 h periods, under illumination of various light intensities, and compared with the performance in modified Fitzgerald medium. TCL-1 cultivation under 1000 μE/m2/s light intensity provided the optimum growth condition in swine wastewater which led to high biomass productivity (55.69 mg/L/h) and CO2 fixation rate (91.8 mg/L/h). TCL-1 in this cultivation also removed 62.5 % Zn content from swine wastewater and bioadsorption route was detected as the major elimination process. The rapid utilization of nitrogen compounds in swine wastewater resulted in the dominant production of protein reached to 59.5 ± 3.1%dwc.