Biomass Production and Nutrient Removal through Cultivation of Euglena gracilis in Domestic Wastewater

Abstract

Laboratory experiments were performed to evaluate the potential of a cultivation of Euglena gracilis strain Z, a kind of microalgae, as a method for biomass production and nutrient removal in domestic wastewater. E. gracilis was found to be able to almost completely utilize ammonium and phosphate in primary settling tank effluent (PSTE) and final settling tank effluent (FSTE), and could grow efficiently while achieving high biomass productions both in PSTE (6.3 × 10³ cells/L) and FSTE (4.5 × 10³ cells/L) on the average. The removal of dissolved organic carbon by E. gracilis was also observed in PSTE, though the dissolved organic carbon and nitrogen were increased after cultivation in FSTE possibly due to the leakage from E. gracilis cells. It was found that removal of microorganisms from PSTE and FSTE by filtration with 1.0 μm－ and 0.2 μm－pore size filters lowered the biomass productivity, indicating that the microbes existing in the wastewater samples may have certain positive effects on the growth of E. gracilis. The results suggest that it is possible to achieve efficient biomass production using E. gracilis in PSTE; this phenomenon is coupled with the co-benefit of nutrient removal.