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

Potentials of biomass production and nutrient removal through cultivation of Euglena gracilis strain Z, a kind of microalgae, in domestic wastewater were evaluated by lab-scale experiments. E. gracilis could almost completely utilize ammonium nitrogen and phosphate in the effluents from primary settling tank (PSTE) and final settling tank (FSTE), and could grow efficiently with a considerably higher biomass production in PSTE than in FSTE. Removal of organic compounds was also observed both in PSTE and FSTE, though removal of total nitrogen in FSTE was insufficient. Filtration of PSTE with 1.0 μmand 0.2 μm-pore size filters lowered the biomass productivity. Filtration of FSTE with 0.2 μm-pore size filter also significantly lowered the biomass productivity, while the decrease was trivial with 1.0 μmpore size filter. The results suggested that efficient biomass production of E. gracilis using domestic wastewater is possible coupled with co-benefit of nutrient removal, and that the indigenous microbes in PSTE/FSTE like protozoa and bacteria may have certain positive effects on the growth of E. gracilis.