Removal of inorganic nitrogen sources from water by the algal biofilm of the aerial microalga Trentepohlia aurea

Abstract

Removal of inorganic nitrogen sources by cells of the aerial microalga Trentepohlia aurea grown on the surface of substrate, such as filter paper, has been investigated in a batch system. When the alga grew on the paper dampened with medium, it actively ingested inorganic nitrogenous compounds in the medium. Immobilized cells on the filter papers were called ‘algal biofilm’ in this study. When the algal biofilms were soaked in modified Bold's Basal medium (using 1 g NH₄Cl l⁻¹ as a N source), the removal rate was 4.25 mg ammonium-N l⁻¹ day⁻¹ in 40 days. In modified medium with added 26 mg nitrite-N, the removal rate of the total inorganic N ion by the biofilms reached 5.11 mg N l⁻¹ day⁻¹. This removal rate of total N ion was higher than that in the medium by addition of 26 mg nitrate-N. In addition, we tried to examine simultaneous removal of ammonium, nitrate, and nitrite ions and growth inhibition of cyanobacteria in the medium by using the algal biofilms. Consequently, it was demonstrated that the algal biofilms of T. aurea could be utilized as a biofunctional material for the purification of wastewater.