Advanced treatment of municipal wastewater using a native microalga Dactylococcus dissociatus MT1 from the Algerian Sahara

Abstract

ABSTRACT Diagram showing the cultivation of the native D. dissociatus MT1 isolated from the Algerian Sahara for tertiary wastewater treatment. The process includes microalgal experimental setup, biomass production, and wastewater treatment, resulting in high removal of nutrient and COD. Inadequately treated municipal wastewater remains a major environmental challenge in Algeria due to the limited efficiency of conventional treatment systems in removing nutrients and organic matter. In this context, preliminary evaluation of microalgae-based wastewater treatment using the native microalga ‘Dactylococcus dissociatus MT1’, previously isolated from the Algerian Sahara, highlighting its potential as sustainable and locally alternative for advanced wastewater polishing. Experiments were conducted using sterilised media, including raw secondary wastewater, filtered secondary wastewater, and synthetic wastewater (SWW), with bold basal medium used as a control. D. dissociatus adapted well to all media, exhibiting specific growth rates between 0.44 and 0.71 d− and maximum biomass concentrations of 960–1,490 mg/L. Nutrient removal assays revealed high bioremediation performance across all media, with ammonium removal reaching 99% and nitrate removal efficiencies of 91–98%. Orthophosphate was eliminated in most media, except SWW, where removal reached 83%. In contrast, SWW exhibited the highest chemical oxygen demand (COD) reduction (100%), compared with 93–97% in real wastewaters. As pH remained below 9 and bacterial activity was excluded, reduction in nutrients and organic matter may have been associated with microalgal uptake. However, the contribution of other physicochemical removal cannot be completely excluded and warrants further investigations.