Photo-sequencing batch reactor with Klebsormidium nitens: a promising microalgal biotechnology for sustainable phosphorus management in wastewater treatment plants

This study aims at improving the existing algal-based wastewater treatment technologies by overcoming some of the major drawbacks of these systems such as large required land area, culture contamination, and energy-intensive algal harvesting. The experiments were carried out in an open photo-sequencing batch reactor at a laboratory-scale for nearly 2 months. A specific strain ACUS00207 of the aeroterrestrial green microalga Klebsormidium nitens (Kützing) Lokhorst was used. The strain is native to Bulgaria and belongs to a species that has never been used before in suspended growth systems for wastewater treatment for phosphorus removal. The culture of K. nitens showed promising results: phosphorus removal rates ranging from 0.4 to 1 mg total phosphorus L−1 d−1, efficient settling properties, and resistance to culture contamination with native microalgae. On the basis of the observed phosphorus removal mechanism of biologically mediated chemical precipitation/phosphorus precipitation, an innovative working mode of the sequencing batch reactor is suggested for reducing the hydraulic retention time and the required land area. HIGHLIGHTS Klebsormidium nitens used for the first time in suspended growth wastewater treatment.; Phosphorus removal rates ranging from 0.4 to 1 mg total phosphorus L−1 d−1.; Efficient settling properties and resistance to culture contamination.; Potential for reduction of the hydraulic retention time and the required land area.