Formation of algal flocs from activated sludge in synthetic medium and secondary treated wastewater

Abstract

BACKGROUND Photogranules seem to be an alternative solution for wastewater treatment and biomass harvesting. The aim of our work was to investigate the formation of algal flocs as an efficient method for the treatment of wastewater and separation of algal cells. RESULTS The progressive change of activated sludge to algal flocs was evaluated under static and stirring conditions using a synthetic substrate (modified Blue Green‐11 medium) and the secondary effluent from an activated sludge wastewater treatment plant. Algal flocs were observed in all cultures by day 10 and a high chlorophyll concentration was detected in all cases reaching values up to 610–630 μg L−1 at the end of the experiment after 30 days. The size of flocs in all cultures at either static or mixing conditions ranged from 330 to 994 μm, resulting in biomass concentration from 330 to 660 mg L−1. The cultures in secondary effluent at static conditions presented the greatest size, and the mean diameter on days 10 and 30 was 250 and 994 μm, respectively. The cultures were efficient in nutrient removal and, by the end of the experiment, nitrates and phosphates were completely consumed. CONCLUSIONS Algal flocs were developed from activated sludge without adding any other flocculant and a highly efficient biomass was developed, which can easily settle and remove nutrients from the medium. © 2022 Society of Chemical Industry (SCI).

Short-Term Toxicity of ZnO Nanoparticles on Microalgae at Different Initial Nutrient Concentrations

“…Nitrogen is often the limiting nutrient in aquatic ecosystems, and its availability can strongly influence microalgae growth rates. In fact, many studies have shown that nitrogen availability can significantly affect the growth, biomass productivity, and biochemical composition of microalgae [1,38]. However, it is important to note that excessive nitrogen concentration can also be harmful to microalgae, as it can lead to overstimulation of growth, an imbalance in the nitrogen-to-phosphorus ratio, and the production of harmful metabolites that can inhibit further growth.…”