Investigating the impacts of a recirculation sedimentation application on microalgae biomass cultivation in wastewater treatment.

Abstract\nNOVELTY STATEMENTCommercial microalgae production is often interrupted by contamination, leading to short production cycles, reinoculation needs, and culture collapses, significantly increasing costs. This study focuses on investigating Recirculated Sedimentation Application (RSA) to control contamination in microalgae culture systems used for wastewater treatment. <italic>Chlorella vulgaris</italic> culture was grown in an unsterilized mixture of tertiary treatment effluent and centrate of anaerobic digestion wastewater sludge over a 90-day experimental period. 60 L raceway reactor was operated under a light intensity of 275 μM m−2.s−1 with a 16:8 h light-dark photoperiod. To evaluate the effect of RSA on biological-based problems, the experiment was conducted in three phases. The benefits of utilizing RSA were established through the following observations: effective removal of contaminants at an acceptable level without releasing the culture; extension of the biofilm formation time on the inner walls; inhibition of heterotrophic bacteria and nitrification; enhancement of the suspended solids retention capacity of the raceway tank (up to 770 mg.L−1); and improvement in ammonium removal rate to approximately 30 mg.L−1d−1. The ideal salinity level for both ammonium removal and biomass concentration in RSA should be below 0.02%. These findings demonstrate the potential of phycoremediation for sustainable wastewater treatment and contribute to environmental bioremediation strategies.This study investigates the effects of recirculated sedimentation using freshly formed and mature algae, based on settleability differences, for microalgae cultivation in open ponds with unsterilized wastewater, with the aim of maintain a stable and productive biomass community. Additionally, this study contributes to expand the current knowledge on several fronts: including removing contaminants without discharging the culture, improving biomass holding capacity of the reactor, reducing biofilm formation on reactor walls, suppressing bacterial growth in the culture media and enhancing ammonium removal rate. To the best of our knowledge, there have not been no previous studies to evaluate the effectiveness of sedimentation for these purposes. [ABSTRACT FROM AUTHOR]