Wastewater treatment technologies by algae-bacteria consortia

Micropollutants (MPs) are a wide variety of chemicals that should be appropriately treated in wastewater before discharge into the environment. In this dissertation, an algae-bacteria consortium system that could effectively treat benzalkonium chloride (BAC) and copper (Cu) together in the same operation was proposed. For this, various microalgae species were screened for their tolerance to various heavy metals (HMs) and BAC. Tetraselmis suecica was the most resilient against BAC, cadmium (Cd), Cu, and zinc (Zn). Later, HM tolerance of a BAC-degrading bacterium, Pseudomonas sessilinigenes BIOMIG1, was determined in terms of the metal effect on growth and BAC degradation. Copper ions inhibited the BAC degradation but not the growth on rich organics. A consortium of these species was established and BAC and Cu were treated by the consortium. Efficient removal of BAC by bacteria and partial removal of copper via adsorption and assimilation were observed at 20 ppm BAC and 1 ppm Cu in synthetic medium. The presence of algae contributed to the survival of bacteria under increasing copper concentrations, and the presence of bacteria supported the algal growth at inhibitory BAC concentrations. The effects of copper at 1 mg Cu/L on T. suecica were also investigated through transcriptomic analysis. Carbohydrate catabolism, nitrogen assimilation, and fatty acid biosynthesis & elongation were upregulated and the expression of metal transporters was altered. The outcomes of this study can be utilized in industrial wastewater treatment using microalgae-bacteria consortia as a sustainable biological remediation approach.