Photocatalytic removal of the cyanobacterium Microcystis aeruginosa PCC7813 and four microcystins by TiO2 coated porous glass beads with UV-LED irradiation

Abstract

Photocatalytic inhibition of M. aeruginosa PCC7813 (7.6x10 5 cells mL -1 d -1 )• 74% removal of four microcystins (intra-and extracellular)• Porous glass beads made from recycled glass used as catalyst support• UV irradiance supplied by low energy UV (365 nm) emitting LEDs

Comparison of UV-A photolytic and UV/TiO2 photocatalytic effects on Microcystis aeruginosa PCC7813 and four microcystin analogues: A pilot scale study

“…Before carrying out the study, UV/TiO2 treatment was expected to be the most effective treatment through damage to the photosynthetic system of M. aeruginosa PCC7813. However, relatively little effect was observed in the An initial decrease of M. aeruginosa PCC7813 cell density at the beginning of the experiment was expected which was what had been observed previously in other studies that evaluated M. aeruginosa cell density after TiO2 photocatalytic treatment (Pestana et al, 2020;Chang et al, 2018;Song et al, 2018;Wang et al, 2018Wang et al, , 2017Pinho et al, 2012). In particular, the study of Pestana et al (2020), was a similar experimental design albeit in a smaller bench scale (30 mL of cell suspension and 700 mg of coated beads, equivalent to 0.2% (w/v) TiO2).…”

“…However, relatively little effect was observed in the An initial decrease of M. aeruginosa PCC7813 cell density at the beginning of the experiment was expected which was what had been observed previously in other studies that evaluated M. aeruginosa cell density after TiO2 photocatalytic treatment (Pestana et al, 2020;Chang et al, 2018;Song et al, 2018;Wang et al, 2018Wang et al, , 2017Pinho et al, 2012). In particular, the study of Pestana et al (2020), was a similar experimental design albeit in a smaller bench scale (30 mL of cell suspension and 700 mg of coated beads, equivalent to 0.2% (w/v) TiO2). The differences in results between * the two studies could be due to the light attenuation of the bubbles being dispersed by the beads.…”

“…A reduction in cell numbers was expected to be observed in the UV/TiO2 treatment on the M. aeruginosa PCC7813 cell density based on previous bench-scale studies (Pestana et al, 2020;Chang et al, 2018;Song et al, 2018;Wang et al, 2018Wang et al, , 2017Pinho et al, 2012). However, the M. aeruginosa cell density could best be represented by a piecewise regression tendency (Figure S6) and significantly rose in the UV/TiO2 treatment over the first eight days with a tendency rate of 0.46 x 10 6 cells mL -1 day -1 (p<0.01), and then decreased after day 8 with a tendency rate of 1 x 10 6 cells mL -1 day -1 (p<0.01; Figure 1C).…”

“…The TiO2 coated beads were manufactured from recycled glass that were prepared as per Pestana et al (2020) and Hui et al (2021) containing approximately 12% (w/w) TiO2. In the TiO2-only samples, no UV illumination was used.…”

Oxidative stress in the cyanobacterium Microcystis aeruginosa PCC 7813: Comparison of different analytical cell stress detection assays

“…previously (Pestana et al, 2020). Microcystins are normally contained within the cells, and are released into the surrounding water along with other intracellular content when cell integrity is compromised.…”