An Environmentally Friendly Method for Testing Photocatalytic Inactivation of Cyanobacterial Propagation on a Hybrid Ag-TiO₂ Photocatalyst under Solar Illumination.

Shu-Yu Chang,Guor-Cheng Fang,Winn-Jung Huang,Ming-Chin Chang,Cheng-Feng Hsu,Hsiu-Lin Chen,Ben-Ren Lu,Yeah Chen

doi:10.3390/ijerph121215023

Abstract

Cyanobacteria were inactivated under sunlight using mixed phase silver (Ag) and deposited titanium dioxide (TiO2) coated on the surface of diatomite (DM) as a hybrid photocatalyst (Ag-TiO2/DM). The endpoints of dose-response experiments were chlorophyll a, photosynthetic efficiency, and flow cytometry measurements. In vitro experiments revealed that axenic cultures of planktonic cyanobacteria lost their photosynthetic activity following photocatalyzed exposure to sunlight for more than 24 h. Nearly 92% of Microcystis aeruginosa cells lost their photosynthetic activity, and their cell morphology was severely damaged within 24 h of the reaction. Preliminary carbon-14 (14CO3−2) results suggest that the complete inactivation of cyanobacteria arises from damage to cell wall components (peroxidation). A small concomitant increase in cell wall disorder and a consequent decrease in cell wall functional groups increase the cell wall fluidity prior to cell lysis. A high dosage of Ag-TiO2/DM during photocatalysis increased the concentration of extracellular polymeric substances (EPSs) in the Microcystis aeruginosa suspension by up to approximately 260%. However, photocatalytic treatment had a small effect on the disinfection by-product (DBP) precursor, as revealed by only a slight increase in the formation of trihalomethanes (THMs) and haloacetic acids (HAAs).

Highlights

Cyanobacteria are present in drinking water reservoirs worldwide and are a serious issue of great concern for drinking water authorities
Photocatalysis with higher Ag-TiO2 dosages resulted in a 17%−92% lower lower chlorophyll content in the cyanobacterial suspension (Figure 2)
Inactivation experiments were performed on two species of cyanobacteria: Microcystis aeruginosa and Oscillatoria tenuisa

Summary

Introduction

Cyanobacteria are present in drinking water reservoirs worldwide and are a serious issue of great concern for drinking water authorities. The potential health hazards of toxin-producing cyanobacteria in drinking water supplies are well known [1]. The presence of cyanobacterial blooms can generate a wide range of toxins, including cyclic peptide hepatotoxins and alkaloid neurotoxins. The potential presence of cyanobacteria and their metabolites in water has led to the upgrading of drinking water treatment facilities with the addition of chemical oxidation, Int. J. Res. Public Health 2015, 12, 15819–15833; doi:10.3390/ijerph121215023 www.mdpi.com/journal/ijerph

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