Photocatalytic inactivation of cyanobacteria with ZnO/γ-Al2O3 composite under solar light.

Cyanobacteria were inactivated by using zinc oxide (ZnO) coated on the surface of g-Al2O3 as a photocatalyst and combining with sunlight. In vitro experiments indicate that axenic cultures of planktonic cyanobacteria lost their photosynthetic activity after photocatalyzed with sunlight exposure exceeding 24 hr. As for Oscillatoria tenuisa, nearly 92% of the cells lost their photosynthetic activity and the cell morphology was severely damaged during 24 hr of the reaction. However, in the case of Microcystis aeruginosa, lower photocatalytic inactivity efficiency was observed, which was attributed to extracellular polymeric secretions (EPSs) surrounding the cells. With a high dosage ZnO catalyst, the dissolved organic carbon (DOC) concentration of the Oscillatoria tenuisa suspension was increased by up to about 190% during photocatalysis. The increased suspension of DOC was attributed to increase liberation of extracellular organic and cell-wall polysaccharides during photocatalysis.

Using respirometer in biodegradation phenomenon of natural organic matters.

This study conducted in monitoring respirometer oxygen consumption of aerobic microorganism during biodegradation processes of ozonated organic matters, which can estimate both biodegraded efficiency and coefficient of natural organic matters (NOMs) in water source. It can be proposed that different ozone dosage might change biodegradation characteristics of organic matters. The result reveals that higher ozone dosage may cause higher biomass yield coefficient of microorganism, and cultured microorganism may easily utilize biodegradation organic matters (BOMs) produced by ozonation, finally increasing overall removal efficiency. Therefore, using respirometer to evaluate the production of BOMs by ozonation before the biological treatment is effective for controling ozone dosage and enhancement of NOMs removal by biological processes.