Sterilization effect of 254 nm UV-C irradiation against cyanobacteria Microcystis aeruginosa

Harmful algal bloom (HAB) produced by several cyanobacterial species is a significant threat to many aquatic ecosystems around the world. Recently frequent occurrence of serious algal bloom in Lake Taihu, Lake Dianchi and Lake Chaohu has become a serious concern in China. Although various methods are currently being used to control toxic blue-green algal water blooms, many of their techniques are of limited use. In this study, the use of 254 nm UV-C radiation to control algal growth was evaluated using Microcystis aeruginosa as test species. The UV-C irradiation of more than 99 μW cm light intensity was found to be lethal to M. aeruginosa. Under incubated conditions with petri dishes and with 20 hours exposure to the UV-C irradiation of 1370 μW cm, almost all the cells settled to the bottom of the incubation Petri dishes, whereas all the unirradiated cells remained in suspension. It was also observed by microstructure and ultrastructure slice-ups that the UV-C radiation had a significant kill and wound effect on algal cells and controlled algal growth. After a UV-C dose of no less than 7.2 J cm, most algae cells dispersed, whereas all the unirradiated cells remained agglomerative.