Bio-control Of Harmful Cyanobacteria In Queshan Reservoir Composite Bioncathode

As a universal phenomenon of freshwater in China, eutrophication has threatened the drinking water sources, such as Queshan reservoir, one of the typical drinking water supply reservoir sourced from Yellow River. The phytoplankton community in Queshan reservoir was investigated and characterized. Microcystis aeruginosa was further studied on its growth as a representative of the dominant group of cyanobacteria. In the mean time, an algicidal bacterium strain designated as FM was isolated from water sample of Queshan reservoir. The algicidal effect of FM on M. aeruginosa was studied and the algicidal mechanism was explored. The main results obtained in this study were as follows:The composition characteristics and seasonal variations of phytoplankton in Queshan reservoir were studied from September,2008to August,2010from10sampling locations. The dominant species are cyanobacteria and diatoms. Therefore, M. aeruginosa, one of the dominant species, was selected as the target for further study.Algicidal bacterium FM was isolated from water sample of Queshan reservoir. Strain FM was identified as Aeromonas sp. based on its morphological characteristics and16S rRNA gene sequence, which was available under the GenBank accession number of HM560619.The algicidal activity of the strain FM was studied. Strain FM could significantly lyse cyanobacteria, including strains of Microcystis, Anabaena, Oscillatoria and Nodularia. Strong algicidal effect of strain FM was observed against M. aeruginosa. Strain FM could lyse more than95%of M. aeruginosa at the concentration ranging from4.6×106to1.4×107cells mL-1, and the threshold concentration of FM for its algicidal activity against exponentially growing M. aeruginosa was2.1×10cfu mL-1.The study of the mechanisms of strain FM on M. aeruginosa showed that the algicidal bacterium removed algae indirectly by secreting extracellular substances. The alga-lytic substances were tested to be non-proteinaceous, heat stable,and with a molecular weight of less than1kDa. The potassium clavulanate and L-lysine, secreted by this isolate, were found to be one cause of lysis. The growth of M. aeruginosa could be inhibited by10mg L-1L-lysine or0.4mg L-1potassium clavulanate.The algicidal activity in reactors with enlarged reaction volume was studied. Algicidal tests in10L system with strain FM harboring in Aquamats showed the removal effect on M. aeruginosa. And the algicidal tests in100L as well as2000L systems, with the extracellular algicidal substances, showed the significant growth inhibition for M. aeruginosa. The results indicated the application potential of the algicidal bacterium.