Fundamental Research On The Method Of Microbiology Which Used In The Governance Of The Algae From The Waterworks Of Dianchi Lake

In recent years, the water pollution in Dianchi Lake becomes serious, and the eutrophication is intensifying. It often leads to a along period of alga-bloom that in a continuous cycle. The outbreak of the alga-bloom not only leads to serious ecological disaster, but also brings many difficulties to the waterworks of Dianchi Lake. In the treatment process of the water with high concentrations of alga, the incident of equipment plug often occurred because the volume of algal residue is very large and difficult to deal with. The control and management of the algal residue in Dianchi Lake has become a key issue. At present, there are three Methods in the removal of the alga. The first one is purely physical, and its effect is minimal. The second one is chemical, it may produce negative impacts and cause re-contamination, although the effect is remarkable. The third one is biological, and it has a more broadly prospect. It takes advantage of the food chain of ecosystems and the allelopathy of plant communities, to effectively inhibit the growth of alga. The object of this study is the algal residues in Dianchi Lake, and the main purpose is to remove the algal residue by microorganisms. The product of the clean water from the process will be supplied for Kuming, after followed-up treatment of the waterworks of Dianchi Lake. Main contents and conclusions are as follows:First of all, algal diversity of water samples which was taken from the algal residue with high concentration of alga and the water samples of the areas where the alga-bloom was not out-breaking were investigated; one of algal species was separated for the follow-up experiment. Secondly, the lytic bacteria strains were isolated and purified from Dianchi Lake, the enzymes'activity of these bacteria was identified. Then, the characteristic test of alga-lying using isolated bacteria, the test on the optimization of alga-lysing and the synergy effect between the alga-lysing bacteria, were carried out. Finally, the engineering applied idea was proposed for removal of algal residue.After the study, the conclusions are as follows:(1)Whether it is spring or autumn, Microcystis aeruginosa is the dominant algae in Dianchi Lake. Compared in different seasons, the diversity of alga are much better in spring than in autumn; in the same reason, the diversity of alga in water samples which was taken from the algal residue is better than the samples of the areas where the alga-bloom was not out-breaking. In this study, one of algal species was successfully isolated by adding glucose into the medium for bacteria, This can provide a kind of materials for the follow-up test It can be found from the study that the value of absorbance at 680nm of Chlorophyll a of the algal species in 95% cold alcohol can represent the number of the cells of this algal species.(2) In this experiment, the alga-lying bacteria were selected by using liquid selection medium with pectin as sole carbon source and solid selection medium with algal residue as the sole carbon source, and the rescreening experiment was designed to reselect alga-lysing strains. Then, 12 strains of alga-lysing bacteria were successfully selected from Dianchi Lake, obviously have strong dissolution of algae. The identification results on morphology,physiological ecology and molecular biology of these strains show that these 12 strains belong to five generas, respectively as Paenibacillus,Bacillus,Pseudomonas,Lysinibacillus and Exiguobacterium. The identification results of enzymes'activity of these bacteria indicated that: z02,z05,z08 which were selected by using liquid selection medium with pectin as sole carbon source have higher pectinase activity. In addition, z03,z07 which were selected by using solid selection medium with algal residue as the sole carbon source also have high pectinase activity. z02 and z07 have the same effect in the pectinase activity, but they have some differences in alga-lysing effect. g22,g00,z01,z04,z06 which pectinase activity are not high, also have a good alga-lysing effect. These study indicate that there are other things or manners existing which can kill algal cells except pectinase, the forms of alga-lysing by bacteria are variety, the type of lysing material is very rich.(3) The alga-lysing test results of these 10 bacteria show that, the higher the initial concentration of bacteria is, the faster and more intense lytic phenomenon happens. By the end of the test the situation is different, this may be due to high concentrations of bacteria, a high content of organic nutrients, while the dominant algae Microcystis aeruginosa in algal residue can multiply rapidly by using organic nutrients. The higher the concentration of bacteria is, the faster the alga breed. Therefore, the alga-lysing effect of the medium and low concentration of bacteria may be better than the high concentration of bacteria. Temperature of 37℃,rotation speed of 150r/min,algal residue content of 2.5% -5%,the initial pH of 7-8,are the best experimental conditions by z05 to dissolve the algal residue. The decline of lytic effect will not be caused when z05 passaged less than three generations. In areas of dissolving the algal residue, z03 and z05 can promote each other.(4) In this study, the engineering applied idea was proposed for removal of algal residue using microbial method, based on preliminary studies. It provides a lot of experiences and references for the waterworks of Dianchi Lake in treatment process for removing the alga. Improved by further research and testing, the results of this study can be expected to achieve the level of engineering applications.