Research On Phytoplankton And Its Metabolite In Source Water And Treatment Process Of A City Waterworks Located In Taihu Lake Basin

Phytoplankton is the primary producer in fresh water, which plays an important role in regulating and warning ecological balance of reservoir. Based on the phytoplankton growth of the two reserviors, seasonal algae variation was analyzed and ecological evaluation of water quality was given under the comprehensive action of water environmental factors. The similarities and differences of algal community structure changes were also compared between the two reservoirs. And the removal of algae and its metabolites was investigated in water process of waterworks. The results provided a scientific basis for the control of phytoplankton.A survey was carried out from July 2014 to June 2015. The results showed that a total of 7 phyla,63 genera,147 species were identified in Hengshan reservoir, Chlorophyta, Bacillariophyta and Cyanophyta was 42.8%,31.3% and 15.6%, respectively. The average abundance of phytoplankton cells was 4.2x106cells/L, and the proportion of the cells was 57.3% of Bacillariophyta,29.8% of Chlorophyta and 8.4% of Cyanophyta. The main dominant species were Cosmarium formosulum, Melosira varians, Melosira granulate etc.. In Youche reservoir, a total of 6 phyla,48 genera,73 species were identified. Chlorophyta, Bacillariophyta and Cyanophyta was 42.5%,37.0% and 6.9%. The average abundance of phytoplankton cells was 2.6x106cells/L, and the proportion of the cells was 61.3%of Bacillariophyta,17.7% of Chlorophyta and 9.2% of Cyanophyta. The main dominant species were Cosmarium formosulum, Melosira varians, Melosira granulate, Synedra ulna etc.. Phytoplankton variation were similar in two reservoirs. However, the abundance of phytoplankton in Hengshan was richer than in Youche.Pearson correlation analysis showed that phytoplankton abundance had a significant correlation with water temperature, secchi depth, dissolved oxygen and total phosphorus, but phytoplankton had no significant correlation with nitrate, nitrite, ammonia, UV254, CODMn, turbidity and pH. The situation in Hengshan reservoir was similar to Youche reservoir, but the subtle differences of correlation coefficient were found between the two reservoirs under different water quality condition. Overall, water environment and nutrients were the main internal causes of phytoplankton structure dynamics in reservoirs.Detection of microcystin was low in both reservoirs. The average MC-LR, MC-YR, MC-RR of microcystin were 0.14?g/L, 0.11?g/L and 0.17?g/L in Hengshan reservoir, while which were 0.09?g/L,0.07?g/L and 0.07?g/L in Youche reservoir, respectively. Therefore, microcystin produced by cyanobacteria was extremely low, and water quality was stable and safe.The average index of Shannon-Wiener in Hengshan reservoir was 2.48 and with the eutrophication index of 51.09, while which were 2.14 and 40.87 in Youche reservoir. Based on the analysis of phytoplankton diversity, dominant populations and eutrophication index, the water quality of Hengshan reservoir was evaluated as medium-eutrophicated, however, Youche reservoir was medium nutritional.