| Since the 21 st Century,the eutrophication of water body generally occured in our country with the rapid growth of economy.Due to the high density of population and the rapid development of industry,the discharge of domestic sewage and industrial wastewater in Beijing should not be underestimated.As a result,the problem of Lake Eutrophication in Beijing was more serious.Therefore,in order to avoid the aggravation of lake pollution,the researchers made an investigation and analysis on the eutrophication status of thirty-three city lakes in Beijing.The results showed that the nutrient elements in thirty-three city lakes were polluted seriously,and the compliance rate of nitrogen content was only 9.1%,and most of the water bodies had reached the level of mild or moderate pollution.Microcystis aeruginosa and Anabaena spiroides were the dominant species of algae bloom,and the contents of odor compounds produced by them were also significantly more than the olfactory threshold.In order to master the growth rule of the dominant algae species in the lake,and to put forward the prevention and control measures,this paper focused on the effects of different temperature conditions on the growth of Anabaena spiroides.The results showed that algal cells had a rapid growth after a short period of adaptation under the condition of 15 ?,and the growth potential was greater than that of the temperature of 25 ? and 35 ?.In addition,the production of 2-MIB was also higher.Especially in the algal cells decline stage,intracellular 2-MIB released into extracellular water,and the water exuded strong earthy musty,which need to focus on the removal of.At the same time,the low temperature environment of 15 ? could cause Anabaena spiroides produce more fluorescent dissolved organic matter,and the content of organic matter in the intracellular and extracellular cells decreased gradually with the increasing of temperature.The traditional treatment technologies on high algae raw water mainly depended on the addition of chlorine dioxide,chlorine,copper sulphate and so on,but they would have the problems of high cost or easy to produce disinfection by-products.Therefore,this paper used hydrogen peroxide and ozone which were green oxidants to oxidize Microcystis aeruginosa and Anabaena spiroides respectively,so as to provide some theoretical guidance for the actual water treatment technology.The results showed that because of the protective mechanism of cell wall and cell membrane,the amount of oxidant was added to the intracellular odor compounds whether ?-cyclocitral or 2-MIB so as to achieve a good degradation effect.Moreover,the removal rate of odor compounds was gradually improved with the extension of reaction time.Due to the influence of ozone half-life or the structure of odor compounds,the secondary kinetic rate constant of ozone oxidation 2-MIB was lower than that of hydrogen peroxide.Because hydrogen peroxide or ozone could produce hydroxyl radical which had a strong oxidation capacity,they could seriously damage the membrane lipids,the cell's internal protein and photosynthesis system,and then inactivate algae cells.The DOM of Microcystis aeruginosa mainly included phenolic compounds,aromatic proteins and microbial metabolites,and the contents of fulvic acid and humic acid were very few.Moreover,there was little difference in the intracellular and extracellular fluorescence intensity of each component.However,there were more humic acids in DOM of Anabaena spiroides,and the extracellular fluorescence intensity was much higher than that in intracellular cells.It was more effective to remove microbial metabolites in DOM by ozone than hydrogen peroxide.Therefore,ozone was more suitable for the algae solution with higher fluorescence index value. |
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