Research On Theories Of UV Damage To Microorganisms And It's Application On The Enhancement Of Activated Sludge Pollutant Removal

The thesis firstly researches the basic theories on UV damages to aquatic microorganisms, as well as reactions of the damages and UV damage resistant principles by microorganisms. It was pointed out that microorganisms evolved to repair themselves strongly and therefore can keep their unique species characteristics though living in high irradiance surroundings.The thesis still finds sensitive difference among microorganisms are owing to different in vivo structure such as membrane structure, membrane elements, internal particles, different sizes and living stages. The differences trick further UV utilization.As the targets of UV irradiation, the thesis sums up the features of bio-P and glycogen accumulated microorganisms.The editor used UV to enhance the pollutant removal rate of activated sludge underline the analysis of the above theories. More than 20% of COD enhanced removal rate and 10% of TP were achieved under the UV irradiation at the dose of 20W(254nm) for 0.5 min..UV mutation was formally recognized as the reason of the enhancement. The thesis recognized that UV mutation resulting in enhancement of activated sludge pollutant removal is impossible, because very little mutant indexed can not achieve such a enhanced removal rate that only dominant bacteria in activated sludge can.At the same, the thesis put forward a hypothesis that the reason of UV enhancement is due to dominant bacteria change of activated sludge by UV irradiation. The activated sludge from Kunming No.l STP was used to prove the hypothesis. Taxonomy of dominant bacteria in the activated sludge including the ratio of them was tested. Unique activated sludge data and in-situ stain monitor data were collected in UV enhanced TP removal experiment to understand how the dominant bacteria changed. Static comparison and dynamic analysis of the data proved that UV enhanced TPremoval is due to the reason of the dominant bacteria changed in activated sludge. UV improved the living surroundings of bio-P accumulated microorganisms and made them dominate the activated sludge resulting in the enhancement. The result fully proved the hypothesis.The new theoretic explanation to UV enhancement of activated sludge improves the understanding of basic theories of UV enhanced activated sludge pollutant removal and finds our way to make use of UV. But what is worth pointing out is that better understanding the characteristics and change regulation of target bacteria UV is very important in these researches. To sum up, the better we understand the bacteria, we may achieve the more ideal enhanced activated sludge removal rate.