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Estudo de díodos emissores de luz para desinfeção de água
| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 8.97 MB | Adobe PDF |
Advisor(s)
Abstract(s)
A água é um recurso essencial à vida e, portanto, a sua qualidade deve ser preservada. Assim sendo, é essencial desenvolver processos de desinfeção eficazes que possam inativar uma variedade de microrganismos presentes nas diferentes fontes de
água. A radiação ultravioleta é extremamente eficaz para garantir a inativação de vários microrganismos presentes em água eliminando ou reduzindo a utilização de desinfetantes químicos. Devido às suas vantagens, os díodos emissores de luz ultravioleta C podem vir a substituir as lâmpadas UV de mercúrio usadas para desinfeção de água. Os ensaios realizados no âmbito deste trabalho tiveram como objetivo principal comparar a eficiência de díodos que emitem luz a diferentes comprimentos de onda (255,
260, 265, 270 e 280 nm) na inativação de microrganismos indicadores de contaminação fecal: Escherichia coli e Enterococcus faecium. Os resultados obtidos revelaram que os díodos emissores de luz foram extremamente eficazes quer na inativação de bactérias inoculadas em tampão fosfato, quer na inativação de microrganismos presentes em matrizes de água superficial. A
eficiência de inativação foi verificada com todos os comprimentos de onda testados. Uma dose de UV baixa (9 mJ/cm2) garantiu uma inativação superior a 6-logs das bactérias alvo inoculadas em tampão fosfato. As amostras foram comparadas antes e após a exposição aos UV LEDs em termos da morfologia das células e da formação de dímeros de ciclobutano pirimidina. A quantidade de dímeros de ciclobutano pirimidina formados após exposição à mesma dose (9 mJ/cm2) de UV foi semelhante independentemente das bactérias alvo e dos comprimentos de onda emitidos pelos LEDs. Os resultados obtidos neste estudo foram promissores no que diz respeito à inativação dos microrganismos alvo, com recurso a UV LEDs. Dessa forma, é possível que esta tecnologia de desinfeção venha a tornar-se num processo de desinfeção eficaz aplicável em estações de tratamento de água.
Implementing effective disinfection water treatment technologies can enhance public health protection by eliminating harmful microorganisms and ensuring access to safe drinking water, which is essential for supporting life. The use of ultraviolet radiation is extremely effective to inactivate a wide range of microorganisms and is highly advantageous since it eliminates or decreases the need for chemical disinfectants. UV-LEDs technology is gaining interest in water disinfection due to its advantages over traditional UV mercury lamps. This research study was conducted to test the effectiveness of LEDs that emit light at different wavelengths (255, 260, 265, 270 and 280 nm) to inactivate two different bacteria used as fecal indicators of water quality: Escherichia coli and Enterococcus faecium. The results obtained revealed that three small light-emitting diodes were effective in inactivating bacteria spiked in phosphate buffer saline solutions, as well as in inactivating microorganisms present at occurrence levels in real surface water matrices. Low UV fluences (9 mJ/cm2) guaranteed an inactivation greater than 6-logs of the two target bacteria spiked in phosphate buffer. To understand the effect of LEDs that emit light at different wavelengths on the morphology of cells, samples collected after exposure to this same UV fluence (9 mJ/cm2) were compared with samples not exposed to the LEDs. Fluorescence microscopy images were analysed to evaluate cell morphology damages after exposure to UV LEDs. The formation of cyclobutane pyrimidine dimers was also measured and the concentration of dimers detected was similar regardless of the target bacteria tested and the wavelength emitted by the LEDs. The results obtained in this study show that LEDs that emit light at different UVC wavelengths are promising to inactive bacteria used as faecal indicators of water quality. This technology may, in the future, become an effective disinfection process applicable in water treatment plants.
Implementing effective disinfection water treatment technologies can enhance public health protection by eliminating harmful microorganisms and ensuring access to safe drinking water, which is essential for supporting life. The use of ultraviolet radiation is extremely effective to inactivate a wide range of microorganisms and is highly advantageous since it eliminates or decreases the need for chemical disinfectants. UV-LEDs technology is gaining interest in water disinfection due to its advantages over traditional UV mercury lamps. This research study was conducted to test the effectiveness of LEDs that emit light at different wavelengths (255, 260, 265, 270 and 280 nm) to inactivate two different bacteria used as fecal indicators of water quality: Escherichia coli and Enterococcus faecium. The results obtained revealed that three small light-emitting diodes were effective in inactivating bacteria spiked in phosphate buffer saline solutions, as well as in inactivating microorganisms present at occurrence levels in real surface water matrices. Low UV fluences (9 mJ/cm2) guaranteed an inactivation greater than 6-logs of the two target bacteria spiked in phosphate buffer. To understand the effect of LEDs that emit light at different wavelengths on the morphology of cells, samples collected after exposure to this same UV fluence (9 mJ/cm2) were compared with samples not exposed to the LEDs. Fluorescence microscopy images were analysed to evaluate cell morphology damages after exposure to UV LEDs. The formation of cyclobutane pyrimidine dimers was also measured and the concentration of dimers detected was similar regardless of the target bacteria tested and the wavelength emitted by the LEDs. The results obtained in this study show that LEDs that emit light at different UVC wavelengths are promising to inactive bacteria used as faecal indicators of water quality. This technology may, in the future, become an effective disinfection process applicable in water treatment plants.
Description
Keywords
Tratamento de águas Díodos emissores de luz ultravioleta Desinfeção Indicadores de contaminação fecal Inativação bacteriana