Medizinische Universität Graz - Research portal
Selected Publication:
Deller, S;.
Effect of solar radiation on survival of indicator bacteria in water environments: Influence of turbidity, depth of water and use of polyethyleneterephtalate bottles.
[ Dissertation ] MUG; 2005.
- Authors Med Uni Graz:
- Deller Sigrid
- Advisor:
- Mascher Franz
- Reinthaler Franz
- Altmetrics:
- Abstract:
- Solar radiation plays an important role in the inactivation of bacteria in water environments and so in surface water used for recreational purposes. In artificial small-scale bathing ponds water is kept clean solely through ecosystems of micro- and macro-organisms; there is no disinfection of water. Therefore it is of great interest to determine factors, responsible for elimination of bacterial impact. Recent global trends in stratospheric ozone depletion caused by atmospheric pollution could increase the amount of UV-B radiation at the earths surface and therefore also in aquatic environments. This has generated a growing interest in how UV-B can effect aquatic ecosystems. For that reason the ability to make qualitative judgments about the effect of UV-B is very important. The recent study should have made its contribution to this subject. Relating to the aspect of drinking water disinfection, UV radiation can help to increase hygienic standard and therefore quality of life. The effects on survival of faecal indicator organisms by different factors influencing the effectiveness of the photooxidation reaction were determined in our experiments. Our research program was conducted to study the effects of numerous variables on the disinfection properties of solar radiation. The variables tested were exposure time, turbidity, depth of water, spore resistance and sample volume. The samples were exposed to sunlight during sunny days during the summer. In analyzing the results from theses experiments, the following conclusions were drawn: Sunlight is bactericidal and plays an important role in controlling the survival of indicator bacteria in natural waters. The inactivation can be directly related to the amount of solar radiation received. High turbidity protects the bacteria from the inactivating effect of sunlight. Experiments revealed that the UV intensity decrease rapidly with increasing water depth. This effect is amplified by increasing turbidity. Tested spores a show much higher resistance against lethal effects of UV exposure than vegetative forms, which must be incorporated in the defining of appropriate indicators of the efficiency of solar radiation on the inactivation of bacteria. Samples stored in ordinary 500ml 2l transparent PET bottles placed in direct sunlight is a proofed possibility for natural drinking water disinfection. Solar disinfection can be done with minimal resources, which is the most important factor for the application in countries of the third world.