UV Radiation in Wastewater Disinfection

Discharging treated municipal wastewater into rivers can pose a potential threat to the aquatic environment and human health. This danger results from the presence of numerous pathogenic microorganisms in the wastewater: viruses, bacteria, protists, fungi and intestinal parasite eggs. That is why it is so important to use highly efficient wastewater treatment methods. The average percentage of bacteria reduction achieved by purification processes is about 99%. However, despite such a high degree of reduction, the amount of indicator of fecal coli bacteria that enter rivers along with the runoff is significant and dangerous, which is why it is so important to use the third stage of wastewater treatment—disinfection. Many methods of wastewater disinfection are commonly used. The main advantage of physical processes, including ultraviolet radiation, is the absence of additional chemicals entering the environment and the avoidance of the formation of disinfection by-products. However, physical processes also have their drawbacks: their effectiveness largely depends on the sensitivity of the organism to radiation (including the phenomenon of photoreactivation), and the use of this method has a local effect and does not protect against re-contamination. The paper presents the results of the research on the effectiveness of UV radiation in the disinfection of treated wastewater, based on indicator bacteria, including: coli and E. coli bacteria, mesophilic and psychrophilic bacteria and spores. The research took into account different flow rates (radiation dose) and the effects of light and temperature on microorganism reconstruction. Traditional and modern methods of assessing the microbiological quality of wastewater were used, i.e. microbiological determinations by traditional culture methods, using luminometer (ATP) and flow cytometer (FCM).