Effekten av fotoreaktivering og partikkelinnhold ved UV-desinfeksjon av renset avløpsvann

UV-disinfection as a treatment method is well suited for wastewater treatment plants of medium size or smaller and is an effective way to inactivate microorganisms. However, the treatment method is dependent on factors related to the quality of the water, which must be properly treated before disinfection. Its’ effectiveness may also be affected by photoreactivation, which is a microorganisms’ ability to reverse the DNA damage caused by UV-disinfection in the presence of visible light. Therefore, the authors of this master’s thesis pose the following research question: To what extent does photoreactivation and particle content affect the UV-irradiation of treated wastewater, and what measures can be taken to reduce the effects of these two factors? To investigate the research question, the authors perform laboratory tests on samples of wastewater from a local wastewater treatment plant. The laboratory tests are designed to compare the degree of inactivation of bacteria in treated wastewater to wastewater affected by an increase of particles and the presence of visible light. The authors conclude that photoreactivation affects UV-irradiation to a small extent, and that the effect of photoreactivation can be reduced by adapting measures that ensure no visible light reaches the inactivated bacteria. As opposed to photoreactivation, the particle content affects UV-irradiation to a significant extent. To reduce the effect of particles on UV-irradiation of bacteria, filtration can be used as a final treatment measure before UV-irradiation