Evaluating of the disinfection and water quality effects on UV application in the primary stage of water treatment

Irradiation of water by UV has been considered as an attractive alternative for disinfection because its low-impact, pathogen killing capacity shows tremendous promise for meeting today's drinking water regulatory requirements. This study has been performed with the objective of utilizing medium pressure lamp in the preliminary stage of municipal water treatment, namely prior to water clarification and filtration. Raw water samples were irradiated for 30 s in a lab-scale closed reactor. Disinfection results showed nearly 2 log reduction in HPC for all the samples without formation of nitrite in excess of its MCL. As in a few previous works the formation of nitrite as an objectionable DBP had been reported, this study was extended by preparing synthetic water samples having different amounts of nitrate and turbidities. As far as the initial nitrate concentration dose not exceed 10 mg/L N-NO3, there would be no risk of nitrite increasing in excess of the MCL. Meeting the goal of at least 90% disinfection for water samples with turbidity levels of as high as 750 NTU is possible by utilizing medium- pressure UV lamp

Dose measurement in ultraviolet disinfection of water and wastewater by chemical method

Chemical methods [actinometry] depend on the measurement of the extent to which a chemical reaction occurs under the influence of UV light. Two chemical actinometers have been used in this research. In one method, the mixtures of potassium peroxidisuiphate butanol solutions were irradiated for various time intervals, and pH-changes were determined. A linear relationship was observed between these changes and UV-dose applied. In another method, the acidic solutions of ammonium molybdate and ethyl alcohol were irradiated and the intensity of blue color developed was determined by titration with potassium permanganate solutions. The volumes of titrant used were then plotted versus the UV-doses. This showed a linear relationship which could be used for dosimeiry. Both of these actometers proved to be reliable. The first is the method of choice with a view to have much accuracy and the second method is preferred because of its feasibility and having advantages of no need to any equipment and non-accessible raw materials