Investigating the Feasibility of Water Disinfection Efficiency Improvement in Non-contact UV Radiation

Despite their simplicity and the low-cost, the conventional non-contact UV systems have low efficiency in water disinfection. The purpose of this study was to examine the possibility of upgrading these systems by some modifications in order to maximize the water contact with the UV radiation and as a result a better disinfection. In this study, two enhanced models of non-contact UV systems were compared to the conventional model. The waterfall model was made with a design based on flowing water from two thin waterfalls around a UV lamp in order to have direct radiation from the lamp’s all exposure areas. Also, the stair type model was designed in which a lamp was fixed over the shiny steel steps. The re­sults of water disinfection in two flow rates of 0.2 and 0.4 L/s were compared with traditional design at the ex­act similar conditions. The disinfection efficiency of this study was measured by reduction of fecal choliforms in water which were evaluated in turbidities of 0.5, 10 and 20 NTU. The disinfection efficiency of the waterfall model in the turbidity of 0.5 NTU was specified to be 3.65 log in reduction of fecal choliforms compared to the conventional model by 2.93 log reduction (P<0.05). Be­sides, this new model was quite capable of disinfecting the water with high turbidities up to 20 NTU. However, the stair type model had less efficiency than the conventional model. The reduction in disinfection efficiency at higher flow rates and turbidities for the waterfall model was much less than conventional model. So, application of the waterfall model in larger scales and for small water treatment facilities is suggested.