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:01 <br />70 <br />60 <br />0 <br />50 <br />c <br />a� <br />i= 40 <br />30 <br />20 <br />10 <br />C <br />The UV transmittance is a ratio of the light intensity at a certain distance from the <br />light source to the light intensity at the light source. Typical UV transmittance ranges <br />from 45% to 70%, depending on the type of wastewater and the treatment processes <br />ahead of the UV disinfection system. The existing UV disinfection system is <br />designed at 65% UVT with dose of 30 mJ/cm2 at peak flow of 7.0 MGD. <br />Figure 3.2 shows the results from the pilot study. The UV transmittance and the <br />leachate flow rate are shown together to show the effect of increased leachate flow on <br />UV transmittance. Prior to adding leachate, the UV transmittance averaged 68%. The <br />leachate flow rate began at 6.7 gpm (9,700 gpd). With minimal effect on the <br />transmittance, after 45 hours of run time, the flow rate was increased to 13 gpm <br />(18,700 gpd). The UV transmittance was still above design valve with an average <br />value of 66%. <br />— 3UV Transmittance Leachate Flow Rate <br />:C <br />70 <br />60 E <br />CL <br />50 1D <br />CO <br />40 0 <br />5= <br />30 CO <br />U <br />CO <br />20 J <br />10 <br />0 <br />0 90 182 274 366 456 547 639 731 821 912 1004 1096 1186 1277 <br />Run Time (hours) <br />Figure 3.2: Long -Term Pilot Study Results <br />After the flow rate was increased to 13 gpm, the UV transmittance began to drop <br />from 66% to 61% over the course of another 45 hours. This indicates that by doubling <br />the flow rate, the UV transmittance saw a decrease of 5% and the leachate flow rate <br />does have an effect on the UV transmittance. The immediate effects on the <br />Prepared by: Bolton & Menk, Inc. Results and Discussion <br />Waste Management/Elk River Leachate Pilot Study I T21.109643 Page 10 <br />