The impact of suspended particles on both UV dose transmission and spectrophotometric
absorbance measurement for unfiltered raw water with turbidity up to 10 NTU was assessed.
Results from bench scale "collimated beam" experiments indicate that a low percentage of total
incident UV light is attenuated by particles at 5 NTU turbidity. However, at a set applied UV
dose, when particles were added to achieve turbidity from 1 to 10 NTU, the average dose in the
collimated beam reactor decreased from 5 to 30 percent respectively, suggesting that spikes in
particles entering a UV reactor may compromise lethal delivery of UV energy if not adjusted for.
UV absorbance coefficients, measured using direct and integrating sphere spectroscopy (which
accounts for scattering effects by particles) were significantly different, suggesting that
suspended particles in unfiltered water both absorb and scatter UV light. When absorbance,
measured using the direct method, was used to model the average irradiance in a UV reactor, the
average UV irradiance was underestimated by 5 to 20 percent at turbidity of 3 to 10 NTU,
respectively, as compared to irradiance calculations made using integrating sphere absorbance
measurements. This analysis suggests that UV systems designed based on direct absorbance
measurements of unfiltered waters with turbidity above 3 NTU may be overly conservative. Includes 29 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 380 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 18 |
| Published : | 06/16/2002 |
