A design has been developed which overcomes the issues mentioned with the earlier reflective chamber designs discussed above. This design uses a double quartz configuration. The inner quartz lamp sleeve isolates the lamp from the water, as is done in most UV systems. A larger outer quartz flow tube is then utilized to create the outer containment of the flow. The reflective material is then positioned outside of the quartz flow tube. Figure 1 shows a cutaway of the design to help visualize the concept.
In this design, the lamp introduces essentially all of its UV directly into the flow tube and the reflector returns the photons to the water flow with only a small fraction of the UV escaping or residing outside the water flow volume at any given time. The UV stays in the water volume until it is absorbed by the target DNA or TOC molecule, rather than get lost (absorbed) by the chamber wall, or residing in a volume outside the water flow. This ensures that the light coming from the same low-pressure lamps is used more efficiently in this chamber than in the conventional or other reflective chambers.
There are two key requirements that are necessary for this design to achieve the significant improvement in performance that it can provide. These requirements must be met simultaneously – satisfying only one or the other will not provide the improved performance. The first requirement is that the reflective material needs to be at least 80-percent reflective to the UV light. The second critical requirement is that the reflective material must enclose at least 80 percent of the treatment zone (80-percent coverage). Tests and simulations have shown that chambers which don’t meet these two requirements do not provide a significant improvement in performance.
The chart in Figure 2 shows the strong increase in UV intensity relative to that in a conventional stainless steel chamber when both requirements are met. There are modest increases in performance over the baseline stainless steel chamber when the reflectance is above 80 percent and the coverage is below 80 percent, and also when the coverage is above 80 percent and the reflectance is below 80 percent, but the really significant increase only occurs when both the reflectance and the coverage are above 80 percent.
Independent research published by the University of Arizona1 has confirmed this effect both theoretically and experimentally. An earlier paper from the Chinese Academy of Sciences and the University of Alberta2 also indicates improvement with higher reflectivity, although this paper does not have enough information to determine the percent coverage.
