Open Channel versus Closed Vessel for Wastewater: Cost Comparison

Ultraviolet Disinfection has gained increasing acceptance as a final treatment step for many wastewater, and reuse applications in the US over the last 20 years. However, as a technology it is vastly different from the chemical treatment it typically replaces and as such, more and more engineers are faced with the challenge of designing systems that meet their clients' disinfection requirements. This responsibility has become increasingly more complex with the various regulations, lamp technologies and equipment configurations currently available.The majority of UV installations for wastewater have been the traditional open channel method consisting of UV lamp rows (modules) being dropped into concrete channels. While this method is proven effective and provides for an easy upgrade there is a closed vessel in pipe UV alternative that has also been proven effective. The closed vessel UV approach and open channel design approach can each provide attractive advantages to certain UV applications.This paper attempts to compare the two UV technology design approaches, by providing real life data on the construction cost, capital cost and O&M cost of installing the necessary concrete channel and level control versus the closed vessel in pipe ultraviolet disinfection equipment to disinfect a wide range of municipal wastewater flows and water quality parameters.Financial figures captured from past and present ultraviolet disinfection projects will be presented. Data will be provided from contractors showing their true costs for the construction, installation and capital investment for both UV disinfection technologies. Included will also be data on the up front cost analysis that was conducted to select the technology of choice.Finally, the paper will expound on the results and offer a conclusion which demonstrates the actual cost of open channel ultraviolet disinfection versus closed vessel ultraviolet disinfection from project inception through construction, installation, capital investment and O&M providing a rule of thumb for the most effective for particular applications.