Rates of inactivation of waterborne coliphages by monochloramine

S W Dee, J C Fogleman
1992 Applied and Environmental Microbiology  
A sophisticated water quality monitoring program was established to evaluate virus removal through Denver's 1-million-gal (ca. 4-million-liter)/day Direct Potable Reuse Demonstration Plant. As a comparison point for the reuse demonstration plant, Denver's main water treatment facility was also monitored for coliphage organisms. Through the routine monitoring of the main plant, it was discovered that coliphage organisms were escaping the water treatment processes. Monochloramine residuals and
more » ... ne residuals and contact times (CT values) required to achieve 99% inactivation were determined for coliphage organisms entering and leaving this conventional water treatment plant. The coliphage tested in the effluent waters had higher CT values on the average than those of the influent waters. CT values established for some of these coliphages suggest that monochloramine alone is not capable of removing 2 orders of magnitude of these specific organisms in a typical water treatment facility. Electron micrographs revealed one distinct type of phage capable of escaping the water treatment processes and three distinct types of phages in all. Denver, Colo., is located in a rain shadow of the Rocky Mountains and, thus, receives an average of only 14 to 15 in. (ca. 36 to 38 cm) of precipitation per year. As a result of being in this rain shadow, combined with high summertime demands for water, the feasibility of recycling sewage into potable water has been explored. Denver's Direct Potable Reuse Demonstration Project was an 8-year, $30-million project intended to produce a potable product from secondarily treated sewage effluent (11, 20, 21) . One of the most important goals for this project was to produce a product water that was equal to or better than Denver's existing drinking water. A preselected point for sampling the existing drinking water was chosen for a water quality comparison. The preselected sampling point for comparison to the reuse plant was the effluent waters emanating from the Denver Water Department's main water treatment plant. Consequently, monitoring of the reuse plant processes for coliphages was accompanied by monitoring the main water treatment plant for coliphages as well. The Denver Water Department serves approximately 891,000 customers through three water treatment plants. The main facility is a 250-million-gal (ca. 946-million-liter)/day treatment plant. Water is impounded in the Strontia Springs Dam and Reservoir located on the South Platte River, 30 mi
doi:10.1128/aem.58.9.3136-3141.1992 fatcat:7j7jc2eourd5dgitax75riw5uu