Denver Water has pioneered a disinfection method that\u2019s saving millions of gallons of water, reducing staff time and nearly eliminating expensive pipe replacement do-overs.<\/p>\n\n\n\n
\u201cWere all the studies and effort and research worth it?\u201d said Fred Sanchez, Denver Water\u2019s water quality manager. \u201cYou\u2019re darn straight it was.\u201d <\/p>\n\n\n\n
Every year, Denver Water installs more than 100,000 feet<\/a> of new water main delivery pipes, which are typically found under a neighborhood\u2019s streets. New pipes are installed for a variety of reasons, such as replacing older pipes, repairing broken pipes and improving the delivery of water to an area. <\/p>\n\n\n\n Before newly installed pipes are put into service, the pipes are cleaned and disinfected \u2014 and then must pass a test showing they can deliver clean, safe water to Denver Water\u2019s customers.<\/p>\n\n\n\n Denver Water uses liquid chlorine, liquid ozone and\/or pressure washing methods to clean and disinfect newly installed pipe. Then crews flush the pipe for hours, sending thousands of gallons of water to the storm sewer before the pipe is tested for harmful bacteria. <\/p>\n\n\n\n In 2019, Denver Water added another technique to its disinfectant arsenal \u2014 gaseous ozone \u2014 becoming one of the first water utilities in the world to do so. <\/p>\n\n\n\n \u201cThis is the next evolution in disinfection methods,\u201d said Ryan Gregg, water quality supervisor. <\/p>\n\n\n\n In 2013, after crews had finished a job installing 1,000 feet of pipe, water quality technicians could not get any of the traditional disinfection methods to work. Tests kept showing bacteria present inside the pipe.<\/p>\n\n\n\n \u201cWe used everything we had, but we could not get it to pass the test,\u201d Gregg said. \u201cSo, we had to replace it. They had to rip it out of the ground and install another 1,000 feet of pipe.\u201d<\/p>\n\n\n\n Crews installed the same type of pipe from the same manufacturer and tried again. <\/p>\n\n\n\n \u201cStill, we could not get it to pass,\u201d Gregg said. \u201cSo they had to replace it a third time.\u201d<\/p>\n\n\n\n This time, crews tried a different pipe material and were able to disinfect it properly. <\/p>\n\n\n\n Perplexed, water quality technicians studied samples from the pipe that had failed to pass the repeated tests. They found that it had been contaminated with Pseudomonas aeruginosa, a kind of bacteria, which, once established, is extremely hard to remove. <\/p>\n\n\n\n All the waste from dealing with chlorine-resistant bacteria \u2014 the water needed for flushing the pipe repeatedly, traffic detours, staff time, money \u2014 left its mark on Denver Water\u2019s scientists. <\/p>\n\n\n\n They started searching for an alternative disinfection technique, one that could eliminate stubborn bacteria without so much waste. <\/p>\n\n\n\n Ozone gas quickly became a contender. <\/p>\n\n\n\n With the help of CDM Smith, a Denver-based engineering firm, and Denver Water\u2019s transmission and distribution group, the utility\u2019s water quality operations techs conducted dozens of pilot studies for five years to see if ozone gas would work. <\/p>\n\n\n\n After each test, researchers were impressed with the results. <\/p>\n\n\n\n \u201cSoon, we had all the data we needed to conduct a full-scale application,\u201d Gregg said. <\/p>\n\n\n\n In the field, Denver Water\u2019s custom-built ozone gas trailer pulls outside air in, separating oxygen (O2<\/sub>) and nitrogen, Gregg said. Then, the concentrated oxygen goes to the other side of the trailer where high-voltage electricity helps to create ozone, or O3<\/sub>. <\/p>\n\n\n\n Alarms and fail-safe measures ensure crews stay safe, and the ozone is then purged and rendered ineffective afterward, said Jill Vandegrift, CDM Smith environmental engineer who worked on the project.<\/p>\n\n\n\n \u201cThere is no concern with the public breathing ozone once the pipe has been disinfected,\u201d she said. <\/p>\n\n\n\n The process is fast and requires little flushing. In fact, gaseous ozone saves Denver Water 13.5 million gallons of water a year and reduces staff time by about 30 days annually. <\/p>\n\n\n\n <\/p>\n\n\n\n![\"Man](\"https:\/\/www.denverwater.org\/sites\/default\/files\/styles\/inline_image_700px_wide\/public\/2022-08\/2-ozone-water-quality-trailer-disinfection-2019.jpg?itok=9jg-7gwW\")
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