Most people probably don’t think about what happens after they empty the dishwater down the drain.But that dishwater has to travel through the city’s 100-mile underground network of pipes all the way to the wastewater treatment plant, where it goes through a complicated cleaning process before it’s safe to reintroduce into the environment.The plant is scheduled to undergo a major facelift later this year. The project will cost an estimated $18 to $24 million and is required by federal and state mandates, said Suzanne Loomis, city engineer/director of public works. The plant improvements also are needed to increase the plant’s capacity and upgrade the plant’s aging infrastructure.“It is a requirement,” Loomis said. “... You need to upgrade and maintain what you have.”“It’s very old technology,” said the city’s water/wastewater superintendent Ed Bonham. “It’s kind of lived its (useful) life.”How it worksLoomis has been working on the project for more than a year already and said the design process is now about 60 percent complete. She said one of the challenges will be to keep the current plant functioning while improvements are made.Loomis said the methods used to treat wastewater sound deceptively simple: microscopic bugs, air and equipment. It’s not really a chemical process, as some might assume.“It’s a biological process,” she said.Ultraviolet light also is used to kill bad material in the wastewater but keep the good. After the water is treated, it discharges into a receiving stream, Slate Creek, which then enters into Sand Creek.Although the plant is not manned 24/7, a computer system is able to alert staff if there is a problem.Elements of the improvement project include floodway modifications, a new access bridge and demolition of some of the older structures.Why it’s neededLoomis said the plant improvements are a vital part of the city’s remaining in compliance with state and federal regulations, such as the amount of “nutrients” such as nitrogen and phosphorus that can be discharged. If the plant were to go out of compliance, the city could face hefty fines, such as $10,000 a day.“It’s not just a slap on the hand,” Loomis said.Right now, the plant processes an average of about 2.5 million gallons a day during a wet year (rainwater can seep in through cracks in the line, Loomis said, though the city is working to make repairs and stop this from happening). The new plant will be able to handle an average of 4.4 million gallons a day, almost doubling the current capacity.The city has been saving back funds to help pay for the project, and staff is finishing up low interest loan paperwork for submittal to the Kansas Department of Health and Environment to see if the project will be eligible for financing through the state.Currently the project is slated to go to bid this spring, and construction is scheduled to begin this summer. The project will take about 18 to 24 months to complete.