The city of Canby is wrapping up improvements to its wastewater treatment plant that include the construction of a new 300,000-gallon liquid storage tank and refurbishments to two existing tanks, as well as some miscellaneous site improvements.
Dave Conner, the wastewater treatment plant's supervisor, said the new tank, 75-feet by 100-feet, is needed to provide more time and backup for the storage of sewage sludge.
"With the smaller tanks, one processes sludge in seven days and the other takes five days," Conner said. "Right now, with the two smaller tanks, if we have any breakdowns we run into time constraints. As we move into the future, those tanks will provide us with more time, which we need; this should add about 17 days to liquid storage for us."
Sludge is processed on what's known as a belt press, which essentially is a conveyor belt, and separated into the tanks. The tanks aerate the sludge, mixing together the primary and secondary waste byproducts, which then run the sludge across the belt press the last part of the wastewater treatment process.
Conner said the sludge has the consistency of a mud ball and that Canby's sewage treatment plant removes anywhere from 1.5 percent solid matter to 2.2 percent solid matter during the process.
Once the sludge is separated out, it is stored inside a large warehouse where truckers come pick it up and haul it to Heard Farms in Roseburg. There, the sludge is processed into a Class B bio-solid, meaning it is treated but still contains higher-detectable levels of pathogens than Class A bio-solids, which then is used as fertilizer on farmland.
The City of Canby has spent $1.7 million as part of a five-year master plan to renovate the town's wastewater treatment plant. This final phase came at a cost of $870,000.
According to the U.S. Environmental Protection Agency, thousands of American cities dumped their raw sewage directly into rivers, lakes and bays as recently as 30 years ago.
Due to strict federal and state standards, treated residuals from wastewater treatment plants, known as bio-solids, are safely recycled with local government making the decision to recycle it as fertilizer, bury it in a landfill or incinerate it.
Currently, the City of Canby's Wastewater Treatment Plant legally releases 1 million gallons of treated sewage a day into the Willamette River – water that is crystal clear after going through grit removal, being broken down using chemicals and bugs, and the removal of any remaining bio-solids on conveyor-type belts.