Where the water goes: Cape's treatment plant filters waste in five-hour process
Saturday, May 24, 2008
Most people don't think twice about what happens once a toilet is flushed.
"They think that's the end," Jim Baylor said. "Really, it's just the beginning."
Baylor, 60, has worked at Cape Girardeau's wastewater treatment plant for 30 years and is now chief operator. The plant, at Third and LaCruz streets in the city's southeast corner, was built in 1962 and expanded in 1977.
Baylor warns people scheduling tours of the plant to expect an odor as they learn about the elaborate filtering system used to clarify wastewater until it's clean enough to pour back into the Mississippi River. All told, water is filtered and skimmed for nearly five hours before being released.
"It's like a mild rotten egg smell," he said. At least on cooler days.
Gravity helps water travel through the city's sewer system, a network of 200 miles of pipes. When hills get in the way, one of 27 lift stations boost the water over. Water from the city's north side travels seven miles to get to the plant.
Rocks, socks and nylon
The force of the 5.5 million gallons of water used in Cape Girardeau daily carries rocks and other debris that have fallen through sewer grates all the way to the plant. As the murky liquid pours into the plant's headworks, a screen holds back rocks and grit, sending them to buckets, which move along a chain and are emptied into a six-cubic-yard bin. Another screen sends piles of paper, cloth and nylon to a second bin.
"You know how socks disappear in a load of wash? This is where they go," he said, pointing to what he calls "the rags."
This is where truly laundered money goes, too.
"But I'm not looking for it," Baylor said, laughing.
As the water moves on, it is infused with city water and begins a leisurely filtering process in 100-foot-long tanks.
"It takes a drop of water two hours to travel 100 feet," Baylor said. During that time, 65 percent of the remaining solids are culled from the water. Thirty percent of the sludge comes from garbage disposals.
The water moves to a 45-foot-tall building for treatment by a honeycomb of plastic, a sprinkler system, worms, slugs and other creatures. The sprinklers, lined up across the top of the building, send water up in a fine shower to help recharge it with oxygen. The water falls though large openings onto the plastic filter, which is 22 feet deep and 100 feet long -- where organisms living among the layers eat the majority of the remaining solids.
While the water is being filtered, any solids removed earlier in the process -- what Baylor calls biomass -- are shunted to storage tanks, where they are treated with a lime slurry and thickened for at least two hours. Rick Randol, one of the plant's lead men, tests the pH level of the sludge, making sure it's high enough -- at least a 12 -- to kill most bacteria. Trucks haul the treated sludge out to farmers' fields, where it is injected into the ground.
"The farmers do not charge us, and we do not charge the farmers," Baylor said. "They use it for wheat, corn, milo, sorghum and soybean crops. But you can't use it on root vegetables."
The plant has been turning sludge into fertilizer since 1988. Before that, it was trucked to a landfill.
Todd Fulton, one of the plant's pretreatment coordinators, tests water from a final filtering tank. It's not clean enough to drink, but it's cleaner than Mississippi River water, Fulton said.
He said people can do two things at home to help keep the city's water cleaner: use low-phosphate detergent and "put grease in a can, not down the drain." Phosphates encourage algae growth. Grease clogs the filtering system.
Less than a quarter-mile west of the plant are a cluster of 20 sinkholes. The holes have been stable for weeks but are still considered a threat to the wastewater treatment plant.
"Until more time has passed and we're confident that the sinkhole activity has stopped, yes, we still consider it at risk," said Ken Eftink, the city's director of development services. "Hopefully not an extreme high risk. The Sprigg Street bridge is considered at a high risk."
Tours of Cape Girardeau's wastewater treatment plant are free but must be scheduled one week in advance. Call 334-5150 for details.
335-6611, extension 127