(MCT)—The orange flare along I-95 near Castor Avenue isn’t lit anymore.
It used to burn off excess methane produced at this Philadelphia sewage treatment plant. But with the completion of a $47.5 million project, the gas now is transformed into heat and electricity, putting the plant front and center in a sewage paradigm shift.
These days, the stinky sludge, the stuff of our toilets, has a new future. Experts see not an abomination, but a resource.
“We are just at the beginning of what we can do with sewage,” says Allison Deines, director of special projects at the Water Environment Research Foundation, a Virginia-based nonprofit for wastewater and storm water issues.
She and colleague Lauren Fillmore, senior program director for energy, lauded Philadelphia as an early adopter.
“It takes a long time just to get a few supporters of innovative technology,” Fillmore says. “I definitely want to credit Philadelphia with being a leader.”
When municipalities started piping sewage away from residential areas, the receiving facilities were known as sewage treatment plants. They did little but settle out the solids.
In the 1980s, in the wake of national clean-water legislation, they became “water pollution control plants.”
Today, “we’re moving toward a new name,” says Philadelphia Water Commissioner Howard Neukrug. “The industry is calling them ‘water resource recovery facilities.’”
At Philadelphia’s Southeast plant, a system recently was installed to recover the heat in the sewage stream, which is about 60 degrees in winter, 75 degrees or more in summer.
The York County, Pa., plant has a process that recovers phosphorus — a fertilizer in limited supply worldwide — for processing and reuse.
Some day, Neukrug and others say, it may be both technologically and economically feasible to mine sludge for other nutrients and heavy metals.
At the city’s Northeast plant in Bridesburg, Pa., the resource is “biogas.”
There, sewage solids are separated and sent to eight 2.1 million-gallon tanks, where bacteria digest the material and reduce its volume. In the process, they give off a flammable gas that is roughly 63 percent methane.
Christopher Crockett, Water Department deputy commissioner for planning and environmental services, likens the process to that in the human stomach, gas and all. Stuff arrives; microbes digest it.
