If you tracked one drop of water through Vancouver’s Marine Park Wastewater Treatment Plant, you’d find that it takes about eight hours to go from raw sewage to reasonably clean.
Some of the leftover solids get pumped over to the West Side plant for still more treatment, removal and eventual incineration. But much of the water that moves through the Marine Park plant winds up diffused in the Columbia River in a condition that’s no more polluted than the river itself, according to Frank Dick, the city’s wastewater engineering supervisor.
“I’m your wastewater guy,” Dick told a group of 15 curious folks who signed up for a live, and only slightly stinky, Saturday morning tour of the Marine Park plant’s innards, supplemented by a stroll upriver to the site where that cleaned-up water emerges from specially designed underground pipes and joins the flow to the Pacific Ocean.
Built in the mid-1990s, the Marine Park plant was an attempt to beautify a naturally unattractive process, Dick said. Mindful of neighbors on a ridge overlooking the site — and the need to educate the public about the importance of water — the city decided to keep tanks and settling ponds full of brown gunk almost entirely covered up, and to add the people-oriented Water Resources Education Center facility as well.
“Visitors from all over the U.S. have come to take a look at our water-treatment plant,” Dick said with pride.
Ten million gallons of wastewater from Vancouver’s greater urban area flow through the Marine Park plant every day, Dick said. The city’s population is approaching 200,000 now, he said, but its wastewater system service area goes far beyond the current city limits, serving around 245,000 people in 60,000 customer accounts.
Plant operators with a private contractor called Jacobs are onsite for eight hours per day to manage the mechanical and chemical intricacies of the process from a central computer control room, Dick said, and to walk around visually inspecting everything. After hours and on weekends, the plant usually hums along automatically.
The four Ps
Talking about wastewater gets gross, but it’s not quite as gross as the wastewater itself. So hold your nose, and here we go.
Pee, poop, toilet paper and puke. Those are the four Ps — the only things that should ever get flushed down your toilet, Dick said.
Never diapers. Never baby wipes. Never leftovers. Never anything that’s not one of those four Ps, Dick said. (Pet waste is not a P. Its chemical composition is different from human waste. Send it to the landfill, Dick said.)
Commercial products like wipes claim to be flushable, but Dick said he’s conducted myriad personal tests of these claims and has never found any supposedly “flushable” product that doesn’t cause problems.
That’s why the five-step process of treating wastewater starts with pretreatment, which means removing all the miscellaneous stuff that never should have gone down the pipe to begin with.
Children’s toys are a frequent find in the pretreatment phase, Dick said. Candy wrappers, other plastic packaging and plenty of faux-“flushable” products are common, too. Cell phones and medical devices aren’t all that rare.
Dick’s favorite rescue at the pretreatment phase was a $50 bill that eventually paid for pizza, he said.
Next, what’s called “grit” — small, hard particles of everything from dirt to kernels of corn — is screened out. Then, the water is piped into six large, rectangular settling tanks where it just sits and sloshes for a while, letting scum float to the surface and sludge sink to the bottom.
“We’re standing on those tanks right now,” Dick said after the tour group stepped onto the roof of the building, which screens the tanks from neighborhood view. After sludge settles to the bottom, Dick said, chain-driven scrapers move it toward the drain that sends it on its way to Vancouver’s West Side treatment plant for more processing and eventual incineration. Meanwhile, scum skimmers remove fat and grease from the top.
Next, compressed air is pumped through the water as it passes through 18-foot-deep basins. The heated air facilitates the action of naturally occurring microbes that break down organic and toxic chemicals. Plant operators must keep an eye on the air flow and the amount of microbes in the system, Dick said.
Finally, the water shoots past intense ultraviolet lights, which kills any remaining bacteria and viruses. After that, the cleaned-up water is piped 800 feet upriver and diffused into the Columbia in a way that’s unnoticeable.
Quality tests of samples are conducted every 24 hours to ensure that all is going right, he said.
“It’s a very complicated process,” Dick said. “In the end, we need to make sure the water we are discharging is cleaner than river water. It’s all about removing stuff.”