Featured Stories

Other Pamplin Media Group sites

Local Weather

Mostly Cloudy

56°F

Portland

Mostly Cloudy

Humidity: 90%

Wind: 7 mph

  • 22 Oct 2014

    Rain 59°F 54°F

  • 23 Oct 2014

    Rain 60°F 50°F


Sewage plant's green practices slash costs

by: PAMPLIN MEDIA GROUP: JIM CLARK - Paul Proctor, project manager for Veolia Water, stands next to the Gresham sewage plants flare that burns excess biogas. By next fall, that gas will instead produce energy, when a second generator becomes operational.All the stuff folks in Gresham, Fairview and Wood Village put down their toilets and other drains is being harnessed to slash energy costs for sewer system customers.

By next year, Gresham’s wastewater treatment plant can lay claim to being totally powered by renewable energy created onsite, much of it from converting methane gas from sewage into electricity.

“We are very proud of our environmental record in a number of areas,” says Gresham Mayor Shane Bemis. “But to be honest, many of our choices to go green are motivated as much by the color of money as they are by our environmental stewardship ethic.”

Eight years ago, when 100 percent of the treatment plant’s power came from Portland General Electric, Gresham paid $44,000 a month for electricity to power and heat the plant, says Alan Johnston, senior engineer with Gresham’s wastewater services division.

In July, the bill was down to just $7,500, says Paul Proctor, project manager for Veolia Water,contracted by the city since 2005 to operate the plant at 20015 N.E. Sandy Blvd.

The treatment plant also is recycling fats, oils and grease, and producing biogas from them. Those innovations put Gresham on the cutting edge of sustainability, albeit in a most mundane environment.

Gresham’s plant serves 118,780 people, processing 4.75 billion gallons of sewage and anything else going down the drains in Gresham, Fairview and Wood Village every year, making it clean enough to be released into the Columbia River.

Municipal water supply and wastewater treatment systems account for 35 percent of the energy used by municipalities, according to the American Council for an Energy-Efficient Economy. Yet less than 10 percent of the nation’s 17,000 wastewater treatment plants produce and use their own energy, Bemis says. “And very few, if any, have done as much as we have.”

Combined, the upgrades are saving Gresham-area utility ratepayers around $280,000 a year, the mayor says.

“Gresham residents get it,” he says.

Long history in field

The city’s multipronged approach dates back 25 years, when it first experimented with turning sewage into electricity.

Biogas, a natural byproduct of wastewater at sewage treatment plants, is channeled into an engine that converts it into electricity.

The city’s first co-generator, purchased in 1987, had constant mechanical problems, Proctor says, and didn’t generate as much energy as projected. In 2005, Gresham replaced the machine with a 400-kilowatt co-generator, a Caterpillar lean-burning engine and generator to be precise. That generated electricity from biogas produced in the anaerobic digesters that also create biosolids, which are used as a fertilizer for harvests not intended for human consumption.

About 4 million dry pounds of biosolids are sold by the plant for agricultural use a year. That’s three rather pungent dump-truck loads a day.

by: JIM CLARK: PAMLIN MEDIA GROUP - Sewage Plant solar panelsThat process creates a heck of a lot of biogas, a combination of methane and carbon dioxide.

The co-generator now powers 51 percent of the plant’s electricity needs. The plant also gets about 18 percent of its electricity from PGE’s clean wind power option.

In 2009, the city looked skyward for its next energy source.

Gresham partnered with a third party to create what was then the largest ground-mounted solar array in the Northwest. That consists of about 2,000 panels along the southern edge of the plant along Sandy Boulevard. The solar power accounts for about 9 percent of the plant’s annual use.

That leaves 80 percent of the plant’s electricity supplied by renewable energy, 60 percent of it produced on site.

By next fall, a second cogenerator will be brought on line to convert excess biogas from the plant’s digesters into electrical power and heat. Right now, the extra methane is literally going up in flames, burned off in a mega-chimney, or flare. Methane is a greenhouse gas far more potent than carbon dioxide.

When that’s completed, the plant will be considered entirely independent from the grid, though it will remain connected to PGE for a backup supply.

Cutting through the FOG

by: JIM CLARK: PAMPLIN MEDIA GROUP - Gresham, Oregon sewage plantFats, oils and grease, often dubbed FOG, are a huge nuisance to most sewer systems, clogging up residential drains and underground pipes.

About a year ago, Gresham’s plant became the first in Oregon — and the second on the West Coast after Millbrae,

Calif. — to recycle fats, oils and grease into the digesters to produce more methane and power, thanks to a $760,000 system.

With the grease skimmed off the top of grease traps from local restaurants and stores, and the bacteria in the digester to eat solids while producing biogas, the process increases the plant’s methane production even more, all while recycling a product — the greasy sludge in the bottom of a fryer after it’s drained of oil — often destined for landfills.

“This is really nasty stuff that no one wants,” Proctor says.

Gresham gets waste grease from three companies whose haulers truck 9,000 gallons of the stuff each day to the plant. Restaurants and grocery stores such as Safeway pay Gresham 8 cents a gallon to take it. The stuff is then deposited into a 12,000-gallon tank that’s heated to prevent it from solidifying. Pumps delivers it to two million-gallon anaerobic digesters. There bacteria digest the solid waste into water, biosolids and biogas, which is fed into the cogenerator to make electricity.

“It’s like our stomachs,” Proctor says. “We eat a lot of good food, we produce a lot of gas.”

In addition to boosting biogas production, the process generates about $25,000 a month from recycling.

Last December, PGE approved net metering for Gresham’s wastewater treatment plant, which commits the utility to buy back surplus power produced at peak periods at the plant. “The meter spins backward if we’re generating more energy than we need,” Proctor says.

Before, the plant had to ratchet down the cogenerator engine if it was producing more electricity than needed at any one time. With net metering, the plant can buy power back from PGE when the sun isn’t out or its cogeneration engines are down, using credits from past sales to PGE.

All these innovations cost money, but the plant employs a single-digit payback philosophy: each investment must pay for itself in less than 10 years. Costs for the fats, oils and grease program will be recouped within three years, by September of 2015.

The innovations also save big bucks. “We’re netting $800,000 a year, half from FOG revenue and half from avoided electricity costs,” Proctor says.

And that means lower costs for raterayers. Bills for Gresham residential customers average $26 a month.