Anammox Bacteria: DEMON Pilot
One day, recycled Pierce County sewage could water the greens at Chambers Bay golf course.
The new source of irrigation water for the course and surrounding parklands is one benefit of a $342 million expansion of the Chambers Creek Regional Wastewater Treatment Plant, county officials say.
While the irrigation system to make use of the reclaimed water possible will take some time, other benefits of the sewer plant upgrade are close.
The project, which is primarily aimed at equipping the plant to handle wastewater from additional households and businesses, is also expected to make the millions of gallons of treated wastewater discharged into Puget Sound each day safer for marine environments.
When the expansion opens this fall after three years of construction, the plant in University Place will become one of the few in the country using a process called deammonification to break down nitrogen-rich ammonia.
“Even though the standards for discharge have not changed, we will have the capacity to produce cleaner water with the new treatment technology,” said Public Works director Brian Ziegler.
The new technique reduced construction costs by allowing the county to build a smaller plant. It also is expected to help the county avoid future costs if federal and state agencies adopt more stringent wastewater treatment standards.
Deammonification has been used in Europe for years, but it is still new in the United States. The method adopted by Pierce County, a patented process called DEMON, is in use at only five other wastewater treatment plants in North America, according to Chandler Johnson, chief technology officer at World Water Works. The company holds the license to the technology in America.
EXPANDING TO HANDLE GROWTH
The 32-year-old plant now handles wastewater from customers from a 117-square-mile area that includes University Place, Lakewood, Steilacoom, DuPont, a portion of Tacoma, and unincorporated areas including Parkland, Spanaway, Midland, South Hill and Frederickson.
After the expansion is complete, the facility’s capacity will grow from 28.7 million gallons a day to as much as 45 million gallons a day, according to Public Works spokeswoman Callene Abernathy. Another expansion will be necessary in the future for the plant to reach its expected total capacity of 60 million gallons of wastewater a day.
One way the county is buying increased capacity is through the deammonification process. It handles the worst of the wastewater, leaving fewer gallons that must be handled by existing treatment processes. The county spent roughly $7 million to install deammonification equipment, but saved an estimated $15 million by being able to install smaller components used in traditional wastewater treatment.
The county will continue to use its current treatment process for the majority of its wastewater when the new plant opens. In that process, the county uses bacteria found naturally in wastewater to reduce nitrogen. Sometimes, liquid methanol is used to accelerate that breakdown, although the county hasn’t needed to use it recently.
The deammonification process introduces different bacteria that are more efficient at nitrogen removal. The county will run roughly 30 percent of the wastewater, the portion composed primarily of human waste, through this new treatment process. The result will be lower nitrogen content in the final product: effluent that ends up in Puget Sound.
18 million gallonsof wastewater discharged daily into Puget Sound
High nitrogen levels are linked to toxic algae blooms that can close shellfish beds and restrict public access to the water. Nitrogen reduces oxygen in the water; low oxygen levels are linked to fish kills.
The county currently dumps approximately 18 million gallons a day of treated wastewater into Puget Sound.
Long term, the new treatment method could save additional money if federal and state agencies require higher levels of nitrogen removal from discharged wastewater, said Kip Julin, Pierce County’s sewer planning and programming manager. The county must renew its permit with the state Department of Ecology every five years to discharge into Puget Sound.
If stricter discharge regulations are imposed, Julin estimated a $40 million to $70 million savings over the next decade because the deammonification technology will meet those standards at the lowest possible cost.
Already, the technology could reduce nitrogen levels more than what is required. But Ziegler said when it comes online at the end of the year, it will be calibrated to meet current standards.
“It doesn’t make sense to our rate payers to be treating at that high level of treatment when we are not required to because it costs more money,” he said.
EVEN CLEANER: RECLAIMED WATER
Producing reclaimed water at the plant is another move toward environmental and financial efficiency, county officials say.
The expanded plant will be able to generate up to 1.5 million gallons of reclaimed water a day. Reclaimed water has a higher treatment standard than treated wastewater and can be used for “anything short of drinking,” Ziegler said.
1.5 million gallons of reclaimed water expected daily from expanded plant
Reclaimed water will be used to clean equipment at the plant. County employees now use treated wastewater for that cleaning, but they have to take precautions because the water is not treated to a level safe for human contact. It is only cleaned to a level acceptable for discharge into Puget Sound, where it will be diluted by the salt water, Ziegler said.
For that same reason, treated wastewater can’t be used to irrigate neighboring Chambers Creek Properties, including the Chambers Bay golf course and the fields around the Environmental Services Building.
A yet unfunded portion of the plan will allow the county to tap storage basins of reclaimed water to replace some of the 65 million gallons of well water the county now uses every year on average to irrigate the golf course and park.
“Reclaimed water is a technology of the future,” Ziegler said. “More and more plants are expecting to go to this level of treatment.”
The three-year expansion of the Chambers Creek Regional Wastewater Treatment Plant is coming in below budget, but above the available funds to pay for the project.
Initial projections put the cost of the upgrade at $353 million. But that figure included $20 million for unplanned expenses that Pierce County didn’t factor into its financing.
That’s because the county “didn’t want to artificially inflate (sewer) rates and collect money if we didn’t have to use the contingency money,” said Public Works director Brian Ziegler.
The final tab for the project will be closer to $342 million, requiring the county to dip into the contingency for $9 million.
The county will cover the overage a number of ways, including by reducing operating costs and postponing a future capital expenditure, Ziegler said.
“We’re not proposing rate increases, we’re not proposing connection charge increases, we’re not proposing borrowing,” Ziegler said.
Sewer rates are expected to continue to increase at a rate meant to keep pace with cost of living. That means ratepayers will see a 3.3 percent increase in 2017 if the Pierce County Council approves a scheduled rate hike.
Current base rates for residential customers served by the Chambers Creek plant are $45.64. That amount could be more for customers in cities that tax the utility.
The county combined $208.8 million in sewer revenue bonds with a $60 million loan, $511,000 in grant funding and an estimated $72 million in cash reserves to pay for the expansion.