Pierce County is testing new sewage treatment technology that could save money and lead to cleaner effluent being discharged into Puget Sound.
If the pilot study at the Chambers Creek Wastewater Treatment Plant is successful, Pierce County would be among the first in the United States to incorporate the process into its treatment system.
The patented process is known as DEMON, short for “de-ammonification.” It uses a naturally-occurring bacteria (anammox) to efficiently remove nitrogen from wastewater before the treated effluent is discharged to the environment – in our case, to Puget Sound.
“Our job is to remove contaminants from the wastewater we receive from over 250,000 customers, and return clean, treated water to Puget Sound,” said Ryan Dooley, project manager for the Pierce County Sewer Utility. “We’re excited to test this technology to see if it can play a key role in our treatment process.”
Dooley said that the $11 million investment in a full-scale DEMON process facility would pay for itself almost immediately by reducing the number and size of new biological process tanks.
Long term, the DEMON process could eliminate the need to purchase an estimated 900 gallons of methanol per day required by a traditional nitrogen removal process. Methanol costs $2 to $4 per gallon, adding as much as $1.3 million per year to plant operating costs.
The DEMON pilot study will cost $150,000 and is part of a Public Works and Utilities project to replace aging infrastructure and increase treatment capacity. The cost of the expansion project is estimated around $305 million and is necessary to accommodate the rising population and economic development in Pierce County. Funding for the expansion comes from sewer rate payer fees and connection charges.
State and federal agencies are studying the extent that pollutants such as nitrogen may harm the health of Puget Sound. As new discharge standards are being considered, Pierce County is laying the foundation to be able to meet them.
For the four-month pilot study, a small-scale DEMON treatment plant was set up at the county’s regional wastewater treatment facility. Patents for the DEMON process, equipment and specialized bacteria seed sludge are held by Drs. Bernard Wett of Austria and Geert Nyhuis of Switzerland. Dr. Wett is personally supervising the DEMON treatment plant startup.
The efficiency of DEMON comes from the anammox bacteria’s ability to shortcut the conversion of nitrite and ammonium (a compound similar to ammonia) to nitrogen gas, a process called anaerobic ammonium oxidation. According to Dr. Wett, it’s possible to remove 90 percent of ammonia and up to 86 percent of all nitrogen from incoming wastewater depending on conditions.
Scientists first discovered the microbial anammox process in nature as part of the nitrogen cycle about 20 years ago. It is now known to be present worldwide in oceans, soil, and lakes. Its specific use as a wastewater treatment process has led to multiple application patents in several European countries.
For more details, including pictures of the pilot project, go to www.piercecountywa.org/sewerexpansion.