Wastewater Resource Reclamation

Wastewater Treatment Division (WTD)

Reclaimed water volumes met

2006 results: 259 Million Gallons (MG)
2006 target: 260 MG

This measure tracks the amount of wastewater that DNRP converts into a resource — reclaimed water. In the long term, DNRP's success in converting wastewater into a resource will depend on the cost of providing treatment and conveyance for reclaimed water relative to the cost of using existing sources and/or providing new sources of surface and groundwater. Factors include more stringent wastewater discharge requirements, closer scrutiny of water rights, more integrated water supply and wastewater planning, and the need to provide water and habitat for salmon recovery.

In the short term, higher costs and the abundance of other, lower-cost supplies, have resulted in low demand for reclaimed water from outside customers. However, both WTD treatment plants continue to reclaim all water needed for their own operations and any needed by customers.

The total volume of water reclaimed declined from 265 MG in 2005 to 259 MG in 2006. Reclaimed water at South Plant was turned off for several days in December to support a Brightwater pipe-cleaning test.

DNRP's goal is to expand the use of reclaimed water where feasible, and produce reclaimed water to match any increase in demand. DNRP will be developing a regional water supply plan that will address the role of reclaimed water in meeting the region's diverse water supply needs.

Biosolids reuse targets met

2006 results: 100 percent
2006 target: 100 percent

This measure represents WTD's ability to produce biosolids, a nutrient-rich organic material produced by treating wastewater solids. King County produces biosolids that meet high regulatory standards and to maintain customers and contracts for biosolids by addressing public perception issues that might affect these markets. The Regional Wastewater Services Plan states "King County shall strive to achieve beneficial use of wastewater solids." Several projects are under way at the treatment plants to improve biosolids quality and reduce digester problems that will help us maintain a target of 100 percent reuse of biosolids. Although 100 percent of available biosolids were reused, the measure requires ongoing attention to ensure this high rate.

WTD's strategy for continuing to meet the target of 100 percent biosolids reuse has several components. To maintain public and customer confidence in biosolids quality and management, King County now operates under and Environmental Management System for biosolids, which was nationally certified in 2004. Other strategies include:

• Ensuring availability of reuse sites for 150 percent of biosolids production.
• Continuing an aggressive industrial pretreatment program to maintain current low metals levels.
• Maintaining an active research and demonstration program that responds to public concerns and identifies potential new uses for biosolids.
• Investigating Class A technologies and determining which ones would be most appropriate and cost-effective for the West Point and South Plant facilities.

Percentage of biogas from wastewater converted to energy

2006 results: 73 percent
2006 target: 75 percent

This measure presents the average amount of biogas utilized at the West Point and South Plant wastewater treatment plants as renewable energy. Biogas, a natural byproduct of the wastewater treatment process, consists of methane (a greenhouse gas) and carbon dioxide. Rather than allowing biogas to be lost to the environment as a waste or pollutant, it can be captured, processed and burned as a renewable energy resource for fuel cell and cogeneration units to provide energy to the treatment plants.

The overall percent of biogas being recycled at the two treatment plants has declined over the past three years due to difficulties with the aging cogeneration facilities at West Point. New cogeneration and fuel cell facilities at South Plant came on line in 2005, however these facilities are not expected to significantly change the percentage recovery achievable at South Plant. Instead, these facilities will be used to generate backup energy for use at the plant.

New cogeneration facilities will come online at West Point in 2007 which will allow greater utilization of the available digester gas. A higher target of 85 percent utilization has been set for 2007.

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