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Energy

An investigation of alternative approaches to optimize biogas management and energy utilization facilities at the Brightwater, West Point, and South Treatment Plants.

View report (6.8 MB)

A detailed study investigating the feasibility of importing brown (restaurant) grease to WTD's South Treatment Plant and co-digesting with sewage solids to increase production of renewable biogas.

View report (5.8 MB)

This report summarizes an initial investigation on the feasibility of implementing a food waste importation program at South Plant in order to increase methane production.

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The results of this two-year project demonstrates whether a molten carbonate fuel cell power plant could be adapted to use anaerobic digester gas as a fuel source and still achieve a power output target of 1 megawatt.

View report (9.8MB), April 2009

Wastewater Solids Processing and Biosolids

King County Wastewater Treatment Division (WTD) and Solid Waste Division (SWD) are evaluating the feasibility of food waste digestion at the WTD South Treatment Plant as a means of diverting organics from landfills and increasing revenues from renewable natural gas generation.

Co-digestion Options Evaluation , January 10, 2020

The Technology Assessment team conducted a biosolids characterization study to determine if it would be possible to oxidize sulfur compounds before the biosolids leave the plant. The study tested whether potassium permanganate (KMnO4), a strong oxidizer known to target sulfur compounds, would reduce biosolids odor if it were added to wastewater solids prior to the centrifuge stage of treatment.

Addition of Permanganate to Biosolids for Odor Control , September 2012

A variety of studies to evaluate and/or improve the operation of West Point's solids digestion process are summarized below:

  • Digester Tracer Studies –  to evaluate mixing effectiveness. Initial testing was inconclusive.
  • Temperature profiles – to evaluate mixing effectiveness by looking for temperature gradients within the digester.
  • Solids profiles – to evaluate mixing effectiveness by looking for solids concentration gradients within the digester.
  • Vmax/Acetate uptake rates –  to evaluate health of a digester tank by measuring how it responds to a known artificial feed source.
  • Digester survey – to establish how actual operating conditions of digesters compare to similar systems in other parts of North America.
  • Recirculation gas monitoring – to determine mixing energy input by establishing the flow of digester gas delivered to each mixing draft tube.
  • Evaluation of instrumentation to better monitor digester operation and online gas composition and liquid stream parameters.

The studies ultimately resulted in a multi-phase capital project designed to improve the stability of the digesters. Results of the studies are summarized in this PowerPoint presentation.

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This report summarizes a demonstration of the VERTAD™ digestion process to provide Class A pathogen reduction through an aerobic deep shaft design.

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This study examined temperature-phased anaerobic digestion to improve volatile solids destruction and/or to accommodate reduced hydraulic residence time in existing digesters.

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This demonstration project determined that the Centridry™ biosolids drying process was capable of producing biosolids of 50 to 60 percent solids content in a mechanically reliable and operator-friendly manner but also revealed serious issues of odor, and hence product acceptability and siting issues.

View report (41 MB)

This study documents food waste management in WTD's service area and the impact on wastewater treatment process unit loading, and to develop and compare alternatives for managing food waste in a more cost-effective way.

View report (5.3 MB)

Wastewater Liquids Processing

Assessment of Anaerobic Digester Foaming

King County's wastewater treatment plant digesters have experienced periodic excessive foaming and gas entrainment. Solids processing at the treatment plants is via conventional anaerobic digestion. An assessment of foaming at the West Point Treatment Plant was completed to determine contributing factors and development management practices. The work included applied research conducted by the University of Washington Department of Civil and Environmental Engineering under the existing Graduate Research Fellowship Program.

More about the study at https://digital.lib.washington.edu/researchworks/handle/1773/44117

Tertiary Filtration for Phosphorus Removal

Based on positive results from laboratory testing using Brightwater Treatment Plant (BWTP) membrane effluent, the University of Washington and MicroHAOPs, Inc. contacted King County about operating a small pilot unit at the BWTP. The pilot system was installed in July 2018 and operated until December 2018. It demonstrated the effectiveness of MicroHAOPS' filtration technology to reduce membrane fouling potential while removing phosphorous . Further information on the MicroHAOPS technology can be found at the following link:

Based on positive results from laboratory testing using Brightwater Treatment Plant (BWTP) membrane effluent, the University of Washington and MicroHAOPs, Inc. contacted King County about operating a small pilot unit at the BWTP. The pilot system was installed in July 2018 and operated until December 2018. It demonstrated the effectiveness of MicroHAOPS’ membrane pretreatment technology to reduce membrane fouling potential while removing phosphorous. Further information on the MicroHAOPS technology can be found at the following link:

https://www.ce.washington.edu/news/article/2018-02-14/start-success-microhaops

The Washington State Department of Ecology has determined that portions of south Puget Sound do not meet Washington State water quality standards for dissolved oxygen. Ecology is concerned that algal growth stimulated by nitrogen loadings to Puget Sound is causing DO depression in near-bottom regions. The Technology Assessment Program conducted this study to evaluate the impact (e.g. costs, footprint, energy, greenhouse gas emissions) of a range of potential future nitrogen removal requirements on the West Point Treatment Plant. The West Point Treatment Plant is a high-purity oxygen (HPO) activated sludge process (non-nitrifying) on a very constrained site with no possibility of expansion.

Report  (5 MB)

The Washington State Department of Ecology has determined that portions of south Puget Sound do not meet Washington State water quality standards for dissolved oxygen. Ecology is concerned that algal growth stimulated by nitrogen loadings to Puget Sound is causing DO depression in near-bottom regions. The Technology Assessment Program conducted this study to evaluate the impact (e.g. costs, footprint, energy, greenhouse gas emissions) of a range of potential future nitrogen removal requirements on the South Treatment Plant. The South Treatment Plant is a conventional activated sludge process (non-nitrifying) with significant space available for future expansion

Report (9 MB)

This work was initiated by project staff at King County in 2009 as part of preparations for a potential flood emergency in the Green River Basin (which is tributary to King County’s South Treatment Plant ) due to concerns about instability of abutments to the Howard Hansen Dam. The objective of this study was to evaluate potential strategies to maximize flow capacity through the secondary system at the South Treatment Plat during a flood event without putting the secondary process at risk of failure after the flood event. This study was limited to evaluation of process effects.

View report (785 KB)

A pilot study was requested by the KC-WTD CSO program to evaluate chemical enhanced primary clarification for CSO treatment. The pilot provided a comparison of treatment with and without lamella plate clarification.

REPORT LINK TO BE ADDED.

King County pilot-tested multiple membrane bioreactor (MBR) technologies. The technology is now being used at King County’s Carnation and Brightwater Treatment Plants.

This demonstration assessed various emerging wastewater treatment technologies designed to produce reclaimed water. This project was awarded the 2002 National Environmental Achievement Award for Research and Technology by the National Association of Clean Water Agencies.

In 2002, King County was interested in introducing wastewater reclamation to its service area. To facilitate this initiative, a demonstration project was conducted to evaluate and pilot test emerging technologies that could meet the County’s goals for effluent water quality, operability, and cost.

The reuse applications ranged from basic tertiary treatments meeting Washington State Class A (Class A) reuse standards to stream augmentation and lake discharge, the latter requiring advanced treatment.

Following an in-depth screening of the individual treatment processes, two aerobic biological treatment trains were selected for testing in a nine-month demonstration period. Treatment processes included a Biological Aerated Filter (BAF) and a Membrane Bioreactor (MBR). Other emerging technologies investigated for their small footprints and enhanced performance included media filtration (Fuzzy Filter) and ballasted flocculation (Actiflo and Densadeg) for primary treatment, Fuzzy Filter and microfiltration for tertiary effluent filtration, and reverse osmosis for advanced treatment.

The objective of the pilot testing program was to assess the ability of emerging wastewater treatment technologies to produce effluent quality meeting reclaimed water standards or more stringent water quality standards associated with other reuse opportunities being considered by King County.

Test Program

The pilot testing was conducted in 2001-2002 at the King County West Point WWTP Test Facility. Facilities were designed and constructed to support testing a number of pilot units with several feed streams. Features of the pilot testing facilities included pumps, interconnecting piping, storage tanks, electrical, instrumentation and control, and SCADA. This project was awarded the 2002 National Environmental Achievement Award for Research and Technology by the National Association of Clean Water Agencies (NACWA).

The following technologies were tested:

Primary Treatment Technologies

Ballasted flocculation – Actiflo system ( 1.2 MB)
Ballasted flocculation – Densadeg system ( 1.5 MB)
Fuzzy Filter ( 5.5 MB)

Secondary (biological) Treatment Technologies

Single-stage biological aerated filter ( 3.2 MB)
Two-stage biological aerated filter ( 1.2 MB)
Membrane bioreactor ( 1.7 MB)

Tertiary Treatment Technologies

Fuzzy filter ( 5.5 MB)
Microfiltration ( 2.8 MB)
Advance treatment using reverse osmosis ( 1.3 MB)

Project Summary

Treatment Trains For Reuse Applications (PDF available soon)

Papers and Posters

Stretching Technologies for Cost Effective Reuse ( 1.9 MB)
In Search of the Perfect Reuse Plant ( 1 MB)
Optimization of Biological Aerated Filter and Microfiltration Operation for Wastewater ( 2.4 MB)

Reclaimed Water Comprehensive Planning (2008-2012)

Reclaimed Water Feasibility Study, March 2008

Purpose and Need Statement, June 2010

This purpose and needs statement lays a foundation for the Reclaimed Water Comprehensive Plan by describing the drivers that have prompted its development. 

For more information about the Technology Assessment Program, contact:

  • Bob Bucher
  • 206-477-9747
  • 201 S. Jackson Street, KSC-NR-5512, Seattle, WA 98104