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OperationsWater Quality

Restoration at West Point Treatment Plant: The Next Delicate Step

By March 8, 2017March 13th, 2017No Comments

It is early March, 2017. If you walk through West Point Treatment Plant, you’ll see clusters of people working on a range of repair and restoration activities: motors here, electrical boxes there, pipe insulation in the tunnels. Four weeks after unprecedented flooding damaged parts of West Point Treatment Plant, cleanup is complete.

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While crews replace damaged equipment and fixtures in affected areas of the plant, a major driver is to return to secondary treatment.

At this time, incoming flows are receiving limited primary treatment. Garbage is being removed in the screenings facility, which was never affected by the incident. Flows are being disinfected with sodium hypochlorite — basically strong bleach — followed by neutralization before discharge to the sound. The next step to restore high effluent quality is to restore secondary treatment.

1402_WPTreatmentProcess_2014Secondary treatment using biological processes is an efficient and effective way to remove up to 90 percent of organic matter. Those processes depend on a healthy population of the right kind of bacteria in the right environment to carry out this work.

In the primary process, mechanical systems remove solids and floating material before the flow is sent to the secondary process. The secondary treatment process relies on beneficial microorganisms to break down the organic solids that weren’t removed during the primary treatment process. Like other living creatures, these microorganisms need the right combination of air, light, food and heat to thrive.

The biologic process steps and the organisms that carry it out are defined by whether they use oxygen — or not. In aeration tanks, the microorganisms work in an oxygen rich environment to remove microscopic solids in the treated effluent. In the digesters, different organisms work in a low oxygen environment to break down solid material. The organisms in the digesters need heat to thrive and do their work.

At West Point, we are restoring electrical and mechanical equipment needed to provide the delicate ecosystem these microorganisms need to treat wastewater to the secondary level. Most importantly, we are restoring systems to manage the solids from the treatment process.

030617SludgePipesElectricians and mechanics are working to repair damaged infrastructure. We have completed the first of four steps to restore secondary treatment. That first step is part of the primary treatment process, in which solids are settled in a tank and fats and oils float to the top where they can be skimmed off.


Primary tanks were pumped out and cleaned


The most important step to restoring secondary treatment is to have a place to send solids from the treatment process. Mechanics are putting primary sludge pumps back into service, which will help us move solids. Crews are replacing pipe insulation that keeps materials moving through pipes warm.


Removing pipe insulation


Pipe insulation awaiting disposal

For the sensitive process of restoring healthy, productive microbial ecosystem, WTD has brought on board specialized scientific expertise. Our experts are tapping historical experience, evaluating approaches to establish biological processes when West Point’s secondary system first came online in 1995.

But we need heat and a hospitable environment to send those solids to, and that means repairing damaged boilers. One of the boilers is already repaired and back in service. Another main boiler is slated for repairs on March 17, which will provide crucial heat to one of the main digesters.


Once the digester is online, and heated to human body temperature, our biology experts can mix the contents and assess the health of the microorganisms that have been in hibernation since Feb. 9. If needed, we can reseed the digesters with new biological material from one of our other treatment plants.

Many restoration activities fall under human control. Acquiring contractors, finding the fittings, pieces and parts we need, refurbishing motors, replacing light fixtures, rewiring — all these are tasks we can speak to from experience, with schedules we can predict. Cultivating the microorganisms in the digesters will be a delicate balance of time, testing and biological expertise.

At the Brightwater Center in Woodinville, artist Ellen Sollod celebrates in blown glass the microorganisms that clean our wastewater.

©  2011 Ellen Sollod, Collection and Transformation (detail). Photo courtesy of the artist. From the King County Public Art Collection.