The poop-Loop scoop: How King County recycles waste and water

By Darrell Rodgers, PhD, Public Health – Seattle & King County

Public health is committed to preventing disease and death from water-borne pathogens. Modern sanitation, including wastewater treatment, is key to keeping our waters clean and the people and animals that live here healthy. But the efficiency of modern sanitation creates an interesting problem.

Today, our waste is “out of sight, out of mind” as soon as we flush the toilet or as soon as the water disappears down the drain. We might know that dirty water goes somewhere, and it gets cleaned. What we don’t know is how the process works, how we affect it, what happens to that waste, and how it is treated to prevent the spread of illness from pathogens.

Most people aren’t aware of the value of our waste.  Calling it “waste” makes our dirty water seem like a throwaway commodity.  In fact, it is a very valuable resource.

King County recognizes that value, and turns our waste into resources, while keeping our waters clean.  Additional filtration and disinfection creates high-quality, odor-free recycled water that can be used to clean streets and water athletic fields and farms. Using recycled water keeps water in rivers and streams for people and fish.

recycled water
The jars of water show how wastewater is transformed into recycled water, and what it looks like compared to drinking water. The jar on the far left, “raw influent,” shows what wastewater as it enters King County’s treatment plants. “Class A reclaimed water” or recycled water is the third jar. Drinking water on the far right. Can you tell the difference?

The water isn’t the only source of renewable resources. During the treatment process of the solids in wastewater (the poop and the food, microorganisms break down the material and release biogas. Biogas creates renewable energy to help power the treatment plants and provide energy for homes and businesses.

Loop is an endlessly renewable resource that returns harvested nutrients back to our land.

The same microorganisms that release biogas also create biosolids, which King County calls Loop®. The wastewater treatment process kills pathogens and harmful bacteria and produces Loop, a nutrient-rich, fertilizer-like product that plants love. Biosolids may seem revolutionary, but returning nutrients and organic matter to the land is a time-tested form of recycling. Since the dawn of agriculture, farmers around the world have used human and animal waste to grow food. Agriculture feeds people, but demands a lot from soils, which can become depleted and less productive without organic inputs. Farmers look for ways to keep that soil healthy and productive, and biosolids such as Loop help accomplish that.

Here in King County, population growth and climate change mean that growing enough food demands more and more from our soils. Climate change threatens the health of our future communities. To help fight climate change, King County recycles 100% of the solids (the poop and the food) as Loop. For more than 40 years, Loop has returned valuable nutrients and organic matter to the soil to grow crops, fertilize working forests, and restore degraded sites into healthy landscapes.

loop on fields
A farm worker spreads Loop on wheat fields, where it enriches the soil with essential nutrients.

Today, we are more aware of our limited resources and the need to use them wisely while protecting our health and our environment. At King County, we know the value of recovering resources to reduce waste and to ensure the public’s health is protected. King County produces Loop according to precise standards. Unlike synthetic fertilizer, or even manure, Loop is held to stringent environmental regulations. As we mimic nature’s cleaning powers, engineering and technology allows us to test and monitor the entire process to ensure the safety and efficacy of Loop.


See how King County cleans wastewater and creates Loop biosolids, biogas, and recycled water. It’s just like nature does it, only faster.

Originally posted August 4, 2017.

One thought on “The poop-Loop scoop: How King County recycles waste and water

  1. It is so important to remember that sewer sludge aka biosolids is NOT just poop – it is a concentration of all domestic and industrial pollutants that go down drains and sewers. It has some good stuff in it, which plants can use, but a huge load of thousands of other contaminants.  Please read what independent scientists have to say on this issue –

    Three Informed Views on Sewer Sludge (aka Biosolids)

    Dr. Caroline Snyder – “Land-applied municipal sewage sludge (biosolids) is a highly complex and unpredictable mixture of biological and chemical pollutants. Biosolids generated in our large industrialized urban centers is very likely the most pollutant- rich waste mixture of the 21st century.”

    Dr. Marilyn Cameron – “We are concerned that farmers are not being provided adequate information about biosolids and the negative impacts that its use could have on your soils, groundwater and surface water sources, livestock health, and property values. Farmers will be the ones left paying the price for any damaged land, contaminated water, or human, wildlife and livestock illnesses, etc. Farmers may also suffer losses resulting from lack of consumer confidence in local foods”

    Dr. Richard Honour – “”Few in any governments appreciate that nearly all chronic diseases are caused by long-term exposure to low levels of environmental contaminants and pollutants. We should be trying to minimize this exposure, not amplifying it. It is time to end land disposal of Toxic Sewer sludge, and look at cleaner, greener alternatives – gasification / pyrolysis.”
    Let’s get on the right side of history, and use this waste resource to make energy. It is time to stop covering Mother Earth with our cities’ toxic sewage.

    And see this link for a great overview of the issues – by Dr. Thomas Maler
    A great article from Scientific American –

    Scientists against land dispersed “biosolids”

    Biosolids on Video – For the section of the film dealing with Toxic Sludge start at the 32.40 minute point …
    Dr David Lewis interview –
    Trailer for upcoming film – Biosludged –
    NFB Crap Shoot –
    Sludge Diet –
    Spreading sewage sludge on farmland –

    The Green Alternative –  The answer is gasification / pyrolysis …not simply dispersing this toxic waste on farms and forests –
    see –
    and see –
    and see –…/plasma-gasification-alberta…
    and see –
    lets get energy out of this resource AND rid the environment of these toxins.

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