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Event Recycling

Biosolids FAQ

General Knowledge

Beneficial Use of Biosolids

Safety of Biosolids

Statistics about Biosolids

Regulatory FAQ

General Knowledge

What are biosolids?
Biosolids are a beneficial resource, containing plant nutrients and organic matter that result from treating domestic wastewater. They are highly processed and thoroughly analyzed to ensure their safety.

Commonly, wastewater treatment is thought of as a way to clean water. The process also creates a food for earthworms and plants-biosolids. Biosolids are not poop. They may have started out as poop, but through treatment processes they are refined and become a good, stable, and valuable source of nutrients.

Biosolids can be recycled as a fertilizer and soil amendment on agricultural land, forests, mine and land reclamation sites. They are a valuable resource because they contain important nutrients for plant growth and soil fertility such as nitrogen, phosphorous, and organic matter as well as essential nutrients such as copper, iron, molybdenum, and zinc. The treatment process differentiates biosolids from sewage and septage. Treated biosolids come in various forms such as, rich moist soil, dried pellets, liquid, or compost.

What are the benefits of recycling biosolids?
Biosolids are a local and renewable resource. Their reuse is the ultimate in recycling. We are taking something that was considered a waste, treating it, and converting it to a valuable product and using it to benefit the environment.

Biosolids are a great soil conditioner. They contain slow-releasing nutrients that are more eco-friendly than chemical fertilizers because they add organic matter to enrich depleted soils and fibrous matter to improve the soil's ability to hold water. Biosolids are highly valued by many - especially farmers - because they contain all of the essential plant nutrients as well as vital organic matter that help plants grow. Biosolids provide these nutrients in organic and inorganic forms. The inorganic forms of the nutrients, like commercial fertilizers, are immediately available to plants, while organic forms release slowly over several growing seasons ensuring long-term enhancement of plant growth. These qualities also make them useful for land reclamation (for example: strip mines, quarries, and gravel pits), landfill covers, composting, and forest land.

Applying biosolids significantly aids in:
  • Plant growth and quality.
    • Biosolids provide essential nutrients such as nitrogen, phosphorus, potassium, and sulfur.

  • A better balance of water and air in the soil for plant growth.
    • The ability of sandy soils to hold water.
    • The ability of heavy clay soils to drain.

  • Wind and water erosion.
  • Increase in soil organic matter.
  • Soil carbon sequestration.
  • Reduction in need for chemical fertilizers (which require enormous amounts of energy and resources to produce).
  • Protecting ground and surface waters.
  • Healthy ecology (happy earthworms!).
    • A healthy environment for soil organisms also helps to limit root borne diseases of plants.
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What is the difference between biosolids and sewage sludge?
"Sewage sludge" refers to the solids that settle out in the wastewater treatment process. Biosolids are produced by treating sewage sludge to meet standards that allow it to be applied to the land for beneficial use. They are strictly monitored and must be used within regulatory requirements. Biosolids have undergone biological, physical, and chemical treatments to reduce pathogens. The term biosolids distinguishes high-quality, treated sewage sludge from raw sewage sludge and from industrial sludge that can contain large quantities of environmental pollutants.

How are biosolids made from my wastewater?
Wastewater and sludge treatment processes vary and are combined in many different ways.

Modern wastewater treatment plants are technologically advanced facilities that require a great deal of knowledge and skill to operate. While many people think only of the treated water discharged into a river or bay, the biosolids portion of wastewater treatment is equally important. Up to forty percent of a wastewater treatment plant's construction and operating costs can be attributed to the systems that produce and treat the biosolids.

Wastewater treatment facilities receive sewage - the solids and liquids from toilets and drains. Most sewage comes from homes and businesses and a smaller amount from industrial sources. For example in King County 95 percent of the wastewater is from homes and businesses, with only 5 percent from industries. Industrial facilities must meet certain standards before industrial wastes can go down the drain. This is called pre-treatment, where specialized processes remove or reduce certain pollutants. In recent decades, these processes have dramatically reduced the amount of heavy metals in sewage.

When sewage reaches a wastewater treatment facility, it goes through many processes and stages. Typically, wastewater enters the treatment plant through a "headworks" which removes sand, gravel, and other heavy materials such as rags, diapers, and plastic bags.

After the headworks, the sewage goes through at least two stages of treatment. During the first treatment, primary clarification, the rate of flow of the wastewater is greatly reduced and solids settle out by gravity. Then, both the solid and liquid parts are sent on for more treatment.

The wastewater then moves on to secondary treatment. This process encourages beneficial bacterial growth which consumes all available food (poop). Once the bacteria have done their job the solids go through a process that kills nearly all the pathogenic organisms commonly found in wastewater, and helps speed the degradation of contaminants sometimes present in wastewater. Next they can be put through another process, which can vary from chemical, heat, or physical treatments to diminish bacteria.

The final step in treating biosolids can involve removing excess water, in a process known as dewatering depending on the desired end product. Dewatering improves transportation costs and also reduces pathogen viability. The end product is usually one of four forms: a rich moist soil, dried pellet, liquid, or compost.

Materials that do not meet the criteria required for biosolids cannot be land applied as a soil amendment and must undergo additional treatments or disposal, by being incinerated or sent to a landfill.

If you want to know how your local treatment plant works, call and ask for a tour.

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What do biosolids look like?
Biosolids generally come in one of four forms: a rich moist soil, dried pellet, liquid, or compost. When dried, biosolids look like fine-textured dark soil.

Dump truck load of "dewatered" biosolids.

Preparation of biosolids for land application.

Biosolids applied on dry land winter wheat, 3-4 dry tons per acre.

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What can I do to protect the quality of our biosolids?

The best way to protect biosolids quality is use fewer cleaning products and chemicals at home, and switch to "biodegradable" or more natural alternatives.

Fats, oil and grease (FOGs) are bad for your home's plumbing, city sewer pipes and home septic systems because they harden and stick to pipe walls causing clogs. FOGs solidify quickly even if you wash them down with hot water and dish soap. Not only can FOGs build up in pipes causing clogs they also create gases that can break down pipes causing cracks. FOGs that do make it all the way to the waste water treatment facility in your area can cause disruptions in the treatment process and equipment problems.

The following items should go in the trash or be recycled, not put in the toilet or the sink:
  • Expired/unwanted prescription or over-the-counter drugs
    • Ideally, these should be returned to "drug take-back" sites if available.

  • Fats, oils and grease (FOGs) from the kitchen:
    • Meat fats.
    • Gravy and sauces.
    • Cooking oil.
    • Shortening, and lard.
    • Margarine, and butter.
    • Salad dressing/mayonnaise.
    • Dairy products.
    • In preventing FOG clogs:
      • Scrape fats, oils and greases into an empty can, cover and store in the freezer. When the can is full, place it in a plastic bag and toss it in the trash.
      • Before washing greasy dishes, wipe them with a paper towel and place the used paper towels in your organics collection container.
      • Some communities have free residential cooking oil recycling where residents can bring in used cooking oil such as that used for deep fat frying.

  • Products labeled "Danger", "Hazardous" or "Toxic."

  • Food products:
    • Egg shells.
    • Spoiled food.
    • Vitamins.
    • Stickers from fruits or vegetables.
    • Coffee grounds.

  • Pet Products:
    • Cat litter.
    • Pet waste.
    • Hairballs.

  • Hygiene Products:
    • Cotton balls.
    • Dental floss.
    • Diapers (cloth, disposable, flushable).
    • Ear swabs.
    • Facial tissue.
    • Band aids.
    • Condoms.
    • Razors.
    • Feminine hygiene products (tampon applicators, sanitary napkins, Etc.).

  • Plastic or other non-organic materials like:
    • Cigarettes.
    • Fertilizers, herbicides, and pesticides.
    • Glue.
    • Lint.
    • Oil.
    • Paint.
    • Paper towels.
    • Pins and needles.
    • Plastic bags and wrappers.
    • Products claiming to be flushable.
    • Rags.
    • Rubber gloves.
    • Scrub pads.
    • Toys.
    • Twist ties.
    • Wipes.
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Do biosolids smell?
Biosolids may have their own distinctive odor depending on the type of treatment and processing at the wastewater treatment plant. Biosolids do have odors, but odors associated with biosolids are more of a nuisance than a threat to human health or the environment. Compounds that contain sulfur and ammonia, which are both plant nutrients, cause most odors. As a way of managing odors at the field, biosolids can be incorporated into the soil within a few hours of application. Composted biosolids are usually quite similar to potting soil or any other organic mulch.

Are there different types of biosolids?
Biosolids used as fertilizer are divided into two categories: Class A and Class B. Class A or Class B biosolids products refer to the level of pathogen reduction that the product has undergone. In practical terms, the difference between Class A and B is based on where and when treatment to reduce pathogens occurs. Class A and B designation also determines how biosolids can be used.

Class A biosolids have received a level of treatment that reduces disease-causing organisms or pathogens to extremely low levels. If the levels of heavy metals are low enough and the treatment includes methods to reduce the possibility that insects and animals will be attracted to the material, Class A biosolids may be distributed as Exceptional Quality biosolids. Biosolids sold or given away in a bag or container, or applied to home lawns and gardens must meet the Exceptional Quality standard.

Class B biosolids have been treated by a process designed to substantially reduce pathogen indicators. This means pathogens are reduced to levels well below those found in manures. With Class B biosolids we rely on the natural environment to eliminate the remaining pathogens. Factors such as heat, wind, and soil microbes create harsh conditions for pathogens; field monitoring has shown a rapid die-off of pathogens when biosolids are applied to forest soils or stored at agricultural sites. As an added layer of public protection, there are many restrictions on the use of Class B biosolids.

Some of these restrictions are:
Different Types of Biosolids
  Class A Class B Raw Sewage Sludge
Percent of Pathogen Indicators Treatment is Designed to Destroy Extremely Low Levels Substantially Reduced Not Reduced
Pollutants Nine metals must be below stringent standards set by U.S. Environmental Protection Agency.*** -
Odor Either handled or processed in a way that does not attract flies and rodents. -
Where can it go? *
  • Sold in bags**
  • Lawns/Gardens**
  • Class B application sites
Preapproved Land Application Sites Cannot be Applied to Land
*As long as the biosolids meet the Pollutant and Vector Attraction standards.
**If "Exceptional Quality" standards are met.
***Arsenic, Cadmium, Copper, Lead, Mercury, Molybdenum, Nickel, Selenium and Zinc.

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Can biosolids be used for composting?
Yes, biosolids composted with sawdust, wood chips, yard clippings, or crop residues make excellent mulches and top soils for horticultural and landscaping purposes. Many professional landscapers use composted biosolids for landscaping new homes and businesses. Home gardeners also find composted biosolids to be an excellent addition to planting beds and gardens.

Composted biosolids must meet certain criteria which include meeting pathogen reduction limits, complying with required sampling and analysis protocols, maintaining of compost temperature and retention time records, and product labeling requirements.

How is Washington's biosolids program funded?
Facilities that work with domestic sewage and biosolids are required to pay a fee to support the state biosolids program. The bigger the facility, and the larger the number of residences, the larger the fee. Beneficial use facilities, who only land apply biosolids, pay a reduced fee to avoid double charging for the same biosolids.

What laws and rules govern the uses of biosolids?
At the national level, under the Federal Clean Water Act, Congress directed the U. S. Environmental Protection Agency to develop standards to regulate biosolids through permits. The U.S. Environmental Protection Agency published 40 CFR Part 503, Standards for the Use or Disposal of Sewage Sludge in 1993. Part 503 contains the primary technical regulations for biosolids management at the federal level.

Washington State has its own authority for managing biosolids. The 1992 State Legislature passed a bill into law which became in part Chapter 70.95J RCW, Municipal Sewage Sludge-Biosolids. Chapter 70.95J recognizes biosolids as a valuable commodity, and directs Ecology to implement a program that maximizes beneficial use. The state program must at least meet federal minimum requirements, and Ecology is authorized to issue permits and to collect fees for permits. Ecology published Chapter 173-308 WAC, Biosolids Management in 1998 and revised the rule in 2007. The state rules include technical requirements, a permitting program, and a fee program. Management of biosolids is covered by permits issued by Ecology.

The permits:
  • Limit application rates.
  • Impose buffers to water wells, surface waters, property lines, roadways, and residential dwellings.
  • Require the protection of groundwater.
  • Restrict where and when biosolids can be applied.
  • Limit the concentration of pollutants.
  • Require removal of garbage.
  • Apply standards for storage.
  • Require transportation plans.
  • Define monitoring requirements.
  • Require monitoring and sampling plans.
  • Mandate the use of Ecology-accredited labs.
  • Specify treatment standards for pathogen reduction.
  • Specify treatment standards for stabilization.
  • Impose restrictions on site access.
  • Limit crop harvesting and use.
The Department of Ecology employs biosolids specialists at its four regional offices located throughout Washington who are responsible for monitoring and enforcing biosolids regulations.

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What is Ecology's role in biosolids management?
Ecology is the regulatory agency for biosolids management in Washington State. Six full-time Ecology employees regulate biosolids with one person in each of Ecology's four regions and two at headquarters.

Ecology biosolids staff is responsible for:
  • Writing and updating the state biosolids rules.
  • Permitting the nearly 380 biosolids facilities across the state.
  • Conducting regular site visits and inspections.
  • Technical assistance to all facilities.
  • Evaluating and entering data submitted by the facilities into a database.
Ecology also receives assistance in regulating biosolids from local health departments.

What is U.S. Environmental Protection Agency's role in biosolids management?
U.S. Environmental Protection Agency does not have a large biosolids presence across much of the country, including in Washington. However, several people who work at U.S. Environmental Protection Agency support the federal biosolids program. U.S. Environmental Protection Agency has several people involved in research on biosolids-related issues who work mainly from a Cincinnati-based research lab. They are required to implement the federal biosolids program and upgrade regulations as new information based on research warrants changes.

Where did the term "biosolids" come from?
Treatment plant operators wanted a term that better characterized the time, expertise, and expense that goes into producing biosolids. The term was adopted after a nationwide challenge to select a better name than sewage sludge. Washington was the first state to adopt and recognize the term in law (1992).

Who decided Washington should recycle its biosolids?
The U.S. Environmental Protection Agency has advocated responsible biosolids management programs for years. In this effort, they have had the support of other organizations and agencies, including the U.S. Department of Agriculture. Washington State's Legislature established a state biosolids program in 1992 when it declared that, "a program shall be established to manage municipal sewage sludge and that the program shall, to the maximum extent possible, ensure that municipal sewage sludge is reused as a beneficial commodity and is managed in a manner that minimizes risk to public health and environment" (State Law, Chapter 70.95J.005 RCW, Municipal Sewage Sludge-Biosolids).

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Beneficial Use of Biosolids

What is beneficial use?
State rules (WAC 173-308-080, Biosolids Management) define beneficial use as the application of biosolids to the land for the purposes of improving soil characteristics including tilth, fertility, and stability, and enhancing the growth of vegetation consistent with protecting human health and the environment.

How and where can biosolids be used?
When processed and applied according to state and federal regulations, biosolids are put to a wide range of uses including:
  • Fertilize agricultural land.
  • Provide organic matter and nutrients to sod farms and nurseries.
  • Top dressing on golf course fairways.
  • Soil conditioner for construction of golf courses, parks, and athletic fields.
  • Landfill cover.
  • Land reclamation.
  • Mine reclamation.
  • Forest fertilization.
  • Erosion control.
  • Improve rangeland soil.
  • Horticulture.
  • Slope stabilization.
  • Roadside aesthetic improvements.
  • Only biosolids that meet the highest quality standards can be used on lawns, gardens, parks, and sports fields.
Indirectly, biosolids are used as feedstock products such as:
  • Compost.
  • Soil amendment mixes.
  • Fabricated soils.
If biosolids were not land applied, where would they go?
Only three things can happen to biosolids at this time. They can be burned; they can be landfilled; or they can be land applied (beneficially used). As directed by state law, Ecology seeks to maximize beneficial use, but requires biosolids to be treated to meet strict quality standards.

Historically wastewater was handled through:
  • Discharging into rivers and other waterways.
    • Since these are the main drinking water sources for most people this resulted in illness and death from diseases such as typhoid.

  • Dumping into oceans.
    • This resulted in contaminated fish and other sea life, "dead" zones, and trash on beaches. Ocean dumping was banned by the Ocean Dumping Ban Act in 1988.

  • Dumping into landfills.
    • This still occurs in many states. Landfill space is limited, so the more biosolids that go into landfills, the less space there is for actual garbage. Landfilling is also expensive.
    • Putting biosolids in landfills enhances the creation of a very potent greenhouse gas, methane. It also means the complete loss of nutrients and organic matter which otherwise could be returned to soils.

  • Incineration.
    • This still occurs in Washington and many other states. Incineration results in air pollution, ash, and the complete loss of nutrients and organic matter which otherwise could be returned to soils.
We create biosolids and have to do something with them. Given the above history, beneficial use offers a reasonable and responsible option.

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How are biosolids used for agriculture?
Agricultural use of biosolids that meet strict quality criteria and application rates have been shown to significantly improve crop growth and yield. Nutrients found in biosolids, such as nitrogen, phosphorus and potassium, and trace elements such as calcium, copper, iron, magnesium, manganese, sulfur and zinc, are necessary for crop production and growth. The use of biosolids reduces the farmer's production costs and replenishes the organic matter that has been depleted over time. The organic matter improves soil structure by increasing the soil's ability to absorb and store moisture.

In Washington during 2012, 93 percent of biosolids were applied to feed or food crops and the other 7 percent to timber. State and federal law allows for many different types of crops to be grown in soil fertilized with biosolids. However, the use of biosolids for food crops is limited by strict time periods that must be followed before a crop can be harvested after applying biosolids to the land.

See a break out of Harvest Restrictions.

How are biosolids used for forestry?
Biosolids have been found to promote rapid timber growth, allowing quicker and more efficient harvest of an important renewable natural resource. Where biosolids have been used, the trees grow faster than those living in unfertilized soils. Biosolids improve forest productivity, increase growth of hybrid poplars, and improve the aesthetic value of Christmas trees. In Washington during 2012, 93 percent of biosolids were applied to feed or food crops and the other 7 percent to timber.

How do biosolids help with land reclamation?
Severely disturbed soils, such as mines, can be reclaimed through the addition of biosolids to replace lost topsoil. Biosolids have been used successfully at mine sites to establish vegetation. Not only do the organic matter and nutrients present in the biosolids reduce the availability of toxic substances often found in highly disturbed mine soils, but they also build a healthy soil layer where little soil has been left.

What happens to biosolids once applied to soils?
In farm applications, biosolids can be plowed or injected into the top six inches of soil, leaving little visible trace on the surface. In forest applications, the biosolids are normally left on the surface to break up and blend naturally into the soils over time.

Biosolids are applied at "agronomic" rates that match plant needs, slowly providing the nutrients to the growing plants, and ensuring that surface runoff and deeper groundwater are unaffected by the application. In all cases, biosolids release plant nutrients slowly, following the normal process of decay. Their exposure to air and sunlight destroys any remaining pathogens in the biosolids within a short time.

Who determines how and where biosolids are applied?
Ecology's permit regulations require that biosolids must meet specific requirements before they can be sold or applied. If biosolids meet the standard to be considered Exceptional Quality they can be handled just like any other soil amendment. However the majority of biosolids are Class B and can only be applied on approved lands with ongoing testing, notification, and monitoring. Wastewater treatment facilities that produce biosolids, and any person applying biosolids on land, must obtain a permit from the Department of Ecology before application.

The land applier performs the first step in determining whether biosolids can be applied to a particular site by examining water supplies, soil characteristics, slopes, vegetation, crop needs, and the distance to streams, lakes, rivers, and groundwater. When an Ecology biosolids coordinator receives a permit application, they review the proposed biosolids sources and proposed land application sites to confirm if they are suitable. Once the draft permit is complete, a notice will appear in the local paper. During the following 30 days, the public can provide comment on the proposed permit and may request a public meeting. At the end of 30 days, the Department of Ecology will consider all comments received and either approve the permit or determine if public comments warrant a public meeting.

How much biosolids can be spread as fertilizer and when?
The amount of biosolids that can be applied and when they can be applied is different for each site. The Department of Ecology issues permits for land application that include a Site Specific Land Application Plan that establishes the amounts and timing of biosolids application.

The amount applied will be based on the:
  • Nutrient needs of the crop.
  • Amount of nutrients in the biosolids.
  • Level of nutrients already in the soil.
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Should I use biosolids in my yard or on my crops?
This is a question that must be answered by each individual. If you are comfortable with how biosolids are produced and understand the limitations on their use, you may want to use them. However, you may not be able to obtain biosolids in some areas of the state. Some people still question some of the technical principles behind biosolids management, and others simply do not like the idea of using biosolids in their soils. If you fall in these latter categories, then biosolids are probably not a product you would be happy using.

Are there regulations for applying biosolids on the land?
Yes, land applied biosolids must meet the strict regulations and quality standards found in Chapter 173-308 WAC, Biosolids Management.

These regulations contain: To determine whether biosolids can be applied to a particular site, an evaluation of the site's suitability is performed.

The evaluation examines:
  • Water supplies.
  • Soil characteristics.
  • Slopes.
  • Vegetation.
  • Crop needs.
  • Distances to surface and groundwater.
  • Proximity to neighbors/residences.
  • Surrounding land use.
There are different rules for different classes of biosolids. Class A biosolids contain no detectible levels of pathogens, must meet strict vector attraction reduction requirements and contain levels of metals below those set by the U.S. Environmental Protection Agency. Class B biosolids are treated, but still contain detectible levels of pathogens, must meet the same metals standard as Class A biosolids and have their vector attraction standards met during treatment or at the site of land application. There are buffer requirements, limits on public access, and crop harvesting restrictions for virtually all forms of Class B biosolids. Nutrient management planning ensures that the correct amount of biosolids is applied to the farmland. The biosolids application is calculated to match the nutrient uptake requirements of a particular crop.

Are there buffer requirements or restrictions on public access to sites with biosolids?
Yes. In general, there are buffer requirements, public access, and crop harvesting restrictions for virtually all forms of Class B biosolids (treated but still containing detectible levels of pathogens). Buffers are applied near water wells, surface waters, property lines, roadways, and residential dwellings. Public access restrictions range from one month to one year depending on the type of application site. However, Exceptional Quality (Class A only) biosolids used in small quantities by the general public have no buffer requirements, or crop type, crop harvesting, or site access restrictions. When used in bulk, Class A biosolids are subject to buffer requirements, but not to crop harvesting restrictions.

If land application of biosolids is so beneficial, why would any plant incinerate them?
Incineration is an option sometimes used when landfill tipping fees are high, distances to alternative disposal or beneficial use sites are unworkable, or beneficial use options are not appropriate.

Advantages and disadvantages of using incineration systems for solids disposal, versus disposing of solids in a landfill or through stabilization followed by use as a fertilizer or soil conditioner, are provided below.

  • Volume reduction.
  • Generation of stable material. Ash is a stable, sterile material, effectively eliminating storage and handling problems.
  • Potential energy recovery.
  • Minimal land area required.
  • Lost nutrient recovery opportunity.
  • High capital investment.
  • In most cases, annual operating costs depend on fuel costs.
  • Consumption of non-renewable resources (oil and/or natural gas).
  • Limited feasibility in nonattainment areas.
  • Potential operating problems. Incinerators experience significant down time for routine maintenance and therefore require redundancy, backup, or storage. High technology instrumentation is required to comply with air pollution control permits.
  • Potential for public opposition.
  • Costs associated with landfill disposal of the ash product.
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Safety of Biosolids

Are biosolids safe?
Biosolids are very similar to dirt. Dirt is formed by nature through the natural breakdown of organic matter and the weathering of rocks and stones. Treatment plants imitate this process. The organic matter of sludge decomposes under controlled conditions, making use of naturally occurring microorganisms. These microbes feed on the organic and inorganic matter as well as other microbes, including pathogenic bacteria.

The National Academy of Sciences reviewed current practices, public health concerns, and regulator standards for biosolids, and concluded that "the use of these materials in the production of crops for human consumption when practiced in accordance with existing federal guidelines and regulations, presents negligible risk to the consumer, to crop production and to the environment." U.S. Environmental Protection Agency and a panel of scientists with biosolids expertise examined all aspects of biosolids in the environment, including potential effects on ground water, air and soil quality, surface runoff, and food crops. Long-term scientific studies have repeatedly shown the safety of land application of biosolids. These studies formed the basis for federal and local biosolids regulations. Monitoring of biosolids, soils, water resources, and plants continue to show benefits from this type of recycling.

Biosolids have been treated and tested to meet specific standards, making them suitable for application to the land.
Some of the parameters tested are:
  • pH (acidity or alkalinity).
  • Total Nitrogen.
  • Ammonia Nitrogen.
  • Potassium.
  • Phosphorus.
  • Lead.
  • Arsenic.
  • Cadmium.
  • Copper.
  • Mercury.
  • Molybdenum.
  • Nickel.
  • Selenium.
  • Zinc.
  • Specific Oxygen Uptake Rate.
  • Salmonella.
  • Fecal Coliform.
Just as with many products, including common chemical fertilizers, restrictions on uses and guidelines are in place. As with many lawn or home garden products such as topsoil or compost, good hygiene practices are encouraged when using biosolids.

Why the bad press about biosolids?
Fear and misinformation - some people have the misconception that biosolids (treated sewage sludge) is fecal matter (poop). In reality, the entire treatment process converts the fecal matter and debris in sewage into a totally different material, biosolids. It may have originated from you, your homes, and neighborhoods, but it has undergone physical, chemical, and biological changes to become a safe and useful end product-biosolids.

When you eat pizza or drink soda, minute traces of those products end up in the sewage. In other words, the ingredients that may be found in small quantities in biosolids originated from you. Just as recycling aluminum cans helps your environment, recycling of biosolids through proper land application also helps your environment by improving soils and diverting it from a landfill or incineration to benefit your local community.

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How do we know what's in biosolids?
When the U.S. Environmental Protection Agency developed the federal rules governing biosolids they conducted national sewage quality surveys. They determined that other than metals, most toxic organic chemicals were not detectable or only detectable at very low concentrations.

State and federal regulations require scheduled sampling based on the amount of biosolids land applied or sold/given away each year to ensure that treatment levels are achieved. The nutrient content of the biosolids is also measured to determine the appropriate application rate for the crop grown.

At a minimum, the following parameters are analyzed, however Ecology can require further testing:
Nutrients Metals Other
Total Kjeldahl Nitrogen (TKN) Arsenic (As) Percent solids
Nitrogen (N) Cadmium (Cd) Volatile solids
Ammonia (NH3) Copper (Cu) pH
Nitrates (NO3) Lead (Pb) CaCO3 (for lime stabilized biosolids)
Total Phosphorus (P)* Mercury (Hg) Alkalinity as CaCO3
Total Potassium (K)* Molybdenum (Mo)
Nickel (Ni)
Selenium (Se)
Zinc (Zn)
*Not required but typically conducted.

Does biosolids recycling affect human health, wildlife, or water quality?
Environmental regulations are designed to reduce the effects that many activities may have on people's health and the environment. The current biosolids rules address the potential impacts on surface water and ground water, harmful effects on plants, and transmission of disease.

These rules include:
  • Assuring proper pollutant source control.
  • Assessing of biosolids quality.
  • Determining appropriate soil, landscape, and crop conditions.
  • Monitoring and oversight of transport, storage, application, and land use before, during, and after application.
  • Limiting access, harvest or grazing until appropriate time periods have elapsed.
Human Health
Biosolids can be safely used to grow food crops. This issue has been studied by agricultural scientists for decades. The safety of food crops was a major consideration in setting the standards for biosolids that could be used in agriculture. Research and field experience confirms that crops are not negatively affected when the regulations are followed. Scientists from Washington State University have repeatedly tested crops fertilized with biosolids and found no differences in quality from those treated with chemical fertilizers.

Scientists at the University of Washington began studying the effects of biosolids on wildlife in the 1970s. They did not find any animals harmed by this practice. Because biosolids makes vegetation grow faster, the wildlife have more nutritious food and better habitat.

The National Marine Fisheries Service (NMFS) evaluated King County's biosolids program and decided that biosolids application posed no risk to Chinook salmon and, in fact, provided an environmental benefit by enhancing forest growth.

Water Quality
Guidelines control how, where, how much, and how often biosolids can be spread to ensure that ground and surface water is not contaminated. Biosolids are applied at a rate that allows the crops to use most of the nutrients as they become available. This keeps the nutrients from ending up in ground and surface waters. Metals in biosolids are in a form that is hard to dissolve in water and tend not to move out of the area they were applied.

Research shows that land application of biosolids poses little or no risk to groundwater. The organic forms of nutrients in biosolids are less water soluble than chemical fertilizers and less likely to leach into groundwater or run off into surface water.

Furthermore, potential impacts to water sources are minimized by proper management practices, including:
  • Not over applying biosolids.
  • Maintaining buffer zones between application areas, surface water bodies, and groundwater.
  • Following soil conservation practices.
The organic nitrogen and phosphorous found in biosolids are used efficiently by crops because these plant nutrients are released slowly throughout the growing season. This enables the crop to absorb these nutrients as the crop grows. This efficiency lessens the likelihood of groundwater pollution by nitrogen and phosphorous which can occur after chemical fertilizer applications. Many metals and organic chemicals that are unsafe in large amounts also occur naturally in the environment, and some, such as zinc and copper, are necessary for the health of plants and animals.

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What about metals in biosolids?
Metals in biosolids do not pose a threat to human health or the environment for multiple reasons. For instance, some metals, such as nickel, zinc, and copper found in biosolids serve as nutrients that are essential for healthy plant growth.

Most sewage comes from homes and businesses, with a smaller proportion coming from industrial sources. Industrial facilities' discharges must meet certain standards before being sent down the drain. This is called pre-treatment, where specialized processes are used to remove or reduce certain pollutants. In recent decades, these processes have dramatically reduced the amount of heavy metals in sewage.

Washington only has 11 municipalities with combined sewer permits. Combined sewers collect sanitary sewage and stormwater runoff. This type of system is no longer being implemented and existing systems are upgraded to prevent overflows. Stormwater can be a significant contributor because it contains contaminants washing off roadways, sidewalks, roofs, and other impervious surfaces. Stormwater also contains contaminants from burning and the resulting air pollution that lands on the impervious surfaces.

There has been an enormous amount of research on metals in biosolids. The extensive risk assessment conducted for the federal biosolids rule set conservative limits on concentrations of metals allowed in biosolids. The research has shown that metals do not move in soils. That means most metals are tightly bound to the biosolids and unable to leach into waterways. In addition, biosolids applied in Washington rarely come close to the lower boundary at which land application would be further restricted based on U.S. Environmental Protection Agency's risk-based standards.

By limiting biosolids application to the agronomic rate and by limiting the allowable pollutants in biosolids, it is virtually impossible that metals in soils at biosolids application sites can accumulate to levels significantly higher than those found naturally and that pose any undue risk to even the most highly exposed individuals, much less to the general public. Guidelines do not permit the application of biosolids with metal concentrations over specific regulated limits. These are conservatively set to prevent toxicity or health impacts in plants, animals and humans.

Metals leaching from plumbing has been reduced a lot over the years by controlling the pH of our drinking waters.

What do I need to know about pathogens (bacteria and viruses) in biosolids?
There are two standards for pathogens in biosolids, Class A and Class B. To be classified as Class A, the biosolids levels of bacteria indicator species need to be virtually non-detectible. Biosolids are Class B if they have gone through a process designed to kill 99 percent of the pathogen indicators, and the remaining are dealt with by limiting human and animal contact while the bacteria is killed by environmental factors such as UV-radiation. Site managers, for Class B biosolids applications, follow procedures such as wait times for harvesting crops, access restrictions, and buffer zones to protect public health. Unless a person ingests fresh biosolids, the treated material poses little health risk to humans.

What about pharmaceuticals, personal care products, and other chemical compounds in biosolids?
Studies have shown that biosolids contain many different chemicals at low concentrations. This is not surprising since we buy, use, and consume thousands of chemicals in our everyday lives. Most of the trace organics found in biosolids result from our use of products containing chemicals. These products include shampoos, laundry detergents, plastics, hand sanitizers, toothpastes, clothing, soaps, furniture, medications, etc.

We are now able to detect these chemicals in minute concentrations due to advances in technologies, whereas previously we were not aware they were present at all. This does not mean they were not present in the past or that the concentrations pose a risk. It just means that we can now find them.

When any chemical enters a sewage system, it can:
  • Move through the system as-is and be discharged with the treated water.
  • Bind to the solids as-is and become part of the biosolids.
  • Evaporate.
  • Be broken down.
If a chemical ends up in biosolids, we know that the chemical has properties that bind it to the solids (otherwise it would have remained with the liquids or evaporated). This tells us it is not readily water-soluble and therefore, unlikely to leach after land application. In addition, the strictly controlled application of the biosolids to soils allows an opportunity for physical and chemical processes occurring within the soil environment to break the chemicals down into ones of lesser or no concern.

Phthalates are a good example of a class of chemicals that can be found in biosolids. Phthalates are mainly used to make plastics flexible for products such as shower curtains. Phthalates are found nearly everywhere in the environment because they are used in countless products and processes. Not surprisingly, the current research on phthalates in biosolids suggests that the chemicals are bound to the biosolids (they do not move) and that they break down quickly in soils (half-lives of 20 to 25 days). Thus, we do not believe that phthalates in biosolids pose any significant risk to human health or the environment.

For perspective, compare the estimated 10 - 50 ppm phthalates in biosolids with the estimated phthalate concentration in:
  • Hair spray: 250 ppm.
  • Spray deodorant: 900 ppm.
  • Household dust: 1,000 ppm.
  • Fragrances: 12,000 ppm.
  • Nail polish: 40,000 ppm.
  • Some plastic products: 600,000 ppm.
Most of us come in contact with many of the trace organics found in biosolids almost constantly in our everyday lives from other sources, particularly consumer products. Few of us ever come into contact with biosolids or crops grown in biosolids. So if there is any risk from these chemicals in biosolids, then the risk from our everyday activities will be much higher.

The U.S. Environmental Protection Agency, other federal agencies, and universities are conducting research on the potential risks of trace chemicals in biosolids. Given the information currently available, Ecology believes Washington's regulations protect human health and the environment while still allowing for the beneficial use biosolids.

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What is the consensus in the scientific community about the safety of using biosolids for food crop production?
The National Academy of Sciences reviewed current practices, public health concerns, and regulator standards, and concluded that "the use of these materials in the production of crops for human consumption when practiced in accordance with existing federal guidelines and regulations, presents negligible risk to the consumer, to crop production and to the environment."

Decades of research and actual application of biosolids have resulted in an overwhelming scientific agreement among qualified researchers that the use of biosolids, in accordance with existing federal and state guidelines and regulations, presents negligible risk to the consumer, to crop production, and to the environment. In fact, the science-based approach used in developing the biosolids standards could serve as a model for policy and regulation in other areas of agricultural production and food safety.

How will I know if my food has been produced using biosolids?
No law requires foods produced with biosolids to be labeled. Biosolids are used around the world to grow crops for both domestic and export markets.

Any type of crop can be grown in Class A biosolids because they contain no detectable pathogens. However, for Class B biosolids the state biosolids rule contains different crop harvesting restrictions based on whether the harvested part of the crop comes into contact with the biosolids and how long the biosolids remain on the soil surface. The result is that there is virtually no chance that crops whose harvested parts may come into contact with biosolids (for example: beets, potatoes, onions, lettuce, cucumbers) will be fertilized with Class B biosolids because the waiting period is just too long.

Harvest Restrictions after Class B Biosolids Application
Crop Type Harvested Part Example Crop Minimum Time After Application to Harvest Percent of WA Biosolids Application (2012)
Food Crops** Below Soil Surface Carrots 3 years & 2 months 0%
Food Crops* Below Soil Surface Carrots 1 year & 8 months 0%
Food Crops Touch Soil Pumpkins 1 year & 2 months 0%
Food Crops Do Not Touch Soil Wheat, Barley 30 days 93%
Feed Do Not Touch Soil Alfalfa, Pasture 30 days
Fiber Crops Do Not Touch Soil Cotton, Flax 30 days 0%
Timber --- Douglas Fir --- 7%
Turf --- Turf Grass 1 year 0%
*When biosolids remain on land surface for 4 months or longer before being incorporated into the soil.
**When biosolids remain on the surface for less than 4 months prior to incorporation into the soil.

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Statistics about Biosolids

What percentage of biosolids is recycled?
Biosolids are applied to less than one percent of the nation's agricultural land. The U.S. Environmental Protection Agency estimates that approximately 7 million tons of biosolids are generated by the 16,500 wastewater treatment facilities nationwide.

  • 60% of all biosolids are beneficially used as a fertilizer on farm land following treatment.
  • 20% is incinerated.
  • 17% ends up buried in a landfill.
  • 3% is landfilled or used as mine reclamation cover.
How much biosolids do we produce in Washington and what happens to it?
In 2012, we estimate that biosolids were applied to less than 0.16 percent of agricultural land in Washington and less than 0.05 percent of the all land.

About 110,000 dry tons of biosolids were handled in 2012.
  • 81% was land applied.
  • 18.5% incinerated.
  • 0.5% landfilled.
Of the biosolids applied to land:
  • 70% applied to agricultural sites.
  • 25% sold for residential or commercial use.
  • 5% applied to forested sites.
From the portion of biosolids applied:
  • 93% grow feed and food crops such as wheat, alfalfa and pasture.
  • 7% on timber.
What do other states do with their biosolids?
Land application of biosolids takes place in all 50 states. The U.S. Environmental Protection Agency estimates that approximately 7 million tons of biosolids are generated by the 16,500 wastewater treatment facilities. Biosolids are applied to less than one percent of the nation's agricultural land.

  • 60% of biosolids are land applied.
  • 20% is incinerated.
  • 17% is disposed of in landfills.
  • 3% is landfill or mine reclamation cover.
In Oregon,
  • 95 % of biosolids are land applied.
In 2001, biosolids were land applied on about 0.11 percent of all Oregon agricultural land.

In California:
  • 70% of biosolids are land applied.
  • 5% is incinerated.
  • 6% is disposed of in landfills.
  • 12% is landfill cover.
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