Frequently Asked Questions about Biosolids Recycling
What are biosolids?
Biosolids are the nutrient-rich organic material produced by treating wastewater solids. After processing and treatment, they can be beneficially recycled as a fertilizer and soil amendment.
Where does the wastewater come from?
Wastewater flows to treatment plants from homes, businesses, and industries. In King County 95% of the wastewater is from homes and businesses, with only 5% from industries. Wastewater pumped from septic systems is also delivered to the treatment plant. This link shows the extent of the sewered system in our region: http://dnr.metrokc.gov/wtd/rwsp/tutorial/current.htm
Are biosolids safe to use?
Yes. The U.S. Environmental Protection Agency (EPA), with the help of scientists from universities and the Dept. of Agriculture, studied biosolids for more than 10 years, then developed regulations that would protect human health and the environment. Biosolids have been recycled safely by King County for more than 25 years. In an independent study, the National Academy of Sciences reviewed current regulations, practices, and public health concerns 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 present negligible risk to the consumer, to crop production and to the environment."
Where can I get biosolids to use in my garden?
In the greater Seattle area, biosolids are composted with sawdust and sold under the name, GroCo. Call GroCo, Inc. at 206-622-5141 for information on purchasing this popular soil amendment.
Other cities may also have biosolids products available for garden use, such as a soil mix or compost. Tacoma makes several products under their trademark name, TAGRO. Info at: www.tagro.com
What about the long-term effects?
The use of biosolids has been one of the most extensively studied practices in the U.S. In some parts of the country, biosolids have been used for over 70 years. The Water Environment Federation recently investigated several long-term application programs. They found that sites with cumulative biosolids loadings equivalent to more than 600 years of annual agronomic rates showed very little, if any, negative impact on the soil-plant system and on water resources.
What about the concerns and recommendations of Cornell University?
Cornell's recommendations for site management are simply what King County has already been doing for many years, based on research and recommendations from local scientists at UW and WSU. These include:
--Limiting applications to keep soil metals low;
--Testing soils before application;
--Applying only at agronomic rates;
--Supplying all landowners with biosolids quality information;
--Monitoring downstream water bodies and wells;
--Calibrating application equipment;
--Maintaining setbacks and buffers;
--Avoiding application to areas prone to runoff;
--Imposing access restrictions for the public.
Because of the low contaminant level in King County’s biosolids, they are safe to apply many times before reaching the site life limits suggested by Cornell.
Are there toxic materials in the biosolids?
In the Seattle area, industries are required to remove hazardous contaminants before the wastewater is discharged to sewers. (For more details about this program, see King County Industrial Waste Program)
The county’s biosolids easily meet EPA’s most stringent standards for safe use on land and crops. 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. King County’s biosolids contain only very small amounts of metals and organic chemicals, thanks to the effective monitoring and pre-treatment requirements placed on industries.
Are there disease-causing organisms (pathogens) in the biosolids?
There are pathogens in raw wastewater that enters the treatment plant. During treatment, the wastewater solids go through a biological digestion process that kills approximately 95% of the pathogens. Biosolids from King County contain no detectable parasites and viruses are only rarely detected. Any remaining pathogens die off quickly when exposed to conditions at application sites. Unless a person actually ingested fresh biosolids, the treated material poses little health risk to humans. Site management procedures such as crop harvest and public access restrictions are followed to protect public health. (See what public health specialists have to say about the safety of biosolids: http://www.metrokc.gov/health/prevcont/biosolid.htm
Why does King County use biosolids on land and crops?
Biosolids enriches the soil with essential nutrients that are released gradually as plants need them. These nutrients include not only organic nitrogen, phosphorus, and potassium, but also minor elements such as chromium, calcium, copper, iron, magnesium, manganese, selenium, sulfur, zinc and others that are necessary for plant growth. Biosolids also add organic matter, which improves the structure of the soil and helps the soil absorb and retain moisture. Recycling biosolids on land captures nutrients that would otherwise be lost and maintains the productivity of soil, one of our most vital resources. Biosolids are a valuable resource that can be used productively rather than treated as a waste to be dumped and buried at considerable cost.
Do biosolids affect the quality of food crops?
This issue has been studied by agricultural scientists for decades. Protection 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. King County applies biosolids to wheat, hops, and other crops in eastern Washington. Scientists from WSU have repeatedly tested the crops fertilized with biosolids and found no differences in quality from those treated with chemical fertilizers.
How can biosolids be good for wildlife and fish?
Scientists at the Univ. of Washington began studying the effects of biosolids on wildlife more than 25 years ago. They have not found any animals that are harmed by this practice. Because biosolids makes vegetation grow faster, animals from deer to mice benefit by having more nutritious food and better habitat.
Recently the National Marine Fisheries Service (NMFS) evaluated the 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. see related press release
Why doesn’t the county just put biosolids in the landfill?
Recycling biosolids in farms, forests and gardens captures the nutrients and provides real benefits to crops and soils. Because the safety of this practice has been demonstrated for decades, Washington State Dept. of Ecology encourages recycling and prohibits landfilling except in emergencies.
What do other communities do with their biosolids?
Although federal and state rules encourage recycling, cities and towns make their own decisions about how to manage biosolids. Options include application to agricultural or forest lands, composting, land reclamation, incineration, or landfilling. All 50 states practice some land application. Nationwide, more than half of all biosolids are applied to agricultural crops; however, this includes less than 1% of the nation’s agricultural lands. In Washington and Oregon, a very high proportion of biosolids is land applied.
