King County does not apply any "raw sewage" or "sewage sludge" as part of any of its biosolids management program.
Composted soil amendments containing biosolids, like GroCo, have been further composted with sawdust, so have much less odor -- usually quite similar to potting soil or any other organic mulch.
GroCo made with Loop
The biosolids program emphasizes beneficial use of this resource and pursues environmental stewardship through diverse public-private partnerships. King County is a member of the Northwest Biosolids Management Association which provides collaborative research, technical assistance and public information for biosolids managers in the region.
Quality and Safety
- Stickers from fruits or vegetables
- Plastic or other non-organic materials like condoms or tampon applicators
- Expired/unwanted prescription or over-the-counter drugs - ideally, these should be returned to "drug take-back" sites, if available.
Also avoid dumping these down the drain:
- Grease and other fats from the kitchen
- Products labeled "danger", "hazardous" or "toxic"
Try to use fewer cleaning products and chemicals at home, and switch to "biodegradable" or more natural alternatives.
Remember: only toilet paper and human waste should get flushed!
Biosolids have been recycled safely by King County for more than 30 years. Monitoring of biosolids, soils, water resources, and plants continue to show benefits to plants and soils with no effect on surface water or groundwater.
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. Less than 3% of the wastewater flowing to county treatment facilities are from industrial sources.
Countless consumer products contain substances that would be toxic at higher concentrations. It's the concentration of a substance that is important. Biosolids contain tiny amounts of organic chemicals from these products, but not enough to be harmful to humans or the environment. That is why the only substances regulated in biosolids are a few metals and nutrients.
Research to-date shows that most organic chemicals are degraded quickly, are not taken up by crops, do not move through soils, and pose much lower risk to humans than our everyday activities. For example, it would take more than 200 years of daily contact with biosolids for a farm worker to be exposed to the same amount of the anti-bacterial compound Triclosan as they would encounter by washing their hands just once with antibacterial soap.
King County biosolids, Loop, contain very small amounts of metals, thanks to the county's Industrial Waste Program, which requires key industries to clean their wastewater in order to protect biosolids quality. Moreover, less than 3% of the flow into county treatment plants is from these industrial sources.
The National Marine Fisheries Service (NMFS) evaluated the county's biosolids program and determined that biosolids application posed no risk to chinook salmon and, in fact, provided an environmental benefit by enhancing forest growth (see related press release).
Loop biosolids have been safely used for nearly 40 years as a soil amendment by King County's customers. The proof? Decades of monitoring data and studies by UW and WSU scientists, demonstrating:
- Increased crop yields
- More productive soil microbial communities
- Increased organic carbon in soils
- Water quality is protected