Biosolids Research and Demonstration

Since 1973, our biosolids program has worked with local universities to develop and test biosolids recycling methods. Research has included effects of biosolids on soils, crops, wildlife and water quality, as well as developing new markets and testing application techniques. Results provide the technical basis for appropriate site management, environmental monitoring, development of regulations, public acceptance and quality assurance for landowners. University scientists act as technical advisors to our projects, providing third party review and oversight.

Forestry

A scientist, a forestland manager and an environmentalist examine tree foliage response to biosolids fertilization.

The University of Washington College of Forest Resources(external link) pioneered the the use of biosolids to enhance forest growth and developed the technical information that was necessary for guiding biosolids use in forests of the Pacific Northwest .

Many aspects of biosolids recycling in forests have been studied by UW faculty and graduate students. Past research projects have included managing nitrogen and phosphorus, soil quality, identifying and managing odor, and long term effects of biosolids, including fate of metals and ecosystem response. The University's C. L. Pack Experimental Forest(external link), near Eatonville, has been the setting of many research and demonstration projects. The Biosolids Interpretive Area located at the gatehouse entrance to the forest was expanded to include examples of mine restoration and landscaping uses of biosolids products in a setting that is readily accessible to the public.

Winter wheat

Wheat plants (right) were taken from the field and provide a close-up comparison of growth response. The large, healthy plants at right came from fields fertilized by biosolids.

At the Boulder Park project, Washington State University scientists studied the effect of biosolids on soils and plant growth and yield. Four 'treatments' were compared: control (nothing added); anhydrous ammonia fertilizer at a rate of 50 lbs/acre of nitrogen; and two rates of biosolids supplying nitrogen at 50 and 100 lbs per acre. Results showed increase crop yield. Other benefits include reduced soil erosion and faster plant establishment, allowing farmers to reduce their use of herbicides. WSU continues to evaluate the long-term economic benefits of biosolids fertilization on additional wheat varieties and locations throughout the northwest.

Compost and turf demonstration

Scientists at the Washington State University Research and Extension Center(external link) in Puyallup have created a compost demonstration garden and conducted research on pasture grass and turf grass production using a variety of biosolids products.

Dahlias grown with GroCo in a WSU demonstration plot.

Soil and ecosystem restoration

A collaborative research effort in Kellogg, Idaho, tested ways to restore vegetation to severely contaminated and eroding hillside soils and reduce the toxicity of wetland soils on this former mine and smelter site.


A badly contaminated and erosion-prone mine spoil pile such as this can be successfully remediated with biosolids.

Partners include the US Environmental Protection Agency, US Department of Agriculture's Agriculture Research Service, University of Washington, University of Idaho and the Northwest Biosolids Management Association. Biosolids from King County and several other municipalities and wood ash are being tested to see how well they can adjust soil pH, immobilize excess soil metals and provide plant nutrients. Initial results show good remediation potential.

Bioaerosols

Recent national debate centered on the potential for pathogens to become aerosolized and carried by wind away from biosolids application sites and pose a risk to human health. Researchers from the University of Arizona studied the generation and fate of such “bioaerosols” and sampled air at King County biosolids application sites and at other sites throughout the country. Results from samples in Washington showed minimal aerosolization taking place; common soil microbes were found at lower concentrations than at other sites. Overall, the study showed that transport distance of microbes is low and overall risk of infection to workers or communities is also very low. The researchers found that dewatering biosolids helps prevent bacteria or viruses from becoming aerosolized.

Sampling a biosolids application area for bioaerosols.