|Puget Sound and the Seattle city skyline.|
|From left: raw sewage, treatment plant effluent, reclaimed water.|
|Demonstration garden irrigated with reclaimed water and amended with biosolids compost.|
|Pure biosolids cake, straight from the digesters.|
|A handful of biosolids composted with sawdust to make GroCo|
Sustainability of biosolids
Similar to animal manure, biosolids are rich in organic matter and nutrients. Farmers clamor for this material because the growth response is incredible. See the photograph below where the biosolids amended plots far outgrew the synthetic fertilizer plots.
|Dryland winter wheat. From left: no fertilizer control, synthetic fertilizer at 50 lbs N/acre, biosolids at 50 lbs N/acre, biosolids at 100 lbs N/acre|
Virgin soils like those found in grasslands, forests, and marshes are full of organic matter, however, human activities like construction and tillage degrade this natural resource. In the natural world, all organic matter gets recycled in the soil, including fallen leaves, excrement, and carcasses. Organic matter, like that found in biosolids, is full of nutrients. As microbes eat the organic matter, nutrients are slowly released to plants, and they excrete sticky substances called exudates (I love that word). The sticky exudates bind soil particles together, which helps prevent erosion and preserve topsoil. All this organic matter also helps loosen up compacted soil and retain water for thirsty plants. People like me will argue that organic matter might be our nation’s greatest resource since it’s organic matter that helps to protect our arable land. But enough with the dirt on dirt, the take home message is: organic matter is good for soil.
|Volunteers haul biosolids compost to garden beds at Alleycat Acres' Beacon Hill site.|
|Andy Bary, WSU soil scientist, collects GPS data points at a long-term dryland wheat study site.|
|Me sampling a Yakima valley hops field, with a long history of biosolids application.|
|UW undergraduate intern and I collect soil samples from a restoration site on Vashon Island, WA, where biosolids composts were used to restore the soil.|
|A year later wildlife and trees are starting to come back to the Vashon Island site.|
|Pretty purple Scabiosa growing in biosolids amended soil.|
Since I live in an urban area, I would like to send out a big thank you to the wastewater treatment operators and program managers who work in the sewers to keep me, my neighbors, and Puget Sound healthy. Thanks folks! Keep up the good work!