view counter

Making Your Garden ‘Bloom’

Biosolids are safe for food ­production; here’s why

The Blue Plains Advanced Wastewater Treatment Facility transforms the ­District’s waste into Bloom, a soil conditioner for gardening and landscaping.

Since I became involved in composting biosolids in the early 1970s, technology for processing wastewater has undergone major changes. Back then, most wastewater treatment facilities had only primary or secondary treatment technology. At the same time, industries were dumping all kinds of waste into sewer systems.
    The Clean Water Act promoted by president Lyndon Johnson led to major changes that now enable us to convert solid waste into usable products while returning more carbon to the earth. The act stopped wastewater dumping into our streams, lakes, Bay and oceans. It established a Biological Waste Management Laboratory managed by the U.S. Department of Agriculture and the Environmental Protection Agency. Studying the science of composting, this laboratory has developed efficient composting systems.
    The Clean Water Act also mandated that wastewater be returned clean to our waterways. Wastewater processing facilities were upgraded to secondary and tertiary systems. Tertiary systems not only return crystal clear water but also generate biosolids that are classified Class A, meaning they can be used to produce agricultural crops.
    The Blue Plains Advanced Wastewater Treatment Facility in Washington, D.C., is the largest plant using the world’s most advanced water treatment technology. Blue Plains processes 300 million gallons of wastewater each day and generates 450 wet tons of biosolids.
    The biosolids are heat-treated to 350 degrees under 87 pounds pressure per square inch. Then they’re infused with active anaerobic microorganisms, and the material moves into the digester. Anaerobic microorganisms are more aggressive in digesting organic carbon compounds than the aerobic microorganisms active in composting. The biosolids remain in the digester for 18 days before filter presses remove excess water.
    The end product is Bloom, a superior soil conditioner.
    Already self-feeding, its production is moving to energy neutral. The digester generates methane gas, used to cook the biosolids. Blue Plains is also installing solar panels over the sludge activators to reduce operating costs.
    Within three years, similar systems will be operating across the country.
    Advanced wastewater treatment and biosolid digestion are only part of the reason you can now safely use processed biosolids in producing food crops. Hard pesticides such as DDT and Chlordane have long been eliminated from use. Pesticides in home use have limited shelf life and are biodegradable. Along with pharmaceuticals, they are destroyed by microbial systems and by the heat.
    Because iron sulfate is added to precipitate the phosphorus from the water, Bloom is not 100 percent organic under current guidelines.
    Bloom is now sold at Homestead Gardens.


Ask The Bay Gardener your questions at DR.FRGouin@gmail.com. Please include your name and address.