The Blue Plains AWWTP previously lime stabilization to treat sludge, producing class B biosolids used for agricultural fertilizer. However, transporting these biosolids to where they can be used was costly—the plant produced 1,200 wet tons of biosolids each day, or about 65 truckloads.
Implementing Cambi THP at Blue Plains AWWTP resulted in an improved, class A biosolid, which DC Water is now providing to soil blenders, landscapers, community groups and governments in DC and Maryland as Bloom. “THP is a digestion preprocessing step that uses heat and pressure to kill pathogens in the biosolids and also breaks down biosolids so they are more readily digested,” says Peter Loomis, CDM Smith project manager. “THP allows higher loading to the digesters, reducing the required retention time and the corresponding digester volume. It also improves the reduction of volatile solids in the digesters, resulting in higher gas production compared to conventional digestion.”
The process reduces the volume of biosolids, produces more biogas to generate more power, and reduces odor issues associated with the transporting and disposing of class B biosolids. These changes are expected to reduce trucking by 50 percent, resulting in less traffic congestion and significantly lower carbon emissions.
THP allows higher loading to the digesters, reducing retention time and resulting in higher gas production compared to conventional digestion.
Design-build can provide creativity and flexibility to address challenges, and greater certainty of project costs.