Dragon Dryer System Provides Safer and Saleable Byproduct
The city of Tallahassee, Fla., is producing Class A biosolids from its T.P. Smith Wastewater Treatment Plant thanks to the newly installed Dragon Dryer sludge drying system from USFilter Davco Products, Thomasville, Ga.
The city of Tallahassees Water Utility contracted with Davco Products to advance its wastewater treatment capabilities, allowing the plant's residual biosolids to be sold as a beneficial fertilizer and soil conditioner to the agricultural market, commercial nurseries and other businesses.
The unique, single-pass-drying unit became fully operational in March 2004. The Dragon Dryer system reduces the wastewater treatment plant's sludge volume ratio from 4 to 1, and nearly eliminates the need for spreading the biosolids on surrounding land.
The Dragon Dryer system utilizes indirect heat, preventing direct contact of the sludge with the heat source. The simple-to-operate system is not only operationally safe, but also effective and energy efficient. Isolating the sludge in the drying chamber allows for greater control of the dehydration process. The city has begun piping off the gases from the system to the air diffusers in the treatment plants aeration basin, resulting in essentially zero emissions.
Like other communities throughout the country, the city of Tallahassee had been land applying its Class B biosolids, which result from the wastewater treatment process. However, site limitations, federal regulations and cost considerations motivated the water utility department to upgrade its operations to Class A status.
"From long-term economical and environmental standpoints, it makes good sense to move to Class A material," says Water Utility engineering manager, Lynne Putnam. "Other municipalities, such as in Milwaukee, have been producing and marketing similar products for years."