Originally posted at http://www.tpomag.com/
By Scottie Dayton
A German-engineered solids-processing technology yields Exceptional Quality biosolids pellets in a smaller footprint and at lower cost than composting.
To produce Exceptional Quality compost, staff from KB BioEnergy, a biosolids management firm, mixed sawdust with primary and waste activated sludge at the Akron (Ohio) Renewable Energy Facility.
In 2009, the sawdust price increased from $3 to $15 per cubic yard. “We used 50,000 to 60,000 cubic yards annually, but compost sales didn’t generate enough revenue to cover the increased cost,” says Annette Berger, vice president of operations. “We needed an economical alternative that dovetailed with upgrading our 25-year-old facility.”
A trip to Germany to investigate anaerobic digestion technologies introduced officials to Schmack Biogas, a member of the Viessmann Group in Schwandorf. “Their reactors were processing manure slurry at 30 percent solids while our municipal technology achieved 3 to 5 percent solids,” says Berger. “When we saw the EUCO Titan system, we wanted it.”
The two-phase, $32 million upgrade reduced annual electricity costs from $360,000 to $30,000 at the facility. The Akron facility now produces Exceptional Quality biosolids pellets, used by a landscaping company as a soil conditioner.
To the test
To test whether the technology would generate biogas from 28 percent solids material, Akron officials contracted with KB BioEnergy to build a pilot plant handling one-third of the water reclamation facility’s primary and waste activated sludge (22 to 25 million gallons per year). The successful pilot provided a baseline for the full-scale system.
Previously, Akron’s 90 mgd (design) water reclamation facility annually pumped 65 to 75 million gallons of blended, thickened sludge under the Cuyahoga River to three holding wells at the renewable energy facility. After processing, the staff managed the composting in four reactor bays. Further curing occurred outside on a concrete slab.
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