The ARA Pustertal wastewater treatment facility treats residential waste water from an association of 14 municipalities with a collection area of 444 square miles, corresponding to a population of approximately 400,000.
A thermal dryer reduced the volume and weight of approximately 16,000 tons/year of sewage sludge containing 20-25% dry matter. The sludge volume was reduced about 75% by drying. The now 85% dry matter was subsequently pelletized but the expense to transport 4,500 tons of pelletized sewage sludge for use as an agricultural fertilizer prompted a search for a better solution.
EISENMANN's Pyrobustor® was installed in 2005 and has been continuously converting the dry sludge pellets into ash since 2006. The combustion heat is used first to heat the thermal oil for heating the sewage sludge drier. Second, it is used to heat the process water for
preheating the air of the sewage sludge drier.
The process yields savings of up to 65% in relation to the primary energy previously needed for the drying process. CO2 emissions are reduced by over 1,300 tons per year.