The city of Fitchburg, Massachusetts operates a multiple hearth incinerator that burns municipal sludge to minimize waste volumes. Although not universally used by municipalities in the United States, incineration is a widely accepted and used method of sludge disposal. The major benefit of incineration is a greatly reduced need for landfill space. An 85 - 95% volume reduction of material needed to be sent to a landfill dump is normal as the result of incineration (1).
Incineration is used extensively in countries with limited open space. Japan incinerates approximately 75% of its municipal solid waste (2). In Europe, on the other hand, Finland reported 90% of such waste is sent to landfill, where as in tiny Denmark 75% of such waste is incinerated (3). How to ultimately dispose of solid waste remains a challenge to municipalities worldwide. In Texas alone, 6.5 pounds of solid waste was generated per person per day in 1998 (4).
The City of Fitchburg Municipal Incinerator
Burning of solid waste will generate harmful gases that must be treated before exiting the stack into the atmosphere(5). The city of Fitchburg, Massachusetts, burns solid sewage sludge in a multiple hearth incinerator located at the East Fitchburg WWTP. In addition to sludge generated there, the city accepts biosolids from other New England municipalities. Fitchburg is paid, on average, $250 per dry ton to destroy this sludge. The incinerator is located next to the municipal airport.
Exhaust gas produced by the incinerator is treated extensively before being allowed to exit the stack and disperse into the environment. Following the incinerator is a tray tower, a venturi scrubber and a wet electrostatic precipitator (WESP). These air pollution control steps remove particulates and heavy metals from the gas exiting the multiple-hearth incinerator.