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What Are We Going To Do With Sludge?
You go to the bathroom, you flush the toilet and, viola, it all goes away.
You prepare food at the sink, grind up what you don't want in the garbage disposal located under the sink, it all goes away.
This material (known as sewage) ends up at the wastewater treatment plant, where a chemical and physical process digests the sewage, leaving a by-product called sludge. Sludge is mostly water with a mix of organic and inorganic solid material.
Keene generates approximately 4,300 wet tons (measured by weight as it arrives at the disposal site), which is currently buried at the Keene landfill. When the landfill closes in a little over a year, sludge will be among the various waste streams we must deal with.
Sludge represents approximately 11 percent of the waste stream generated in the City of Keene. Several years ago, a Biosolids Disposal Committee was formed within the Department of Public Works to evaluate the existing technologies to deal with sludge efficiently and economically. After reviewing dozens of biosolids technologies for a variety of factors, including disposal cost, proven reliability, odor control, marketability, the ability to add other organic material such as leaves and yard trimmings and beneficial reuse (the ability to use the final product in a positive manner), the Biosolids Disposal Committee recommended a composting technology called the CompTainer, developed by Green Mountain Technologies of Whitingham, Vermont.
The CompTainer system is comprised of specially designed rolloff containers that are filled with sludge and an amendment (such as leaves and yard trimmings), creating a contained static pile in 40 cubic yard modules. After a retention time of 17 days, the rolloffs are emptied and the compost is cured for a period of 30 to 60 days. The container has an electronic temperature monitoring system which sends data to a computer, which allows for automated air flow control, eliminating the need for operator intervention.
The City Council approved the Biosolids Disposal
Committee recommendations and engineering of the facility will begin shortly.
Construction of the biosolids composting facility is scheduled for Spring
of 1998, with startup in early Summer 1998. Initially, compost generated
by the facility will be used for final cover material during closure of
the landfill. Other outlets for the compost include some agricultural uses,
gravel pit reclamation and highway projects.
Duncan Watson is the solid waste coordinator for the Keene Public Works
Department.