The bioreactor (enhanced cell) was constructed with a double liner, meaning that two of the composite liner systems were constructed one on top of the other. The reason for this is that liquid additions to the landfilled waste were planned to accelerate decomposition, and regulators were concerned that this might increase the possibility of groundwater contamination. A drawback however, is that the double liner system doubles the initial construction costs. To facilitate drainage from the enhanced cell, gravel was placed as a protective layer over the liner system pictured above.
After the liner system is in place, non-bulky curbside waste and green waste are layered alternately. Sensors are place in the cell during filling to monitor temperature, moisture content and gas pressure.
The final lift of waste was placed in a pyramid shape to facilitate drainage of rainwater, and was covered with a final layer of green waste (including a load of melons in the center of the picture). The shredded tires in the foreground (about 500 tons) were distributed on top of the final layer of green waste to create a 2-foot thick "horizontal blanket" landfill gas collection layer. This layer of shredded tires is not normally constructed in landfills, but one of the goals of the project is to assess their performance in this application, as they are plentiful and affordable.
A geofilter was placed over the shredded tire layer to prevent the migration of soil particles that could clog the voids in the shredded tires. Then, a one-foot thick layer of soil was placed and graded over the geofilter. The white pipelines pictured above are landfill gas collection lines
Finally, a plastic membrane liner was placed on the surface of the cell to prevent the escape of landfill gas. Sand bags were used to hold the plastic in place.
Above: Control Cell; Below: Enhanced Cell
Seen side-by-side, one can see the effects of microbial decomposition in the enhanced cell as it sags considerably more than the control cell.
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