Geotube containers that are filled late in the year are often left onsite over the winter to experience the dewatering advantages that the freeze-thaw cycle brings. Once the thawing begins, those previously frozen Geotube® containers can give up a lot of water—in some cases up to 50% of their volume.

This dramatic reduction in volume means that the containers can be topped up with additional slurry materials once they are fully thawed. Or, if the solids are destined for disposal, the reduced volume will mean much less material to transport and lower costs for hauling and tipping fees.

Expansion helps with consolidation of solids

Dewatering benefits from the freeze-thaw cycle because water expands as it freezes. The Bishop Solids Management Solution, with Geotube® containers, can attain 15 – 18% solids within a few days of dewatering, but that means there’s still a good amount of water remaining as cold temperatures set in. The formation of ice crystals and the expansion of the water compress the solids and once the thaw occurs, more water is released and the solids are further consolidated.

The results can be quite dramatic. At a recent wastewater lagoon desludging project, our crew filled Geotube® containers to a maximum height of 7.5 feet. The containers were left on site over the winter and after thawing in the spring, the height was reduced almost by half.

Some of our clients that are equipped with a permanent Bishop Solids Management Solution take full advantage of freeze-thaw cycles in their sludge management plans.

The North Rustico Wastewater Treatment Facility in Prince Edward Island, Canada uses several large Geotube® containers setup outdoors to dewater waste sludge, with a smaller container in a greenhouse that is used during the winter months. The outdoor containers are left to freeze over the winter and can be topped up in the spring once they thaw and release more water. This enables the plant to use Geotube containers for several seasons, replace them less often, and reduce operating costs.

Read the feature article about the North Rustico WWTF in Go With the Flow magazine published by the Atlantic Canada Water and Wastewater Association.