ARTICLE
City of London relies on strength and durability of Geotube® containers for award-winning ash dewatering solution
After dewatering thousands of tonnes of ash, using dozens of Geotube® containers, the Greenway Wastewater Treatment Plant (WWTP) in London, Ontario reports that the five-year-old system continues to “exceed expectations” for reliability and performance.
“We selected Geotube® containers for our ash dewatering system for their strength and durability,” says Mark Elliott, Senior Engineering Technologist with the City of London.
“Each unit is built using a sturdy fabric and seam design that allows the bags to be pumped to higher maximum heights. This was an important consideration for us from the outset of the project because it meant that Geotube® containers would enable us to maximize our dewatering process in the smallest footprint possible.”
Sludge from the Greenway WWTP, along with sludge from five other plants is incinerated at the site, producing ash that is sent to storage lagoons. As the City grew and sludge volumes increased, plant managers began exploring new technologies to simplify handling and disposal of the ash. Bishop Water’s award-winning Geotube® dewatering system not only achieves this, it also eliminates the need to expand the storage lagoons.
The innovative ash dewatering facility occupies an area of only 1,200m3 – significantly less space than adding two more storage lagoons, which would have been three times larger at approximately 4,600 m3.
Geotube® system exceeds expectations
“We started with a test pilot using Geotube® containers in 2011,” Elliott says. “The initial results were great so we decided to install a full-scale Geotube® dewatering system. The performance of the system has not only met our expectations, it’s exceeded them. We’ve continued to use the Geotube® containers because they’re reliable, easy-to-maintain and consistently produce high-quality filtrate.”
The high strength, woven polyethylene fabric in Geotube® containers, along with a polymer specifically selected for the site, provides exceptional solids retention and helps achieve a strong dewatering performance. Currently, it takes about two months to fill two Geotube® containers, which can hold 900 tonnes of ash combined. Once they’re filled, it takes about 100 trucks to transport the dry solids from the Greenway WWTP to a landfill. At its maximum capacity, the laydown area can handle seven 18 m x 13 m Geotube® containers simultaneously.
“Our experience working with Bishop Water has been excellent,” Elliott says. “The staff are great to deal with and they’ve continued to check in with us 2 to 3 times a year to see how the Geotube® bags are functioning. Given the opportunity, I would work with Bishop Water again without a doubt.”
