ARTICLE
Operators traded wheelbarrows for Bishop Solids Management solution to reduce time and labour in sludge handling
It used to take almost a month to dewater the same volume of sludge that is now done in less than a day at the Meteghan Sewer Treatment Plant (STP) in the Municipality of Clare, Nova Scotia, according to Jody Comeau, Treatment Plant Operator. The dramatic savings are possible after replacing sand drying beds with a simple, low-energy Bishop Solids Management Solution, which uses only Geotube® containers, polymers and gravity to collect and dewater sludge in a single step.
The comprehensive dewatering system, designed and supplied by Bishop Water, has been operating since November 2016. Waste sludge from the plant is now pumped directly from the sludge storage tank to a Geotube container. As the sludge is pumped, Bishop Water’s Venturi Emulsion Polymer Activation System (VEPAS) injects polymer directly into the sludge line and activates the polymer in a single pass, with no mechanical mixing required. In many cases, the optimal polymer dose can produce dry solids from waste sludge in excess of 50%.
The one-step, venturi-based VEPAS eliminates many of the components used in mechanical polymer systems, such as mixers and aging tanks, which not only increase the size of mechanical systems, but also require operator attention for maintenance and cleaning.
Once the run is finished, Jody says he can clean any remaining polymer out of the compact VEPAS system in about 10 minutes and have it ready to go for the next session.
“Our sludge does experience some variability depending on the time of year and how long it’s been held in the storage tank,” Jody says. “It only takes a few minutes to test the sludge and set the VEPAS, using the touch screen interface, to add the ideal polymer dose.” The VEPAS enables operators to easily change the rate of polymer flow prior to starting the waste sludge pumps or while the system is operating to address any variability in the sludge consistency.
VEPAS and Geotube® replace labour-intensive sludge handling
“The Bishop Solids Management Solution is far less labour intensive than our drying beds,” Jody says. “I now have much more time to spend on more important tasks like plant process optimization and reducing inflow and infiltration in the collection system.”
Prior to commissioning the Bishop Water system, Jody says that operators would spend many hours raking dry sludge by hand from the drying beds and piling it onto wheelbarrows. Each bed contained about 50 wheelbarrows of dry sludge that was then loaded onto trucks for disposal.
Jody says the municipality is investigating the possibility of land applying composted solids from the Geotube® containers onto a former landfill site, further reducing disposal costs and truck traffic.
“Bishop Water and the local representative, Scotia Tech, were extremely helpful and responsive during the training process and in providing ongoing support,” Jody says. “We’re quite pleased with the way the system is working.
