Eganville Waste Water Treatment Plant Dewatering

TenCate Geosynthetics, Pendergrass, Ga., United States

In 2002, Ontario’s legislature and the Ministry of Environment (MOE) produced a policy paper announcing their intent to eliminate the land application of untreated septage. While 90 percent of residents in Ontario used local sanitary sewers to dispose of their waste and were unaffected by the policy, there were still more than one million residents in rural areas using septic tanks. Haulers across Ontario were left in a bind, scrambling to find methods to treat and dispose of the septage. Local municipalities and private haulers had to come up with alternate methods to treat and dispose of the septage. For the small town of Eganville (population 3,455), located in Bonnechere Valley, the solution was found in Geotube® dewatering containers.

The project included designing and constructing a permanent cost-effective dewatering and processing facility that would provide a long-term solution for the treatment of septage and bio-solids from the wastewater treatment plant. The process for haulers to empty their truckloads at the dewatering facility is simple and straightforward. Haulers are required to pull their tanker trucks up to the septage station and empty the load from their tanker into the 10,000 gallon (38,000 l) underground holding tank. After emptying their truck, haulers can drive away. They no longer have to spend time land applying septage to fields. A simple bar screen removes solid waste, such as plastics, during emptying to ensure no large objects are pumped into the tank. The septage is mixed with a submersible pump located in the tank. As the waste is being pumped into a Geotube container, it is mixed with a polymer solution to promote flocculation. Once the waste is pumped into the Geotube, dewatering takes place. As the solids fall to the bottom of the Geotube, clear filtrate flows from the container. The filtrate flows by gravity over the concrete pad on which the containers are located to an underground filtrate storage tank. Once full, the filtrate is then sent back to the head works of the treatment plant where it is further treated to meet the stringent MOE discharge criteria. Once dewatered, the solids are removed and are land applied. Reflecting the township’s commitment to this project, Bonnechere Valley Township partnered with Renfrew County and the MOE to continue evaluating the dewatering and treatment of septage utilizing Geotube dewatering technology. Beginning in 2008, the township has handled the operation, evaluation and reporting for this septage management project. Analysis and testing were conducted on three types of materials for comparison: raw septage, septage filtrate and dewatered septage solids.

From April to December 2008, roughly 500 m3 (650yd3) of septage was received and processed. At the end of the year, the Geotube container measured approximately 0.6 meter high. This equated to almost 35 cubic meters of dewatered septage in the 10 to 12 percent solids range.

In addition to the positive test results, this collaborative effort with MOE has generated plenty of interest at the local, county and provincial levels of government. The township is continuing the sampling and evaluation of the Geotube dewatering process in 2009. A final report is planned for early 2010. The results should provide a meaningful review of the dewatered material and its benefits as a soil amendment nutrient. All of the pathogens and metals in the dewatered material have been well below MOE levels for land application use.

By addressing the challenges facing the septage haulers across the province, Bonnechere Valley Township is demonstrating environmental responsibility by choosing a treatment option for septage and bio-solids that does not produce a waste, but an odorless reusable nutrient.