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Turning wastewater treatment plants into resource recovery centers
Elora is one of several small communities that dot the picturesque township of Center Wellington, Ontario, Canada. Tourists and locals alike enjoy the spectacular Elora Gorge, gentle rolling hills and beautiful surrounding farmland. Hybrid cars and horse-drawn Mennonite buggies coexist to give the region a timeless, old-world charm.
Critical to the future success of Center Wellington is the Elora Wastewater Treatment Plant (WWTP), which operates silently and unobtrusively within a stone’s throw of a major new condominium development and existing retail project. The WWTP reflects a triumph for the community, including its local residents, staff, council members and area growers alike.
In 2012, the township council approved a significant, $21.3-million project to expand the treatment plant and modify the main pumping station feeding the facility. The council saw the plant upgrade as an important opportunity to modernize the facility and transform the plant into a resource recovery center capable of converting biosolids generated in the community into a high-quality biofertilizer product.
An Expensive Problem
The decision was motivated in part by the fact that Center Wellington is home to a thriving agricultural community. The council wanted to continue providing local growers with nutrients while simultaneously reducing or eliminating expensive biosolids storage problems.
“We had run out of space to store liquid, Class B biosolids on-site over winter,” said Colin Baker, managing director of infrastructure for Center Wellington.
As a result, the township was forced to use an off-site contractor for storage. With biosolids production increasing due to regional growth, this was becoming a very costly problem: “We were paying thousands of dollars per month to lease space at a nearby disposal facility,” Baker said.
Plus, the annual costs for this option were not just restricted to the storage rental fee—which had to be paid year-round whether or not it was in use, and which also was escalating at two to three times the rate of inflation. There were further costs associated with trucking and applying low-solid, Class B biosolids, which had to be given away, as they could not be sold.
These combined factors were not considered to be sustainable; therefore, staff and council required a better, long-term, fiscally and environmentally sustainable plan.
The Technology Selection
A local construction contractor won the competitive bid to expand the treatment plant and modify the pumping station with Triton Engineering Services Ltd., the township’s engineering firm, providing engineering design and construction management.
Lystek’s low-cost, thermal hydrolysis process (THP) was pre-selected and specified as a mandatory part of the overall strategy to upgrade the plant’s biosolids management processes. A technology licensing agreement and an operating support agreement were also executed for the patented biosolids management system from the company.
Christine Furlong, P.E., of Triton Eng., considered a number of biosolids management options, including anaerobic and aerobic digestion with liquid storage and dewatering with cake storage.
“Lystek was selected because, when combined with an effective dewatering strategy, the process reduces typical issues associated with Class B biosolids. The result is a substantial reduction in the volume of end product requiring management, as well as a smaller storage building,” Furlong said. “We also liked the fact that the process is returning organic material back to the earth and is practically odor-free.”
The Thermal Hydrolysis Process
Lystek’s thermal hydrolysis process utilizes a combination of low heat, alkali and high-shear mixing to produce a high-solid, pathogen-free, nutrient-rich biofertilizer that is recognized as a Class A EQ (Exceptional Quality) product by the U.S. Environmental Protection Agency (EPA) and registered with the Canadian Food Inspection Agency (CFIA) as a commercial-grade fertilizer. This means that the customer has a product that can be sold, not given away, further offsetting the cost of operations over time.
Another feature of the process is destruction of pathogens. It produces a Class A quality end-product that is safer for operating staff and suitable for long-term use by growers, particularly as compared to Class B biosolids—and this renewable resource can be utilized the same way as any commercial fertilizer.
Ease of operation was an additional requirement for the process: “Our plant operations staff also has to look after other plants and lift stations,” Baker said. “Ease of operation following a training period was a key requirement.”
As with any new technology, some training and a ramp-up period is required. However, while the system requires monitoring by plant staff, the process itself is fully automated and requires minimal involvement or oversight.
A Storage Solution
The complete fixed-price solution included turn-key design, build, and installation of all processing equipment, utilities, electrical and PLC controls to meet the township’s standards. The system was easy to integrate with third-party dewatering for a compact, easy-to-maintain biosolids management solution.
The processing capacity of the system is 5 cu meters (or 5.5 wet tons) of biosolids per hour. The process has significantly reduced the space needed for storage by taking the solids concentration of biosolids from roughly 3% to 15%. “In our experience, it’s much easier to handle and store than a dewatered or dry product,” Furlong said.