Get the Scoop on Low-Temperature Thermal Hydrolysis

A Saskatchewan treatment facility makes big strides in biosolids quality with thermal hydrolysis process.
Get the Scoop on Low-Temperature Thermal Hydrolysis
Cliff Dyck, left, wastewater foreman, and Eric Anderson, operator, on berm surrounding the covered biofertilizer storage lagoon.

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Sometimes clean-water plants don’t care to be the first in their area to install a new technology. That’s not the case in North Battleford, Saskatchewan, where a new low-temperature thermal hydrolysis process is converting biosolids to nutrient-rich fertilizer.

Developed and marketed by Lystek International, the new process has enabled North Battleford to stop landfilling biosolids. Cliff Dyck, wastewater foreman, couldn’t be happier:

“Would I do it all over again? Yes. There’s no question.”

The Lystek system uses low-pressure steam, alkali addition, and high-speed shearing in a closed reactor. The end product remains fully pumpable with conventional liquid handling and application equipment. Dyck reports that the process fits into a small footprint and uses conventional on-hand equipment. Operators started it up in December 2014, and the fertilizer end product is being applied to city-owned agricultural land.

For its leadership in bringing new biosolids technology to western Canada, the city won a 2015 Environmental Award from the Canadian Association of Municipal Administrators in the category for populations 20,000 or less. The award recognizes commitment to environmentally sustainable governance, protecting the environment and combating climate change.  

Sophisticated process

The North Battleford Wastewater Treatment Plant is rated as a Level 4 (complex) plant, even though it treats a modest average flow of about 1.5 mgd from a population of 14,000. The city, 1 1/2 hours northwest of Saskatoon, is an agricultural and oil production area.

The headworks consist of a Hycor 6 mm screen (Parkson Corp.) and a Hycor screw press to remove moisture from rags. A Eutek stacked-tray vortex system (Hydro International) removes grit before the flow travels to rectangular bioreactors with fine-bubble diffusers (Sanitaire - a Xylem Brand). The aerobic-anoxic process accomplishes nitrogen and phosphorus removal as well as COD reduction.

After final clarification in two Dorr-Oliver circular basins (Ovivo USA), a low-pressure, high-intensity UV system (TrojanUV) disinfects the effluent. A local power plant treats the water further, then uses it as boiler make-up water. In turn, the power plant sends its wastewater back to the treatment plant — a closed-loop recycling system of sorts. An expanded equalization tank to handle heavy summer rains was completed in 2015.

Better biosolids

For years, North Battleford thickened its biosolids, dewatered with polymer and centrifuges, and trucked the cake to the local landfill. The process was costly, created odors, and wasted a valuable resource, according to city officials.

The Provincial Water Security Agency didn’t like the practice, either, and ordered the city to implement a more environmentally friendly approach by Nov. 1, 2015. The city issued a request for proposals for a process that would be cost-effective and allow beneficial reuse of the biosolids, Dyck says.

City leaders selected the Lystek system, developed at the University of Waterloo, Ontario, based on a design-build proposal including commissioning, permitting and initial operational assistance. The proposal also created a cost-sharing partnership with the city. Lystek manages sales of the final fertilizer product and shares revenues.

“Our engineering consultant came up with several options, but Lystek was the lowest cost by far,” says Dyck. He especially likes the way the system fits neatly into existing buildings: “We have a small footprint here. With the Lystek process, we could use all of our existing equipment. The reactor, boiler, and chemical feed and storage tanks all fit within our building.

“It’s also easy to maintain. Lystek gave us three weeks of training, and our guys caught on real fast. It’s automated but not high-tech. The boiler is so small you don’t need an engineering certificate to operate it. Those were big-time cost savings.”

Applying the heat

Except for the final product, much of the city’s biosolids system remains the same. Waste solids are thickened to 2 to 3 percent in an existing drum thickener (Alfa Laval Ashbrook Simon-Hartley) and dewatered to 14 to 15 percent in one of two centrifuges (Alfa Laval Ashbrook Simon-Hartley). A cationic water-soluble polymer is added before the thickener and centrifuge.

The same augers that were used to transport the cake to the trucks now deliver the material to a Lystek holding tank, and then into the reactor. There it is heated with low-pressure steam from an independent boiler to 70 to 75 degrees Celsius (158 to 167 degrees Fahrenheit), mixed with alkali to raise the pH to 9.5 to 10.0, and is exposed to high-shear mixing for up to 45 minutes. The process breaks down cell walls and hydrolyzes complex molecules into simpler compounds.

“The biofertilizer product stabilizes very fast,” reports Dyck. “After 45 to 60 minutes, we pump the product out to our storage lagoon, which is lined and covered with plastic to keep out contaminants. The material doesn’t stratify. It stays mixed. We withdrew the first batch of 2,900 cubic meters (765,000 gallons) after a year, and it looked good.”

Closed system

The material is pathogen free and meets Canadian Food Inspection Agency standards for Class A biosolids. It has a moisture content of about 85 percent.

The first land application of the product was on city-owned cropland near the treatment plant leased to a farmer. “We just made the first subsurface injection last October,” says Dyck. The revenue will help recover some of the operational costs. “Lystek is managing that,” says Dyck. “They have an agronomist on staff who handles contact with the farmers.”

The final product has an earthy, ammonia smell that is not objectionable — a big improvement over the odor issues that occurred at the landfill. “Everything is sealed up,” says Dyck. “We have a vacuum pump in the building that draws air off the process and discharges it at the roofline. When the product is injected properly in the field, there should be no problems.”

Dyck, who’s been with the city for 30 years and holds a Class 4 operator’s license, has a staff of Nathan Martell, Paul Kryzanowski, Dan Suberlak and Eric Anderson. They rotate on two-week shifts, alternating between the laboratory, maintenance and the dewatering building. In addition, the team shares Anand George, instrument technician, and Don Bush, maintenance mechanic, with the water treatment plant.

Lessons learned

After just over 12 months of operating the Lystek system, Dyck has two suggested improvements for his operation and those at future sites. “The chemical tank could be sized so that a plant could take a full tanker load of chemicals and realize the cost savings,” he says. “We did not have enough space in our building for a larger tank.”

The second suggestion also involves space: “We have limited space to perform maintenance on the equipment on top of the tanks. We are designing a stairs-and-catwalk system so that we can safely perform maintenance on the equipment.”

Those issues aside, it’s a process that has put North Battleford on the map as a biosolids leader in western Canada.


Lystek elsewhere

While the North Battleford installation is the first Lystek process in western Canada, the process operates in several places in Ontario, and a new regional processing facility is under construction at the Fairfield-Suisun Sewer District in California.

According to Kevin Litwiller, company spokesman, the process operates in Guelph, the Town of St. Marys, Third High Farms, and the Township of Centre Wellington in Ontario, and at the company’s own Organic Materials Recovery Centre in Southgate, Ontario.

Southgate is a regional facility serving multiple municipalities and can process up to 165,000 U.S. tons of material per year. In addition to producing fertilizer, Lystek says the process can also enhance biogas production when the end product is returned to the digester. The end product can also serve as a carbon source for biological nutrient removal systems.



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