Tri-Cities Airport Puts Worms to Work to Treat Deicing Wastewater

The early bird gets the worm and don’t open a can of worms are familiar phrases. Well, here’s a new one for you: The worm ate my glycol.

It applies at Tri-Cities Airport (PSC) in Pasco, WA. In a unique twist, the airport is partnering with a wastewater treatment company to conduct an eco-friendly pilot program that uses worms to treat deicing wastewater from its airfield. The innovative system from BioFiltro removes harmful substances like ethylene glycol and propylene glycol so wastewater can safely be discharged into the city’s system.

As the third-largest commercial airport in Washington state, PSC has been experiencing increased airline activity, making it more critical than ever to address a variety of environmental issues. Managing wastewater from aircraft deicing operations during winters is one of the most pressing on its list.

A Needed Change

Buck Taft, director at PSC, explains that the airport’s previous wastewater management system collected wastewater from its two deicing pads in a 30,000-gallon storage tank. Once the tank filled to a specified level, fluid was discharged into the Pasco Wastewater Treatment Facility for free—an arrangement made before PSC’s significant increase in airline activity. When the associated increase of deicing wastewater containing high levels of biological oxygen demand (BOD) started to overload the municipal system, city leaders asked the airport to make a change.

Taft learned about BioFiltro, a wastewater treatment company based in Davis, CA, from the economic development director at The Port Authority of Pasco, which manages both the Port of Pasco and PSC.

BioFiltro offers a patented nature-based process for wastewater treatment. Its BIDA (Biodynamic Aerobic) system relies on a filtration method powered by composting worms, which help treat wastewater by consuming organic matter and maintaining aerobic conditions.

After learning more about the company’s technology, Taft quickly saw potential for collaboration. In April 2024, the company and airport launched a pilot program that was initially set to last six months but was extended to one year due to its promising results.

How Does It Work?

Although PSC is the first airport to trial BioFiltro’s worm-powered system, the company is already established in the food/beverage and livestock industries. Patrick Beckett, the vice president of quality and research/development for BioFiltro, cites wineries as one example of a sector where the company has a proven track record. Wineries, he explains, produce wastewater that’s highly concentrated in organic waste, with high BOD levels. They also face increasing regulatory action and don’t find it cost-effective to devote a great deal of land to dispose of wastewater—both issues airports also face.

Beckett reports that BioFiltro removes 90 to 99% of the BOD from wastewater at wineries—reducing it from tens of thousands of milligrams per liter (mg/L) to just tens. In comparison, PSC’s deicing wastewater has BOD in the 30,000 mg/L range.

The pilot program at PSC uses an onsite mobile treatment unit housed in a 20 -by 8-foot shipping container. The BIDA system inside includes a vermifilter, which is a woodchip filter inoculated with up to a few million composting worms (vermi is Latin for worm). BioFiltro’s rule of thumb is to use thousands of worms per square meter or hundreds per square foot. The worms are sourced from the company’s existing systems—in this case, a treatment system at a winery also in Washington.

Under the woodchip filter layer is a mesh that prevents the chips from falling through, and a drainage pallet that allows water to drain to the bottom and helps create a small air chamber at the bottom of the filter. Standard irrigation equipment is used to pump wastewater from the storage tank and apply it to the surface of the filter. After water hits the surface, gravity causes it to percolate through the filter and drain out the bottom. From there, it is pumped into a storage tank where it awaits discharge into the city system. The entire process takes about four hours. As wastewater flows through the filter, organic matter is broken down. The result is cleaner water with significantly lower BOD levels.

The worms play two prominent roles in this process. First, as they burrow throughout the filter, they eat and help maintain aerobic conditions by opening up channels and preventing the accumulation of solids. Secondly, the worms ingest solids and microbes as they burrow. As a result, the system does not produce a lot of sludge or biosolids. Instead, it produces worm poop or vermicompost, a premium quality bio-fertilizer and soil amendment. If inclined, PSC could use the natural byproduct for landscaping, in a circular upcycling of its waste.

Green Advantages

Another eco-friendly benefit of the BIDA system is low energy consumption. “Typical aerobic treatment systems that pump air or oxygen into water or those that use a pressurized system to push water through a membrane can consume a lot of energy,” Beckett says. “Most of our energy consumption comes from relatively low horsepower pumps because the worms are assisting in that aeration process.”

The system also has no to low chemical inputs, although some applications require a base, like potassium hydroxide, to adjust the pH level. The wastewater at PSC was supplemented with nitrogen and phosphorus to make it more nutritionally balanced for the worms.

Another upside is simplicity. Although some training is required, Beckett notes that the operational burden is relatively low compared to most traditional wastewater technologies. Generally, that includes basic preventive maintenance and monitoring the pipes and pumps. The systems have telemetry and control features that monitor the water level in the tank, the status of pumps, and the water chemistry before and after treatments—all from a remote computer or cellphone.

Part of a Larger Project

The BIDA wastewater treatment system is a small component of a $2.5 million deicing pad expansion being designed by Mead & Hunt. Ryan Bergstrom, project manager with the firm, has been collaborating with BioFiltro to get the industrial discharge permitting approved with the city of Pasco.

In February, the project team was working through the FAA-required environmental process for the overall initiative. Once approved, the project is slated for design in 2025 and construction to begin in 2026.

The project will expand the current footprint of PSC’s deicing pads to accommodate the growing number and size of aircraft at the airport, including a shift from 70-seat regional jets to 150-seat mainline aircraft. The current footprint doesn’t accommodate the simultaneous deicing of two mainline aircraft.

The expansion will include a permanent home for the now-mobile vermifilter, and tie it into the current trench drains and other deicing infrastructure. “We don’t need to reinvent the wheel,” Bergstrom remarks. “We want to build upon what’s already there and repurpose and reconfigure the existing pavements and infrastructure as much as we can.”

For other airport operators exploring the idea of adding a vermifilter, Beckett advises assessing their existing footprint of land, where the infrastructure can be located and what collection infrastructure is already in place. “It’s always useful to have a reasonable idea of the flow profile. Not just what your annual flow volume is, but how it varies in shorter time scales,” he adds. “If anyone is interested in working with us, we can certainly go in and collect that data for them if they don’t have it.”

Bergstrom offers a friendly reminder about the competitive bid process when using federal funding: “The FAA has some pretty strict rules on sole source and proprietary products. The BioFiltro BIDA system is a proprietary system, and there are likely components of it that would be ineligible for FAA funding. So, if airports want to implement this, it’s likely they’ll have to pay for a portion of it with their own money.” Other components for the system, such as general piping and concrete structures, would likely be eligible.

Metrics of Success

The effectiveness of PSC’s alternative treatment system will be judged on two factors. No. 1 is reduction in BOD levels. “The [city] wastewater treatment plant has told the airport that if they can get the BOD level down to between 2,000 and 4,000, they can accept it,” Bergstrom explains. BioFiltro’s system has already demonstrated its ability to reduce BOD levels from around 33,000 mg/L to the target range of 2,000 to 4,000 mg/L, qualifying it for safe discharge.

The worms themselves are the other key indicator of success or failure. Beckett explains that a good worm population is essential for optimal benefits, and BioFiltro has established a very healthy worm population in the pilot system at PSC, which gives him confidence that everything is working well. “The worms are kind of like a canary in the coal mine,” he relates. “You can always know how healthy a filter is by the worm population. They’re doing well, so that means we should be able to keep it aerobic, get good performance and then also produce some really high-quality vermicompost when it comes time to replace the filter media.”

According to Taft, the airport has been paying about $5,600 per month for the treatment system during its test program, but he expects ongoing costs to decrease once the full-scale system is implemented and running smoothly. “This has proven to be a really great option for us,” he reports. “It allows us to continue to operate and discharge with minimal cost, because the cost of this system compared to the cost of trucking or recycling this stuff is not even close.”

A mobile unit houses the treatment trial. An upcoming expansion of the deicing pads will include a more permanent home for the worms.

Wider Potential

As the pilot program at PSC nears conclusion this March, Taft sees a more sustainable wastewater treatment process emerging not only for his airport, but also the industry at large. “If it works here, I believe it will work anywhere,” he says. “It’s very scalable, so I’m very optimistic. I think this has potential to really help airports that are struggling with this discharge, especially airports in or around residential areas,” where a smelly aerated pond that attracts wildlife is less-than-ideal.

Bergstrom sees the system as a viable option for airports throughout the U.S. that rely on deicing to keep operations flowing in the winter months. “It feels like it’s a good solution to a problem that a number of airports across the country—particularly in the snow regions—are experiencing and trying to deal with,” he says. “It sure is looking promising that this would be another tool for airports to consider using if local jurisdictions are able to support it as well.”

A BIDA system could be a great fit for any airport that generates a large volume of impacted stormwater but lacks the infrastructure necessary to support glycol recycling, Beckett adds. “That stormwater is often treated—at relatively high cost—at local public treatment facilities. I think that’s a perfect space for our technology.”

BioFiltro’s technology also could help airports meet increasingly stringent environmental regulations. “I’m excited, because this could really be transformative for airports throughout the country, especially as cities inevitably start clamping down on the amount of BODs they want to accept into their systems,” Taft says. “This greatly reduces that BOD in an environmentally friendly way, and for the most part, in a fairly cost-effective way.”