With safety as North Texas Municipal Water District’s number one priority, Bosstek’s odor and dust control equipment provides the safety and efficiencies required and is an integral part of their operations.
By Michael Kelley
To say that waste disposal has changed in the last two or three decades is an understatement. More municipalities across the U.S. are employing a system of waste transfer stations, which have made the collection infrastructure more economical and logistically efficient to better serve both urban and rural communities.
This system has several benefits. It effectively addresses the solid waste needs of communities, reduces vehicle emissions, allows meticulous waste management, and offers greater control over dust and odor for the benefit of the surrounding residents and employees. These are among the reasons why the North Texas Municipal Water District (NTMWD) chose to build a series of transfer stations to manage waste for the more than 930,000 people it serves.
In August 2017, NTMWD completed the construction of its newest transfer facility, the Lookout Drive Transfer Station. To mitigate dust and odor, NTMWD installed two atomized mist cannons. The success of the cannons led to the purchase and installation of two additional cannons at another of the organization’s existing transfer station facilities.
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How the NTMWD Solid Waste System Works
NTMWD provides solid waste disposal services to five cities (Allen, Frisco, McKinney, Plano, and Richardson), as well as Collin County and the surrounding area. Solid waste is picked up from residents and businesses and delivered to one of three transfer stations (two in Plano and one in Richardson). NTMWD transfer stations are enclosed areas where dust and odor can be contained and mitigated.
There, the waste is loaded onto larger NTMWD trucks and transported to the 121 Regional Disposal Facility in Melissa, TX. The landfill processes more than 1 million tons per year and the transfer stations are permitted to process up to 3,370 tons p/d of both MSW and C&D waste through its three locations:
• Lookout Drive Transfer Station (Richardson)
• Parkway Transfer Station (Plano)
• Custer Road Transfer Station (Plano)
This process saves money by ensuring smaller waste collection vehicles do not have to travel the additional distance to the landfill. Fewer trucks on the road reduce both traffic and vehicle emissions.
NTMWD Service and Sustainability
The newest facility, Lookout Drive Transfer Station, uses a standard system for weighing vehicles as they enter and leave the site. Refuse is deposited onto the 33,000 square foot “tipping floor” where front-end wheel loaders push the piles toward a 15-foot wide, 60-foot-long opening in the floor. Material drops down into the loadout tunnel where open top transfer trailers collect the debris. Located behind the loadout tunnel is a stationary tamper/crane with a claw attachment helping to ensure waste goes completely down the chute and then tightly packs the refuse in trailers. Once loaded, trailers are then covered and driven 26 miles to the 121 Regional Disposal Facility in Melissa, TX.
Neutralizing the Odor
The Lookout Drive Transfer Station is located near populated areas with homes, a golf course, parks, sports fields, etc. The comfort and safety of local communities are a priority for the organization, and retaining high air quality standards is at the heart of the transfer station operation.
Odor is the most prevalent and noticeable concern. Living near a waste disposal site should not mean nearby communities need to remain indoors just because the wind has changed. Volatile
organic compounds (VOC) common to MSW emit a wide variety of source smells such as ammonia and hydrogen sulfide. Unpleasant odor emissions would not only reduce the quality of life for nearby residents, but they can also have a direct impact on property values and resale.
NTMWD uses an odor neutralizer to manage odor emissions at their source. It is metered into the DustBoss® system and dispersed as a fine mist that’s effective and environmentally safe.
“It was our goal to proactively treat odor so surrounding communities wouldn’t even notice our operation,” said Mike Friesen, Assistant Deputy of Solid Waste for the North Texas Municipal Water District. “The same goes for dust. The physical building does a good job of containing the dust, but we wanted to get ahead of dust issues and create optimal working conditions inside the facility as well.”
DustBoss® cannons
Dropping Debris, Rising Dust Clouds
A major source of dust emissions occurs during the initial waste drop-off. As garbage trucks back in and the hydraulic lifts push or dump the material onto the tipping floor, a thick cloud of dust can be created, filling a portion of the building.
The sorting and pushing of material disrupts the waste and can cause dust to become airborne when pushed by the front-end wheel loaders. As the waste material is dropped and loaded into trailers, the turbulence from the impact and the vertical airflow through the tunnel below forces the particulates back up through the shaft and into the building.
The fine particulates can get into the air intakes of equipment, causing filters to clog prematurely. Excessive dust can even congeal engine grease, resulting in gears and bearings wearing and seizing. This can shorten equipment life and cause extra maintenance, which eventually results in expensive downtime.
Double Duty Dust Control
The first two DustBoss DB-30 Injektor™ units were mounted at the Lookout Transfer Station approximately 10 feet above the tipping floor so that they could get above the piles and cover more of the tipping floor area. The cannons are comprised of a rugged stainless-steel cylinder with a powerful 3 phase, 7.5 HP fan generating 8,000 CFM (226.50 CMM). Water is fed through an inline 30 mesh 595 micron filter system to remove impurities. The water is then mixed with a measured and consistent amount of neutralizer by a dosing pump before it reaches a misting ring with 30 nucleating nozzles. These specially designed nozzles fracture the pressurized water into millions of tiny droplets.
The microscopic size of the droplets allows the even and consistent distribution of the neutralizer so it can travel on ambient air currents with odor molecules. This is also an efficient delivery system for the water needed for airborne dust control. To become airborne, particulates need to be approximately 200 microns (µm) in size and can become invisible at ~100µm (fine sand dust). Particulate matter (PM) emissions of 10µm or smaller are highly regulated by OSHA and EPA. These emissions are small enough to bypass the body’s natural defenses and get deep into the lungs, potentially causing serious chronic lung diseases after extended exposure.
Standard hoses and sprinklers produce droplets 200µm to 1000µm in size, far too large to offer effective airborne dust control. The DustBoss delivers atomized droplets approximately 15µm to 200µm in size, which allows them to travel on air currents with the regulated dust and interact with individual particulates. Once the droplet and particulate collide, the combined mass causes both to fall to the ground.
Droplet size also pertains to the neutralizer that NTMWD employs, evenly distributing the chemical in a small enough medium to allow it to travel with the odor. The DB-30 Injektor is specifically designed with a metered dosing pump that precisely injects chemicals into the water stream before it enters the manifold to be delivered. The metering pump housing is constructed from chemical-resistant, fiber-reinforced thermoplastic, with ceramic ball valves. The pump head features PVC fittings and connections, and exposed fasteners are stainless steel for exceptional durability. The assembly can deliver a range of chemical volumes from a minimum of 0.003 GPH (.009 LPH) to a maximum of 2.5 GPH (9.5 LPH).
With a throw of 30 meters (100 feet), the unit’s 0-50º vertical adjustment and 70º oscillation range increase the coverage area to 6,100 square feet (566 square meters). Operators use a touch screen interface on the control box at the base of each elevated unit to set the volume of water, throw distance, vertical settings, and oscillation range. This offers exacting control for the constantly changing operational conditions and traffic volumes.
“The dynamic of creating a mist of dosed atomized droplets made this a highly effective method of double duty odor and dust control,” Friesen pointed out. “When the machine is on, we can see the dust get pulled from the air and dragged to the ground before it reaches air intakes or exhaust vents.”
Water Conservation
Texas can have long dry periods that result in excess water usage across the state. As a local water district, NTMWD is fully aware of the importance of water conservation and minimizing water usage wherever possible. The operators of NTMWD’s solid waste transfer stations are also very mindful of the workplace hazards of standing water and pooling within the facility. These concerns are addressed using atomized mist technology.
The mounted DB-30 Injecktor cannons are fed by a standard 1-inch hose attached to a booster pump, fed by a city water source with limited pressure. Old methods of dust control like hoses or sprinklers require being attached to hydrants that use approximately 500-1500 gpm (1893-5678 lpm) of water. The pressure delivered by the booster pump—rather than relying on high pressure from the hydrant—means the design uses only around 7 gpm (26 lpm). This greatly reduces the amount of pooling and standing water in the area.
Bi-Annual Maintenance
Workers at NTMWD only need to do maintenance on the DustBoss every six months to keep it in top condition. Although the main water line leading to the manifold has a filter system, microscopic impurities and minerals can still bypass the mesh and clog the nucleating nozzles. Moreover, the lines are checked and flushed if needed. Since the system runs all day, every day, maintenance staff also check the fan system and mounting.
The DustBoss® Quick Release Manifold is a standout feature that operators identified as a significant time saver. The stainless steel manifold has 30 nucleating nozzles that can experience buildup from minerals and impurities. The quick release bracket allows removal and replacement of the manifold in approximately five minutes, with no tools required. Replaced with a clean ring for minimal downtime, the removed manifold is then set in a descaling solution and put into storage for the next replacement. “With a simple maintenance schedule, we’ve experienced zero downtime in the six plus years we’ve been using the DustBoss system,” Friesen added. “We simply turn them on and forget them.”
Award Winning Safety
In 2022, SWANA gave its Safety Award for Biggest Safety Improvement to NTMWD’s Solid Waste System. The organization cites several factors that played a role in the award, and Friesen says the DustBoss units were one of the main factors in producing a safer workplace. “Improving visibility is key to keeping our employees and our customers safe,” Friesen added.
DustBoss By Design
“We are currently installing two DustBoss machines at our Custer Road Transfer Station, and our Parkway Transfer Station will have units installed during the facility expansion scheduled for next year. Going forward, any new transfer station will have a DustBoss as part of the original design,” Friesen said. “Safety is our number one priority, and this equipment provides the safety and operational efficiencies we require. The technology will be an integral part of our operations moving forward.”
Friesen concluded, “Our experience with the machines and BossTek service has been excellent.” | WA
Michael Kelley is President of BossTek, a global leader in dust and odor control solutions for the storage and handling of clinker, petcoke, coal, rock, and aggregate, as well as controlling air quality during port unloading, recycling and scrap processing, mining, earth moving, and demolition activities. The company’s DustBoss product line uses atomized mist technology propelled by powerful fans to capture fugitive particles over a wide area. For more information, call (309) 693-8600 or visit https://bosstek.com.