Attacking odor at the source

When it comes to waste management, odors often can be an operation’s greatest enemy. As the need for residential and commercial development grows, facilities such as transfer stations, waste- water treatment plants and landfills are now in greater proximity to the general public, meaning odor suppression has become even more critical to being a good neighbor.

According to the Solid Waste Association of North America (SWANA), the production of unpleasant smells is a natural consequence of waste decomposition, primarily because of the breakdown of organic material by bacteria under aerobic and anaerobic conditions at landfills and other facilities.

This process releases a combination of gases, including methane, carbon dioxide and a variety of volatile organic compounds, which often are the main contributors to the notorious odors associated with landfills and other facilities, SWANA says.

An increase in complaints can wreak havoc on an operation’s bottom line, with hefty fines linked to improper odor management. To address these issues head-on, odor control systems can be implemented to contain and mitigate unpleasant smells, reducing community pushback and contributing to a cleaner and more pleasant environment.

Brad Ritter, CEO of Mist Works, an outdoor cooling and mist systems provider, says a few key methods typically are employed for odor suppression:

• Biofilters—These solutions often are used by wastewater treatment plants using microorganisms to biologically degrade, or “eat” away at, odor-causing contaminants.
• Granule solutions—These options employ a powder that encapsulates and eliminates odors at open waste piles or landfills, though effectiveness can diminish once a pile is disturbed.
• Vapor solutions—These options use a combination of vaporized chemicals and advanced delivery mechanisms to disperse odor-neutralizing agents, which can attach to odor molecules in the air.

Misting systems

Each method has its unique advantages, Ritter says, and the best choice depends on the application and environment. Often, a combination of methods is used to achieve optimal odor control.

Most common at larger facilities are misting solutions, which comprise a mist pump, a chemical dosing pump, a chemical tank, tubing, fittings and nozzles. According to Ritter, the dosing pump extracts the odor-control solution from the chemical tank and channels it to the mist pump, where the concentrated solution is mixed with water and propelled through a delivery system at pressures exceeding 800 pounds per square inch.

This delivery system includes high-pressure tubing and fittings that position the nozzles appropriately for optimal distribution. The odor control solution is atomized through the nozzles, effectively attaching to and neutralizing odors in the air.

The pump location is determined by where the client has water and power. Nozzles are best placed where odor is created and where it escapes, Ritter says. In an enclosed transfer station, nozzles are placed around doors and exhaust fans. Nozzles also can be placed over the active waste pile with fans to encapsulate odors at the source.

The quantity of nozzles varies, but systems usually incorporate in the range of 100-300 nozzles.

The right solution

The best odor suppression method largely depends on the type of application, with some facilities more suited for mist solutions than others, Ritter says.

At landfills, where limited water access can pose challenges for misting systems, a trailer-mounted system with a large water tank can be used.

Because of the resources needed to operate them, misting systems at landfills achieve the best results during operating hours, with granule solutions employed during off hours.

“They’ll use a type of … ground cover that we have, a powder, and they’ll go and [spread] this powder out, and that will seal the odor in so that people aren’t smelling it over the weekend while they’re not spraying,” Ritter says.

When operational, misting systems usually are placed at the bottom or top of the hill at a landfill, he adds. Odor is heavier than air, Ritter says, so it tends to build up and collect in certain areas.

To pinpoint the natural path of odor, operators will conduct smoke tests with a fogger to see how wind travels.

“You would think that being down in a hole and the wind coming through there and blowing up the hill, that the odor would just shoot a mile high up in the sky and be gone,” Ritter says. “And really, what it does is it goes up the hill, … crosses the hill and goes right back down the other side … to the bottom.”

In the early morning when humidity is high, odor builds up into what Ritter describes as a “big bubble.” When the sun rises and the breeze strengthens, the odor can move across neighborhoods or highways, leading to complaints.

At transfer stations, however, it’s more likely for a misting system to be used 24/7. Typically located closer to cities and towns, these facilities are equipped with water and power, so a permanent installation with automated timers is common.

Immediate results

Recently, Mist Works partnered with a municipal solid waste transfer station that needed more comprehensive odor management. When operations began, the facility was situated far enough away from the city so complaints were rare. As time passed, however, developers began buying the land nearby.

When residents began moving in, odor complaints became more frequent.

“Imagine going into your backyard to grill some burgers and the pungent odor of garbage penetrates your olfactory system. Eventually, you start to complain to the city,” Ritter says.

Facing fines of nearly $20,000 per day, the transfer station invested in a Mist Works odor suppression system. With the help of the indoor misting system, the facility’s odors were mitigated almost immediately, Ritter says.

“It’s almost like a bottle of Febreze [that you] spray on your couch cushion,” he says. “It eats it out right then [and there]. So, if the wind was blowing and you were a half mile away, it would take time for [the system to catch up], but as far as right there at the nozzle, it’s instantaneous.”

The author is associate editor of Waste Today and can be reached at hrischar@gie.net.