Driven by odor and dust, air quality is an ongoing concern in solid waste operations.
“Odor problems from waste disposal operations have been concerning operators and local inhabitants alike for decades,” notes Rick O’Sadnick, senior scientist at Benzaco Scientific. An increasing number of regulations for odor control are being written into operating permits.
“Since odor levels or degrees of noxiousness are not easily quantified, these regulations are typically based on the number of complaints,” he adds. “If there are too many complaints, a regulatory body will fine the offending facility and, in some cases, even shut it down.”
In an effort to make these regulations more scientifically based, odor-panel testing, as well as field olfactometer monitoring, has become popular, says O’Sadnick, adding that tools such as the Nasal Ranger are designed to identify the efficacy and effectiveness of an odor management program.
In providing training to regulators on odors, Mike Lannan, president of Tech Environmental, notes that there are four important factors which they must understand: frequency, intensity, duration, and offensiveness.
“There is no such thing as odor-free. You have to consider those factors when making an assessment,” adds Lannan, whose company provides services—including dispersion modeling—in air quality, odor control, fugitive dust, and health and safety compliance.
Jesse Levin, NCM Odor Control president, indicates that air quality and dust problems in the waste industry are diagnosed in a few different ways.
“Generally speaking, air quality and dust issues are not brought up until site workers start complaining or the company has an environmental manager and managing team that is truly thinking about the quality of the environment in which their workers operate,” notes Levin.
Laura Haupert, OMI Industries’ director of research and development, adds that odor issues are usually diagnosed after a solid waste facility neighbor complains about an odor problem.
“A group will usually survey the area to determine the location of the odor issue. In a landfill, the working face is often the source of the most offending odors. Other odorous locations at a landfill include new incoming waste, landfill gas from decomposing organic material, and leachate ponds.”
To technically diagnose the problem, NCM Odor Control’s air modeling division offers consulting services to evaluate the impact of dust and how it may or may not affect the air quality at a specific site through determining the contribution of dust from one or more pieces of equipment or locations on a specific site.
NCM Odor Control maintains a suite of EPA-approved models accounting for local wind and topography to determine the movement of dust.
“The models provide a causal link between dust emissions and the concentration of dust in the vicinity of a single source or multiple sources,” says Levin. “The models contain state-of-the-art dispersion algorithms coupled with powerful graphics to provide compelling, scientifically defensible data to the movement and density of dust. We use these same models to design and optimize the installation of dust control systems.”
The methods of diagnosing air quality and dust problems vary but are typically rooted in the permitting process, points out Nick Waechter, BossTek dust and odor management specialist, adding that dust and odor are major air quality concerns, so facilities such as plants and landfills are required to obtain a permit.
“It is up to each facility to determine how they are going to meet the requirements of that permit; however, it is often not until complaints arise that dust and odor control solutions are sought out and implemented,” adds Waechter. “If a facility starts getting complaints, health and safety professionals come onsite to determine the extent of the issue.”
In addressing these issues, a department of environmental quality may require air quality monitoring stations to be put in place as well as provide suggestions on how to address the problem at hand, notes Waechter.
Transfer stations have more odor potential as solid waste from smaller packer trucks is consolidated into larger loads to be transported to a disposal site, creating a higher volume of material.
“The key for most transfer stations is you want to use the first in, first out approach and make sure that things do not tip in the transfer station too long,” says Lannan. “Depending on the proximity of the nearest neighbor, a lot of the transfer stations have a minimal overnight policy, meaning they have between 0 and 10% of the total throughput of the day left at the end of each day. Some facilities require it all to be off the floor and into a truck or rail car by the end of the day because there are neighbors nearby.”
Minimizing odor is site dependent, with best management practices based on a facility’s size, says Lannan.
“Some are smaller than others relative to their throughput,” he says. “As an air quality engineer, I worry a bit about carbon monoxide and other things building up from the trucks and other off-road equipment such as the excavators, the front-end loaders running inside. You have to have some ventilation from the building and in the summertime, you have to have some heat relief. There will be emissions from the building.”
Masking agents are designed to overpower bad odors with a strong fragrance, says O’Sadnick.
“Many times, the result is a fragrant version of the malodor, but always at a higher overall odor intensity,” he adds. “Often, so much fragrance is needed that the treatment costs grow higher and the fragrance itself becomes a nuisance. Ultimately the masking treatment fails since the fragrance inevitably separates from the odor, causing two intensely distinct odors.”
For operations needing to quickly identify a solution, a complex odor counteractant is often the solution, says O’Sadnick.
“By correctly applying vapor phase technology, Benzaco Scientific is able to take advantage of certain essential oils that solubilize—absorb—malodorous molecules, thus reducing the opportunity for these molecules to reach the sensory cells.
“Adsorption—a surface phenomenon where molecules attach with a temporary electrical bond which in effect changes the shape of the molecules reaching odor receptors—is also used,” he adds.
Many malodors have a dualistic or pluralistic effect, says O’Sadnick, adding that they are only malodorous when present at certain concentrations but, when reduced in level, take on an acceptable odor.
“A complex odor counteractant is akin to noise-canceling headphones for the nose,” he contends. “Sewage sludge plus cherry masking agent equals cherry flavored sewage sludge. Sewage sludge plus Benzaco’s Odor-Armor equals no odor.”
There are two odor control choices: to treat the odor as it comes out or to treat it in a recirculating manner within the building, Lannan points out.
“The odor control system is not connected to the exhaust, but it’s circulating in the building,” he says. “The exhaust is coming out in a continuous stirred-tank reactor type environment where it’s a steady state because air is going in and coming out, but you’re treating it within the volume.”
With odor potential for drifting out as doors are opened and closed, the key in a transfer station is to minimize the dust, Lannan points out.
“Most cities and states typically allow a 50% reduction of dust for a misting system as a good rule of thumb,” says Lannan. “You usually get more than that, especially since you get a lot of the heavier dust. The odor will adhere to the dust particles and take the odor outside. Having a mist system full of dust actually does help odor migration from the transfer station.”
Disposal sites are a third opportunity for dust and odor to manifest in solid waste operations.
Tech Environmental is working at one facility which has had issues with visible smoke leading to odor concerns. Lannan says the problem emanates from ductwork from the mass burn before it is emitted.
“Odor can be minimized after combustion at a mass-burn facility by making sure you have very tight ductwork and everything is under a negative pressure,” he says.
Misting and counteractives can be used at a mass burn facility, although there are typically not a lot of odor control standalone technologies in such situations, says Lannan. He says his company spends significant time helping solid waste operations balance the air flow “because obviously there’s a large demand for oxygen in the mass burner and if you can pull that air from areas where you have some of the waste, that can help minimize the potential for release as trucks go in and out.”
One of the best ways to deal with odor at a landfill is to “mix the waste and to understand what’s coming in,” says Lannan.
“The odor potential is highly related to the type of material coming in,” he points out. “You want to make sure you mix the material together and understand how much odor potential you have from different sources and how all of those—such as paper, fiber, waste from wastewater treatment plants—have to be managed together. Landfills are very large and have a lot of exposed surface area, so you can’t always minimize it to the point where you don’t have to worry about odor emission releases.”
Landfills often need gas collection systems, notes Lannan, adding that “throughout the country, gas collection systems are only required for certain size landfills or landfills that have the potential for higher levels of hazardous waste.
“In the Northeast or in landfills in cities throughout the country or densely-populated areas, gas collection systems are installed not just for large facilities per the EPA requirements, but also for odor control.”
Factors to consider in odor control include capture, ventilation, control, and dispersion, says Lannan.
“Unfortunately, a landfill has very little dispersion potential from the surface,” he says. “However, once you capture it, you do have some ability to adjust dispersion. To start off, you want to make sure you cap it or capture it, so you need to put down either a temporary tarp or cap—something that will prevent infiltration so you can balance the landfill. Depending on the gas quality, you might need to pre-treat it before you then destroy it thermally.”
There are other ways to control odors at a landfill, such as those associated with wastewater raw sludge and digestive sludge, both of which have two different odor potentials, Lannan says.
Mitigating odors at the landfill also encompasses “putting the onus of responsibility on the supplier of that material to not only provide it in a fresh form at their site, but to confirm it in transit on the rail car or in the truck that it will arrive in a manner that won’t be odorous, to begin with,” says Lannan.
Regarding dust, there are two types, Lannan points out: fugitive and air quality or health dust.
“The public can confuse those,” he adds. “Dust that you can see and is noisome is very different than dust that comes from diesel emissions from the trucks, front-end loaders, and excavators and is very fine.
“If you can minimize the fugitive dust, people don’t see it and they won’t have the impression that there is this health concern,” says Lannan. “When people start talking about dust, they’ll start talking about air quality but there really is not that much diesel emissions that are going to be a health concern.”
Key to handling fugitive dust is doing misting within a building and also keeping the traffic speed down, says Lannan, adding that “most dust issues come from the trucks moving on areas that are dusty, so it’s about maintenance.”
Maintenance encompasses spraying down driveways, keeping them wet, and cleaning them daily with street sweepers, says Lannan. An extra step, Lannan adds, might entail a wheel wash on the trucks.
“In a small facility, the potential for dust is very small because if you only have a few trucks an hour, it’s very minimal,” says Lannan. “If you have a facility that has many trucks an hour, then you want to have a wash station to wash off the trucks before they leave the site. That helps with both dust and odor because there is odor attached to the dust.”
Facilities also can have particulate filters, says Lannan.
Transfer stations in the state of New York require particulate control for nuisance dust, says Lannan.
“This is one of those situations where you can have it as a recirculating system such as a baghouse or cartridge-style within the building or you could apply something to the exhaust so that only when the emissions actually leave the building is it a problem,” says Lannan.
To ascertain whether dust is an air quality issue versus a nuisance issue, Tech Environmental conducts assessments.
“Do we need to knock down the dust within a building for the workers? Is it OK for the dust to be at a certain level with misting in the building, or do we need to treat it before exhaust?” notes Lannan.
Sometimes a situation will require only a temporary approach geared toward temporary problems, says Waechter.
“Demolition companies, for example, might not want to install a permanent remediation system at a site on which they will only be working for a couple months,” adds Waechter. “In this case, it would make sense to use a solution that is mobile and can be moved from site to site.”
In the past, water trucks or fire hoses have been used to fight fugitive dust, Waechter points out.
“The problem with these options is that they require repeat application and therefore have significantly higher labor costs associated with their use,” adds Waechter. “They also tend to use far more water, raising costs and introducing the possibility of over-saturation and runoff. Further, these techniques are only successful at ground-level suppression. They have virtually no effect on airborne dust particles.”
Atomized misting cannons have become the industry standard for dust control, and their ability to be easily transported—combined with their ease of use—makes them an ideal solution for temporary air quality control, says Waechter.
For companies whose need for a solution only spans a few weeks or months, the cannons can be rented, providing premium dust and odor control solutions without the capital equipment cost of taking ownership, Waechter adds.
“This option also allows contractors to select the models best suited to each project size and scope without accruing any maintenance responsibilities,” says Waechter.
Jody Smith, sales manager for Buffalo Turbine, points out that after it is determined from within a facility or from those subject to odors that there is an issue, one temporary solution is to rent equipment to be placed between the source of the odor and the source of the complaints with equipment made to broadcast the agents needed to be effective in large-scale treatments.
Some temporary solutions NCM Odor Control presents to its clients start with looking at the equipment a site or end user may already own “so we can utilize that versus coming in and recommending costly solutions,” says Levin. “In the end, the client may need the costly solutions, but to start we try to utilize what might already be in place.”
Some solutions may include water trucks and rental equipment in the form of a dust control system that NCM manufactures, such as a fan unit.
OMI’s temporary solution would be to place an odor control fan at the site of the odor, such as a unit that sprays Ecosorb liquid onto the moving working face of a landfill, says Haupert.
For a permanent solution, facilities strategically place equipment in problem areas, monitoring the situation “and use only the machines in the areas that are problems that day or week,” adds Smith.
Buffalo Turbine machines require fuel or an electric source to operate, says Smith.
“The diesel machine runs for about 11 hours without refueling,” he adds. “The electric machines would be subject to the source of power, such as grid power or a generator.”
Permanent solutions are necessary when the need for dust and odor control is ongoing, points out Waechter, explaining that the main types of dust control include collection, containment, and suppression.
Collection involves the use of bag houses or central collectors which collect the dust and filter it out using giant bags or other receptacles. “This can be a valid solution where dust amounts are relatively small and can be recycled,” says Waechter. “However, the initial cost of ductwork and other components can be high and ongoing maintenance is required to empty receptacles and maintain the equipment.”
Containment involves addressing the issue where it originates. Solutions could be as simple as using a cover such as a tarp or other barrier or spraying with a sealant that contains the bulk material until it is disturbed, says Waechter.
Another common but more stable method of containment would be to build a structure around the stockpile or source of dust, Waechter adds.
Suppression is the third and most common solution, says Waechter.
“Historically, suppression included hand spraying using sprinklers, water trucks, or fire hoses,” adds Waechter. “Hand spraying is often unproductive because it creates water droplets far too large to efficiently trap airborne particles, limiting its effectiveness to surface wetting.
“Hoses and sprinkler nozzles can produce droplets that are 3,000 microns or larger in size. The optimum size for airborne dust management is between 50 to 200 microns so that the droplets and solid particles have the greatest chance of colliding.”
Atomized misting cannons are specifically designed for this purpose, with specialized nozzles that create optimized droplets in a spray pattern to deliver the right balance of coverage area and hang time, says Waechter.
“Cannons are also able to deliver dust-trapping mist that requires significantly less water than hand spraying, reducing the chance of oversaturating the treated material and affecting its integrity,” adds Waechter.
Frequently, a combination of the three types is used.
“Facilities often use containment by building a structure around the source of dust while also adding atomized misters at the transfer points and locations where trucks or conveyor belts are being unloaded,” says Waechter.
Permanent solutions for odor control also vary depending on the size of the facility and source of the odor, notes Waechter.
“One method used is the implementation of perimeter misting systems, which involves water lines surrounding the site delivering a mist of water and odor treatment chemical,” says Waechter.
It’s one of the more expensive solutions, Waechter adds, which also holds limitations in terms of growth as a facility expands beyond existing boundaries.
Chemical injection systems—often used in wastewater treatment—are another option. That involves injecting chemicals directly into the process water line. Mobile misting cannons distribute air treatment agents using water as the vehicle.
“The unique air atomizing nozzle creates droplets as small as 15 microns in diameter, the optimum size to chase and attach to odor vapor, eliminating odor by changing its molecular structure rather than just masking it,” adds Waechter.
NCM’s permanent solutions come in the form of high-pressure atomizing systems, says Levin.
One of the systems NCM offers for outdoor projects or sites where there is not a concern about the material getting saturated is a fan misting system.
The unit is available in many options
—including single fan and dual fan—with different-sized water tanks offered based on end users’ needs and also come with gas or diesel generator power.
In some cases where the goal is to treat for dust onsite but ensure workers do not get soaked and the material is not oversaturated, NCM Odor and Dust Control designs a high-pressure atomizing system that focuses on the source of the dust, such as equipment.
The company also has the ability to change out the type of nozzles from atomizing to more of a direct flow for large areas where saturation is not a concern, giving waste operations multiple treatment options off of one unit, says Levin.
A permanent solution would be implementing a vapor phase unit designed and installed by OMI which has perforated ducting to go around the perimeter of the landfill and/or a leachate pond, notes Haupert, adding that the vapor phase unit would dispense Ecosorb on an ongoing basis or when an odor issue was detected.
The frequency of treatment often depends on the type of application, says Waechter.
“For example, with composting and waste treatment, a large volume of odor molecules escapes while processing—therefore, constant or regular treatment will be significantly more important than it might be in other settings,” adds Waechter.
In the case of landfills, odor control is needed constantly, says Haupert.
“In solid waste, new odors sources are brought to a landfill each day,” she adds. “Also, as the working face is moved around, new odors are produced and decomposing organic waste produces new odors regularly that must be controlled.”
If a complaint originates from the community against the site, it often takes longer to satisfy it, Levin says, adding, “There are always a few in the community you won’t satisfy. In those cases, we work with a client to determine what is a valid or invalid complaint.
“Distinguishing between those two helps our communication with the regulatory agency in showing that some people or businesses are complaining to complain versus what we identified as a legitimate issue.”
With the use of the correct agent using Buffalo Turbine equipment, the time frame to turn a complaint into satisfaction can be a same-day process with temporary equipment, says Smith.
“Once some data can be established as to the highest priority problem area, permanent equipment can be put into place,” he adds.
The typical time frame depends on the needs of the site, says Haupert.
At sites with serious issues, OMI’s rental units can be shipped out the same day or next day and installed quickly to begin to fix the problem immediately, she adds.
In any operation, time is a key resource, points out Waechter.
“Failure to meet air quality regulations can bring even large operations to a complete stop. When facilities receive complaints, it is imperative to find an effective solution as quickly as possible to prevent downtime or even worse: a lawsuit. Thus, a supplier’s response time is critical,” says Waechter.
One effective way of approaching dust control starts with the design phase of a new project, points out Levin, adding that it provides the opportunity to directly work with the general contractor.
A recent project was for a dust control project with Waste Management in northern California, says Levin.
“Waste Management operators gave input into what they thought would work with the equipment that was being installed and their operational plan,” adds Levin. “In the end, we designed a custom multi-zone dust control system tied to the site’s operating equipment turning on and off the dust control misting nozzles as the equipment operates throughout the day.”
The site also has remote controls, allowing site operators to turn on or off a specific area to treat for dust as needed throughout the working day, says Levin.
In other projects, a site is already operational, such as one in which NCM Odor and Dust Control were involved in for a northern Florida Republic Services.
“The site installed these large fans that were sold to the site as a dust control solution when in reality all the fans do is move the air around and move the dust particulate to dead spaces within the site,” notes Levin.
NCM Odor and Dust Control custom-designed a high-pressure atomizing dust control system that focuses on treating the dust at the source and not letting it get airborne, says Levin.
Technology in this industry is always evolving and ongoing research and development continues to broaden the horizons of dust and odor control, notes Waechter.
“For example, atomized mist technology can now be obtained in stationary rings and spray bars for point-source suppression,” he says, adding that tower mounts are also available to extend coverage areas even further.
“Quick-release manifolds and other innovations have made service quicker and easier than ever before, and custom rings and other shapes can be built to customer specifications,” says Waechter.
The most recent advancements have come in the design and development of a family of trailer-mounted systems that can be specified with their own generator and water tank to serve remote sites, Waechter adds.
“With a range of equipment sizes to serve a broad array of applications, atomized mist technology is bringing highly effective dust and odor control to a wider variety of industries and operating conditions than ever before,” says Waechter.