September/October 1995
A few scrap recycling companies are cleaning up contamination using bioremediation, a natural process that relies on microbes to break down some types of contaminants. What is it? How does it work? And how could it help you? Here are some answers.
By Kent Kiser
Kent Kiser is an associate editor of Scrap Processing and Recycling
If someone told you that bugs can be used to eat up contaminants in soil or groundwater, you might be tempted to call the person crazy and dismiss the idea as just another snake oil claim.
But wait! While the idea may sound improbable, even outlandish, it isn't. It describes in a nutshell the process of bioremediation, an environmental engineering technology whereby microbes--nicknamed bugs--are used to clean up some types of contaminants. The process is being used at a variety of sites, including scrap recycling facilities.
The U.S. EPA has called bioremediation "one attractive alternative to conventional methods of cleaning up hazardous waste," and the agency has gone so far as to develop "a strategic plan for its acceptance and use by the technical and regulatory communities."
Currently, there are reportedly several hundred sites in at least 36 states using bioremediation for federal--and state--regulated treatability studies, full-scale cleanups, and site-planning activities. "Bioremediation is being used more now because the technology has become more widely accepted by federal and state regulatory agencies and because there is ample documentation available to show its effectiveness," asserts Michael B. Place , department head of geosciences for Versar Inc. ( Lombard , Ill. ), an environmental risk management and consulting firm.
In other words, bugs represent a hot cleanup strategy at the moment, and they could be in your future.
Understanding the Process
Bioremediation is generally divided into two categories: intrinsic and engineered.
Intrinsic, or passive, bioremediation is the natural decay of organic matter--a process as old as life and happening all around, all the time. Basically, it is nature taking its course, without human intervention.
Engineered bioremediation is an enhanced, manipulated version of the intrinsic process. By controlling variables such as water, oxygen, and nutrients, it's possible to create an ideal operating environment for microbes and, thus, accelerate the degradation of target contaminants. Engineered bioremediation was first used to treat industrial contamination in the early 1970s but has only attracted serious interest in the scrap recycling industry in the past five years or so.
In basic terms, bioremediation is the breakdown of hazardous organic compounds through the use of microscopic bacteria and/or fungi that use the contaminant as a source of energy, or "food." Microbes accomplish their task by secreting enzymes that break the chemical bonds of the contaminant. When these bonds are broken, the contaminant--also called an electron donor--transfers electrons to an electron acceptor such as oxygen. The microbes use the energy produced by this bond-breaking activity as "food" to grow and reproduce, resulting in more enzyme production and increased destruction of the contaminant.
Contaminants can also be degraded through a related process called cometabolism in which microbes produce enzymes while degrading certain compounds that fortuitously break down a contaminant that normally resists biodegradation. While consuming methane, for example, some bacteria release enzymes that transform chlorinated solvents.
When bioremediation occurs aerobically--that is, in the presence of oxygen--microbes degrade organic compounds quickly, leaving behind water, carbon dioxide, and biomass, which appears as a gelatinous substance that reportedly makes an excellent fertilizer.
In an anaerobic, or oxygen-deprived, environment, microbes break down contaminants by passing electrons to an oxygen "substitute" such as a nitrate, a sulfate, carbon dioxide, or a metal. In the process, they produce byproducts such as methane, ammonia, and hydrogen sulfide, if sulfur is present.
Bioremediation ends when the microbes consume the target contaminant--their energy/food source--and gradually start to die o leaving behind a remediated site.
Getting Started
While the process of bioremediation is straightforward, engineering a program to clean up a specific contaminant isn't so simple. "You don't just throw fertilizer on the ground and let the bugs go to town," says Dennis Caputo, vice president of environmental and safety compliance for Proler International Corp. (Houston), a scrap recycling company that has been using bioremediation for a decade. Thus, if you're considering using bioremediation, it's a good idea to consult a specialist to help you implement a program that will produce the desired results.
Though environmental engineering firms take different approaches, a general first step is to conduct an environmental audit of your site in which you tour the operation and identify potentially contaminated areas. "You must do a full site analysis to discover if bioremediation is the correct approach for your situation," Caputo says.
A crucial part of this audit is determining what type of contamination you're dealing with, as this can decide whether bioremediation is a viable option. Thus far, bioremediation has proved itself most effective at degrading petroleum-based hydrocarbons such as grease, hydraulic and lubricating oils, gasoline, antifreeze, transmission and brake fluids, motor oil, diesel fuel, and paint thinner. It can also transform a few chlorinated compounds, such as pentachlorophenol, but has had limited success treating PCBs and is generally unable to remediate metal contamination.
After identifying the type of contamination, you must determine its severity because "there's a point at which the concentration of hydrocarbons can be toxic to the microbes," says Place. That toxicity point varies from site to site based on such factors as geochemical conditions and type of contamination, but experts note that it can range from just 2 or 3 percent for some materials up to 40 percent for certain types of petroleum and oil contaminants.
In the audit, you should also assess how widespread the contamination is, whether groundwater is affected, what indigenous microbes and nutrients are present in the soil, what the soil conditions are, and what cleanup standards must be met. These and other factors will help determine whether you can use bioremediation at all and, if so, whether you can conduct it in situ--that is, in place, right where the contamination is--or whether you'll need to do it ex situ, which entails moving the contaminated soil or water to another location for treatment, either on- or off-site.
So, let’s assume you've identified hydrocontamination on a small parcel at your plant, and after reviewing the extent of the contamination, you decide to use in situ bioremediation to clean up the property. Now what?
As a preliminary step to bioremediation treatment, some experts suggest applying a soap-like buffer solution--a surfactant--to the soil to partially break up heavy oils and greases and, hence, make them easier for microbes to degrade. Some recent studies, however, indicate that surfactants can inhibit microbes from producing enzymes or limit the effect of such enzymes. As a result, bioremediation engineers recommend carefully evaluating each site to determine what combination of surfactants and other procedures should be used to bring about the best results.
Bring on the Bugs
When it comes to dealing with microbes--the workhorses of this process--your choices are to stimulate microbes already present in the contaminated soil or water, or introduce new ones to the site to work with or in lieu of indigenous microbes.
The latter "imported" microbes come in a dry product that must be hydrated for 24 hours to make the bugs active and acclimated to their new environment. This solution is then either sprayed over the surface of the contaminated area or, for deeper contamination, dispersed via innoculation points--perforated plastic tubes sunk in the ground. (Some bioremediation specialists assert that innoculation points don't adequately disperse imported microbes throughout a site. Instead, they suggest, the soil should be excavated, inoculated with microbes, then returned to its original location.)
In any case, one type of microbe doesn't single-handedly degrade a contaminant. Instead, scores of different microbes work together to dismantle different parts of a hydrocarbon molecule and, thus, achieve degradation. For instance, LRC Technologies L.L.C. (Metairie, La.), an environmental cleanup firm specializing in bioremediation technology, uses microbe formulas that contain up to 37 different strains of bugs, notes Julie Diefenthal, one of the firm's principals.
Today, commercial bioremediation projects use only naturally occurring microbes, but in the not-too-distant future, genetically engineered microbes--dubbed GEMs--could hit the scene. Among other advantages, GEMs are expected to degrade contaminants faster than natural microbes, and they can reportedly be programmed to degrade only certain types and amounts of contaminants. They may also be able to take on tougher-to-degrade contaminants such as PCBs and change the geochemical environment around metal contaminants to reduce their mobility. Currently, however, the EPA doesn't allow GEMs to be used due to concerns that they could cause unexpected problems in the environment after completing their task.
Making Happy Microbes
Whether you opt to go with indigenous or imported microbes, or both, to "provide the right environment for them to be able to multiply substantially," Caputo says.
To do their best remediation work, microbes need three things: an electron acceptor such as oxygen to promote the degradation reaction; nutrients such as nitrogen, phosphorus, potassium, sulfur, iron, calcium, magnesium, or chloride to stimulate their growth and metabolism; and moisture.
By circulating oxygen and nutrients through the site, you create a microbial population explosion and kick off a feeding frenzy. "Once the microbes have consumed the nutrients introduced, they will turn their attention to the released organic contaminants," Place explains.
The oxygen content of a site can be increased through such basic techniques as tilling the soil regularly--if the contamination isn't too deep--or using more-elaborate techniques such as bioventing, air sparging (injection of air into saturated soils), and soil vapor extraction (induction of air flow by a vacuum). Hydrogen peroxide is also sometimes injected underground because it releases oxygen as it decomposes.
Nutrients, meanwhile, are usually dissolved in water and applied to a site by hose, sprinkler, or sprinkler system. But it's important to avoid overwatering a bioremediation site, experts stress, suggesting that the optimum saturation level can range from 25 to 45 percent, depending on the site.
After getting all the components in place, you have to maintain the bioremediation site to ensure that the microbes have an ideal operating environment. "It's almost like a gardening procedure," Diefenthal says, adding that "the conditions are almost the same as when you're trying to grow grass."
Throughout, you should monitor the process, taking samples to see if the concentration levels of contaminants are decreasing and if there are telltale signs of successful bioremediation, such as the presence of carbon dioxide or other degradation byproducts. According to Bruce Iverson, project manager for Montgomery Watson (Madison, Wis.), an environmental engineering firm, monitoring is an especially important element of the bioremediation remedy when state and federal environmental agencies require evidence reductions in concentrations of the contaminant are due to biodegradation and not due to the contaminant migrating in soil or groundwater.
Reviewing Bio's Strengths
To many bioremediation vendors and users, the technology's biggest selling point is that it costs a reported 33 to 50 percent less than conventional cleanup methods such as landfilling, incineration, and solidification of contaminated soil and pump-and-treat practices for contaminated groundwater.
In the simplest in situ cases, a bioremediation project requires minimal capital expenses and no sophisticated equipment, only a tiller to aerate the soil and a hose and sprinkler to add water and nutrients to the site. More-involved projects can be more expensive, of course, requiring installation of innoculation points and watering systems, or perhaps excavation and relocation of soil for ex situ treatment. Small or large, however, the costs of maintaining and monitoring bioremediation sites can be minimized by having company employees, rather than outside contractors, perform the required tasks.
One scrap company that knows all about the costs of bioremediation is Miller Compressing Co. (Milwaukee), a scrap recycling firm that is performing in situ bioremediation of a 7-acre leased parcel of property contaminated with emulsified oils from turnings.
In this project, Miller Compressing found that the contamination was initially limited to the top 3 feet of soil, but the site's shallow and fluctuating water table carried the contamination deeper. To prepare the site for bioremediation, therefore, Miller Environmental Technologies L.L.C.--an environmental engineering firm half-owned by Miller Compressing--dug air sparging lines 12 feet deep to increase the oxygen content of the soil and installed an underground sprinkler system with pop-up watering heads.
Despite these costs, as well as the ongoing personnel expenses to monitor the site, Joe Kovacich, a vice president of Miller Compressing, asserts, "We analyzed our options and found that in situ bioremediation was at least three times less expensive than other techniques. Based on our site-specific engineering and design, as well as our bench- and field-scale microbiological testing, we conservatively estimate that it will cost $14 to $15 per cubic yard to remediate the site."
Bioremediation's cost per cubic yard will vary from project to project, of course, and could be as high as $45 for engineered systems, experts note. Even so, fees to excavate and dispose of contaminated soil generally tend to be higher, ranging from around $50 to $90 depending on the state.
Another touted advantage of bioremediation is that it's a natural process that degrades contaminants into harmless elements and produces no hazardous byproducts when complete mineralization—conversion to mineral, or inorganic, form--occurs. This, some argue, makes it safer for the environment than conventional remediation methods an—perhaps of greatest concern—can eliminate liability concerns. “If you use bioremediation on-site, you eliminate the potential for transportation liability, and by breaking down the containment, you erase the long-term liability issue,” Dienfenthal says. “We consider bioremediation to be a permanent solution.”
In contrast, landfilling and incineration simply move organic contaminants from one location or medium to another, injuring the environment and leaving the liability door open, assert bioremediation experts. Incineration, for instance, can reportedly volatilize contaminants and, hence, exacerbate air pollution. And hauling contaminated soil off-site "not only presents the potential for transportation liability, but also for long-term liability," says Diefenthal. "Even if you dispose of contaminated soil in an approved landfill, the contamination still exists and you technically still own the soil."
One final benefit of bioremediation is that it's usually less-intrusive and less-disruptive than conventional remediation methods. In most cases, for instance, extensive soil excavation isn’t required and the process can be even used under rail lines, buildings, and equipment foundations, which precludes the need to disturb them. Technically, recyclers can even continue operating on sites underground bioremediation, through most bioremediation specialists advise against this. “The process can work faster if you don't operate on the property and potentially add addition contaminants through some ongoing process," Kovacich asserts.
Some 'Significant Caveats'
For all of bioremediation's admirable qualities, there are a few "significant caveats" about the technology, Caputo asserts. For starters, there's the time factor. Though Diefenthal asserts that some sites can be remediated in weeks, the majority of bioremediation projects are "certainly measured in terms of months and could be measured in terms of years," Caputo says. For just one example, Miller Compressing expects its bioremediation project to take at least a year and a half. "One of the cons of the process is that you do need time," Kovacich states.
While the bioremediation process can be sped up, it can only go as fast as allowed by a host of uncontrollable variables, including soil conditions; temperature; the type, severity, and depth of contamination; the amount of material to be cleaned up; and the cleanup standard to be met.
The time required for bioremediation can be a serious disincentive to companies that need to execute a rapid cleanup to meet government requirements or get valuable plant space quickly back into operation. "Time is a site-specific issue, but it's one of the considerations you must factor in when comparing different cleanup alternatives to understand the overall cost of the remedy," Iverson says.
Bioremediation is also hampered by its limited scope, being used primarily to treat hydrocarbon contamination, and it can reportedly have difficulty remediating some contaminants to acceptably low levels. "If you're dealing with very low levels from a regulatory standpoint, bioremediation might not be a viable option for you," says Caputo.
Further, the technology continues to face skepticism in the marketplace due to the perception among some that it's mysterious and unproven, not to mention scare stories about salespeople who have promised more than the process can deliver. Such people have "tainted the industry," Diefenthal says, by selling the process without providing the necessary technical and training support. Such situations have prompted some to call for the federal government to step in and develop licensing requirements for bioremediation practitioners.
Another challenge facing bioremediation is the increasing number of controls that state environmental agencies are putting on it. "States are more closely regulating biological treatment today in comparison with the past to the point where there is now a substantial body of regulations you have to abide by to use this on the state level," Caputo points out. Indeed, monitoring requirements and permit applications can be extensive. In addition, some states are imposing lower regulatory thresholds and, in some cases, prohibiting in situ in favor of ex situ treatment. States also differ in how sensitive they are to the use of nutrients in bioremediation that could filter down or be injected into groundwater.
Despite these drawbacks, Place asserts, "the trend over the past few years has been that states are becoming more accepting of this technology, with cost being one of the driving factors." Iverson concurs, stating, "For the more demonstrated types of contaminants, we've found state agencies to be receptive to bioremediation under the right circumstances."
A Bug in Every Plant?
Though far from a panacea, bioremediation offers at least another option among cleanup technologies. And by all accounts it's an option that more scrap recyclers will choose in the future. "I definitely think bioremediation has a bright future in the scrap industry," Iverson says.
One promising application of bioremediation in processing facilities, Kovacich notes, would be to implement in situ treatment in operating areas that face continual potential for contamination. In such situations, microbes would address releases as they occur, thus preventing the areas from becoming seriously contaminated. "We can treat oils as they're deposited while an operation continues," Kovacich remarks, "as well as remediate underneath parts of a functioning operation."
This and other opportunities could help boost bioremediation's appeal to and presence in the scrap industry. "Recyclers are very interested in it because most of them weren't aware this option even existed," Kovacich asserts, concluding, "It's a great opportunity for the industry."
A few scrap recycling companies are cleaning up contamination using bioremediation, a natural process that relies on microbes to break down some types of contaminants. What is it? How does it work? And how could it help you? Here are some answers.