&EPA United States : Environmental Protection Office of Emergency and Remedial Response Washington, DC 20460 Qffica of Research and Development Cincinnati, OH 45368 EPA/540/S-94/502 April 1994 Engineering Bulletin In Situ Biodegradation Purpose Section 121(b) of the Comprehensive Environment Response, Compensation, and Liability Act (CERCLA) man- dates the Environmental Protection Agency (EPA) to select remedies that "utilize permanent solutions and alternative technologies or resource recovery technologies to the maxi- mum extent practicable" and to prefer remedial actions in which treatment "permanently and significantly reduces the volume, toxicity, or mobility of hazardous substances, pollutants and contaminants as a principal element." The Engineering Bulletins comprise a series of documents that summarize the latest information available on selected treatment and site remediation technologies and related issues. They provide summaries of and references for the latest information to help remedial project managers, on- scene coordinators, contractors, and other site cleanup managers understand the type of data and site characteris- tics needed to evaluate a technology for potential applica- bility to their Superfund or other hazardous waste site. Those documents that describe individual treatment tech- nologies focus on remedial investigation scoping needs. Addenda will be issued periodically to update the original bulletins. Abstract In situ biodegradation may be used to treat low-to- intermediate concentrations of organic contaminants in- place without disturbing or displacing the contaminated media. Although this technology has been used to degrade a limited number of inorganics, specifically cyanide and nitrate, in situ biodegradation is not generally employed to degrade inorganics or to treat media contaminated with heavy metals. During in situ biodegradation, electron acceptors (e.g., oxygen and nitrate), nutrients, and other amendments may be introduced into the soil and groundwater to encourage the growth of an indigenous population capable of degrad- ing the contaminants of concern. These supplements are used to control or modify site-specific conditions that impede microbial activity and, thus, the rate and extent of contaminant degradation. Depending on site-specific cleanup goals, in situ biodegradation can be used as the sole treatment technology or in conjunction with other biological, chemical, and physical technologies in a treat- ment train. In the past, in situ biodegradation has often been used to enhance traditional pump and treat technolo- gies by reducing the time needed to achieve aquifer cleanup standards. One of the advantages of employing an in situ technol- ogy is that media transport and excavation requirements are minimized, resulting in both reduced potential for volatile releases and minimized material handling costs. Biological technologies that require the physical displace- ment of media during treatment (e.g., "land treatment" applications involving excavation for treatment in lined beds or tilling of non-excavated soils) assume many of the risks and costs associated with ex situ technologies and cannot strictly be considered in situ applications. As of Fall 1993, in situ biodegradation was being considered or implemented as a component of the remedy at 21 Superfund sites and 38 Resource Conservation and Recovery Act (RCRA), Underground Storage Tank (UST), Toxic Substances Control Act (TSCA), and Federal sites with soil, sludge, sediment, or groundwater contamination [1, p. 13]'[2][3]. This bulletin provides information on the technology's applicability, the types of residuals pro- duced, the latest performance data, the site requirements, the status of the technology, and sources for further information. Technology Applicability In situ biodegradation has been shown to be poten- tially effective at degrading or transforming a large number of organic compounds to environmentally-acceptable or less mobile compounds [4, p. 54][5, p. 103][6][7][8][9]. Soluble organic contaminants are particularly amenable to biodegradation; however, relatively insoluble contaminants may be degraded if they are accessible to microbial degrad- * [reference number, page number] Printed on Recycled Paper ------- v>EPA United States Environmental Protection Agency Office of Emergency and Remedial Response Washington, DC 20460 Office of Research and Development Cincinnati, OH 45268 EPA/540/S«94/50a ApriM994 Engineering Bulletin Ih Situ Biodegradation Treatment Purpose Section 121(b) of the Comprehensive Environment Response, Compensation, and Liability Act (CERCLA) man- dates the Environmental Protection Agency (EPA) to select remedies that "utilize permanent solutions and alternative technologies or resource recovery technologies to the maxi- mum extent practicable" and to prefer remedial actions in which treatment "permanently and significantly reduces the volume, toxicity, or mobility of hazardous substances, pollutants and contaminants as a principal element." The Engineering Bulletins comprise a series of documents that summarize the latest information available on selected treatment and site remediation technologies and related issues. They provide summaries of and references for the latest information to help remedial project managers, on- scene coordinators, contractors, and other site cleanup managers understand the type of data and site characteris- tics needed to evaluate a technology for potential applica- bility to their Superfund or other hazardous waste site. Those documents that describe individual treatment tech- nologies focus on remedial investigation scoping needs. Addenda will be issued periodically to update the original bulletins. Abstract In situ biodegradation may be used to treat low-to- intermediate concentrations of organic contaminants in- place without disturbing or displacing the contaminated media. Although this technology has been used to degrade a limited number of inorganics, specifically cyanide and nitrate, in situ biodegradation is not generally employed to degrade inorganics or to treat media contaminated with heavy metals. During in situ biodegradation, electron acceptors (e.g., oxygen and nitrate), nutrients, and other amendments may be introduced into the soil and groundwater to encourage the growth of an indigenous population capable of degrad- ing the contaminants of concern. These supplements are used to control or modify site-specific conditions that impede microbial activity and, thus, the rate and extent of contaminant degradation. Depending on site-specific cleanup goals, in situ biodegradation can be used as the sole treatment technology or in conjunction with other biological, chemical, and physical technologies in a treat- ment train. In the past, in situ biodegradation has often been used to enhance traditional pump and treat technolo- gies by reducing the time needed to achieve aquifer cleanup standards. One of the advantages of employing an in situ technol- ogy is that media transport and excavation requirements are minimized, resulting in both reduced potential for volatile releases and minimized material handling costs. Biological technologies that require the physical displace- ment of media during treatment (e.g., "land treatment" applications involving excavation for treatment in lined beds or tilling of non-excavated soils) assume many of the risks and costs associated with ex situ technologies and cannot strictly be considered in situ applications. As of Fall 1993, in situ biodegradation was being considered or implemented as a component of the remedy at 21 Superfund sites and 38 Resource Conservation and Recovery Act (RCRA), Underground Storage Tank (UST), Toxic Substances Control Act (TSCA), and Federal sites with soil, sludge, sediment, or groundwater contamination [1, p. 13]'[2][3]. This bulletin provides information on the technology's applicability, the types of residuals pro- duced, the latest performance data, the site requirements, the status of the technology, and sources for further information. Technology Applicability In situ biodegradation has been shown to be poten- tially effective at degrading or transforming a large number of organic compounds to environmentally-acceptable or less mobile compounds [4, p. 54][5, p. 103][6][7][8][9]. Soluble organic contaminants are particularly amenable to biodegradation; however, relatively insoluble contaminants may be degraded if they are accessible to microbial degrad- * [reference number, page number] Printed on Recycled Paper ------- ers. Classes of compounds considered amenable to biodeg- radation include petroleum hydrocarbons (e.g., gasoline and diesel fuel), nonchlorinated solvents (e.g., acetone, ketones, and alcohols), wood-treating wastes (e.g., creo- sote and pentachlorophenol), some chlorinated aromatic compounds (e.g., chlorobenzenes and biphenyls with fewer than five chlorines per molecule), and some chlorinated aliphatic compounds (e.g., trichloroethene and dichloroethene). As advances in anaerobic biodegradation continue, many compounds traditionally considered resis- tant to aerobic biodegradation may eventually be de- graded, either wholly or partially, under anaerobic condi- tions. Although not normally used to treat inorganics (e.g., acids, bases, salts, heavy metals, etc.), in situ biodegrada- tion has been used to treat water contaminated with ni- trate, phosphate, and other inorganic compounds. Although in situ biodegradation may be used to remediate a specific site, this does not ensure that it will be effective at all sites or that the treatment efficiency achieved will be acceptable at other sites. The complex contaminant mixtures found at many Superfund sites frequently result in chemical interactions or inhibitory effects that limit con- taminant biodegradability. Elevated concentrations of pes- ticides, highly chlorinated organics, and some inorganic salts have been known to inhibit microbial activity and thus system performance during in situ biodegradation. Treatability studies should be performed to determine the effectiveness of a given in situ biological technology at each site. Experts based out of EPA's Risk Reduction Engineering Laboratory (RREL) in Cincinnati, Ohio and the Robert S. Kerr Environmental Research Laboratory (RSKERL) in Ada, Okla- homa may be able to provide useful guidance during the treatability study and design phases. Other sources of general observations and average removal efficiencies for different treatability groups are contained in the Superfund Land Disposal Restrictions (LDR) Guide #6A, "Obtaining a Soil and Debris Treatability Variance for Remedial Actions," (OSWER Directive 9347.3-06FS, September 1990) [10] and Superfund LDR Guide #6B, "Obtaining a Soil and Debris Treatability Variance for Removal Actions," (OSWER Direc- tive 9347.3-06BFS, September 1990) [11]. Limitations Site- and contaminant-specific factors impacting con- taminant availability, microbial activity, and chemical reac- tion rates may limit the application of in situ biodegrada- tion. Variations in media composition and contaminant concentrations can lead to variations in biological activity and, ultimately, inconsistent degradation rates. Soil char- acteristics (e.g., non-uniform particle size, soil type, mois- ture content, hydraulic conductivity, and permeability) and the amount, location, and extent of contamination can also have a profound impact on bioremediation. The following text expands upon these factors. The biological availability, or bioavailability, of a con- taminant is a function of the contaminant's solubility in water and its tendency to sorb on the surface of the soil. Contaminants with low solubility are less likely to be distrib- uted in an aqueous phase and may be more difficult to degrade biologically. Conversely, highly soluble com- pounds may leach from the soil before being degraded. In ^m^. general, however, poor bioavailability can be attributed to '^^k contaminant sorption on the soil rather than a low or high / contaminant solubility. The tendency of organic molecules to sorb on the soil is determined by the physical and chemical characteristics of the contaminant and soil. In general, the leaching potential of a chemical is proportional to the magnitude of its adsorption (partitioning) coefficient in the soil. Hydrophobic (i.e., "water fearing") contami- nants, in particular, routinely partition from the soil water and concentrate in the soil organic matter, thus limiting bioavailability. Additionally, contaminant weathering may lead to binding in soil pores, which can limit availability even of soluble compounds. Important contaminant prop- erties that affect sorption include: chemical structure, contaminant acidity or basicity (pKa or pKb), water solubil- ity, permanent charge, polarity, and molecule size. In some situations surfactants (e.g., "surface acting agents") may be used to increase the bioavailability of "bound" or in- soluble contaminants. However, it may be difficult to iden- tify a surfactant that is both nontoxic and not a preferred substrate for microbial growth. Soil solids, which are comprised of organic and inor- ganic components, may contain highly reactive charged surfaces that play an important role in immobilizing organic constituents, and thus limiting their bioavailability. Certain types of inorganic clays, possess especially high negative charges, thus exhibiting a high cation exchange capacity. Alternatively, clays may also contain positively charged •^^ surfaces, causing these particles to exhibit a high anion J exchange capacity. Soil organic matter also has many highly reactive charged surfaces which can limit bioavailability [12]. Bioavailability is also a function of the biodegradability of the target chemical, i.e., whether it acts as a substrate, co-substrate, or is recalcitrant. When the target chemical cannot serve as a metabolic substrate (source of carbon and energy) for microorganisms, but is oxidized in the presence of a substrate already present or added to the subsurface, the process is referred to as co-oxidation and the target chemical is defined as the co-substrate [12][1 3, p.4]. Co- metabolism occurs when an enzyme produced by an organ- ism to degrade a substrate that supports microbial growth also degrades another non-growth substrate that is neither essential for nor sufficient to support microbial growth. Co- oxidation processes are important for the biodegradation of high molecular weight polycyclic aromatic hydrocarbons (PAHs), and some chlorinated solvents, including trichloroethene (TCE). However, like surfactants, cometabolites (e.g., acetate and phenol) may be more readily mineralized by the indigenous microorganisms than the target organics [1 3, p. 4]. Microbial activity can be reduced by nutrient, mois- ture, and oxygen deficiencies, significantly decreasing bio- degradation rates. Extreme soil temperatures, soil alkalin- ^^^ ity, or soil acidity can limit the diversity of the microbial *^N population and may suppress specific contaminant degrad- Engineering Bulletin: In Situ Biodegradation Treatment ------- r ers. Spatial variation of soil conditions (e.g., moisture, oxygen availability, pH, and nutrient levels) may result in inconsistent biodegradation due to variations in biological activity. While these conditions may be controlled to favor biodegradation, the success of in situ biodegradation de- pends in a large part on whether required supplements can be delivered to areas where they are needed. Low hydraulic conductivity can hinder the movement of water, nutrients, aqueous-phase electron acceptors (e.g., hydrogen perox- ide and nitrate), and, to a lesser extent, free oxygen through the contamination zone [14, p. 155]. Restrictive layers (e.g., clay lenses), although more resistant to contamina- tion, are also more difficult to remediate due to poor permeability and low rates of diffusion [1 3, p. 4]. Low percolation rates may cause amendments to be assimilated by soils immediately surrounding application points, pre- venting them from reaching areas that are more remote, either vertically or horizontally. During the simultaneous addition of electron acceptors and donors through injec- tion wells, excessive microbial growth or high iron or manganese concentrations may cause clogging in the well screen or in the soil pores near the well screen [15]. Variable hydraulic conductivities in different soil strata within a contaminated area can also complicate the design of flow control; minor heterogeneities in lithology can, in some cases, impede the transfer of supplements to specific sub- surface locations. Microbial activity may also be influenced by contami- nant concentrations. Each contaminant has a range of concentrations at which the potential for biodegradation is maximized. Below this range microbial activity may not occur without the addition of co-substrate. Above this range microbial activity may be inhibited and, once toxic concentrations are reached, eventually arrested. During inhibition, contaminant degradation generally occurs at a reduced rate. In contrast, at toxic concentrations, contami- nant degradation does not occur. The concentrations at which microbial growth is either supported, inhibited, or arrested vary with the contaminant, medium, and micro- bial species. Given long-term exposure, microbes have been known to acclimate to very high contaminant concen- trations and other conditions inhibiting microbial activity. However, if prompt treatment is a primary goal, as is the case during most remedial activities, toxic conditions may need to be addressed by pH control, metals control (e.g., immobilization), sequential treatment, or by introducing microbial strains resistant to toxicants. Numerous biological and non-biological mechanisms (e.g., volatilization, sorption, chemical degradation, migra- tion, and photodecomposition) occur during biological treatment. Since some amendments may react with the soil, site geochemistry can limit both the form and concen- tration of any supplements added to the soil. Thus, care must be employed when using amendments to "enhance" biological degradation. For example, ozone and hydrogen peroxide, which can be added to enhance dissolved oxygen levels in soil or groundwater systems, may react violently with other compounds present in the soil, reduce the sorptive capacity of the soil being treated, produce gas bubbles that block the pores in the soil matrix, or damage the bacterial population in the soil [4, p. 43]. Nitrogen and phosphorus (phosphate) must also be applied cautiously to avoid excessive nitrate formation [4, p.47] and the precipi- tation of calcium and iron phosphates, respectively. Exces- sive nitrate levels in the groundwater can cause health problems in humans, especially children. If calcium con- centrations are high, the added phosphate can be tied up by the calcium and, therefore, may not be available to the microorganisms [16, p. 23]. Lime treatment for soil pH adjustment is dependent on several soil factors including soil texture, type of clay, organic matter content, and aluminum concentrations [4, p. 45]. Since changes in soil pH may also affect the dissolution or precipitation of mate- rials within the soil and may increase the mobility of hazardous materials, pH amendments (acid or base) should be added cautiously and should be based on the soil's ability to resist changes in pH, otherwise known as the soil's "buffering capacity" [4, p. 46]. Since the buffering capacity varies between soils, lime and acidification requirements should be determined on a site-specific basis. Finally, high concentrations of metals can have a det- rimental effect on the biological treatment of organic contaminants in the same medium. A number of metals can be oxidized, reduced, methylated (i.e., mercury), de- methylated, or otherwise transformed by various organ- isms to produce new contaminants. The solubility, volatil- ity, and sorption potential of the original soil contaminants can be greatly changed in the process [1 7, p. 144], leading to potential significant lexicological effects, as is the case during the methylation of mercury. To avoid these compli- cations, it is sometimes possible to pretreat or complex the metals into a less toxic or teachable form. Technology Description During in situ biodegradation, site-specific characteris- tics are modified to encourage the growth of a microbial population capable of biologically degrading the contami- nants of concern. Presently, two major types of in situ systems are being employed to biodegrade organic com- pounds present in soils, sludges, sediments, and groundwa- ter: bioventing systems and "traditional" in situ biodegra- dation systems, which usually employ infiltration galleries/ wells and recovery wells to deliver required amendments to the subsurface. In general, bioventing has been used to treat contaminants present in the unsaturated zone. Tradi- tional in situ biodegradation, on the other hand, has mostly been used to treat saturated soils and groundwater. The occasional treatment of unsaturated soil using traditional in situ biodegradation techniques has been generally limited to fairly shallow regions over groundwater that is already contaminated. Traditional In Situ Biodegradation Traditional in situ biodegradation is generally used in conjunction with groundwater-pumping and soil-flushing systems to circulate nutrients and oxygen through a con- taminated aquifer and associated soil. The process usually Engineering Bulletin: In Situ Biodegradation Treatment ------- involves introducing aerated, nutrient-enriched water into the contaminated zone through a series of injection wells or infiltration trenches and recovering the water down-gradi- ent. Depending upon local regulations and engineering concerns, the recovered water can then be treated and, if necessary, reintroduced to the soil onsite, discharged to the surface, or discharged to a publicly-owned treatment works (POTW). A permit may be required for the re-injection of treated water. Note that a variety of techniques can be used to introduce and distribute amendments in the subsurface. For example, a lower horizontal well is being used at the Savannah River Site near Aiken, North Carolina to deliver air and methane to the subsurface. A vacuum has been applied to an upper well (in the vadose zone) located at this site to encourage the distribution of air and methane within the upper saturated zone and lower vadose zone [18][19]. Figure 1 is a general schematic of a traditional in situ biodegradation system [20, p. 113][16, p. 13]. The first step in the treatment process involves pretreating the infiltration water, as needed, to remove metals (1). Treated or contaminated groundwater, drinking water, or alterna- tive water sources (e.g., trucked water) may be used as the water source. If groundwater is used, iron dissolved in the groundwater may bind phosphates needed for biological growth. Excess phosphate may be added to the infiltration water at this point in the treatment process in order to complex the iron [20, p. 111 ]. The presence of iron will also cause a more rapid depletion of hydrogen peroxide, which is sometimes used as an oxygen source. Surface active agents may also be added at this point in the treatment process to increase the bioavailability of contaminants, especially hydrophobic or sorbed pollutants, while meth- ane or other substances may be added to induce the co- metabolic biodegradation of certain contaminants. In continuous recycle systems, toxic metals originally located in the contaminated medium may have to be removed from the recycled infiltration water to prevent inhibition of bacterial growth. The exact type of pretreatment will vary with the water source, contamination problem, and treat- ment system used. Following infiltration water pretreatment, a biological inoculum can be added to the infiltration water to enhance the natural microbial population (2). A site-specific inocu- lum enriched from site samples may be used; commercially available cultures reported to degrade the contaminants of concern can also be used (e.g., during the remediation of "effectively sterile soils"). Project managers are cautioned against employing microbial supplements without first as- sessing the relative advantages associated with their use and potential competition that may occur between the indigenous and introduced organisms. The ability of mi- crobes to survive in a foreign and possibly hostile (i.e., toxic) environment, as well as the ability to metabolize a wide range of substrates should be evaluated. The health effects of commercial inocula must also be carefully evalu- ated, since many products on the market are not carefully screened or processed for pathogens. It is essential that independently-reviewed data be examined before employ- ing a commercially-marketed microbial supplement [21]. Nutrient addition can then be employed to provide nitrogen and phosphorus, two elements essential to the biological activity of both indigenous and introduced or- ganisms (3). Optimum nutrient conditions are site-specific. Trace elements may be added at this stage, but are normally available in adequate supply in the soil or groundwater. During contaminant oxidation, energy is released as electrons are removed. Since oxygen acts as the terminal electron acceptor during aerobic biodegradation, oxygen concentrations in the subsurface may become depleted. To avoid this complication, air, oxygen, and other oxygen Figure 1. Schematic Diagram of Traditional In Situ Biodegradation of Soil and Groundwater _^;^_^. „,, „ _ n\ I \\ i i\ ?»,&-$&v ^;^^>, :s -1\, ,^/Ao or^1J, 1V>• i-V i 4\ i f ^ ^v"* vv c% %% 'j^ < •• * K ** ^^^- ^ ''''•"*< ^r , s J^t.-/'. \'^u<'A^;«.,^.-XC':*'-; Direction of Groundwater Flow Zone of low permeability (i.e., clay, bedrock) ^\ Engineering Bulletin: In Situ Biodegradation Treatment ------- r sources (hydrogen peroxide and ozone) can be added to the infiltration water (4). To prevent gas binding in the subsurface, and a subsequent reduction in the effective soil permeability, oxygen amendment/supplementation meth- ods must be carefully selected. During anaerobic degrada- tion, alternative electron acceptors (nitrate, carbonate, or sulfate) may be added to the infiltration water in place of oxygen. Alternatively, during the co-oxidation of a target substrate, a co-substrate (methanol or acetate) may be added to the infiltration water [22]. just before the water is added to the soil or groundwa- ter, chemical additives may be used to adjust the pH (neutral is recommended for most systems) and other parameters that impact biodegradation (5). Care should be taken when making adjustments to the pH, since contami- nant mobility (especially of metals) can be increased by changing the pH [4, p. 45]. Site managers are also cau- tioned against employing chemical additives that are per- sistent in the environment. The potential toxicity of addi- tives and any synergistic effects on contaminant toxicity should also be evaluated. During in situ bioremediation, amendment concentra- tions and application frequencies can be adjusted to com- pensate for physical/chemical depletion and high microbial demand. If these modifications fail to compensate for microbial demand, remediation may occur by a sequential deepening and widening of the active treatment layer (e.g., as the contaminant is degraded in areas near the amend- ment addition points, and microbial activity decreases due to the reduced substrate, the amendments move farther, increasing microbial activity in those areas). Additionally, hydraulic fracturing may be employed to improve amend- ment circulation within the subsurface. The importance of using a well-designed hydraulic delivery system and thoroughly evaluating the compatibil- ity of chemical supplements was demonstrated at sites in Park City, Kansas; Kelly AFB, Texas; and Eglin AFB, Florida. Air entrainment and iron precipitation resulted in a contin- ued loss of injection capacity during treatment at the Park City site [23][24] and calcium phosphate and iron precipi- tation resulted in the failure of the two field tests at Kelly and Eglin AFBs, respectively [25]. Bioventing Bioventing uses relatively low-flow soil aeration tech- niques to enhance the biodegradation of soils contami- nated with organic contaminants. Although bioventing is predominantly used to treat unsaturated soils, applications involving the remediation of saturated soils and groundwa- ter (e.g., using air sparging techniques) are becoming more common [26][27]. Aeration systems similar to those em- ployed during soil vapor extraction are used to supply oxygen to the soil (Figure 2). Typically a vacuum extrac- tion, air injection, or combination vacuum extraction and air injection system is employed [28]. An air pump, one or more air injection or vacuum extraction probes, and emis- sions monitors at the ground surface are commonly used. Although some systems utilize higher air flow rates, thereby combining bioventing with soil vapor extraction, low air pressures and low air flow rates are generally used to maximize vapor retention times in the soil while minimizing contaminant volatilization. An interesting modification to traditional aeration techniques has been proposed at the Picatinny Arsenal in New jersey. Here researchers and project managers have proposed collecting TCE vapors at the surface, amending them with degradable hydrocar- bons (methane, propane, or natural gas) capable of stimu- lating the cometabolic degradation of vapor-phase TCE, and then re-injecting the amended vapors into the unsatur- ated zone in an attempt to encourage the in situ bioremediation of the TCE remaining in the subsurface [29][30][31][32][27]. Off-gas treatment (e.g., through biofiltration or car- bon adsorption) will be needed during most bioventing applications to ensure compliance with emission standards and to control fugitive emissions. Off-gas treatment sys- tems similar to those employed during soil vapor extraction may be used. These systems must be capable of effectively collecting and treating a vapor stream consisting of the original contaminants and/or any volatile degradation prod- ucts generated during treatment. Although similar vapor treatment systems may be employed during soil vapor extraction and bioventing, less concentrated off-gases would be expected from a bioventing system than from a soil vapor extraction system employed at the same site. This difference in concentration is attributed to enhanced bio- logical degradation within the subsurface. Nutrient addition may be employed during bioventing to enhance biodegradation. Nutrient addition can be accomplished by surface application, incorporation by till- ing into surface soil, and transport to deeper layers through applied irrigation water. However, in some field applica- tions to date, nutrient additions have been found to provide no additional benefits [33], Increasing the soil temperature may also enhance bioremediation, although in general high temperatures should be avoided since they can de- crease microbial population and activity. Heated air, heated water, and low-level radio-frequency heating are some of the techniques which can be used to modify soil tempera- ture. Soil core analyses can be performed periodically to assess system performance as determined by contaminant removal. A control plot located near the bioventing system, but not biovented, may also be used to obtain additional information to assess system performance. Process Residuals During in situ biodegradation, limited but potentially significant process residuals may be generated. Although the majority of wastes requiring disposal are generated as part of pre- and post-treatment activities, process residuals directly arising from in situ biological activities may also be generated. These process residuals may include: 1) par- tially degraded metabolic by-products, 2) residual con- tamination, 3) wastes produced during groundwater pre- and post-treatment activities, and 4) volatile contaminants that are either directly released into the atmosphere or Engineering Bulletin: In Situ Biodegradation Treatment ------- collected within add-on emission controlXtreatment sys- tems. The following text expands upon the specific types of process residuals, their control, and their impact on disposal requirements. Ultimately biological technologies seek to mineralize hazardous contaminants into relatively innocuous by-prod- ucts, specifically carbon dioxide, water, and inorganic salts. However, a number of site- and contaminant-specific fac- tors may cause the partial degradation or "biotransforma- tion" of a contaminant and the generation of an intermedi- ate by-product. These metabolic by-products may be located in either the saturated or unsaturated zones. The identity, toxicity, and mobility of these partially degraded compounds should be determined since intermediate deg- radation products can be as toxic or more toxic than the parent compound. Since metabolic by-products can accu- mulate in the soil and groundwater, future remedial actions may be necessary. In addition to intermediate degradation by-products, residual contamination may persist in the soil following treatment. Microbes are capable of degrading only that fraction of the contamination that is readily available for microbial incorporation. As a result, biologically resistant contaminants and contaminants that remain sorbed to the soil and sediment during the remedial action cannot be degraded. Depending on the nature of the contaminants and media, the "bound" fraction may slowly desorb over long periods of times (months to years), potentially re- contaminating "treated" media near the residual contami- nation [34][35]. Additionally, fluctuations in the water table may result in the recontamination of previously remediated soils if groundwater contamination, specifically contamination associated with the presence of a light non- aqueous phase layer (LNAPL), has not been effectively addressed. Above-ground activities taken to ensure that the reme- dial action complies with regulatory requirements and adequately guards against cross-contamination and un- controlled releases may result in the generation of a signifi- cant volume of waste requiring disposal. For example, when groundwater is used to deliver amendments to the subsurface, it may be necessary to pre-treat the water before it can be re-introduced to the subsurface. Addition- ally, in order to protect water quality outside of the treat- ment zone from contaminant or amendment migration, a down-gradient groundwater recovery and treatment sys- tem designed to collect and treat amendment- and con- taminant-laden groundwater may be needed. The residu- als produced by these add-on treatment processes will eventually require disposal. Significant volatile emissions may also be produced during in situ biodegradation (e.g., bioventing). Depend- ing on their concentration, toxicity, and total volume, these emissions, which may consist of the original contaminant or any volatile degradation products produced during treat- ment, may need to be controlled, collected, or treated. Ultimately, the by-products of an emissions treatment/ control system will require disposal. Site Requirements In situ biodegradation normally requires the installa- tion of wells or infiltration trenches; therefore, adequate Figure 2. Bioventing Low rate air injection Surface monitoring to ensure no emissions Air extraction Air extraction Biodegradation of contaminated soils Monitoring of soil gas to assess vapor biodegradation Biodegradation of vapors Engineering Bulletin: In Situ Biodegradation Treatment ------- access roads are required for heavy equipment such as well- drilling rigs and backhoes. Soil-bearing capacity, traction, and soil stickiness can limit vehicular traffic [17, p. 61]. In general, the area required to set up mixing equip- ment is not significant. However, space requirements increase as the complexity of the various pre- and post- treatment systems increases. During the installation of infiltration galleries and wells, several hundred up to several thousand square feet of clear surface area will be required. Climate can also influence site requirements. If periods of heavy rainfall or extremely cold conditions are expected, a cover may be required. Electrical requirements will depend on the type of technology employed. Standard 220V, three-phase electri- cal service may be used to supply power to pumps and mixing equipment. Since water is used for a variety of purposes during biological treatment, a readily available water supply will be needed at most sites. Municipal water or clean groundwater may be used. Contaminated ground- water may be used if permitted by the appropriate regula- tory agency. The quantity of water needed is site- and process-specific. Waste storage is not normally required for in situ biodegradation. Onsite analytical equipment for conducting pH and nutrient analyses will help improve operation efficiency and provide better information for process control. During bioventing applications, air emissions monitors at the ground surface are commonly used. Regulatory Considerations and Response Actions Federal mandates can have a significant impact on the application of in situ biodegradation. RCRA LDRs that require treatment of wastes to best demonstrated available technology (BDAT) levels prior to land disposal may some- times be determined to be applicable or relevant and appropriate requirements (ARARs) for CERCLA response actions. The in situ biodegradation technology can pro- duce a treated waste that meets treatment levels set by BDAT, but may not reach these treatment levels in all cases. The ability to meet required treatment levels is dependent upon the specific waste constituents and the waste matrix. In cases where in situ biodegradation does not meet these levels, it still may, in certain situations, be selected for use at the site if a treatability variance establishing alternative treatment levels is obtained. Treatability variances are justified for handling complex soil and debris matrices. The following guides describe when and how to seek a treatability variance for soil and debris: Superfund LDR Guide #6A, "Obtaining a Soil and Debris Treatability Variance for Reme- dial Actions" (OSWER Directive 9347.06FS, September 1990) [10], and Superfund LDR Guide #6B, "Obtaining a Soil and Debris Treatability Variance for Removal Actions" (OSWER Directive 9347.06BFS, September 1990) [11]. Another ^^ approach could be to use other treatment techniques with //2P^ in situ biodegradation to obtain desired treatment levels, for example, carbon treatment of recovered groundwater prior to re-infiltration into the subsurface. When determining performance relative to ARARs and BDATs, emphasis should be placed on assessing the risk presented by a bioremediation technology. As part of this effort, risk assessment schemes, major metabolic pathways of selected hazardous pollutants, human health protocols for metabolite and pathogenicity tests, and fate protocols and issues for microorganisms and metabolites must be assessed [36]. A detailed summary of the findings of the June 17-18, 1993 EPA/Environment Canada Workshop in Duluth, Minnesota addressing Bioremediation Risk Assess- ment should be available in early 1994. Performance Data Performance data for Superfund sites are limited. The first record of decision (ROD) selecting in situ biodegrada- tion as a component of the remedy was in FY87. Since then, in situ biodegradation of soil or groundwater contaminants has either been considered or selected at 22 Superfund sites and 30 RCRA, UST, TSCA, and Federal sites [1][2][3]. The following two subsections address traditional in situ and bioventing applications, respectively; a third subsection has been included to briefly address information sources and data concerns related to remedial efforts performed in the private sector. Traditional In Situ Bioremediation Methane and phenol were employed during a series of stimulus-response studies investigating the co-metabolic degradation of TCE, cis-dichloroethene (c-DCE), trans- dichloroethene (t-DCE), and vinyl chloride (VC) at the Moffet Field site in California. Both sets of experiments used indigenous bacteria and were performed under the induced gradient conditions of injection and extraction. During the first set of experiments, methane, oxygen, and TCE (from 50 to 100 ^ig/L), c-DCE, t-DCE, and VC were added to the soil to stimulate methanotrophic degradation of the injected chlorinated aliphatic compounds. Approxi- mately 20 percent of the TCE added to the system was degraded within the 2-meter hydraulically-controlled biostimulated zone. Approximately 50 percent of the c- DCE, 90 percent of the t-DCE, and 95 percent of the VC were also degraded. During the second set of tests, meth- ane was replaced with phenol in order to stimulate growth of an indigenous phenol-utilizing population. During 4 weeks of testing, the concentration of TCE injected into the subsurface was raised from an initial concentration of 62 jig/L to a final concentration of 1000 ng/L A bromide tracer was used to determine transformation extent. Up to 90 percent of the TCE in the 2-meter biostimulated zone was degraded, demonstrating that even at relatively high TCE concentrations significant removal efficiencies can be achieved in situ through phenol and dissolved oxygen (DO) addition. During the course of the project, transformation yields (i.e., grams of TCE per grams of phenol) ranging from 0.0044 to 0.062 were obtained for varying concentrations Engineering Bulletin: In Situ Biodegradation Treatment ------- of phenol and TCE. Future studies at the site will determine whether a compound more environmentally acceptable than methane or phenol can be used to induce an indig- enous population that effectively degrades TCE [37][7][8]. A 40- by 120-foot test zone in an aquifer that receives leachate from an industrial landfill at the Du Pont Plant near Victoria, Texas was used to demonstrate the in situ biotrans- formation of tetrachloroethene (PCE), TCE, DCE, chloroethane, and VC to ethane and ethylene using micro- bial reductive dehalogenation under sulfate-reducing con- ditions. Croundwater from this zone was alternately amended with either benzoate or sulfate and circulated through the aquifer. Initially PCE and TCE concentrations were approximately 10 and 1 micro-mole (uM), respec- tively. After a year of treatment the halogenated com- pounds were reduced to concentrations near or below 0.1 ^iM. PCE and TCE degraded to DCE rapidly following the introduction of benzoate. A decrease in sulfate concentra- tions led to increases in the vinyl chloride concentrations. Therefore, sulfate concentrations were kept above 10 mg/ L until the DCE was further biodegraded. After approxi- mately 6 months of treatment, most of the DCE, chloroethane, and VC biodegraded to produce ethane and ethylene [38]. A field-scale in situ bioremediation system, consisting of down-gradient groundwater extraction wells and an up- gradient infiltration system, was installed at a gasoline- contaminated site owned by the San Diego Gas and Electric Company. [Note: extracted groundwater was amended with nutrients (nitrate and phosphate) prior to re-infiltra- tion into the subsurface]. Due to the relatively low rate of groundwater extraction (approximately 800 to 900 gallons per day) and the low hydraulic gradient at the site (0.004), it took nearly 2 years (until June/July 1991) for the added nitrate to reach the down-gradient well and overtake the xylene (BTX) plume. BTX concentrations, which ranged from 25 to 50 mg/L for the preceding 2-year period, dropped markedly as nitrate levels in the groundwater increased. By late August 1991, benzene and toluene concentrations had dropped below the detection limit (0.01 mg/L), and total xylene concentrations had dropped to 0.02 mg/L. The coincident occurrence of nitrate appear- ance and BTX loss in the aquifer, as well as an eight-fold increase in the percentage of denitrifiers present in the groundwater (from 1 to 8 percent), points to a potential stimulatory effect nitrate may have on BTX loss in situ [5]. An in situ bioremediation system consisting of four injection and three recovery wells was employed to treat gasoline contamination present in the saturated zone at a former service station in Southern California. During treat- ment, recovered groundwater was amended with hydro- gen peroxide (from 500 to 1,000 mg/L) and nutrients and re-injected into the aquifer. Prior to treatment, total fuel hydrocarbons in the saturated clay soils ranged from below detection limits to 32 mg/kg as BTX. Maximum groundwa- ter concentrations were 2,700 ^ig/L for benzene; 6,600 ^ig/ L for toluene; 4,100 ng/L for xylene; and 45,000 ng/L for TPH [4]. After 10 months, BTX and TPH levels in the groundwater and saturated soils had dropped below the detection limits. Roughly 1,350 kilograms of hydrogen peroxide were introduced to the aquifer over 10 months, roughly two times the estimated requirements based on the estimated mass of hydrocarbon in the saturated zone (i.e., 110 kg of fuel hydrocarbon and 2 to 3 kg of dissolved hydrocarbons). After 34 months of treatment, soil hydro- carbon concentrations ranged from below the detection limit to 321 ppm as TPH; benzene was not detected in any samples [39]. Following successful laboratory treatability testing, General Electric performed a 10V2-week field study to investigate the biodegradation of polychlorinated biphe- nyls (PCBs) in the Hudson River sediment. Initial PCB concentrations in the sediment ranged between 20 and 40 ppm. The study attempted to enhance the aerobic bacteria native to the upper Hudson River. Six caissons were installed at the Hudson River Research Station (HRRS) to isolate sections of the river bottom for this field study. Because of extensive, naturally occurring dechlorination, approximately 80 percent of the total PCBs encountered in the sediments were mono-, di-, and trichlorobiphenyls. Biodegradation was stimulated using oxygen and nutrient addition. Mixing was employed to enhance the dispersal of oxygen and nutrients within the sediment. Between 38 and 55 percent of the PCBs present in the sediment were removed by aerobic degradation during the study. This corresponds to the percentage biologically available PCBs [9]. Bioventing In May 1992, the U.S. Air Force began a Bioventing Initiative to examine bioventing as a remedial technique at contaminated sites across the country. The Air Force's decision to examine bioventing on such a large scale was prompted by a successful demonstration of the technology at Tyndall AFB, Florida, where bioventing coupled with moisture addition removed one-third of the TPH and nearly all of the BTEX in JP-4 contaminated soils during 7 months of treatment. The Bioventing Initiative targets 138 sites with diesel fuel, jet fuel, or fuel oil in soil. In selecting sites for the initiative, the Air Force looked for characteristics appropriate for bioventing, such as deep vadose soil, heavy hydrocarbon contamination, and high air permeability. The chosen sites represent a wide range of depths to groundwater, hydrocarbon concentrations, and soil tex- tures. Preliminary testing has been completed and 33 systems have been installed at Battle Creek Air National Guard Base and the following AFBs: Beale, Eglin, Eielson, F.E. Warren, Galena, Hanscom, Hill, K.I. Sawyer, McGuire, Newark, Offutt, Plattsburgh, Robins, Vandenberg, and Westover. According to the Air Force, initial results are very promising with degradation rates measured as high as 5,000 mg/kg per year [40][41]. The EPA RREL, in collaboration with the U.S. Air Force, initiated two 3-year pilot-scale bioventing field studies in mid-1991 at JP-4 contaminated fuel sites located at Eielson AFB near Fairbanks, Alaska and at Hill AFB near Salt Lake City, Utah. Four soil plots are being used to evaluate passive, active, and buried heat tape soil-warming methods 8 Engineering Bulletin: In Situ Biodegradation Treatment ------- during the Eielson study. The fourth plot was vented with injected air but not artificially heated. Roughly 1 acre of soil is contaminated from a depth of 2 feet to the water table at 6 to 7 feet. At the Hill site, a series of soil gas cluster wells capable of obtaining samples up to 90 feet deep is being used with a single air injection well and two groundwater wells to remediate JP-4 contamination found at depths ranging from 35 feet to perched water at approximately 95 feet. Inert gas tracer studies, regular soil gas measurements at several locations and depths, and periodic in situ respirom- etry tests to measure in situ oxygen uptake rates are being performed. Final soil hydrocarbon analyses will be con- ducted at both sites in mid-1994 and compared with the initial soil data. In situ respirometry data from the Hill site (Table 1) indicate that petroleum hydrocarbons are being removed at a significant rate. Intermediate respirometry data from the test and control plots at the Eielson site indicate that higher biodegradation rates are being ob- tained at higher soil temperatures.[42][43]. Table 2. Groundwater Quality After Seven Months of Biosparging at the U.S. Coast Guard Air Station in Traverse City, Michigan Well Depth (ft) Control 16 17.5 20.5 22 Sparge Plot 15 18 19.5 21 Benzene (US/L) 9.9 228 70 57 1.9 <1 <1 <] Xylenes (ng/L) 19 992 38 7.7 5.3 5.0 <1 <"• Total Fuel Carbon (u,g/L) 2,880 4,490 956 783 559 <6 <6 <6 Table 1. Rates of Biodegradation, Averaged Over Depth, at Three Wells at Hill AFB Well CW-1 CW-2 CW-3 Depths (ft) 20-90 60-90 10-90 Rate (mg/kg/day) September 1991 0.97 0.59 0.56 September 19921 0.30 0.36 0.32 1 Since bioventing is being performed on a sandy soil, with little to no naturally occurring organic matter, a biodegradation rate approaching zero would indicate that biodegradation had finished. In November 1991, a pilot-scale bioventing system originally used to treat gasoline-contaminated vadose soils at the U.S. Coast Guard Air Station in Traverse City, Michi- gan was converted into a groundwater biosparging pro- cess. Eight 2-inch diameter sparge wells were installed to a depth of 10 feet below the water table. A control plot located in the vicinity of the contaminated plume, but not biosparged, was established to help assess the system's performance. After 12 months of biosparging, one-third of the oily phase residue below the water table, as well as almost all the BTEX initially present within the groundwater plume, was removed. (See Table 2 for groundwater quality data after 7 months of biosparging.) The globular nature of the oily residue limited the surface area in contact with the introduced air, thus restricting the biodegradation and vaporization of the oily-phase contaminants [44][45]. Non-Superfund Sites In situ biodegradation has been applied at many sites in the private sector. Those interested in accessing informa- tion generated in the private sector may want to refer to the following EPA Publications: U.S. Environmental Protection Agency. Bioremediation Case Studies: Abstracts. EPA/600/R-92/044, March 1992. U.S. Environmental Protection Agency. Bioremediation Case Studies: An Analysis of Vendor Supplied Data. EPA/600/9-92/043, March 1992. Most of the data contained in these resources were directly supplied by the vendor and have not been techni- cally reviewed by EPA. Since independently-reviewed data are not always available from privately sponsored remedial efforts, in part due to proprietary issues [46, p. 1 -1 ], readers should use these data cautiously. Often the quality of the data used to determine system effectiveness has not been substantiated by the scientific community. Thus, many vendor claims of effectiveness, specifically regarding intro- duced organisms and surface-active agents, are not sup- ported within the scientific literature. Furthermore, many bioremediation firms have only limited experience working with the complex wastes normally associated with Super- fund sites. Typically these firms deal only with gasoline and petroleum product leaks and spills. Additionally, many of the systems currently on the market involve the use of in situ biodegradation in combination with other above-ground treatment technologies such as carbon adsorption, air stripping, and biological reactors. In situ biodegradation is believed to enhance the total removal efficiency of the system. However, in many cases, it is unclear how much of the degradation occurred as a result of biological or non- biological mechanisms (volatilization, chemical destruc- tion, etc.). How much biodegradation actually takes place in the soil or groundwater, in contrast to ex situ biodegra- dation, is not always clear. Engineering Bulletin: In Situ Biodegradation Treatment ------- Technology Status In situ biodegradation either has been considered or selected as the remedial technology at 21 Superfund sites, as well as 38 RCRA, UST, TSCA, and Federal sites[l][2][3]. Table 3 lists the location, primary contaminants, treatment employed, and status of these sites. Information has also been included on three in situ biotechnology demonstra- tions presently being performed under the U.S. EPA Super- fund Innovative Technology Evaluation (SITE) Program and seven sites selected for performance evaluations under the U.S. EPA Bioremediation Field Initiative. The data obtained during the SITE demonstrations and Bioremediation Field Initiative performance evaluations will be used to develop reliable cost and performance information on biotreatment technologies and applications. The majority of the information found in Table 3 was obtained from the August 1993 version of "Bioremediation in the Field" [1], These sites have been sorted numerically by Region and then alphabetically by site name. Sites employing "in situ land treatment" were not included in this list since these applications typically involve a signifi- cant amount of material handling. Additionally, some of the information was modified based on phone calls made to the various site project managers. This resulted in the removal of the American Creosote Works site in Florida and four pesticides sites (i.e., the Joliet Weed Control District site in the Joliet, Montana; the Lake County Weed Control site in Ronan, Montana; the Miles Airport site in Miles City, Montana; and the Richey Airport site in Richey, Montana) [47], which are no longer considering in situ treatment. Quarterly updates of this information can be obtained from subsequent versions of "Bioremediation in the Field". Most of the hardware components of in situ biodegra- dation systems are available off-the-shelf and present no significant availability problems. Selected cultures, nutri- ents, and chemical/biological additives are also readily obtainable. Bioremediation, particularly in situ applications, which avoid excavation and emissions control costs, are generally considered cost effective. This can be attributed in part to low operation and maintenance requirements. During set up and operation, material handling requirements are mini- mal, resulting in lowered worker exposures and reduced health impacts. Although in situ technologies are generally slow and somewhat difficult to control, a large volume of soil may be treated at one time. It is difficult to generalize about treatment costs since site-specific characteristics can significantly impact costs. Typically, the greater the number of variables requiring control during biological treatment, the more problematic the implementation and the higher the cost. For example, it is less problematic to implement a technology in which only one parameter (e.g., oxygen availability) requires modification than to implement a remedy that requires modification of multiple factors (e.g., pH, oxygen levels, nutrients, microbes, buffering agents, etc.). Initial concen- trations and volumes, pre- and post-treatment require- ments, and air emissions and control systems will impact final treatment costs. The types of amendments employed (e.g., hydrogen peroxide) can also impact capital cost and costs associated with equipment and manpower required during their application. In general, however, in situ bioremediation is consid- ered to be a relatively low-cost technology, with costs as low as 10 percent of excavation or pump and treat costs [7, p. 6-16]. The cost of soil venting using a field-scale system has been reported to be approximately $50 per ton as compared to incineration, which was estimated to be more than ten times this amount. A cost estimate of about $15 per cubic yard for bioventing sandy soil at a JP-4 jet fuel contaminated site has been reported by Vogel [48]. Exclu- sive of site characterization, the biological remediation of JP-4 contaminated soils at the Kelly Air Force Base site was estimated to be $160 to $230 per gallon of residual fuel removed from the aquifer [9]. At the French Limited site in Texas, the cost of bioremediation is projected to be almost three times less expensive than incineration. Because of the large amount of material requiring treatment at this site, it has been projected that cleanup goals will be achieved in less time by using bioremediation rather than incineration. EPA Contact Technology-specific questions regarding in situ bio- degradation may be directed to: Steve Safferman, EPA-RREL Cincinnati, Ohio (513)569-7350 John Matthews, EPA-RSKERL Ada, Oklahoma (405) 436-8600 Acknowledgments This bulletin was prepared for the U.S. Environmental Protection Agency, Office of Research and Development (ORD), Risk Reduction Engineering Laboratory (RREL), Cin- cinnati, Ohio, by Science Applications International Corpo- ration (SAIC) under Contract No. 68-C8-0062 and Contract No. 68-CO-0048. Mr. Eugene Harris served as the EPA Technical Project Monitor. Mr. Jim Rawe served as SAIC's Work Assignment Manager. This bulletin was authored by Mr. Rawe and Ms. Evelyn Meagher-Hartzell of SAIC. The following other Agency and contractor personnel have contributed their time and comments by participating in the expert review meetings or independently reviewing the document: Mr. Hugh Russell Ms. Tish Zimmerman Mr. Al Venosa Dr. Robert Irvine Dr. Ralph Portier Mr. Clyde Dial EPA-RSKERL EPA-OERR EPA-RREL University of Notre Dame Louisiana State University SAIC w Engineering Bulletin: In Situ Biodegradation Treatment ------- Table 3. Superfund, RCRA, UST, TSCA, and Federal Sites Site Location (Regions) Primary Contaminants Status/Cost Treatment Chariestown Navy Yarc Boston, MA (t) General Electric - Woods Pond Pittsfield, MA(1) FAA Technical Center - AreaD Atlanta County, Nj (2) General Electric - Hudson River, NY (2) Knispel Construction Site Horsehead, NJ (2) Picatinny Arsenal NJ(2) Plattsburgh AFB Plattsburgh, NY (2) ARC ainesville, VA (3) Dover AFB Dover, DE (3) .A. Clarke & Son redericksburg, VA (3) Charleston AFB Iharieston, SC (4) glin AFB L(4) avannah River Site Uken, NC (4) tallworth Timber eatrice, AL (4) Hied Chemical onton, OH (5) moco Production Co. alaska, Ml (5) &F Trucking ompany ochester, MN (5) endixCorp./Allied 1 utomotive Site . Joseph, Ml (5) Sediments: wood preserving (PAHs). Sediments: PCBs. Volume: 250 gallons. Soil (saturated sand)/groundwaten petroleum (Jet fuel, NAPLs). Volume: 33K cubic yards. Sediments: PCBs, cadmium, chromium, lead. Volume: 150 cubic feet. Soil/groundwater: petroleum. Soil (vadose)/soil vapors: solvents CTCE). Groundwater: petroleum. oil: solvent (chlorobenzene). Volume: 2,000 cubic yards. Soil (vadose sand and silt)/ground- water: petroleum, PAHs, TCE, solvents, metals (lead, iron, manganese). 'olume: 365K cubic yards. Sediments/soil: wood preserving. /olume: 119K cubic yards. oil (vadose sand): petroleum (jet uel), solvents (1,1 -DCE; 1,1,1 -TCA; TCE; VC; trans-1,2-DCE; PCE; and ichloromethane), lead. /olume: 25 cubic yards. oil (vadose): petroleum (jet fuel). oil(yadose)/groundwater/sediments: hlorinated solvents (TCE and PCE). oil (sand, silt)/groundwater: wood reserving (PCP). ediments (coal and coke fines): PAHs, rsenic, olume: 500K cubic yards. oil (saturated)/groundwater: BTEX. oil (vadose and saturatedrg)/ground- ater: petroleum (lube oil). olume: 700 cubic yards. roundwater: solvents (TCE, DCE, CA, VC). Design: pilot scale TS underway. Design: lab scale TS underway. Design: pilot scale TS completed 8/927 Expected cost: capital, S286K; O&M, S200K Predesign: lab scale TS completed. Incurred cost: S2.6M. Completed: full scale 10/89 Start date: 01/89. ncurred cost: O&M, $25K. Design: lab scale studies completed. Design: pilot scale. Start date (est.): 3/94. Completed: full scale 6/91. "tart date: 10/89. Four separate processes are planned. Field and lab TS results are expected 2/94 and 11/94. Design: pilot scale TS started 7/92 Expected cost: $23M. >ilot scale TS started 11/92. Expected completion 12/93. Completed field scale study. Operational: pilot scale research tudy. redesign. esign: pilot scale TS study ompleted. xpected cost: $26M lot scale TS completed. perational: full scale. tart Date: 4/91. curredcost: J341K. edesign: lab scale TS underway. In situ treatment. Ex situ treatment Aerobic and anaerobic. Anaerobic treatment, confined treatmen facility, nutrient addition. Nutrient addition (soil, water). Groundwater re-injection. Aerobic treatment. Less than 1% of site underwent bioremediation. Aerobic treatment, hydrogen peroxide, nutrient addition (water). 100% of site underwent bioremediation [25]. Aerobic treatment, bioventing. Co-metabolic degradation (methane, propane, or natural gas) [27]. Aerobic treatment, bioventing. Aerobic treatment, bioventing. Exogenous organisms. 5% of the site underwent bioremediation. Aerobic treatment, bioventing, air parging. Ex situ land treatment. T situ treatment, creosote recovery. 5% of site will undergo bioremediation. ierobic treatment, bioventing. Less than 0% of the site under bioremediation. Aerobic treatment, bioventing. Nutrient nd hydrogen peroxide addition [27]. erobic treatment, horizontal wells, methane addition [18][19], n situ aerobic treatment, nutrient ddition. Ex situ treatment, activated udge, continuous flow. Exogenous and idigenous organisms. 100% of site will ndergo bioremediation. erobic treatment 50% of site will ndergo bioremediation. erobic treatment, air sparging [49]. situ treatment. Ex situ treatment equencing batch reactor, continuous ow. AeroDic conditions. 75% of site nder bioremediation. erobic and anaerobic treatment. Engineering Bulletin: In Situ Biodegradation Treatment 11 ------- Table 3. Superfund, RCRA, UST, TSCA, and Federal Sites (continued) Site Location (Regions) Primary Contaminants Status/Cost Treatment n-named site2 uchanan, Ml (5) alesburg/Kopper alesburg, IL (5) entchells raverse City, Ml (5) enworth Truck Company hillicothe, OH (5) J. Sawyer AFB vlarquette, Ml (5) vlayville Fire Department vlayville, Ml (5) vlichigan Air National Guard -attle Creek, Ml (5) Newark AFB Newark, OH (5) Onalaska Municipal Landfill Lacrosse County, Wl (5) Parke-Davis Holland, Ml (5) Reilly Tar & Chemical 1«2 St. Louis Park, MN (5) Sheboygan River and Harbor Sheboygan, IL (5) West K&L Avenue e Landfill 1 Kalamazoo, Ml (5) Wright-Patterson AFB Dayton, Ohio (5) Dow Chemical Company Plaquemine, LA (6) French Limited Crosby, TX (6) Kelly AFB San Antonio, TX (6) roundwater: BTEX, PCE, TCE, DCE. oil: phenols, chlorophenol, PNAs, CP, PAHs. oil/groundwater: petroleum. oil (vadose)/groundwater: olvents (BTEX, acetone, TPH). oil (vadose sand): petroleum. iroundwater: petroleum. >oil (vadose: sand, silt): petroleum, heavy metals. Soil (vadose: silt, clay): petroleum gasoline). volume: 60 cubic yards. Soil (vadose and saturated sand): solvents (TCE), petroleum (total lydro-carbons), wood preserving naphthalene). Volume: 5,000 cubic yards. Soil/groundwater: petroleum, solvents, arsenic, chloride, zinc. Soil (vadose loam): wood preserving (PAHs). Sediments (sand, silt, clay): PCBs. Volume: 2,500 cubic yards. Croundwater: solvents (acetone; TCE; trans-1,2-DCE; 1,2-DCA; 1,1-DCA; BTEX; VC; methyl isobutyl ketone; MEK. Soil (vadose: sand, silt, clay): petroleum (jet fuel). Volume: 7.5K cubic yards. Croundwater: solvents (1,1-DCA; 1,2-DCA;1,1,1-TCA;1,1-DCE, chloroethane). Volume: 90K cubic yards. Sediments (sand, silt)/sludge/soil (sand, silt, clay)/groundwater: PCBs, arsenic, roleum (BAP, VOCs), arsenic. Soil (vadose clay): petroleum (jet fuel), solvents (Pc£ TCE, VC, DCE). ilot field study started 3/93. xpected completion 3/94. redesign. tart date (est): 12/92. )perational: full scale. tart date: 9/85. esign: lab scale TS completed. ull scale system being installed. ield TS report expected 10/93. Operational: full scale since 5/90. Completion date (est): 1 /94. Design: pilot scale TS started ->/92 tart date (est): 9/93 Expected cost: capital, $3,000; O&M, $1,268. Design: pilot scale TS started 8/92. Expected completion 8/94. Expected cost: capital, $35K; O&M, $2K. Design: lab scale TS completed 3/92. Expected cost: capital, $400K; O&M, $20K. 'redesign. Design: pilot scale TS started 11 /92. Expected completion 11/95. ncurred cost: $25K. Expected cost: $70K. Lab and pilot scale TS are being conducted. Design: pilot and lab scale TS ongoing. Predesign: pilot scale studies planned. Expected completion 3/94. Design: pilot scale started 3/93. Expected cost: capital, $1M; O&M, $50K. Incurred cost: capital, $250K; O&M, $10K. Operational: full scale since 1 /92 Expected cost: $90M. Operational: full scale since 2/93 Completion data (est): 9/94. erobic treatment. Nutrient addition. 100% of site nder bioremediation. erobic treatment, biosparging. situ aerobic treatment, hydrogen eroxide, nutrient addition nitrogen, phosphorus). Ex situ reatment, CAt bioreactor. 100% of te will undergo bioremediation. Aerobic treatment, bioventing. Aerobic treatment, air sparging. 00% of site will undergo lioremediation. icrobic treatment, bioventing. 00% of site will undergo jioremediation. Aerobic treatment, bioventing. 40% of site under bioremediation. Aerobic treatment, bioventing. 20% of site will undergo bioremediation. n situ treatment. Ex situ treatment, ixed film. Aerobic treatment, bioventing, nutrient addition [50]. n situ treatment, capping of sediments. Ex situ treatment, confined treatment facility (tank). Aerobic and anaerobic conditions. Anaerobic treatment under sulfate reducing conditions. Aerobic treatment, bioventing. 100% of site will undergo bioremediation. Anaerobic treatment, nutrient addition. Less than 1% of site under bioremediation. Experiencing; nutrient dispersion problems [46]. Aerobic treatment, pure oxygen dissolution system, nutrient addition (soil, water, sediments). 100% of site under bioremediation. Aerobic treatment, bioventing. 12 Engineering Bulletin: In Situ Biodegradation Treatment ------- Table 3. Superfund, RCRA, UST, TSCA, and Federal Sites (continued) Site Location (Regions) Primary Contaminants Status/Cost Treatment Fairfield Coal & Gas Faiffield,IA(7) Offutt AFB LaPlatte, NE (7) ParkCrty1 Park City, KS (7) Burlington Northern Tie Plant Somers, MT (8) Geraldine Airport Geraldine, MT (8) Idaho Pole Company Bozeman, MT (8) Hill AFB1 Salt Lake City, UT (8) Libby Groundwater Site1 Libby, MT (8) Public Service Company1 Denver, CO (8) Beale AFB Marysville, CA (9) Converse/Montabello Corporation Yard Montabello, CA (9) :ormer Service Station Los Angeles, CA (9) Orvi ppers Company, inc. Marine Corps Air/ Ground Combat Center Twenty-Nine Palms, CA(9) ^aval Air Station Fallen allon, NV (9) slaval Weapons Station >eal Beach, CA (9) Oakland Chinatown Oakland, CA (9) Soil (saturated: sand, silt clay)/groundwater: coal tar (BTEX, PAHs): Soil (vadose: sand, silt): petroleum (TRPH), arsenic, barium, lead, zinc. Volume: 700 cubic yards. Groundwater: petroleum (lube oil), benzene. Volume: 700K cubic feet. Soil/groundwater: wood preserving (PAHs). Volume: 82K cubic yards. Soil (vadose: sand, silt, loam, clay): pesticides (aldrin; dieldrin; endrin; chlordane; toxaphene; b-BHC; 4,4'-DDE; 4,4'-DDT; 4,4'-DDD); herbicides (2,4-D). Sediments/soils/groundwater: PCP, PAHs, dioxins/furans. Soil: petroleum (JP-4 jet fuel). Soil (vadose and saturated)/ groundwater: wood preserving (PAHs, Dyrene, PCP, dioxin, naphthalene, anenanthrene, benzene, arsenic). /olume: 45K cubic yards. roundwater: petroleum. Volume: 12M gallon. Soil (vadose silty clay): petroleum [gasoline, diesel), solvents (TCE), lead. volume: 163K cubic yards. Soil (vadose silt): petroleum (gas, diesel). oil/groundwater: petroleum. Volume: 3,000 cubic yards. Soil (vadose: sand, clay, gravel, cobbles): wood preserving (PCP, PAHs, dioxins/furans), arsenic, chromium. Volume: 110K cubic yards. Soil: petroleum (jet fuel, gasoline, diesel, aviation fluid, luid). transmission Soil (vadose and saturated ilt)/groundwater: petroleum (jet fuel, >-xylene. naphthalene, 1-methyl naphthalene, n-butylbenzene), irsenic. Jroundwater: petroleum. oil (saturated sand): groundwater: petroleum. Design: pilot scale TS started 12/91. Expected completion 12/93. Expected cost: 51.6M. Design: pilot scale TS started 8/92 Design: pilot scale TS completed. Incurred cost: J275K. Expected cost: J650K. Installed: full scale. Start date (est): 7/92. Expected cost: J11M. Predesign. Predesign. Operational: full scale since 9/91. Completion date (est): 9/94. Operational: three pilot scale efforts ongoing. ncurred cost: $4M. TS results available (est): 8/93 and 4/94. Completed: full scale 3/92. Start date: 06/89. incurred cost: S500K. Seven processes are planned. 4 are in design (pilot scale), 2 are in predesign (full scale), and 1 is presently operating completion date 7/95). Lxpected cost: capital J500K; O&M, 136K. Design: pilot scale TS started 5/93 Expected completion 12/93. Completed: full scale 3/91 Start date: 11/88. ncurred cost: 51.6M. 'redesign; pilot scale TS planned. Ixpected completion 11 /94, Expected cost: capital, S4.5M; O&M, S7.7M, Design: full scale. Design: pilot scale TS started 0/92. S conducted or in progress: aboratory scale. 'olume: 10K cubic yards. Completed: full scale 8/90. >tart date: 3/89. Aerobic treatment, injection and extraction wells, hydrogen peroxide, nitrate addition. Aerobic treatment, bioventing. 10% of site under bioremediation. Groundwater: in situ treatment. Possible bioventing for soils. Anaerobic and aerobic conditions [23][24]. In situ treatment. Ex situ land treatment. Aerobic conditions. 80% of site will undergo bioremediation. In situ treatment. Ex situ treatment. Aerobic and anaerobic conditions. In situ treatment, oxygen enhancement, nutrient addition. Ex situ treatment, fixed film, slurry reactor. Aerobic conditions. Aerobic treatment, bioventing. 100% of site under bioremediation [4(5]. In situ treatment (groundwater), ex situ and treatment (soil), nutrient addition [soil, water). Also, treatment of groundwater in bioreactor. Aerobic :onditions. 75% of site under bioremediation. Aerobic treatment, hydrogen peroxide, nutrient addition, combined bioprocess. n situ aerobic treatment, bioventing. :x situ aerobic treatment, pile. Results of 4 bioventing TS expected 2/94. Aerobic treatment, bioventing, nutrient addition. 10% of site under bioremediation. Aerobic treatment, hydrogen peroxide, nutrient addition (water), closed loop system. 65% of site underwent )ioremediation. Aerobic treatment, nutrient addition. 30% of site will undergo bioremediation. '20 year remedial effort) Aerobic treatment, bioventing. Aerobic treatment, bioventing, nutrient addition (soil), oil/water separation. Aerobic and anaerobic treatment. Aerobic treatment, hydrogen peroxide nd nutrient addition. Engineering Bulletin: In Situ Biodegradation Treatment 13 ------- Table 3. Superfund, RCRA, UST, TSCA, and Federal Sites (continued) Site Location (Regions) Primary Contaminants Status/Cost Treatment San Diego Cas and Electric San Diego, CA (9) Williams AFB2 Phoenix, AZ (9) East 15th Street Service Station Anchorage, AK (10) Eielson AFB' Fairbanks, Alaska (10) FairchildAFB Spokane, WA (10) Soil (sand): petroleum (gasoline). Volume: 1,200 cubic yards. Soil (vadose): petroleum (JP-4 jet fuel). Soil: petroleum (TPH diesel). Volume: 1,500 cubic yards. Soil (sand/silt): petroleum QP-4 jet fuel). Soil (vadose and saturated silt)/groundwater: petroleum, solvents (TCE). Completed: full scale 4/93. Start date: 10/89. Pilot field testing started 5/92. Test completed 6/93. Operational: full scale since 6/92. Incurred cost: J75K. Expected cost: $200K. Operational: pilot full scale. Start date: 9/91. Completion date (est): 9/94. 3 separate processes are planned. The first process is in pre-design; a pilot scale TS should start 1/95. The remaining two started pilot scale TSs in 4/93. Aerobic treatment. 100% of site underwent bioremediation [5]. In situ treatment, bacterial supplementation (non-indigenous micro aerofilic bacteria). Aerobic treatment, bioventing. 20% of site under bioremediation. Aerobic treatment, bioventing, soil warming [42] Aerobic treatment, bioventing, nutrient addition. TS - Treatability Study 1 Bioremediation Field Initiative 2 Superfund Innovative Technology Evaluation (SITE) Demonstration REFERENCES 1. U.S. Environmental Protection Agency. Bioremediation in the Field. EPA/540/N-93/002, August 1993. 2. U.S. Environmental Protection Agency. Superfund Inno- vative Technology Evaluation Program: Technology Pro- files, Sixth Edition. EPA/540/R-93/526, November 1993. 3. U.S. Environmental Protection Agency. Bioremediation Field Initiative. EPA/540/F-93/510, September 1993. 4. U.S. Environmental Protection Agency. Handbook on InSitu Treatment of Hazardous Waste-Contaminated Soils. EPA/540/2-90/002, Cincinnati, Ohio, January 1990. 5. Gersberg, R.M., W.J. Dawsey, and H. Ridgeway. Draft Final Report: In-Situ Microbial Degradation of Gasoline. EPRI Research Report Number RP 2795-2. 6. Norris, R.D., K. Dowd, and C. Maudlin. The Use of Mul- tiple Oxygen Sources and Nutrient Delivery Systems to Effect In Situ Bioremediation of Saturated and Unsatur- ated Soils. Presented in: Symposium on Bioremediation of Hazardous Wastes: Research, Development, and Field Evaluations. EPA/600/R-93/054, May 1993. 7. Hopkins, G.D., L. Semprini, and P. McCarty. Field Evaluation of Phenol for Cometabolism of Chlorinated Solvents. In: Symposium on Bioremediation of Hazard- ous Wastes: Research, Development, and Field Evalua- tions. EPA/600/R-93/054, May 1993. 8. 9. Hopkins G.D., L. Semprini, and P.L. McCarty. Evalua- tion of Enhanced In Situ Aerobic Biodegradation of CIS- and Trans-1-Trichloroethylene and CIS- and Trans-1,2- Dichloroethylene by Phenol-Utilizing Bacteria. In: Bioremediation of Hazardous Wastes. EPA/600/r-92/ 126, August 1992. Abramowicz, et al. 1991 In Situ Hudson River Research Study: A Field Study on Biodegradation of PCBs in Hudson River Sediments - Final Report. February 1992. 10. U.S. Environmental Protection Agency. Superfund LDR Guide #6A: Obtaining a Soil and Debris Treatability Vari- ance for Remedial Actions. OSWER Directive 9347.3- 06FS, September 1990. U.S. Environmental Protection Agency. Superfund LDR Guide #6B: Obtaining a Soil and Debris Treatability Vari- ance for Removal Actions. OSWER Directive 9347.3- 06BFS, September 1990. Sims, ]., R. Sims, and J. Matthews. Bioremediation of Contaminated Surface Soils. EPA/600/9-89/073, August 1989. Sims, J., R. Sims, R. Dupont,). Matthews, and H. Russell. Engineering Issue - In Situ Bioremediation of Contami- nated Unsaturated Subsurface Soils. EPA/540/S-93/501, May 1993. Piotrowski, M.R. Bioremediation: Testing the Waters. Civil Engineering, August 1989. pp. 51-53. 11 12 13. 14. 14 Engineering Bulletin: In Situ Biodegradation Treatment ------- 15. U.S. Environmental Protection Agency. International Evaluation of In-Situ Biorestoration of Contaminated Soil and Groundwater. EPA/540/2-90/012, September 1990. 16. U.S. Environmental Protection Agency. Handbook: Re- medial Actions at Waste Disposal Sites (Re- vised). EPA/625/6-85/006, Cincinnati, Ohio, October 1985. 17. U.S. Environmental Protection Agency. Review of In- Place Treatment Techniques for Contaminated Surface Soils. Volume 2: Background Information for In Situ Treatment. EPA/540/2-84/003b, Cincinnati, Ohio, No- vember 1984. 18. Hazen, T.C. Test Plan for In Situ Bioremediation Dem- onstration of the Savannah River Integrated Demonstra- tion Project DOE/OTD TTP No.: SR 0566-01 (U). U.S. Department of Energy, WSRC-RD-91-23, Revision 3, April 23, 1992. 19. U.S. Department of Energy. Cleanup of VOCs in Non- Arid Soils - The Savannah River Integrated Demonstra- tion. WSRC-MS-91-290, Rev. 1, pg. 6. 20. U.S. Environmental Protection Agency. Technology Screening Guide for Treatment of CERCLA Soils and Sludges. EPA/540/2-88/004, September 1988. 21. U.S. Environmental Protection Agency. SITE Demon- stration Bulletin - Augmented In Situ Subsurface Bioremediation Process, BIO-REM, Inc., EPA/540/MR- 93/527, November 1993. 22. McCarty P. and J. Wilson. Natural Anaerobic Treatment of a TCE Plume, St Joseph, Michigan, NPL Site. In: Bioremediation of Hazardous Wastes. EPA/600/R-92/ 126, August 1992. 23. Hutchins, S.R., and J.T. Wilson. Nitrate-Based Bioremediation of Petroleum-Contaminated Aquifer at Park City, Kansas: Site Characterization and Treatability Study. In: Hydrocarbon Bioremediation. R.E. Hinchee, B.C. Alleman, R.E. Hoeppel, and R.N. Miller, ed. CRC Press, Boca Raton, Florida, 1994. 24. Kennedy, L.G., and S.R. Hutchins. Applied Geologic, Microbiological, and Engineering Constraints of In-Situ BTEX Bioremediation. Remediation. Winter 1992/93. 25. New York State Department of Environmental Conserva- tion. Final Report, Knispel Construction Company, Horseheads, New York, October 1990. 26. Marley, M.C., et al. The Application of the In Situ Air Sparging as an Innovative Soils and Groundwater Reme- diation Technology. Groundwater Monitoring Review, pp. 137-144, Spring 1992. 27. Federal Remediation Technologies Roundtable. Synop- ses of Federal Demonstrations of Innovative Site Reme- diation Technologies. EPA/542/B-92/003, August 1992. 28. U.S. Environmental Protection Agency. Vendor Informa- tion System for Innovative Treatment Technologies (VISITT). EPA/540/2-91/001, June 1991. 29. U.S. Environmental Protection Agency. A Citizen's Guide to Bioventing. EPA/542/F-92/008, March 1992. 30. U.S. Environmental Protection Agency. Bioremediation in the Field. EPA/540/2-91 /018, August 1991. 31. U.S. Environmental Protection Agency. Bioremediation in the Field. EPA/540/N-91/001, March 1992 32. U.S. Environmental Protection Agency. The Superfund Innovative Technology Evaluation Program: Technology Profiles, Fifth Edition. EPA/540/R-92/077, December 1992. 33. Hinchee, R.E., D.C. Downey, R.R. DuPont, P.K. Aggarwal, and R.N. Miller. Enhancing Biodegradation of Petroleum Hydrocarbons through Soil Venting. Jour- nal of Hazardous Materials, Vol. 27, 1991. 34. Nelson, C.H. A Natural Cleanup. Civil Engineering, March 1993. 35. Wilson, J.T., and D.H. Kampbell. Retrospective Perfor- mance Evaluation on In Situ Bioremediation: Site Char- acterization. In: Symposium on Bioremediation of Hazardous Wastes: Research, Development, and Field Evaluations. EPA/600/R-93/054, May 1993. 36. Day, S., K. Malchowsky, T. Schultz, P. Sayre, and G. Saylor. Draft Issue Paper: Potential Risk, Environmental and Ecological Effects Resulting From the Use of GEMS for Bioremediation. U.S. Environmental Protection Agency, Office of Pollution Prevention, April 1993. 37. Hopkins, G.D., L. Semprini, and P.L. McCarty. Field Study of In Situ Trichloroethylene Degradation in Groundwater by Phenol-Oxidizing Microorganisms. In: Abstract Proceedings Nineteenth Annual RREL Hazard- ous Waste Research Symposium. EPA/600/R-93/040, April 199 3. 38. Beeman, R., S. Shoemaker, j. Howell, E. Salazar, and J. Buttram. A Field Evaluation of In Situ Microbial Reduc- tive Dehalogenation by the Biotransformation of Chlori- nated Ethylenes. In: Bioremediation of Chlorinated Polycyclic Aromatic Hydrocarbon Compounds. R.E. Hinchee, A. Leeson, L. Sempini, and S.K. Ong, ed. CRC Press, Boca Raton, Florida, 1994. 39. Norris, R.D., K. Dowd, C. Maudlin, and W.W. Irwin. The Use of Multiple Oxygen Sources and Nutrient Delivery Systems to Effect In Situ Bioremediation of Saturated and Unsaturated Soils In: Hydrocarbon Bioremediation. R.E. Hinchee, B.C. Alleman, R.E. Hoeppel, and R.N. Miller, ed. CRC Press, Boca Raton, Florida, 1994. 40. U.S. Air Force Correspondence. Subject: Air Force's Bioventing Initiative. July 1993. 41. U.S. Environmental Protection Agency. Bioremediation in the Field. EPA/540/N-92/004, October 1992. 42. Sayles, G.D., R.E. Hinchee, C.M. Vogel, R.C. Brenner, and R. N. Miller. An Evaluation of Concurrent Bioventing of Jet Fuel and Several Soil Warming Meth- ods: A Field Study at Eielson Air Force Base, Alaska. In: Symposium on Bioremediation of Hazardous Wastes: Research, Development, and Field Evaluations. EPA/ 600/R-93/0-54, May 1993. 43. Sayles, G.D., R.E. Hinchee, R.C. Brenner, and R. Elliot. Engineering Bulletin: In Situ Biodegradation Treatment 75 GOVERNMENT PRINTING OFFICE: 1994 - 550-067/80224 ------- |