Bioremediation of Relcalcitrant Compounds - Chapter 7 pot

215 chapter seven Polycyclic aromatic hydrocarbons (PAHs): improved land treatment with bioaugmentation Hap Prichard, Joanne Jones-Meehan, Cathy Nestler, Lance D. Hansen, William Straube, William Jones, John Hind, and Jeffrey W. Talley Contents 7.1 Land-farming background 217 7.1.1 Polycyclic aromatic hydrocarbons 217 7.1.1.1 Chemical structure and source of contamination 217 7.1.1.2 Toxicity and benzo(a)pyrene toxic equivalent factors 217 7.1.1.3 PAH bioavailability 220 7.1.1.4 Problem summary 221 7.1.2 Available treatment options 222 7.1.3 Thrust area: early studies 222 7.1.3.1 Solid phase treatments 224 7.1.3.2 Slurry phase treatment 226 7.1.3.3 Performance comparison 226 7.1.3.4 The flask-to-field selected treatment option (land farming) 228 7.1.3.5 Microbiological studies 228 7.2 Objectives 241 7.3 Technical approach 242 7.3.1 Site description 242 L1656_C007.fm Page 215 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC 216 Bioremediation of Recalcitrant Compounds 7.3.2 Soil characterization 243 7.3.3 Flask (bench-scale) experimental design 244 7.3.4 Flask (bench-scale) materials 244 7.3.4.1 Bacteria 244 7.3.4.2 Amendments 244 7.3.5 Flask (bench-scale) methods 245 7.3.5.1 Isolation and characterization of PAH-degrading bacteria 245 7.3.5.2 Biosurfactant production 247 7.3.5.3 Bioaugmentation 248 7.3.5.4 Carrier technology development 249 7.3.5.5 Biostimulation 251 7.3.5.6 Microcosm preparation 252 7.3.5.7 Microbial analysis 252 7.3.5.8 Chemical analysis 252 7.3.6 Pilot studies: experimental design 253 7.3.6.1 LTU objectives 255 7.3.6.2 Trough study objectives 255 7.3.7 Land treatment units: assembly 255 7.3.8 Trough study: assembly 255 7.3.9 Pilot-scale materials 257 7.3.10 Pilot-scale methods 259 7.3.10.1 Sampling design 259 7.3.10.2 Physical analysis 260 7.3.10.3 Chemical analysis 260 7.3.10.4 Microbial analysis 261 7.3.10.5 Metabolic analysis 261 7.3.10.6 Statistical analysis 261 7.4 Accomplishments 262 7.4.1 Flask studies 262 7.4.1.1 PAH removal 262 7.4.1.2 Biosurfactant production 266 7.4.1.3 Nutrient amendment 267 7.4.1.4 Vermiculite carrier technology 268 7.4.2 LTU pilot project 270 7.4.2.1 Chemical characteristics 270 7.4.2.2 PAH removal 271 7.4.2.3 Microbial characterization 273 7.4.2.4 Soil respiration 276 7.4.3 Trough pilot project 276 7.4.3.1 Chemical characterization 276 7.4.3.2 PAH removal 276 7.4.3.3 Microbial characterization 282 7.4.3.4 Metabolic analysis: trough soil respiration 283 7.4.4 Comparison of LTUs and troughs 284 7.5 Conclusions on utility in remediation 285 L1656_C007.fm Page 216 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC Chapter seven: Polycyclic aromatic hydrocarbons (PAHs) 217 7.5.1 Conclusions from flask studies 285 7.5.2 Conclusions from LTUs 286 7.5.3 Conclusions from trough study 286 7.5.4 Utility to remediation of highly contaminated soil 287 7.6 Recommendations for transitional research 288 7.6.1 PAH availability in soil and regulatory cleanup levels 288 7.6.2 Phytoremediation of PAHs 288 7.7 Technology transfer 289 References 290 7.1 Land-farming background 7.1.1 Polycyclic aromatic hydrocarbons 7.1.1.1 Chemical structure and source of contamination Polycyclic aromatic hydrocarbons (PAHs) are multiringed, organic com- pounds, characteristically nonpolar, neutral, and hydrophobic. PAHs have two or more fused benzene rings in a linear, stepped, or cluster arrangement. Although there are more than 100 known PAHs, Table 7.1 provides the chemical structure, abbreviated name, and molecular weight for the 15 PAHs that were analyzed in this study. PAHs occur naturally as components of incompletely burned fossil fuels, and they are also manufactured. Several of these manufactured homologues are used in medicines, dyes, and pesticides, but most are found in coal tar, roofing tar, and creosote, a commonly used wood preservative. PAHs are major chemical constituents of a wide variety of contaminants found at Department of Defense (DOD) installations. They are found in burning pits and as spills of creosote, fungicides, heavy oils, Bunker C fuels, and other petroleum-based products. The higher-molecular-weight (HMW) homo- logues are particularly recalcitrant and toxic. Some lower-molecular-weight PAHs are volatile, readily evaporating into the air. Others will undergo photolysis. Because they are hydrophobic and neutral in charge, PAHs are strongly adsorbed onto soil particles, especially clays. Park et al. (1990) studied the degradation of 14 PAHs in two soils. They found air phase transfer (volatilization) an important means of contaminant reduction only for naphthalene and 1-methylnaphthalene (the two-ring compounds). Abi- otic mechanisms accounted for up to 20% of the total reduction but involved only two-and three-ring compounds. Biotic mechanisms were responsible for the removal of PAHs over three rings. The persistence of PAHs in the environment, coupled with their hydrophobicity, gives them a high potential for bioaccumulation. 7.1.1.2 Toxicity and benzo(a)pyrene toxic equivalent factors The 15 compounds examined in this study (Table 7.2) are grouped together because (1) more information is available on them and (2) they are suspected L1656_C007.fm Page 217 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC 218 Bioremediation of Recalcitrant Compounds Table 7.1 Molecular Weights and Structures for the 15 PAH Homologues Analyzed PAH Homologue Abbreviation Molecular Weight (amu) Structure Naphthalene NAPHTH 128 Acenaphthylene ACENAY 152 Acenaphthene ACENAP 154 Fluorene FLUORE 166 Anthracene ANTHR 178 Phenanthrene PHENAN 178 Fluoranthene FLA 202 Pyrene PYR 202 Benzo(a)anthracene a BAANTHR 228 Chrysene a CHRYS 228 Benzo(k)fluoranthene a BKFLANT 252 Benzo(a)pyrene a BaP 252 Benzo(g,h,i)perylene a BGHIPY 276 Indeno(1,2,3-c,d)pyrene a I123PY 276 Dibenzo(a,h)anthracene DBAHANT 278 a Indicates a BaP toxic equivalent compound. See Table 7.2 for values. Table 7.2 Toxic Equivalency Factors for the Seven PAHs of Greatest Environmental Significance Compound (Abbreviation) Toxic Equivalent Factor (by Nisbet and LaGoy, 1992) Benzo(a)anthracene (BAANTHR) 0.1 Chrysene (CHRYSE) 0.01 Benzo(b)fluoranthene (BBFLANT) 0.1 Benzo(k)fluoranthene (BKFLANT) 0.1 Benzo(a)pyrene (BaP) 1.0 Indeno(1,2,3-c,d)pyrene (I123PYR) 0.1 Dibenzo(a,h,)anthracene (DBAHANT) 1.0 L1656_C007.fm Page 218 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC Chapter seven: Polycyclic aromatic hydrocarbons (PAHs) 219 to be the most harmful of the PAHs. The effects they exhibit in animal and human studies are representative of the class as a whole. In addition, these are the PAHs to which the public is most commonly exposed. Also, they are found in highest concentration on National Priority List hazardous waste sites (ATSDR, 1995a and 1995b). As a class of compounds, PAHs have been classified as carcinogens, mutagens, and immunosuppressants. Even slight differences in PAH chem- ical structure and activity result in different toxic potencies and different health effects from the individual PAHs. The importance of PAH chemical structure as an indicator of potential carcinogenicity has been reviewed in Pitot and Dragan (1996). Some PAHs have been classified as carcinogens only in laboratory animals. Others, including benzo(a)pyrene (BaP) and benzo(a)anthracene, have been identified as human carcinogens. Still others are possible carcinogens or not classifiable because the testing is incomplete. Tumors usually occur at the point of entry into the body (i.e., the skin, lungs, eyes, intestines). However, metabolism of these compounds can result in an increase in their toxic potency and tumor formation in secondary organs (i.e., bladder, colon, liver). Metabolites of these compounds can also be carried into cells where they form adducts with DNA through covalent bonding. The best-studied mutation is in the 12th codon of the Hras codon The PAHs elicit multiple responses from the body’s immune system due to their effects on humoral and cell-mediated immunity as well as host resis- tance (Burns et al., 1996). The mechanisms of PAH immunosuppression have been reviewed by White et al. (1994). BaP is often used as an indicator for risk assessment of human exposure because it is highly carcinogenic, per- sistent in the environment, and toxicologically well understood. This breadth of knowledge does not exist for most of the other PAH compounds. Because PAHs occur as mixtures of different concentrations of different homologues, toxic equivalency factors (TEFs) were proposed, similar to those used in the risk assessment of mixtures of polychlorinated biphenyls (PCBs). The Environmental Protection Agency (EPA, 1984) took the first step by separating PAHs into carcinogenic and noncarcinogenic compounds. All of the PAHs were rated, using BaP as a reference and giving it a value of 1.00. However, this method led to an overestimation of exposure risk because the carcinogenicity of most of the compounds was unknown and the inter- actions between compounds in mixtures had not been determined. In an attempt to overcome this liability, Nisbet and LaGoy (1992) developed a new method based on the compounds’ response while testing one or more PAHs concurrently with BaP in the same assay system (usually lung or skin cell carcinoma). BaP remained the reference carcinogen, assigned the value of 1.00. Sixteen other PAHs were ranked in comparison to BaP carcinogenicity. This system was tested by Petry et al. (1996), who assessed the health risk of PAHs to coke plant workers. There are drawbacks to any system that uses equivalency factors. The uncertainties in this case arise primarily from deal- ing with inconsistent mixtures. Carcinogenic potency could be affected by differences in bioavailability, a competition for binding sites, cocarcinogenic L1656_C007.fm Page 219 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC 220 Bioremediation of Recalcitrant Compounds action, or the effects of metabolism. Nevertheless, Petry et al. (1996) found that the BaP equivalents developed by Nisbet and LaGoy (1992) were valid markers for PAH health risk assessment. Environmental risk assessment, in slight contrast to human health risk, looks at the PAHs that usually occur in contaminated environmental systems and that have the highest TEFs (by the Nisbet and LaGoy (1992) system). The seven PAHs listed in Table 7.2 have the highest environmental risk: benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-c,d)pyrene, and dibenzo(a,h)anthracene. 7.1.1.3 PAH bioavailability As indicated earlier, contaminants react chemically and physically with dif- ferent kinds of soil particles, which change the physical and chemical natures of both components. Biological availability, or bioavailability, is used to describe both the amount of toxin available in soil to harm organisms (humans, other animals, plants) and, in the case of bioremediation, the amount of toxin available to be metabolized by microorganisms after con- taminant–soil interactions. In situ bioremediation is a managed or spontane- ous process in which microbiological processes are used to degrade or trans- form contaminants to less toxic or nontoxic forms, thereby remedying or eliminating environmental contamination. Although these microbiological processes may decrease contaminant concentrations to levels that no longer pose an unacceptable risk to the environment or human health, the contam- inants that remain in treated soils still might not meet stringent regulatory levels, even if they represent site-specific, environmentally acceptable end- points (National Research Council, 1997). PAHs in soils may be biodegraded by microorganisms to a residual concentration that no longer decreases with time or that decreases slowly over years with continued treatment (Thoma, 1994; Luthy et al., 1994; Loehr and Webster, 1997). Further reductions are limited by the availability of the PAHs to microorganisms (Bosma et al., 1997; Erickson et al., 1993). Additionally, as contaminants age they become less available than freshly contaminated material. The adherence and slow release of PAHs from soils are other obstacles to remediation (National Research Council, 1994; Moore et al., 1989). Because they bind with soils and suffer subsequent slow-release rates, residual PAHs may be significantly less leachable by water and less toxic as measured by uptake tests (Gas Research Institute, 1995; Alexander, 1995; Kelsey et al., 1997). Generally, contaminants can only be degraded when they exist in the aqueous phase and in contact with the cell membrane of a microorganism (Fletcher, 1991). The contaminant serves as a growth substrate for the microorganism and is incorporated into the cell through membrane transport and utilized as an energy source in the cell’s principal metabolic pathways. However, physical or chemical phenom- ena can limit the bulk solution concentration of the contaminant and thus significantly reduce the ability of the microorganism to assimilate the con- taminant. Therefore, the availability of the contaminant can control the over- all biodegradation of these compounds. L1656_C007.fm Page 220 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC Chapter seven: Polycyclic aromatic hydrocarbons (PAHs) 221 Other important factors relevant to biodegradation and bioavailability are the location and density of microorganisms. The majority of bacteria in the environment are attached to surfaces, and their distribution in and on soils is very patchy. The majority of these bacteria range in size from 0.5 to 1.0 µm, whereas micropores present in soils measure far less than 1 µm. It is generally believed that bacteria are attached predominantly to the surface of soil particles and not to the interior surfaces of the micropores. It has been estimated that more than 90% of the microorganisms present in geologic matrices accumulate on the surfaces of soil (Costerton et al., 1987). Therefore, the majority of contaminant–microbial interactions occur in the biofilm that develops within macropores on the surfaces of soils. This suggests that partitioning of an organic contaminant from the solid phase of the soil to the aqueous phase in the larger pore spaces controls soil biovailability. These partitioning mechanisms may include chemical bond- ing, surface complex formations, electrostatic interactions, and hydrophobic effects (Schwarzenbach et al., 1993; Stumm, 1992). For hydrophobic contam- inants such as PAHs, sorption increases with the content of the organic matter in the soil/sediment and the degree of hydrophobicity of the specific PAH. Typically, the rate of desorption can be attributed to the mass transfer of the sorbate molecules from sorption sites on and in the soil. Active bacteria should correspond to the higher available PAH concentrations, which occur where desorption is the most intense. Current methods for assessing sorption and sequestration of PAHs on soils do not provide a basic understanding of the bioavailability of recalci- trant PAHs. They also lack information to aid interpretation of results of ecotoxicological testing of residuals after biotreatment. Whether residual PAHs remaining after biotreatment represent an acceptable cleanup end- point requires understanding of the mechanisms that bind contaminant PAHs within soil or sediment. Research is needed that will assess the fun- damental character of the binding of PAHs in parallel with the development of biotreatment and ecotoxicity testing, to show how the nature of PAH association with soils relates to bioavailability and achievable treatment endpoints. 7.1.1.4 Problem summary PAHs are large, multi-ring compounds, many of which are toxic to humans and the environment. Whereas the lighter-molecular-weight homologues may be removed by volatilization, the higher-molecular-weight compounds are increasingly more toxic and more resistant to both chemical and biolog- ical degradation. PAHs are tightly bound to the humic fraction of the soil. The binding strength increases with exposure time, making aged soils more difficult to remediate. Research was needed to: • Increase the availability of the PAHs for biological degradation • Establish remediation endpoints that maintain public health and safe- ty and are realistically achievable L1656_C007.fm Page 221 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC 222 Bioremediation of Recalcitrant Compounds The Flask to Field PAH project (Flask, for short) focused on the first of these objectives, increasing the availability of PAH compounds for biological degradation and increasing the overall biodegradation of the high-molecu- lar-weight homologues. 7.1.2 Available treatment options Treatment of PAH-contaminated soil can be performed either ex situ or in situ , and each of these has both abiotic and biotic technologies available. Of the ex situ treatments, the abiotic choice is a destructive technology — incin- eration. Biotic options include slurry bioreactors and compost reactors. The available abiotic in situ treatments include soil flushing and stabilization. Electrokinetic (E-K) separation is in preliminary development. Biotic treat- ments performed in situ include bioventing, phytoremediation (on soils with low PAH concentrations), and land farming. These options generally sepa- rate into either of two treatment approaches: highly engineered solutions such as solid phase or slurry phase treatment, and minimally engineered in situ treatment. Examples of each strategy are presented in Table 7.3, along with a summary of the inherent benefits and limitations associated with each technology. The difficulties associated with the use of biotreatments have been analyzed in Talley and Sleeper (1997), with reviews of pertinent tech- nologies. Detailed information including cost summaries and case studies can be obtained at http://www.frtr.gov 7.1.3 Thrust area: early studies The approach taken during the Flask studies separated the objective into two broad tasks: (1) isolating and characterizing a microorganism, or consortium of microorganisms capable of degrading the higher-molecular-weight PAHs, and (2) selecting a means of releasing the PAHs from the soil into the sur- rounding soil pore spaces where it would, presumably, be available to degra- dation. Each of these tasks was further separated into smaller research areas. In order to find an organism that would degrade higher-molecular-weight PAHs, a new isolation method was developed. New and existing strains were characterized and metabolic pathways have been described. It became neces- sary to explore the potential of cometabolism for the degradation of these PAHs. At the same time, the effects of chemical surfactants on soil–PAH bind- ing were studied. Bacteria that are natural surfactant producers were isolated and the biosurfactant activities were compared to the chemical surfactants. When a decision for bioaugmentation had been made, a method had to be found to deliver the chosen microorganisms into the contaminated soil. Several different technologies contributed to the Flask portion of the study, as illustrated in Figure 7.1: slurry reactors, land farming, and composting. The project began with an examination of available treatment options. Three prom- ising technologies were selected: a high-technology system of slurry bioreac- tors and two low-technology soil treatment systems — composting and land L1656_C007.fm Page 222 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC Chapter seven: Polycyclic aromatic hydrocarbons (PAHs) 223 Table 7.3 Summary of Existing Treatment Options for PAH-Contaminated Soil Technology Examples Benefits Limitations Factors to Consider Solid phase Land farming Composting Engineered soil cell Soil treatment Cost efficient Modestly effective for HMW PAHs Low O&M costs Perform on site, in place Space requirements Extended treatment time Control of abiotic loss Mass transfer Bioavailability Catabolic capabilities of indigenous microflora Presence of metals and other organics pH, temperature, moisture control Biodegradability Bioreactors Aqueous reactors Soil slurry reactors Most rapid degradation Controlled conditions Enhanced mass transfer Use of surfactants and inoculants Material input requires physical removal Relatively high capital costs Same as solid phase Toxicity of amendments Toxic concentrations of contaminants In situ Biosparging Bioventing GW circulation In situ bioreactors Least cost Noninvasive Complements natural attenuation processes Soil and water treated simultaneously Physicochemical control Extended treatment time Monitoring progress and effectiveness Same as solid phase Chemical solubility LNAPL/DNAPL present Geological factors Regulatory aspects for groundwater Source: Modified from Mueller, J. et al., Antonie Leeuwenhoek , 71, 329–343, 1997. L1656_C007.fm Page 223 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC 224 Bioremediation of Recalcitrant Compounds farming. Research in each of these technologies provided insight into areas of PAH bioremediation useful to the final treatment selection: isolation and char- acterization of PAH-degrading bacteria and elucidation of the degradation pathways, surfactant chemistry, bioaugmentation, and microbial carrier tech- nology. This produced a final treatment with aspects of all three technologies. For field studies, land farming with bioaugmentation and biostimulation was selected as the treatment option for PAH-contaminated soils. The treatments and the technologies that support them are discussed in the following sections. 7.1.3.1 Solid phase treatments Solid phase treatments, commonly known as land farming and composting, are two of the most commonly applied technologies for the remediation of PAH-contaminated soil (Gray et al., 2000; Harmsen, 1991; Mueller et al., 1991a, 1991b; Mueller-Hurtig et al., 1993; Yare, 1991). Most PAH-contami- nated soils contain a significant number of PAH degraders that have been enriched because of the presence of the PAHs, but they are often constrained in their degradation capability because of some limiting factor. Common limiting factors include inadequate aeration, poor contact of the microorgan- isms with the PAHs due to the adherence of the PAHs to surfaces and nonaqueous phase liquid (NAPL) materials, and the absence of sufficient nitrogen to sustain extensive mineralization of the contaminant carbon. Any engineering activity that reduces these limitations brings the native degrad- ers into action. Advantages of solid phase treatment are that large quantities of contam- inated soil can be treated at the same time and that operation and mainte- nance activities (costs) are minimal. In general, contaminated soil is placed in aboveground treatment areas that are designed for proper effluent collec- tion, and then the soil is handled in specific ways to enhance indigenous microbial activity. Composting usually involves the addition of readily Figure 7.1 Project history leading to the selection of land farming as a PAH treatment technology. Remediation of Soil PAHs Bioslurry Composting To o expensive ineffective Nutrient amendments bioaugmentation Bulking agents mixing Modified Land farming nutrient amendment, bulking agent, bioaugmentation and limited tilling Traditional landfarming Incomplete degradation L1656_C007.fm Page 224 Monday, July 11, 2005 11:47 AM © 2006 by Taylor & Francis Group, LLC [...]... 1 1-1 12 Rade, Norway (2) Creosote FLA 1 2-1 , FLA 1 2-2 13 Lillestrom, Norway (3) Creosote FLA 1 3-1 * 14 Lillestrom, Norway (4) 15 Drammen, Norway Creosote Creosote 16 Hommelvik, Norway Creosote FLA 1 4-1 FLA 1 5-1 *, FLA 1 5-2 , FLA 1 5-3 None PYR 9-1 PYR 1 0-1 PYR 1 1-1 , PYR 1 1-2 , PYR 1 1-3 PYR 1 2-1 , PYR 1 2-2 PYR 1 3-1 , PYR 1 3-2 PYR 1 4-1 PYR 1 5-1 , PYR 1 5-2 PYR 1 6-1 , PYR 1 6-2 17 Boston, MA (sediment) 18 Boston, MA... 3-3 FLA 4-1 *, FLA 4-2 FLA 5-1 , FLA 5-3 * 6 Pensacola (American Creosote Works (ACW)), FL 7 Fence Post, FL 8 Tyndall AFB, FL Creosote FLA 6*, FLA 6-2 PYR 1-1 PYR 2-1 PYR 3-1 , PYR 3-2 None PYR 5-1 , PYR 5-3 None Creosote Diesel and jet fuel 9 Port Newark, NJ (sediment) Fuel 10 Port Newark, NJ Fuel 11 Rade, Norway (1) Creosote FLA 7- 1 FLA 8-1 PYR 7- 1 None FLA 9-1 * FLA 1 0-1 *, FLA 1 0-3 FLA 1 1-1 12 Rade, Norway... Table 7. 4 Amount of PAHs Remaining Following Biodegradation of PAH Fractions by Selected Strains of PAH Degraders Isolate/ Strain Initial Uninoculated CRE 7a N3P2b UN1P1b EPA 505b PRY-1c Two-Ring PAHs 149.5 71 .3 1 .7 0.5 0.5 0.3 4.8 (0)d (NA) (98) (99) (99) (100) (93) a Three-Ring PAHs 168.1 1 07. 0 14.8 4.9 3.4 2.2 70 .6 (0) (NA) (86) (95) ( 97) (98) (34) Four-, Five-, and Six-Ring PAHs 60.0 55.9 47. 2 46.1... situations In the case of © 2006 by Taylor & Francis Group, LLC L1656_C0 07. fm Page 238 Monday, July 11, 2005 11: 47 AM Bioremediation of Recalcitrant Compounds Mineralization of 14C-Fluoranthene as CPM of CO2 238 25000 Strain FLA 1 0-2 Strain FLA 1 0-1 Strain FLA 9-1 Strain EPA 505 20000 15000 10000 5000 0 0 2 4 6 Days 8 10 12 Figure 7. 7 Effect of 0.48 mM Triton X-100 on the mineralization of radiolabeled FLA... Group, LLC L1656_C0 07. fm Page 228 Monday, July 11, 2005 11: 47 AM 228 Bioremediation of Recalcitrant Compounds of these higher-molecular-weight PAHs appeared to plateau in the slurry reactor, whereas degradation was still occurring at the end of the solid phase reactor experiment Thus, the added time of treatment may be rewarded by a greater extent of degradation 7. 1.3.4 The flask-to-field selected treatment... Indenopyrene Total PAHs PCP a 0.5 7 14 3 39 21 15 3 3 1 1 1 . 268 7. 4.2 LTU pilot project 270 7. 4.2.1 Chemical characteristics 270 7. 4.2.2 PAH removal 271 7. 4.2.3 Microbial characterization 273 7. 4.2.4 Soil respiration 276 7. 4.3 Trough pilot project 276 7. 4.3.1. (0) 377 .6 (NA) Uninoculated 71 .3 (NA) 1 07. 0 (NA) 55.9 (NA) 234.1 (NA) CRE 7 a 1 .7 (98) 14.8 (86) 47. 2 (16) 63 .7 (73 ) N3P2 b 0.5 (99) 4.9 (95) 46.1 (18) 51.5 (78 ) UN1P1 b 0.5 (99) 3.4 ( 97) . 255 7. 3.9 Pilot-scale materials 2 57 7.3.10 Pilot-scale methods 259 7. 3.10.1 Sampling design 259 7. 3.10.2 Physical analysis 260 7. 3.10.3 Chemical analysis 260 7. 3.10.4 Microbial analysis 261 7. 3.10.5