厌氧微生物菌群XH-1对2,4,6-三氯苯酚的降解特性

有机污染物2,4,6-三氯苯酚(2,4,6-TCP)普遍存在于地下水和河流底泥等厌氧环境中。为了探究厌氧微生物菌群XH-1对2,4,6-TCP的降解能力,本研究以2,4,6-TCP为底物,接种XH-1建立微宇宙培养体系,并以中间产物4-氯苯酚(4-CP)和苯酚为底物分别进行分段富集培养,利用高效液相色谱分析底物的降解转化,同时基于16S rRNA基因高通量测序分析微生物群落结构变化。结果表明: 2,4,6-TCP(122 μmol·L^-1)以0.15 μmol·d^-1的速率在80 d内被完全降解转化,降解中间产物分别为2,4-二氯苯酚(2,4-DCP)、4-氯苯酚和苯酚,所有中间产物最终在325 d被完全降解。高通量测序结果表明,脱卤杆菌和脱卤球菌可能驱动2,4,6-TCP还原脱氯,其中,脱卤球菌可能在4-CP的脱氯转化中发挥重要作用,并与丁酸互营菌和产甲烷菌联合作用彻底降解2,4,6-TCP。     

Anaerobic dechlorination of pentachlorophenol in fixed-film and upflow anaerobic sludge blanket reactors using different inocula

Longterm performance and stability of two upflow anaerobic sludge blanket (UASB) reactors inoculated with granular sludge and treating a synthetic waste water containing pentachlorophenol (PCP) and phenol were studied. A similar system consisting of two fixed-film reactors inoculated with anaerobic digested sewage sludge were further studied. One reactor in each series received glucose in addition to the phenols. Dechlorination of PCP proceeded via two different dominating pathways in the respective reactor systems, suggesting that two distinct microbial populations were present, probably originating from the different inocula. Dechlorinating activity was maintained for more than 18 months in the UASB reactors and was generally higher than in the fixed-film reactors. In the fixed-film reactors, dechlorination of PCP suddenly decreased after 15.5 months of operation compared to earlier performance. Since no operational parameters had been changed, this indicated that the enriched culture was unstable on a longterm basis. Addition of yeast extract to the medium restored activity. General process stability in both reactor systems was clearly enhanced by the addition of glucose and was superior in the UASB/granular sludge system. The better performance and the higher stability in the UASB/granular sludge reactor highlights the importance of thorough screening of inocular prior to start-up of processes treating waste waters containing xenobiotic compounds.Abbreviations PCP pentachlorophenol - TeCP tetrachlorophenol - TCP trichlorophenol - DCP dichlorophenol - UASB upflow anaerobic sludge blanket - HRT hydraulic retention time     

水稻土泥浆体系中多氯联苯的微生物厌氧脱氯

考察了厌氧水稻土泥浆体系中高氯代多氯联苯混合物Aroclor1260的脱氯过程,并对体系中的微生物群落结构变化进行分析.结果表明： Aroclor1260可在厌氧水稻土泥浆体系中发生脱氯,经过128 d,总消减率达到55.5%,在泥浆体系中引入驯化的脱氯富集培养体反而使脱氯效果下降,消减率为46.9%.Aroclor1260的主要脱氯过程发生在五、六、七氯联苯,其中七氯联苯脱氯过程最显著,五氯联苯作为脱氯产物有一定累积.有机物厌氧发酵产生的H₂会被脱氯过程所消耗,从而将体系中的氢分压维持在较低水平,抑制产甲烷过程而保证脱氯过程的持续进行.不同条件和培养方式驯化得到的微生物群落结构差异较大,富集培养体引入可能导致其与原体系中脱氯相关菌群竞争,从而改变体系原有菌群结构,这可能是导致其脱氯效率下降的原因.     

Scale-up issues for in situ anaerobic tetrachloroethene bioremediation

For the full scale implementation of in situ anaerobic bioremediation of tetrachloroethene (PCE) in groundwater, the following issues must be addressed: which organic substrates at which concentration would be most effective in promoting dechlorination and are economical; how far the substrate, electron acceptor, and nutrients can be transported in the aquifer; and the placement of delivery and recovery wells for distributing these amendments. In a microcosm study, almost all of the tested inexpensive substrates supported reductive dechlorination of PCE through vinyl chloride (VC) under methanogenic conditions. A minimum of about 60 mg L⁻¹ of organic carbon was needed to dechlorinate 23 μM PCE with a single feeding. In a second microcosm study dechlorination stopped at 1,2-dichloroethene (DCE) in microcosms fed higher concentrations of several substrates. At the highest concentrations the substrates inhibited DCE production. Three field tracer tests were conducted to evaluate methods to distribute the amendments across the aquifer. The natural groundwater gradient is not sufficient to distribute substrate evenly. Groundwater injection at 60 times the natural flux rate increased the distribution of substrate. A mixing strategy of cross-gradient injection further increased the distribution of the substrate. Ammonia-nitrogen, sulfate, and phosphate were retarded relative to the substrate and inorganic tracer. Received 30 October 1995/ Accepted in revised form 07 June 1996     

Riboflavin- and cobalamin-mediated biodegradation of chloroform in a methanogenic consortium

Chloroform (CF) is an important priority pollutant contaminating groundwater. Reductive dechlorination by anaerobic microorganisms is a promising strategy towards the remediation of CF. The objective of this study was to evaluate the use of redox active vitamins as electron shuttles to enhance the anaerobic biodegradation of CF in an unadapted methanogenic consortium not previously exposed to chlorinated compounds. Only negligible degradation of CF was observed in control cultures lacking redox active vitamins. The addition of riboflavin (RF), cyanocobalamin (CNB12), and hydroxycobalamin (HOB12) enabled biodegradation of CF. The reactions were predominantly catalyzed biologically as evidenced by the lack of any CF conversion in heat-killed controls amended with the cobalamins or minor conversion with RF. In live cultures, significant increases in the rate of CF conversion was observed at substoichiometric molar ratios as low as 0.1 to 0.01 vitamin:CF for RF and CNB12, respectively. At the highest molar vitamin:CF ratios tested of 0.2, the first-order rate constant of CF degradation was 5.3- and 91-fold higher in RF and CNB12 amended cultures, respectively, compared to the unamended control culture. The distribution of biotransformation products was highly impacted by the type of redox active vitamin utilized. Cultures supplemented with RF provided high yields of dichloromethane (DCM). On the other hand, cobalamins promoted the near complete mineralization of organochlorine in CF to inorganic chloride and lowered the yield of DCM. In cultures where no or little CF bioconversion occurred, prolonged exposure to CF resulted in cell lysis, as evidenced by the release of intracellular chloride. The results taken as a whole suggest that the anaerobic bioremediation of CF-contaminated sites can greatly be improved with strategies aimed at increasing the concentration of redox active vitamins.     

Enhanced anaerobic biotransformation of carbon tetrachloride with precursors of vitamin B12 biosynthesis

Relatively low concentrations of Vitamin B₁₂ are known to accelerate the anaerobic biotransformation of carbon tetrachloride (CT) and chloroform (CF). However, the addition of vitamin B₁₂ for field-scale bioremediation is expected to be costly. The present study considered a strategy to generate vitamin B₁₂ by addition of biosynthetic precursors. One of the precursors, porphobilinogen (PB) involved in the formation of the corrin ring, significantly increased the CT biotransformation rates by 2.7−, 8.8- and 10.9-fold when supplemented at 160, 500 and 900 μM, respectively. A positive control with 10 μM of vitamin B₁₂ resulted in a 5.9-fold increase in the CT-bioconversion rate. PB additions provided high molar yields of inorganic chloride (57% of CT organochlorine), comparable to that obtained with vitamin B₁₂ supplemented cultures. The primary substrate, methanol, known to induce vitamin B₁₂ production in methanogens and acetogens, was required for PB to have a significant impact on CT conversion. The observation suggests that PB’s role was due to stimulating vitamin B₁₂ biosynthesis. The present study therefore provides insights on how to achieve vitamin B₁₂ enhanced rates of CT bioremediation through the use of less complex compounds that are precursors of vitamin B₁₂. Although PB is a costly chemical, its large impact points to corrin ring formation as the rate-limiting step.     

Aerobic and Anaerobic Biodegradation of Aged Pentachlorophenol by Indigenous Microorganisms

Pentachlorophenol (PCP) use as a general biocide, particularly for treating wood, has led to widespread environmental contamination. Biodegradation has emerged as the main mechanism for PCP degradation in soil and groundwater and a key strategy for remediation. Examining the microbial biodegrading potential for PCP at a contaminated site is crucial in determining its fate. Hundreds of studies have been published on PCP microbial degradation, but few have described the biodegradation of PCP that has been in contact with soils for many years. The bioavailability of “aged” hydrophobic organics is a significant concern. PCP- and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)-contaminated soil samples from several depths at a former wood treatment site were placed under varying conditions in the laboratory to determine the anaerobic and aerobic potential for biodegradation of chlorophenols at the site. PCP biodegradation occurred in both anaerobic and aerobic soil samples. Rapid aerobic degradation occurred in samples spiked with 2- and 4-chlorophenol, but not with 3-chlorophenol. Reductive dechlorination of PCP in anaerobic samples resulted in the accumulation of 3-chlorophenol. In most anaerobic replicates, 3-chlorophenol was degraded with the appearance of detectable, but not quantifiable amounts of phenol. These results indicate excellent potential for remediation at the site using the indigenous microorganisms under both aerobic and anaerobic conditions. However, a fraction of the PCP was unavailable for degradation.     

Chlorophenol dechlorination and subsequent degradation in denitrifying microcosms fed low concentrations of nitrate

The potential of using nitrate as a terminal electron acceptor to stimulate anaerobic degradation of mixtures of monochlorophenols (MCPs) or dichlorophenols (DCPs) was evaluated. Contaminated and non-contaminated soils were added to water saturated anaerobic microcosms supplemented with 1 mM or 5 mM nitrate. Denitrification and dechlorination activity were present in three diverse soil types and were maintained upon refeeding both nitrate and the appropriate chlorophenol. However, dechlorination activity could only be serially transferred in enrichments with an added electron donor such as acetate. Dehalogenation activity in enrichments from four of the primary microcosms showed at least five different dechlorination reactions, each mediated by different microbial communities. Three of these are distinct ortho-dechlorinating paths; two are meta-dechlorinating and one is the para-dechlorination of 3,4-DCP. Simultaneous dechlorination and denitrification was observed and both activities could be maintained in microcosms but only in the presence of low nitrate concentrations. Dechlorination and denitrification were mediated by two separate microbial communities; one that dechlorinates without use of nitrate and one that denitrifies while oxidizing the dechlorinated aromatic ring. There was no evidence that dechlorination is mediated by the denitrifying community, however the maintenance of a denitrification potential using low (< 1 mM) nitrate concentrations may be useful for completing the food chain by stimulating the mineralization of phenol and benzoate.     

Bacterial growth based on reductive dechlorination of trichlorobenzenes

An anaerobic mixed bacterial culture was enriched forbacteria dechlorinating 1,2,3- and1,2,4-trichlorobenzene (TCB) to dichlorobenzenes byexclusive use of non-fermentable substrates and theapplication of vancomycin. Growth and dechlorinationoccurred in a purely synthetic medium with formate orhydrogen, acetate, and TCB. Neither acetogenesis normethanogenesis was detected in the culture. Repeatedsubculturing maintaining high dechlorinatingactivities was also achieved when only hydrogen andTCB were supplied. This indicated that reductivedechlorination of TCB was the primary energyconservating process. The number of dechlorinatingbacteria was strictly limited by the amount of TCBsupplied in the medium. In addition, thedechlorinating activity could be maintained only inthe presence of TCB. A most probable number analysisshowed that the dechlorinating species amounted to atleast 6 10⁵ cells per ml at a total cell numberof about 2 10⁶ cells per ml. Vitamin B₁₂significantly stimulated the dechlorinating activity.     

A new VFA sensor technique for anaerobic reactor systems

A key parameter for understanding and controlling the anaerobic biogas process is the concentration of volatile fatty acids (VFA). However, this information has so far been limited to off-line measurements using labor-intensive methods. We have developed a new technique that has made it possible to monitor VFA on-line in one of the most difficult media: animal slurry or manure. A novel in situ filtration technique has made it possible to perform microfiltration inside a reactor system. This filter enables sampling from closed reactor systems without large-scale pumping and filters. Furthermore, due to its small size it can be placed in lab-scale reactors without disturbing the process. Using this filtration technique together with commercially available membrane filters we have constructed a VFA sensor system that can perform automatic analysis of animal slurry at a frequency as high as every 15 minutes. Reproducibility and recovery factors of the entire system have been determined. The VFA sensor has been tested for a period of more than 60 days with more than 1,000 samples on both a full-scale biogas plant and lab-scale reactors. The measuring range covers specific measurements of acetate, propionate, iso-/n-butyrate and iso-/n-valerate ranging from 0.1 to 50 mM (6-3,000 mg). The measuring range could readily be expanded to more components and both lower and higher concentrations if desired. In addition to the new VFA sensor system, test results from development and testing of the in situ filtration technique are being presented is this article.     

Metabolism of halohydroquinones inRhodococcus chlorophenolicus PCP-1

The actinomyceteRhodococcus chlorophenolicus PCP-1 metabolises pentachlorophenol into ultimate inorganic end products via tetrachloro-p-hydroquinone. This intermediate was further dehalogenated in the cytoplasm requiring reductant in the cell free system. Tetrafluoro-p-hydroquinone and tetrabromo-p-hydroquinone were also dehalogenated. Chlorophenol analogs, thiol blocking agents and molecular oxygen inhibited the activity. The dehalogenating reactions led to 1,2,4-trihydroxybenzene, which was further metabolized into maleic acid.Abbreviations PCP pentachlorophenol - TeCH tetrachloro-p-hydroquinone - TeFH tetrafluoro-p-hydroquinone - TeBH tetrabromo-p-hydroquinone - THB trihydroxybenzene     

Evaluation of Slow Release Substrates for Anaerobic Bioremediation

A variety of food-grade organic substrates were evaluated to identify materials that could be used to support long-term anaerobic bioremediation processes in the subsurface. In this work, the rate and extent of biogas production was used as an indicator of the potential for substrate fermentation to H₂ and acetate, the primary electron donors used in reductive dechlorination. The rate and extent of biogas (primarily CO₂+ CH₄) evolution varied widely between the different substrates. For many of the substrates, biogas generation declined to very low levels within 100 days of substrate addition. However, a few substrates including several vegetable oils and sucrose esters of fatty acid (SEFAs) did support biogas production for extended time periods. Column studies demonstrated that both soybean oil and a SEFA could support sulfate reduction, methanogenesis and reductive dechlorination of perchloroethene (PCE) to cis-dichloroethene (cis-DCE) for over 14 months. The slower degradation rate of the SEFAs could be used to control substrate degradation rate in the subsurface, increasing substrate lifetime and reducing the required reinjection frequency.     

Evaluation of Slow Release Substrates for Anaerobic Bioremediation

A variety of food-grade organic substrates were evaluated to identify materials that could be used to support long-term anaerobic bioremediation processes in the subsurface. In this work, the rate and extent of biogas production was used as an indicator of the potential for substrate fermentation to H₂ and acetate, the primary electron donors used in reductive dechlorination. The rate and extent of biogas (primarily CO₂+ CH₄) evolution varied widely between the different substrates. For many of the substrates, biogas generation declined to very low levels within 100 days of substrate addition. However, a few substrates including several vegetable oils and sucrose esters of fatty acid (SEFAs) did support biogas production for extended time periods. Column studies demonstrated that both soybean oil and a SEFA could support sulfate reduction, methanogenesis and reductive dechlorination of perchloroethene (PCE) to cis-dichloroethene (cis-DCE) for over 14 months. The slower degradation rate of the SEFAs could be used to control substrate degradation rate in the subsurface, increasing substrate lifetime and reducing the required reinjection frequency.     

脱卤单胞菌属在厌氧降解有机氯化物及污染场地修复应用中的研究进展

脱卤单胞菌 Dehalogenimonas 是绿弯菌门 (Chloroflexi) 脱卤球菌纲 (Dehalococcoidia) 的一个属。脱卤单胞菌属目前包含 Dehalogenimonas lykanthroporepellens、Dehalogenimonas alkenigignens 和 Dehalogenimonas formicexedens 这 3 个已正式命名的物种,其成员均为严格厌氧的专性有机卤呼吸细菌,利用氢气和甲酸作为电子供体,以氯代烷烃 (例如 1,2,3-三氯丙烷、1,2-二氯丙烷和 1,2-二氯乙烷) 作为电子受体,通过介导还原性脱氯反应获得能量进行生长。我国污染场地地下水中氯代烷烃等有机氯污染较为突出,脱卤单胞菌的产能方式使其在污染场地原位修复中具有重要的应用价值。新近发现的 WBC-2 菌株和"Candidatus Dehalogenimonas etheniformans" GP 菌株可以脱氯降解某些氯代烯烃,其中 GP 菌株能够将一氯乙烯完全脱氯至乙烯,拓展了有限的一氯乙烯脱氯菌种资源,丰富了脱卤单胞菌的生态学功能。文中围绕脱卤单胞菌属的生理生化特性、生态功能及基因组信息进行综述,旨在为污染场地有机氯污染物的清理及工程实施提供理论指导。     

Anaerobic dechlorination of trichloroethene,tetrachloroethene and 1,2-dichloroethane by an acetogenic mixed culture in a fixed-bed reactor

An anaerobic enrichment culture with glucose as the sole source of carbon and energy plus trichloroethene (TCE) as a potential electron acceptor was inoculated with material from a full size anaerobic charcoal reactor that biologically eliminated dichloromethane from contaminated groundwater (Stromeyer et al. 1991). In subcultures of this enrichment complete sequential transformation of 10 µM TCE viacis-dichloroethene and chloroethene to ethene was reproducibly observed. Maintenance of this activity on subcultivation required the presence of TCE in the medium. The enrichment culture was used to inoculate an anaerobic fixed-bed reactor containing sintered glass Raschig elements as support material. The reactor had a total volume of 1780 ml and was operated at 20 °C in an up-flow mode with a flow rate of 50 ml/h. It was fed continuously with 2 mM glucose and 55 µM TCE. Glucose was converted to acetate as the major product and to a minor amount of methane; TCE was quantitatively dehalogenated to ethene. When, in addition to TCE, tetrachloroethene or 1,2-dichloroethane were added to the system, these compounds were also dehalogenated to ethene. In contrast, 1,1,1-trichloroethane was not dehalogenated, but at 40 µM severely inhibited acetogenesis and methanogenesis. When the concentration of TCE in the feed was raised to 220 µM, chloroethene transiently accumulated, but after an adaptation period ethene was again the only volatile product detected in the effluent. The volumetric degradation rate at this stage amounted to 6.2 µmol/l/h. Since complete transformation of TCE occurred in the first sixth of the reactor volume, the degradation capacity of the system is estimated to exceed this value by factor of about ten.Abbreviations CA chloroethane - 1,1-DCA 1,1-dichloroethane - 1,2-DCA 1,2-dichloroethane - 1,1-DCE 1,1-dichloroethene - c-DCE cis-1,2-dichloroethene - t-DCE trans-1,2-dichloroethene - PCE tetrachloroethene, perchloroethene - 1,1,1-TCA 1,1,1-trichloroethane - TCE trichloroethene - VC chloroethene, vinyl chloride     

Complete dechlorination of tetrachloroethene to ethene in presence of methanogenesis and acetogenesis by an anaerobic sediment microcosm

An anaerobic consortium taken from brackish sediments, enriched byPCE/CH₃OH sequential feeding, was capable of completely dechlorinating tetrachloroethene(PCE) to ethene (ETH). In batch experiments, PCE (0.5 mM) was dechlorinated to ethene (ETH) in approximately 75 h with either CH₃OH or H₂ as the electron donor. When VC (0.5 mM) was added instead of PCE it was dechlorinated without any initial lag by the PCE/CH₃OHenriched consortium, although at a lower dechlorination rate. In batch tests H₂ could readilyreplace CH₃OH for supporting PCE dechlorination, with a similar PCE dechlorination rate andproduct distribution with respect to those observed with methanol. This indicates that H₂ productionduring CH₃OH fermentation was not the rate-limiting step of PCE or VC dechlorination.Acetogenesis was the predominant activity when methanol was present. A remarkable homoacetogenicactivity was also observed when hydrogen was supplied instead of methanol.     

Enhancement of anaerobic carbon tetrachloride biotransformation in methanogenic sludge with redox active vitamins

Carbon tetrachloride (CT) is an important groundwater pollutant which is only subject to biotransformation in the absence of oxygen. The anaerobic biotransformation of CT is influenced by electron shuttling compounds. The purpose of this study was to evaluate the impact of redox active vitamins on CT (100 M) metabolism in a methanogenic sludge consortium (0.5 g VSSl^-1) supplied with volatile fatty acids as electron donor (0.2 g CODl^-1). The redox active vitamins, tested at concentrations ranging from 0.5 to 20 M, were riboflavin (RF) and two forms of vitamin B12, cyanocobalamin (CNB12) and hydroxycobalamin (HOB12), and these were compared with a redox mediating quinone, anthraquinone-2,6-disulfonate (AQDS). Substoichiometric concentrations of RF, CNB12, HOB12 at molar ratios of vitamin:CT as low as 0.005 significantly increased rates of CT-bioconversion. These are the lowest molar ratios of vitamin B12 reported having an impact on dechlorination. Additionally, this study constitutes the first report of RF having a role in reductive dechlorination. At molar ratios of 0.1 vitamin:CT, RF, CNB12, HOB12 increased the first order rate constant of CT bioconversion by 4.0-, 13.3-and 13.6-fold, respectively. The redox active vitamins also enhanced the rates of abiotic CT conversion in heat killed sludge treatments, but the rates were approximately 4- to 5-fold lower than the corresponding vitamin enhanced rates of biological CT conversion. The addition of CNB12 or HOB12 to the live methanogenic sludge consortium increased the yield of inorganic chloride (Cl^-) from CT-converted. Chloroform was a transient intermediate in CNB12 or HOB12 supplemented cultures. In contrast, the addition of RF increased the yield of chloroform from CT-converted. Taken as a whole the results clearly demonstrate that very low concentrations of redox active vitamins could potentially play an important role in accelerating the anaerobic the bioremediation of CT as well as influencing the proportions of biotransformation products formed.     

The mineralization of chloroform in river sediments

The formation of¹⁴CO₂ from 3 μg l⁻¹ labelled chloroform was studied in anaerobic Dutch river sediments. All incubations were performed under anaerobic conditions. The observed first order mineralization kinetics showed half-lives of 2–37 days at 20°C in 12 muddy sediments. In contrast most of the sandy sediment samples did not show a mineralization of chloroform. Most probable number analysis revealed about 3.10⁴ chloroform mineralizing bacteria per g of dry sediment in a muddy sediment and 1–2.10³ chloroform mineralizing bacteria per g of dry sediment in a sandy sediment. Therefore the persistence of chloroform in sandy sediments is not caused by the absence of chloroform mineralizing bacteria but by the inactivity of these bacteria. This inactivity of the sandy sediments might allow chloroform from infiltrating river water to reach the groundwater. Mud samples from a relatively unpolluted site showed a similar chloroform mineralization rate compared with the polluted sediments from the rivers Rhine and Meuse. The data indicate that the reductive dechlorination of aliphatic compounds is not influenced at the polluted sites.     

Monitoring anaerobic sequential batch reactors via fractal analysis of pH time series

Efficient monitoring and control schemes are mandatory in the current operation of biological wastewater treatment plants because they must accomplish more demanding environmental policies. This fact is of particular interest in anaerobic digestion processes where the availability of accurate, inexpensive, and suitable sensors for the on‐line monitoring of key process variables remains an open problem nowadays. In particular, this problem is more challenging when dealing with batch processes where the monitoring strategy has to be performed in finite time, which limits the application of current advanced monitoring schemes as those based in the proposal of nonlinear observers (i.e., software sensors). In this article, a fractal time series analysis of pH fluctuations in an anaerobic sequential batch reactor (AnSBR) used for the treatment of tequila vinasses is presented. Results indicated that conventional on‐line pH measurements can be correlated with off‐line determined key process variables, such as COD, VFA and biogas production via some fractality indexes. Biotechnol. Bioeng. 2013; 110: 2131–2139. © 2013 Wiley Periodicals, Inc.     

Ethanol and toluene removal in a horizontal-flow anaerobic immobilized biomass reactor in the presence of sulfate

In this study it is reported the operation of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor under sulfate-reducing condition which was also exposed to different amounts of ethanol and toluene. The system was inoculated with sludge taken from up-flow anaerobic sludge blanket (UASB) reactors treating refuses from a poultry slaughterhouse. The HAIB reactor comprised of an immobilized biomass on polyurethane foam and ferrous and sodium sulfate solutions were used (91 and 550 mg/L, respectively), to promote a sulfate-reducing environment. Toluene was added at an initial concentration of 2.0 mg/L followed by an increased range of different amendments (5, 7, and 9 mg/L). Ethanol was added at an initial concentration of 170 mg/L followed by an increased range of 960 mg/L. The reactor was operated at 30(+/-2) degrees C with hydraulic detention time of 12 h. Organic matter removal efficiency was close to 90% with a maximum toluene degradation rate of 0.06 mg(toluene)/mg(vss)/d. Sulfate reduction was close to 99.9% for all-nutritional amendments. Biofilm microscopic characterization revealed a diversity of microbial morphologies and DGGE-profiling showed a variation of bacterial and sulfate reducing bacteria (SRB) populations, which were significantly associated with toluene amendments. Diversity of archaea remained unaltered during the different phases of this experiment. Thus, this study demonstrates that compact units of HAIB reactors, under sulfate reducing conditions, are a potential alternative for in situ aromatics bioremediation.