Biodegradation of anionic surfactants by isolated bacteria from activated sludge

Sodium dodecyl sulphate, (SDS) is an anionic surfactant that widely used all over the world. They will eventually end-up and accumulate in household or industrial sewage. Due to their high foaming capabilities, which can cause numerous problems in sewage treatment facilities as well as direct toxic effects on many different organisms in ecosystem; they are generally considered as serious pollutants. In this survey, two different bacteria were isolated from Tehran municipal activated sludge. Biochemical tests as well as 16S rRNA gene sequencing for identification have been applied. After experiments to optimize the pH and temperature for growth of the two bacterial isolates, the extent of SDS utilization was evaluated by HPLC method. Two bacterial isolates show which ability to rapidly and actively degrade SDS upon using it as their sole source of carbon. The identification tests have indicated the two isolates to be Acinetobacter johnsoni and Pseudomonas beteli. The Pseudomonas beteli and Acinetobacter johnsoni isolates were able to degrade 97.2% and 96.4% of the original SDS levels after 10 days of growth; respectively. Mixed culture of the two isolates did not significantly increase SDS utilization, (97.6%). In conclusion, the results of this study suggest that growth of simple bacteria such as Acinetobacter or Pseudomonas in household and industrial sewage can be cost-effective method anionic surfactants elimination.     

Fast bioremediation of petroleum-contaminated soils by a consortium of biosurfactant/bioemulsifier producing bacteria

Biodegradation of petroleum hydrocarbons as a decontamination mechanism is a relatively slow process. This study aimed to investigate the impact of a tailored consortium of bacteria with higher capacities in biosurfactant production and biodegradation on the acceleration of the biodecontamination process. To this end, 18 biosurfactant producing bacteria were isolated from the crude oil-contaminated soil samples of Isfahan refinery, and the activity of the produced biosurfactants was measured in terms of surface tension reduction and emulsification E24 test. Then, the isolates screened for the biodegradation of kerosene hydrocarbons and chemical structure of the purified biosurfactants produced by the most efficient isolates were partially characterized. Next, the isolates were sorted based on their surfactant activity and biodegradation efficiency, and the higher ranked bacteria thus selected were utilized to form an efficient consortium removing hydrocarbons from the oil-contaminated soil samples in a slurry phase system. The consortium consisted of Bacillus subtilis tb1 and Pseudomonas aeruginosa species having the highest biodegradation capabilities and surface activities. The results revealed that the hydrocarbon removal efficiency of the consortium was at least 25 % higher than single species, and the final removal efficiency for the consortium could be reached in a considerably shorter time.     

Biodegradation of polycyclic aromatic hydrocarbon by a halotolerant bacterial consortium isolated from marine environment

The biodegradability of polycyclic aromatic hydrocarbons such as naphthalene, fluorene, anthracene and phenanthrene by a halotolerant bacterial consortium isolated from marine environment was investigated. The polycyclic aromatic hydrocarbons degrading bacterial consortium was enriched from mixture saline water samples collected from Chennai (Port of Chennai, salt pan), India. The consortium potently degraded polycyclic aromatic hydrocarbons (> 95%) at 30g/L of sodium chloride concentration in 4 days. The consortium was able to degrade 39 to 45% of different polycyclic hydrocarbons at 60 g/L NaCl concentration. Due to increase in salinity, the percent degradation decreased. To enhance polycyclic aromatic hydrocarbons degradation, yeast extract was added as an additional substrate at 60g/L NaCl concentration. After the addition of yeast extract, the consortium degraded > 74 % of polycyclic aromatic hydrocarbons at 60 g/L NaCl concentration in 4 days. The consortium was also able to degrade PAHs at different concentrations (5, 10, 20, 50 and 100 ppm) with 30 g/L of NaCl concentration. The polycyclic aromatic hydrocarbons degrading halotolerant bacterial consortium consists of three bacterial strains, namely Ochrobactrum sp., Enterobacter cloacae and Stenotrophomonas maltophilia.     

Biodegradation of phthalic acid esters in sewage sludge by composting with pig manure and rice straw

To comparatively study the biodegradation of phthalic acid esters (PAEs) in sewage sludge by composting with pig manure or with rice straw, four composting modes were designed: Mode 1 (sewage sludge + pig manure + intermittent aeration), Mode 2 (sewage sludge + pig manure + continuous aeration), Mode 3 (sewage sludge + rice straw + intermittent aeration) and Mode 4 (sewage sludge + rice straw + continuous aeration). Physicochemical parameters of composts were measured according to standard methods and PAEs were analyzed by gas chromatography coupled with mass spectrometry (GC/MS). The biodegradation of each PAE was also discussed. The results showed that Mode 1 was the best mode to biodegrade PAEs, which might be related to the wide class of indigenous microbial communities in pig manure and high efficiency of intermittent ventilation for providing oxygen. During the biodegradation process, di(2-ethylhexyl) phthalate was the most abundant and decisive for the removal of total PAEs. It showed a first-order kinetic degradation model. In conclusion, composting with pig manure could be suggested as an effective detoxification process for the removal of PAEs from sewage sludge, providing a safe end product.     

Population structures shift during the biodegradation of crude and fuel oil by an indigenous consortium

Petroleum and fuel oil are complex mixtures of recalcitrant hydrocarbons. The biodegradation of these hydrocarbons needs the action of a vast variety of enzymatic capacities. A microbial consortium offers the capability to degrade complex substrates through the assembly of different biochemical reactions, providing a metabolic versatility superior to axenic cultures. In this work, the microbial population dynamics, taxonomy, and the catabolic capacity of a stabilized consortium exposed to fuel and crude oil was analyzed through metagenomics. The stabilized consortium degraded 59% of crude oil components after 8 days, and 34% of fuel oil components after 130 days. Population dynamics analysis indicates that in fuel oil the biodiversity richness was higher; however, denaturing gradient gel electrophoresis similarity dendrogram shows significant changes in the microbial population during crude oil degradation. Taxonomy studies indicate a great genera divergence; only eight microbial genera were common in both samples. In crude oil, the Limnobacter sp. was the most abundant specie (15.6%), while Sphingomonas wittichii (7.9%) and Novosphingobium aromaticivorans (7.6%) were abundant in fuel oil. These microorganisms have been reported to participate in the degradation of aliphatic and aromatic hydrocarbons. Functional analysis suggests that fuel and crude oil components changed the interactions between the consortium members affecting the collective metabolic functionality.     

Isolation and characterization of a novel native Bacillus strain capable of degrading diesel fuel

The ability of native bacteria to utilize diesel fuel as the sole carbon and energy source was investigated in this research. Ten bacterial strains were isolated from the oil refinery field in Tehran, Iran. Two biodegradation experiments were performed in low and high (500 and 10000 ppm, respectively) concentration of diesel fuel for 15 days. Only two isolates were able to efficiently degrade the petroleum hydrocarbons in the first test and degraded 86.67% and, 80.60 % of diesel fuel, respectively. The secondary experiment was performed to investigate the toxicity effect of diesel fuel at high concentration (10000 ppm). Only one strain was capable to degrade 85.20 % of diesel fuel at the same time (15 days). Phenotype and phylogeny analysis of this strain was characterized and identified as diesel-degrading bacteria, based on gram staining, biochemical tests, 16S rRNA gene sequence analysis. These results indicate that this new strain was Bacillus sp. and could be considered as Bacillus Cereus with 98 % 16 S rRNA gene sequence similarity. The results indicate that native strains have great potential for in situ remediation of diesel-contaminated soils in oil refinery sites.     

Biodegradation of phenol from a synthetic aqueous system using acclimatized activated sludge

Phenol is one of the aromatic hydrocarbons. Phenol and its derivatives are highly toxic. These pollutants can be observed in the effluents of many industries. This research investigates the removal of phenol by the use of activated sludge in a batch system. The effects of influencing factors on biodegradation efficiency have been evaluated. The main factors considered in this study were the volume of acclimatized activated sludge inoculation, pH, temperature, and initial concentration of phenol. The inoculation volumes of 1, 3, and 5 mL of acclimatized activated sludge were taken into account. Different pH values of 3, 5, 7, 9, and 11 were examined. The experiments were conducted for temperatures of 25, 30, 35, and 40 °C and initial phenol concentrations of 400, 800, 1,000, and 1,500 ppm. The results show that the acclimatized activated sludge has a high capacity for the removal of phenol. From a 100-mL aqueous solution was removed 1,500 ppm of phenol after 80 h. Furthermore, maximum phenol removal was observed for an inoculation volume of 5 mL for three different phenol concentrations of 100, 400, and 800 ppm. The best pH was 7 for the biodegradation process, and the optimum temperature was 30 °C. It was further found that an increase in the phenol concentration increased its removal time. Moreover, the activated sludge could effectively remove about 99.9 % of phenol from a synthetic aqueous solution in a batch system.     

Richness of drilling sludge taken from an oil field quagmire: potentiality and environmental interest

The drilling sludge represents a complex environment, containing several types of pollutants that can be even used as nutrients by indigenous microorganisms, like hydrocarbon-degrading bacteria, having good potentialities for the biodegradation of petroleum products. In this study, a drilling sludge was collected from drilling quagmire. Physicochemical characterization of the drilling sludge was done. Its mineralogy was obtained by diffractometry. The indigenous aerobic sludge hydrocarbon-degrading bacteria were checked by counting on Bushnell–Haas medium, and their isolation and purification were performed by the selective microbial enrichment technique in a batch-enriched Bushnell–Haas culture, with crude oil as the sole carbon source. Isolates were characterized, and their power to emulsify crude oil was determined by emulsification index and oil spreading tests. Environmental conditions in the quagmire, like temperature, pH and moisture, were suitable for bacterial development. Physicochemical characteristics of the drilling sludge showed richness in chemical elements and promote microbial life. Fifteen different colonies of hydrocarbon-degrading bacteria were isolated and purified; they have diversified morphological and microscopic aspects. Most isolates had a good emulsification index (between 31 and 76 %). Oil spreading test gave clear zone diameters >28 mm, with a maximum of 60 mm. The results of these investigations prove the elementary, mineralogy and microbiology richness of drilling sludge and reveal the high diversity of its indigenous hydrocarbon-degrading bacterial flora. These properties can be exploited for the own restoration of petroleum quagmires in oil fields, by means of bioremediation applications and by integrating indigenous microorganisms.     

Activated sludge acclimation for toluene and DEHP degradation in a two-phase partitioning bioreactor

The effect of activated sludge acclimation on the biodegradation of toluene in the presence of a biodegradable non-aqueous phase liquid, di (2-ethylhexyl) phthalate (DEHP), in a two-phase partitioning bioreactor was characterized. The influence of the presence of DEHP, at a ratio of 0.1 % (volume ratio), and of the acclimation of activated sludge (AS) on the biodegradation of hydrophobic VOC was studied. AS was acclimated to both toluene and DEHP simultaneously. Using acclimated cells, 73 and 96 % improvement of the mean biodegradation rates was recorded for toluene and the organic solvent (DEHP), respectively, if compared to the values recorded in the absence of acclimation, during tests performed in Erlenmeyer flasks. Degradation rates were further improved by the use of acclimated AS in a reactor with a large head space; degradation yields for toluene and DEHP were above 99 and 89 %, respectively.     

Effect of sulphur species on the hydrocarbon biodegradation of oil sludge generated by a gas processing facility

Oily sludge from gas processing facilities contains components that are major environmental pollutants. Biodegradation is an alternative treatment, but can be affected by other components of the sludge, such as sulphur compounds, so it is important to evaluate the effect of these on oil biodegradation in order to prevent negative impacts. This work studied the transformation of sulphur compounds in oily sludge biodegradation systems at the microcosm level. The predominant sulphur compounds in the original sludge were elemental sulphur and pyrite (9,776 and 28,705.4 mg kg^?1, respectively). In the biodegradability assays, hydrocarbon concentrations decreased from 312,705.6 to 186, 760.3 mg kg^?1 after 15 days of treatment. After this time, hydrocarbon degrading activity stopped, corresponding with a decrease in hydrocarbon degrading bacteria. These changes were related to a reduction in pH that inhibits biodegradation. During the assay, sulphur compounds were gradually oxidized and transformed. The concentration of sulphate increased from 5,096 to 64,868.3 mg kg^?1 after 30 days in the assay, although controls were unchanged. Therefore, it is important to determine changes to the main compounds of the waste in order to assess their impact.     

Methane oxidation capacity of methanotrophs isolated from different soil ecosystems

Methane is one of the potential greenhouse gases contributing to global climate change, with a global warming potential of about 25 times than that of carbon dioxide. Aerobic methane oxidation (methanotrophy) is the key process that counteracts emission of methane to atmosphere. In this study, methane oxidation capacity of different methane-oxidizing bacteria (methanotrophs) isolated from six different ecosystems was investigated. Methanotrophic consortium isolated from dumpsite proved to be most effective in oxidizing methane. Initially, methane oxidation rate was found to be 0.72 ± 0.036 mM/day; in course of the study consortium M5 showed an increase in methane oxidation rate up to 1.7 ± 0.016 mM/day. A maximum of 0.78 mol of CO₂ production was found during methane oxidation in methanotrophs from dumpsite (M5). While varying temperatures, methane oxidation rate was in the range of 1.3–1.7 mM/day which has been found in the temperature range of 30–40 °C. Even at higher temperature (50 °C), 0.076 ± 0.14 mM of the methane was utilized per day. Methane oxidation was assessed by Michaelis–Menten kinetics. By varying the methane concentration, methane oxidation was studied and kinetic parameters such as V _max and K _m were derived using Lineweaver–Burk plot and found to be 1.497 mM/day and 2.23 mM, respectively. In methane mitigation approach, Methane soil sink is very essential because a balance between methane production by methanogens and consumption by methanotrophs plays an important role in methane emission reduction. Enhancing the methane soil sink will be a cost-effective method to cut down methane emission.     

Start-up of halophilic nitrogen removal via nitrite from hypersaline wastewater by estuarine sediments in sequencing batch reactor

Nitrogen removal from hypersaline wastewater was successfully started up by inoculating estuarine sediments for 140 days. Efficient ammonia and total nitrogen removal was sustained under specific ammonia loading of 0.016–0.139 kg N/[kg VSS day] in a sequencing batch reactor. Stable nitrite accumulation was observed during nitrification. The specific ammonia consumption rate was higher than the value of freshwater activated sludge and salt-acclimated freshwater activated sludge. With methanol as carbon source, specific nitrite reduction rate of halophilic denitrifiers was much less than the freshwater counterpart. Halophilic activated sludge was characterized as good settling and flocculation prosperity with small floc size and net-like sludge structure. The abundance of ammonia-oxidizing bacteria outnumbered ammonia-oxidizing archaeas in both estuarine sediments and the activated sludge. Nitrifier population was dominated by the halophilic members of genus Nitrosomonas. This study demonstrated the application of mixed halophilic consortia for efficient nitrogen removal, overcoming the limits and difficulties of applying freshwater bacteria for saline wastewater treatment.     

Impact of activated sludge acclimation on the biodegradation of toluene absorbed in a hydrophobic ionic liquid

Classical hydrophobic ionic liquids such as 3-butyl-1-methylimidazolium bis(trifluoroethylsulfonyl)imide or 3-butyl-1-methylimidazolium hexafluorophosphate application, as a non-aqueous liquid phase in a two-partitioning bioreactor to biodegrade hydrophobic volatile organic compounds by activated sludge, have been already reported in the literature, especially when the activated sludge was beforehand acclimated to the targeted volatile organic compound. In this study, four hydrophobic ionic liquids were used as non-aqueous liquid phase in a two-phase partitioning bioreactor to biodegrade toluene using non-acclimated activated sludge. The preliminarily results allowed to select two ionic liquids, 1-octylisoquinolinium bis(trifluoromethylsulfonyl)imide and allyl-diethylsulfonium bis(trifluoromethylsulfonyl)imide. The activated sludge was acclimated to both toluene and the considered ionic liquid. The results were compared to those obtained with non-acclimated activated sludge. The use of non-acclimated activated sludge for toluene biodegradation led to long lag times and low biodegradation rates. Thus, the acclimation to toluene improved the biodegradation rates; however, acclimation to both toluene and ionic liquid did not result in a significant improvement in the biodegradation rate compared to an acclimation to toluene alone. The activated sludge acclimation had a positive impact on toluene biodegradation and allowed to totally overcome the inhibitory effect of the presence of ionic liquid. The most relevant acclimation strategy seems to be a prior acclimation to toluene, whereas acclimation to the non-aqueous liquid phase can be achieved during the culture, namely by performing successive batches for instance, or a continuous operation.     

Applicability of upflow anaerobic sludge blanket (UASB) reactor for typical sewage of a small community: its biomass reactivation after shutdown

In this study, the characteristics of sewage of small community were determined for 6 months to ascertain the type of treatment required in subtropical conditions. The results demarcated sewage of this community as a medium-strength wastewater (chemical oxygen demand: 475 mg/L, biochemical oxygen demand: 240 mg/L and total suspended solids: 434 mg/L). Chemical oxygen demand to sulphate ratio of the sewage (11.6) established that it was amenable to anaerobic digestion. The temperature, strength, biodegradability and components of sewage were suitable for anaerobic digestion, and thus, upflow anaerobic sludge blanket reactor (UASB) was selected for its treatment. These reactors are often shutdown in small communities due to environmental and/or socio-economic factors. The ability of two UASB reactors, seeded with cow dung (UASB_CD) and activated sludge of a dairy treatment plant (UASB_ASDIT) to restart after a long idle period of 12 months, was investigated along with sludge analysis by scanning electron microscope. Biomass in both reactors reactivated rapidly after shutdown period and within 30 days after substrate feeding achieved uniform removal efficiencies for chemical oxygen demand, total suspended solids, total dissolved solids, chloride and oil and grease. Chemical oxygen demand removal efficiency of both reactors became uniform and remained close to 80% after 30 days through reactivation of microbes in sludge bed due to adequate food and temperature conditions. During restart-up, at an average organic loading rate of 0.902 kg COD/m³ per day, methane yields of 0.091 and 0.084 m³/kg COD removed were achieved for UASB_CD and UASB_ASDIT reactors, respectively.     

Anaerobic digester sludge as nutrient source for culturing of microalgae for economic biodiesel production

After decades of ‘living dangerously’, the human kind has paused to think of Mother Nature. Alternate energy sources are being developed as a part of this realization. The use of indigenous sources of nutrients would considerably bring down the cost of production. A mixed consortium of Chlorella vulgaris, Arthrospira platensis, and tap water-originated Scenedesmus dimorphus was cultured using natural seawater, anaerobic digester sludge, and its growth was compared with synthetic commercial media like Zarrouk’s media, NaNO₃ media, and NH₄Cl media. A spectrophotometric method was standardized for regular biomass estimation. The dry biomass of a 15-day pure, batch culture of Arthrospira was found to yield around 600 mg/L in anaerobic digester sludge, whereas the pure batch culture of chlorella’s growth was hindered mainly due to the presence of bacteria and grazers. Regular microscopic observation and biomass monitoring revealed a drastic reduction in grazing activity, with the use of autoclaved AD sludge, resulting in a strong and stable microalgal mixed consortia. The consortia growth in AD sludge was found to be better than with the synthetic media with no cost of nutrient. The mixed consortia yielded a biomass up to 600 mg/L and lipid of 21.18%. The lipid generated from AD sludge had around 95% unsaturates and contained around 5% omega-3 fatty acids. The use of anaerobic digester sludge in a non-sterile condition reduces the total cost of the biodiesel production process as a whole and introduces a decentralized system for waste water treatment as well.     

Reuse of dewatered sewage sludge conditioned with skeleton builders as landfill cover material

High water and organic content of sewage sludge constricts its reuse and disposal. It is often necessary to solidify/stabilize the dewatered sludge with solidifying agents before landfill disposal. In this study, the sewage sludge was conditioned with skeleton builders, i.e., fly ash and lime combined with ferric chloride for the purpose of improving the dewatering efficiency. The dewatered sewage sludge was then directly reused as landfill cover materials since the skeleton builders also play a role in solidification of sludge. The geotechnical properties of the dewatered sewage sludge were investigated. The results show that the plasticity index of the dewatered sludge increases compared to that of the dewatered sludge without any conditioner, and the permeability coefficient changes from 10^?8 to 10^?5 cm s^?1. Furthermore, the strength of specimens increase with curing days. Microstructure analyses reveal that the main hydrated products are calcium silicate hydrate and ettringite, which contribute to the solidification/stabilization of the dewatered sludge. The results indicate that the dewatered sewage sludge conditioned with skeleton builders can be used as landfill covers. This study provides an alternative for traditional sewage sludge treatment and disposal.     

菲降解菌的降解特性及酶促反应动力学研究

通过对取自MBR膜生物反应器中的活性污泥加入菲进行富集培养、驯化,分离、纯化出一株能以菲为唯一碳源和能源的短杆状革兰氏阴性菌J-1,细菌长2～5μm,宽1～3μm;研究了初始底物浓度、温度、pH对菌株J-1降解菲的影响,探讨了菌株J-1胞内酶对菲降解的底物抑制动力学。试验表明:菌株J-1在48h内能将不同浓度菲的水溶液中的菲完全降解;菲浓度增加,达到完全降解的时间延长。温度对细菌的降解能力影响较大,菌株J-1对菲降解的最佳温度为28℃。1.15mg·L-1的菲,28℃时48h内能完全降解,而相同时间内10℃时的降解率仅为36.65%。菌株J-1对pH的波动具有一定的适应性,pH在一定范围内(6.0～8.4)变化对菲降解的影响不大,降解反应的最佳pH为7.2。菌株J-1对菲的降解符合一级动力学反应方程。较高的底物浓度对酶促降解反应具有抑制作用,酶促反应的最大速率常数vm=1.17mg·L-1·h-1,米氏常数Km=61.70mg·L-1;底物抑制常数kS=49.60mg·L-1;最佳底物浓度[S]opt=55.32mg·L-1。     

不同环境条件对固定化细菌吸附低浓度Cd2+规律的影响

采用固定化技术将吸附重金属能力较强的优势细菌固定,然后将其对Cd²⁺进行吸附规律研究。结果表明：固定化细菌对Cd²⁺吸附是动态过程,120 min达到吸附平衡;随着重金属Cd²⁺浓度的增加,固定化细菌对其吸附量呈线性增加,而随着离子强度的增加,固定化细菌对其吸附量呈线性降低;当吸附体系pH=6时吸附量最大;环境温度对固定化细菌吸附影响不显著;共存Pb²⁺降低了固定化细菌对Cd²⁺的吸附量。     

Cytotoxic and genotoxic evaluation and chemical characterization of sewage treated using activated sludge and a floating emergent-macrophyte filter in a municipal wastewater treatment plant: a case study in Southern Brazil

This study was conducted to evaluate the chemical parameters and the cytotoxic and genotoxic potential of raw domestic sewage and effluents from treatment with activated sludge and a floating emergent-macrophyte filter from a domestic wastewater treatment plant in the city of Novo Hamburgo, Rio Grande do Sul, Brazil. The physicochemical analysis revealed that both treatment systems achieved the legal emission pattern for biochemical oxygen demand, chemical oxygen demand, and suspended solids, but ammoniacal nitrogen and E. coli values were above the limits in the macrophyte treatment effluent. Phosphorous values were above the maximum permitted for both treatments. The results obtained from the Allium cepa test and the micronuclei test in fish did not demonstrate any significant differences in both cytotoxicity (mitotic index) and genotoxicity (chromosome aberration and micronucleus) endpoints between the negative control group and the exposed groups. However, the comet assay in fish revealed a DNA damage increase in animals exposed to the 30 % concentration of the macrophyte effluent and two concentrations of the activated sludge treatment effluent (10 and 75 %), which suggests that these two treatment systems may increase wastewater genotoxicity.     

Methoxychlor bioremediation by defined consortium of environmental Streptomyces strains

Methoxychlor is an organochlorine pesticide used worldwide against several insect pests, resulting in human exposure. This pesticide mimics endocrine hormone functions, interfering with normal endocrine activity in humans and wildlife. For this reason, it is imperative to develop methods to remove this pesticide from the environment, and though, bioremediation using microorganisms results as an excellent strategy. Five Streptomyces spp. strains previously isolated from organochlorine-polluted sites and capable to grow and remove methoxychlor were combined as different mixed cultures to increase methoxychlor removal. From the 39 consortia tested, one consortium (Streptomyces spp. A6, A12, A14, M7) was selected because of its high pesticide removal and specific dechlorinase activity to be assayed on slurry and soil systems. This consortium showed higher biomass values (8.3 × 10⁶ ± 5.7 × 10⁵ CFU mL^?1) and methoxychlor removal (56.2 ± 2.3 %) on enriched slurry than in non-enriched slurry (7.3 × 10⁵ ± 1.2 × 10⁵ CFU mL^?1 and 45.6 ± 7.4 % of pesticide removal). In soil systems, Streptomyces consortium showed higher growth (1.0 × 10¹¹ ± 5.0 × 10¹⁰ CFU g^?1) than in enriched slurry, although differences in methoxychlor removal between both culture conditions were not statistically significant. Therefore, the selected Streptomyces consortium may be suitable for the development of in situ (soil) and ex situ (slurry bioreactor) bioremediation methods because of their potential to remove methoxychlor from different systems.