Intrinsic Bioremediation Research Articles

Metagenomic 16S rRNA analysis and predictive functional profiling revealed intrinsic organohalides respiration and bioremediation potential in mangrove sediment

BackgroundMangrove sediment microbes are increasingly attracting scientific attention due to their demonstrated capacity for diverse bioremediation activities, encompassing a wide range of environmental contaminants.Materials and methodsThe microbial communities of five Avicennia marina mangrove sediment samples collected from Al Rayyis White Head, Red Sea (KSA), were characterized using Illumina amplicon sequencing of the 16S rRNA genes.ResultsOur study investigated the microbial composition and potential for organohalide bioremediation in five mangrove sediments from the Red Sea. While Proteobacteria dominated four microbiomes, Bacteroidetes dominated the fifth. Given the environmental concerns surrounding organohalides, their bioremediation is crucial. Encouragingly, we identified phylogenetically diverse organohalide-respiring bacteria (OHRB) across all samples, including Dehalogenimonas, Dehalococcoides, Anaeromyxobacter, Desulfuromonas, Geobacter, Desulfomonile, Desulfovibrio, Shewanella and Desulfitobacterium. These bacteria are known for their ability to dechlorinate organohalides through reductive dehalogenation. PICRUSt analysis further supported this potential, predicting the presence of functional biomarkers for organohalide respiration (OHR), including reductive dehalogenases targeting tetrachloroethene (PCE) and 3-chloro-4-hydroxyphenylacetate in most sediments. Enrichment cultures studies confirmed this prediction, demonstrating PCE dechlorination by the resident microbial community. PICRUSt also revealed a dominance of anaerobic metabolic processes, suggesting the microbiome’s adaptation to the oxygen-limited environment of the sediments.ConclusionThis study provided insights into the bacterial community composition of five mangrove sediments from the Red Sea. Notably, diverse OHRB were detected across all samples, which possess the metabolic potential for organohalide bioremediation through reductive dehalogenation pathways. Furthermore, PICRUSt analysis predicted the presence of functional biomarkers for OHR in most sediments, suggesting potential intrinsic OHR activity by the enclosed microbial community.

An integrated evaluation of bioenhanced in situ LNAPL dissolution

Performance evaluation of in situ bioremediation processes in the field is difficult due to uncertainty created by matrix and contaminant heterogeneity, inaccessibility to direct observation, expense of sampling, and limitations of some measurements. The goal of this research was to develop a strategy for evaluating in situ bioremediation of light nonaqueous-phase liquid (LNAPL) contamination and demonstrating the occurrence of bioenhanced LNAPL dissolution by: (1) integrating a suite of analyses into a rational evaluation strategy; and (2) demonstrating the strategy's application in intermediate-scale flow-cell (ISFC) experiments simulating an aquifer contaminated with a pool of LNAPL (naphthalene dissolved in dodecane). Two ISFCs were operated to evaluate how the monitored parameters changed between a “no bioremediation” scenario and an “intrinsic in situ bioremediation” scenario. Key was incorporating different measures of microbial activity and contaminant degradation relevant to bioremediation: contaminant loss; consumption of electron acceptors; and changes in total alkalinity, pH, dissolved total inorganic carbon, carbon-stable isotopes, microorganisms, and intermediate metabolites. These measurements were integrated via mass-flux modeling and mass-balance analyses to document that in situ biodegradation of naphthalene was strongly accelerated in the “intrinsic in situ bioremediation” scenario versus “no bioremediation.” Furthermore, the integrated strategy provided consistent evidence of bioenhancement of LNAPL dissolution through intrinsic bioremediation by a factor of approximately 2 due to the biodegradation of the naphthalene near the pool/water interface.

Assessment of the intrinsic bioremediation capacity of a complexly contaminated Yamuna River of India: a algae-specific approach

Nearly 57 million people depend on Yamuna’s water for their daily needs and agriculture. This is the first study of assessment of the Yamuna River for five major pollutants – Nitrate, Sulfate, Phosphate, Silicon, and Chloride, and the role of inhabitant algal species for phycoremediation. Water samples were collected from 11 different locations across three different seasons and it was found that the concentration of these pollutants varies in different locations and seasons. The concentration of Nitrate 392.93 mg/L at ITO Monsoon 2021, Phosphate 86.25 mg/L at Baghpat, Silicon 257.34 mg/L at Faridabad, Sulfate 2165.949 mg/L at ITO during winter 2020, and Chloride 4400.741 mg/L at Old bridge during Monsoon 2021 are found maximum. A significant variation (p < 0.05) in the concentrations of Nitrate, Sulfate, Phosphate, Silicon, and Chloride before and after treatment with microalgae was observed in water samples. All six algae significantly remove all the pollutants, and the maximum pollutants removed are Phosphate and Nitrite. Scenedesmus sp., removes the highest 99.21% Phosphate and 86.31% Nitrate, whereas 78.50% of Sulfate was removed by Klebsormidium sp. The highest 92.77% Silicon and 86.20% Chloride were removed by Oocystis sp. This finding suggests that out of six algae, Scenedesmus sp., in the Yamuna water has grown primarily at all the sites and reduces maximum pollutants. The outcomes from this study confirms that Yamuna River is highly contaminated at all the sites from these five major pollutants and algae are still survive in highly contaminated Yamuna water where no other plants are grown and phycoremediate the water bodies even in the presence of very high-stress condition. These algae can further be utilized for biotreatment of any contaminated water body.

Increasing in situ bioremediation effectiveness through field-scale application of molecular biological tools.

Leveraging the capabilities of microorganisms to reduce (degrade or transform) concentrations of pollutants in soil and groundwater can be a cost-effective, natural remedial approach to manage contaminated sites. Traditional design and implementation of bioremediation strategies consist of lab-scale biodegradation studies or collection of field-scale geochemical data to infer associated biological processes. While both lab-scale biodegradation studies and field-scale geochemical data are useful for remedial decision-making, additional insights can be gained through the application of Molecular Biological Tools (MBTs) to directly measure contaminant-degrading microorganisms and associated bioremediation processes. Field-scale application of a standardized framework pairing MBTs with traditional contaminant and geochemical analyses was successfully performed at two contaminated sites. At a site with trichloroethene (TCE) impacted groundwater, framework application informed design of an enhanced bioremediation approach. Baseline abundances of 16S rRNA genes for a genus of obligate organohalide-respiring bacteria (i.e., Dehalococcoides) were measured at low abundances (101-102 cells/mL) within the TCE source and plume areas. In combination with geochemical analyses, these data suggested that intrinsic biodegradation (i.e., reductive dechlorination) may be occurring, but activities were limited by electron donor availability. The framework was utilized to support development of a full-scale enhanced bioremediation design (i.e., electron donor addition) and to monitor remedial performance. Additionally, the framework was applied at a second site with residual petroleum hydrocarbon (PHC) impacted soils and groundwater. MBTs, specifically qPCR and 16S gene amplicon rRNA sequencing, were used to characterize intrinsic bioremediation mechanisms. Functional genes associated with anaerobic biodegradation of diesel components (e.g., naphthyl-2-methyl-succinate synthase, naphthalene carboxylase, alkylsuccinate synthase, and benzoyl coenzyme A reductase) were measured to be 2-3 orders of magnitude greater than unimpacted, background samples. Intrinsic bioremediation mechanisms were determined to be sufficient to achieve groundwater remediation objectives. Nonetheless, the framework was further utilized to assess that an enhanced bioremediation could be a successful remedial alternative or complement to source area treatment. While bioremediation of chlorinated solvents, PHCs, and other contaminants has been demonstrated to successfully reduce environmental risk and reach site goals, the application of field-scale MBT data in combination with contaminant and geochemical data analyses to design, implement, and monitor a site-specific bioremediation approach can result in more consistent remedy effectiveness.

Water-lifting and aeration system improves water quality of drinking water reservoirs: Biological mechanism and field application

Reservoirs have been served as the major source of drinking water for dozens of years. The water quality safety of large and medium reservoirs increasingly becomes the focus of public concern. Field test has proved that water-lifting and aeration system (WLAS) is a piece of effective equipment for in situ control and improvement of water quality. However, its intrinsic bioremediation mechanism, especially for nitrogen removal, still lacks in-depth investigation. Hence, the dynamic changes in water quality parameters, carbon source metabolism, species compositions and co-occurrence patterns of microbial communities were systematically studied in Jinpen Reservoir within a whole WLAS running cycle. The WLAS operation could efficiently reduce organic carbon (19.77%), nitrogen (21.55%) and phosphorus (65.60%), respectively. Biolog analysis revealed that the microbial metabolic capacities were enhanced via WLAS operation, especially in bottom water. High-throughput sequencing demonstrated that WLAS operation altered the diversity and distributions of microbial communities in the source water. The most dominant genus accountable for aerobic denitrification was identified as Dechloromonas. Furthermore, network analysis revealed that microorganisms interacted more closely through WLAS operation. Oxidation-reduction potential (ORP) and total nitrogen (TN) were regarded as the two main physicochemical parameters influencing microbial community structures, as confirmed by redundancy analysis (RDA) and Mantel test. Overall, the results will provide a scientific basis and an effective way for strengthening the in-situ bioremediation of micro-polluted source water.

An electric field immobilizes heavy metals through promoting combination with humic substances during composting

The aim of this study was to explore a novel method to immobilize heavy metals (HM) in composting through increasing the combination of these with humic substances. An electric-field assistant technique was applied to strengthen biomass biodegradation and assess the impact on the humification process and HM immobilization in composting. Results demonstrated that the application of an electric field enriched bacterial abundance and enhanced bacterial metabolism. Humic substance and humic acid (HA) contents in compost product were significantly increased by 19 and 69%, respectively. The HA-complexed Cu, Zn, As, Cd contents were increased by 34, 41, 29 and 135.1%, respectively, which was attributed to the promotion of HA formation since a positive correlation between HA and HA-complexed HM (R2 = 0.60–0.87) was established. The evidence presented here supports the future development of electric field implementation as an intrinsic bioremediation technique for HM immobilization.

Methanogens and Their Syntrophic Partners Dominate Zones of Enhanced Magnetic Susceptibility at a Petroleum Contaminated Site

Geophysical investigations documenting enhanced magnetic susceptibility (MS) within the water table fluctuation zone at hydrocarbon contaminated sites suggest that MS can be used as a proxy for investigating microbial mediated iron reduction during intrinsic bioremediation. Here, we investigated the microbial community composition over a 5-year period at a hydrocarbon-contaminated site that exhibited transient elevated MS responses. Our objective was to determine the key microbial populations in zones of elevated MS. We retrieved sediment cores from the petroleum-contaminated site near Bemidji, MN, United States, and performed MS measurements on these cores. We also characterized the microbial community composition by high-throughput 16S rRNA gene amplicon sequencing from samples collected along the complete core length. Our spatial and temporal analysis revealed that the microbial community composition was generally stable throughout the period of investigation. In addition, we observed distinct vertical redox zonations extending from the upper vadose zone into the saturated zone. These distinct redox zonations were concomitant with the dominant microbial metabolic processes as follows: (1) the upper vadose zone was dominated by aerobic microbial populations; (2) the lower vadose zone was dominated by methanotrophic populations, iron reducers and iron oxidizers; (3) the smear zone was dominated by iron reducers; and (4) the free product zone was dominated by syntrophic and methanogenic populations. Although the common notion is that high MS values are caused by high magnetite concentrations that can be biotically formed through the activities of iron-reducing bacteria, here we show that the highest magnetic susceptibilities were measured in the free-phase petroleum zone, where a methanogenic community was predominant. This field study may contribute to the emerging knowledge that methanogens can switch their metabolism from methanogenesis to iron reduction with associated magnetite precipitation in hydrocarbon contaminated sediments. Thus, geophysical methods such as MS may help to identify zones where iron cycling/reduction by methanogens is occurring.

Determining the impact of biofilm in the bioaugmentation process of benzene-contaminated resources

Recently, petroleum contamination in groundwater has become one of the most common environmental problems. Bioaugmentation is proposed as a fully functional and economical technology by the addition of microorganisms to remove pollutants. The aim was to study the effect of biofilm formation of different species during the bioaugmentation of benzene removal in a Permeable Reactive Barrier (PRB) system based on calcium peroxide (CaO2) nanoparticles. Therefore, at first 3 strains identified with the ability to form biofilms and benzene degradation were isolated from groundwater. Subsequently, dissolved oxygen (DO), pH, the concentration of benzene, and microbial count of experimental columns were measured. Further, the examination of the biofilm formation on glass bead surfaces in bioaugmented and control reactors was also studied by confocal laser scanning microscopy (CLSM). The results of bioaugmentation show that adding Pseudomonas lini and Pseudarthrobacter polychromogenes can remove almost 80% of benzene from effluent after 70 days. Therefore, the study reveals the effect of bioaugmentation over intrinsic bioremediation. Also, the thicker and concentrated biofilm of Pseudomonas lini can be seen. This system provides a novel environmentally friendly technology for the in situ bioremediation of benzene.

Remarkable shift in structural and functional properties of an animal charcoal-polluted soil accentuated by inorganic nutrient amendment

BackgroundSoils polluted with animal charcoal from skin and hide cottage industries harbour extremely toxic and carcinogenic hydrocarbon pollutants and thus require a bio-based eco-friendly strategy for their depuration. The effects of carbon-free mineral medium (CFMM) amendment on hydrocarbon degradation and microbial community structure and function in an animal charcoal-polluted soil was monitored for 6 weeks in field moist microcosms consisting of CFMM-treated soil (FN4) and an untreated control (FN1). Hydrocarbon degradation was monitored using gas chromatography-flame ionization detector (GC-FID), and changes in microbial community structure were monitored using Kraken, while functional annotation of putative open reading frames (ORFs) was done using KEGG KofamKOALA and NCBI’s conserved domain database (CDD). ResultsGas chromatographic analysis of hydrocarbon fractions revealed the removal of 84.02% and 82.38% aliphatic and 70.09% and 70.14% aromatic fractions in FN4 and FN1 microcosms in 42 days. Shotgun metagenomic analysis of the two metagenomes revealed a remarkable shift in the microbial community structure. In the FN4 metagenome, 92.97% of the population belong to the phylum Firmicutes and its dominant representative genera Anoxybacillus (64.58%), Bacillus (21.47%) and Solibacillus (2.39%). In untreated FN1 metagenome, the phyla Proteobacteria (56.12%), Actinobacteria (23.79%) and Firmicutes (11.20%), and the genera Xanthobacter (9.73%), Rhizobium (7.49%) and Corynebacterium (7.35%), were preponderant. Functional annotation of putative ORFs from the two metagenomes revealed the detection of degradation genes for aromatic hydrocarbons, benzoate, xylene, chlorocyclohexane/chlorobenzene, toluene and several others in FN1 metagenome. In the FN4 metagenome, only seven hydrocarbon degradation genes were detected. ConclusionThis study revealed that though CFMM amendment slightly increases the rate of hydrocarbon degradation, it negatively impacts the structural and functional properties of the animal charcoal-polluted soil. It also revealed that intrinsic bioremediation of the polluted soil could be enhanced via addition of water and aeration.

Dexmedetomidine inhibits apoptosis of astrocytes induced by oxygen-glucose deprivation via targeting JAK/STAT3 signal pathway

ObjectiveThere is an increasing interest concerning the contribution of astrocytes to the intrinsic bioremediation of ischemic brain injury. The aim of this work was to disclose the effects and mechanism of dexmedetomidine (DEX) on the apoptosis of astrocytes under oxygen glucose deprivation (OGD) condition. MethodsPrimary cultured astrocytes separated from Sprague-Dawley (SD) rats were subjected to OGD treatment. Astrocytes were transfected with si-JMJD3 or pcDNA3.1-JMJD3 and then treated with DEX or JAK/STAT inhibitor (WP1066) before cell apoptosis was detected by TUNEL apoptosis kit. Western blot was applied to assess the level of apoptosis-related proteins Caspase-3, Bax and Bcl-2. Astrocyte cell viability was assessed by measuring the lactate dehydrogenase (LDH) level using a LDH assay kit. ResultsAstrocytes received OGD treatment had increased LDH and elevated apoptotic rate (P < 0.05). DEX could suppress OGD induced cytotoxic effect on astrocytes, as evidenced by decreased LDH release and suppressed cell apoptosis rate (P < 0.05). Meanwhile, DEX and WP1066 treatment were also found to inhibit the phosphorylation level of STAT1 and STAT3 (P < 0.05), indicating the DEX could suppress the activation of JAK/STAT signal pathway. JMJD3 overexpression in astrocytes could suppress the anti-apoptotic function of WP1066 in OGD treated astrocytes and hamper the protective effect of DEX in cell apoptosis (P < 0.05), suggesting that DEX and JAK/STAT signal pathway inhibits OGD induced apoptosis in astrocytes by down-regulating JMJD3. ConclusionDEX protects astrocytes against apoptosis via inhibiting JAK2/STAT3 signal pathway and downregulating JMJD3 expression in vitro.

Integrative isotopic and molecular approach for the diagnosis and implementation of an efficient in-situ enhanced biological reductive dechlorination of chlorinated ethenes

Based on the previously observed intrinsic bioremediation potential of a site originally contaminated with perchloroethene (PCE), field-derived lactate-amended microcosms were performed to test different lactate isomers and concentrations, and find clearer isotopic and molecular parameters proving the feasibility of an in-situ enhanced reductive dechlorination (ERD) from PCE-to-ethene (ETH). According to these laboratory results, which confirmed the presence of Dehalococcoides sp. and the vcrA gene, an in-situ ERD pilot test consisting of a single injection of lactate in a monitoring well was performed and monitored for 190 days. The parameters used to follow the performance of the ERD comprised the analysis of i) hydrochemistry, including redox potential (Eh), and the concentrations of redox sensitive species, chlorinated ethenes (CEs), lactate, and acetate; ii) stable isotope composition of carbon of CEs, and sulphur and oxygen of sulphate; and iii) 16S rRNA gene sequencing from groundwater samples. Thus, it was proved that the injection of lactate promoted sulphate-reducing conditions, with the subsequent decrease in Eh, which allowed for the full reductive dechlorination of PCE to ETH in the injection well. The biodegradation of CEs was also confirmed by the enrichment in 13C and carbon isotopic mass balances. The metagenomic results evidenced the shift in the composition of the microbial population towards the predominance of fermentative bacteria. Given the success of the in-situ pilot test, a full-scale ERD with lactate was then implemented at the site. After one year of treatment, PCE and trichloroethene were mostly depleted, whereas vinyl chloride (VC) and ETH were the predominant metabolites. Most importantly, the shift of the carbon isotopic mass balances towards more positive values confirmed the complete reductive dechlorination, including the VC-to-ETH reaction step. The combination of techniques used here provides complementary lines of evidence for the diagnosis of the intrinsic biodegradation potential of a polluted site, but also to monitor the progress, identify potential difficulties, and evaluate the success of ERD at the field scale.

Isolation, characterization and determination of biotechnological potential of oil-degrading bacteria from Algerian centre coast.

The Algerian coastline is exposed to several types of pollution, including hydrocarbons. The aim of this work was to isolate oil-degrading bacteria and to explore the intrinsic bioremediation potential of part of its contaminated harbour. A collection of 119 strains, capable to grow on mineral medium supplemented with hydrocarbons, were obtained from polluted sediment and seawater collected from Sidi Fredj harbour (Algiers). Twenty-three strains were selected for further studies. Sequencing of the 16S rRNA gene showed that most isolates belong to genera of hydrocarbonoclastic bacteria (Alcanivorax), generalist hydrocarbons degraders (Marinobacter, Pseudomonas, Gordonia, Halomonas, Erythrobacter and Brevibacterium) and other bacteria not known as hydrocarbon degraders (Xanthomarina) but were able to degrade hydrocarbons. Strains related to Marinobacter and Alcanivorax were frequently isolated from our samples and resulted the most effective in degrading crude oil. Screening of catabolic genes alkB and xylA revealed the presence of alkB gene in several bacterial strains; one isolate harboured both catabolic genes while other isolates carried none of the studied genes. However, they grew in the presence of crude oil implying the existence of other biodegradation pathways. The samples of seawater and sediment from the Algerian coast contain high level of hydrocarbon-degrading bacteria that could be interesting and useful for future bioremediation purposes. This investigation demonstrates the diversity of hydrocarbon-degrading bacteria from a marine-contaminated area in Algeria, and their variable biodegradation abilities.

Associating potential 1,4-dioxane biodegradation activity with groundwater geochemical parameters at four different contaminated sites

1,4-Dioxane (dioxane) is a groundwater contaminant of emerging concern for which bioremediation may become a practical remediation strategy. Therefore, it is important to advance our heuristic understanding of geochemical parameters that are most influential on the potential success of intrinsic bioremediation of dioxane-impacted sites. Here, Pearson's and Spearman's correlation and linear regression analyses were conducted to discern associations between 1,4-dioxane biodegradation activity measured in aerobic microcosms and groundwater geochemical parameters at four different contaminated sites. Dissolved oxygen, which is known to limit dioxane biodegradation, was excluded as a limiting factor in this analysis. Biodegradation activity was positively associated with dioxane concentrations (p < 0.01; R < 0.70) as well as the number of catabolic thmA gene copies (p < 0.01; R = 0.80) encoding dioxane monooxygenase. Thus, whereas environmental factors such as pH, temperature, and nutrients may influence dioxane biodegradation, these parameters did not exert as strong of an influence on potential biodegradation activity as the in situ concentration of substrate dioxane at the time of sampling. This analysis infers that aerobic sites with higher dioxane concentrations are more likely to select and sustain a thriving population of dioxane degraders, while sites with relatively low dioxane concentrations would be more difficult to attenuate naturally and may require alternative remediation strategies.

Changes in metals and polyaromatic hydrocarbon contents of a spent lubrication oil-polluted soil after exposure to sodium azide and hydroxlamine hydrochloride solutions: implications for intrinsic bioremediation

Changes in metals and polyaromatic hydrocarbon contents of a spent lubrication oil-polluted soil after exposure to sodium azide and hydroxlamine hydrochloride solutions: implications for intrinsic bioremediation

Using intrinsic bioremediation for petroleum–hydrocarbon contaminated groundwater cleanup and migration containment: Effectiveness and mechanism evaluation

Intrinsic bioremediation (IB) is the major mechanism causing the containment of petroleum hydrocarbons in groundwater. The effectiveness and mechanisms of IB on the contaminant removal were evaluated in this study. Groundwater was analyzed for the efficiency of IB, dominant bacteria, bacterial diversity, and biodegradation rates. Concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) and methyl tert-butyl ether (MTBE) dropped from 6.5 and 0.14 mg/L in source area to 67 and 19 µg/L at the 145 m downgradient area. The biodegradation capacities for BTEX (50.9 mg/L) and MTBE (58.5 mg/L) were higher than the BTEX (6.5 mg/L) and MTBE (0.14 mg/L) concentrations within the plume. The bacterial diversities were assessed by 16S rRNA-based denatured gradient gel electrophoresis and nucleotide sequence analyses. More than 21 petroleum–hydrocarbon biodegrading bacterial species were detected in groundwater indicating that contaminants could be biodegraded by natural-occurring bacteria. The calculated MTBE and BTEX first-order decay rates were 5.7 × 10−4 and 1.3 × 10−3 per day, respectively. The high decay rates indicate that IB mechanisms played important roles in contaminant removal. The observed evidences of IB processes in highly contaminated areas included: (1) decreased electron acceptors, (2) production of degradation byproducts, (3) increased microbial populations and alkalinity, and (4) decreased electron donors and pH.

Biostimulation of Indigenous Microbial Community for Bioremediation of Petroleum Refinery Sludge.

Nutrient deficiency severely impairs the catabolic activity of indigenous microorganisms in hydrocarbon rich environments (HREs) and limits the rate of intrinsic bioremediation. The present study aimed to characterize the microbial community in refinery waste and evaluate the scope for biostimulation based in situ bioremediation. Samples recovered from the wastewater lagoon of Guwahati refinery revealed a hydrocarbon enriched [high total petroleum hydrocarbon (TPH)], oxygen-, moisture-limited, reducing environment. Intrinsic biodegradation ability of the indigenous microorganisms was enhanced significantly (>80% reduction in TPH by 90 days) with nitrate amendment. Preferred utilization of both higher- (>C30) and middle- chain (C20-30) length hydrocarbons were evident from GC-MS analysis. Denaturing gradient gel electrophoresis and community level physiological profiling analyses indicated distinct shift in community’s composition and metabolic abilities following nitrogen (N) amendment. High throughput deep sequencing of 16S rRNA gene showed that the native community was mainly composed of hydrocarbon degrading, syntrophic, methanogenic, nitrate/iron/sulfur reducing facultative anaerobic bacteria and archaebacteria, affiliated to γ- and δ-Proteobacteria and Euryarchaeota respectively. Genes for aerobic and anaerobic alkane metabolism (alkB and bssA), methanogenesis (mcrA), denitrification (nirS and narG) and N2 fixation (nifH) were detected. Concomitant to hydrocarbon degradation, lowering of dissolve O2 and increase in oxidation-reduction potential (ORP) marked with an enrichment of N2 fixing, nitrate reducing aerobic/facultative anaerobic members [e.g., Azovibrio, Pseudoxanthomonas and Comamonadaceae members] was evident in N amended microcosm. This study highlighted that indigenous community of refinery sludge was intrinsically diverse, yet appreciable rate of in situ bioremediation could be achieved by supplying adequate N sources.

Strategies of Bioremediation for the Degradation of Petroleum Hydrocarbons in the Presence of Metals in Mangrove Simulated

Contamination by oil spills in coastal ecosystems, especially in mangrove zones, has been common in countries with oil industry. The aim of this study was, therefore, to evaluate the efficiency of application of the two models developed for pilot‐scale remediation, intrinsic bioremediation (indigenous microorganisms), and phytoremediation (Avicennia schaueriana). The degradation of hydrocarbons was determined by gas chromatography (GS) with flame ionization detector. The metals Al, Fe, Pb, Cr, Cu, Zn, and Ni were determined by flame atomic absorption spectrometry in the mangrove simulated with sediment of Todos os Santos Bay, Brazil. These models also monitor other biogeochemical parameters (nitrogen, phosphorus, total organic carbon, pH, redox potentioal, dissolved oxygen, salinity, temperature, bacterial density). The integrated assessment of data showed that both techniques were effective in degrading organic compounds from oil but that phytoremediation is the most efficient (89% removal). The intrinsic bioremediation model has no direct correlation with metal concentrations, but a positive correlation with Al and Ni was found in the hydrocarbon removal by phytoremediation.Avicennia schauerianarepresents efficiency in phytoextraction and phytostimulation. The results suggest that the phytoremediation model, through its various mechanisms, may become a technique for the removal of petroleum hydrocarbons in the presence of metals in mangrove ecosystems near industrial areas.

Remediation of diesel‐contaminated soil using in situ chemical oxidation (ISCO) and the effects of common oxidants on the indigenous microbial community: a comparison study

AbstractBACKGROUNDIn this study, batch experiments were conducted using diesel‐contaminated soil collected from a former gas station to evaluate the efficiency of diesel removal by in situ chemical oxidation (ISCO) and the effects of different oxidants on the indigenous microbial community.RESULTSDiesel removal efficiencies by persulfate, permanganate, and hydrogen peroxide under different concentrations (1, 3, 5, and 10%) ranged from 48 to 93% during a 120‐day reaction. The performance of diesel removal in the oxidant‐alone systems was persulfate &gt; permanganate &gt; hydrogen peroxide. Oxidant persistence was positively correlated with diesel removal performance. Higher diesel removal efficiencies were observed in the chemical oxidation systems with the presence of microbes. The adverse effects of the oxidants on intrinsic microbes followed the sequence persulfate &gt; permanganate ≈ hydrogen peroxide. The addition of hydrogen peroxide and permanganate caused increased microbial diversity while more serious destruction to the microbial community was observed in the persulfate solution due to low pH (&lt;3.5).CONCLUSIONThe results suggest 1 to 3% of oxidant addition was more suitable for the application of ISCO coupled with intrinsic bioremediation. The addition of 5% oxidants could also be considered. However, pH should be controlled when persulfate is applied. © 2015 Society of Chemical Industry

Intrinsic bioremediation potential of a chronically polluted marine coastal area

A microbiological survey of the Priolo Bay (eastern coast of Sicily, Ionian Sea), a chronically polluted marine coastal area, was carried out in order to discern its intrinsic bioremediation potential. Microbiological analysis, 16S rDNA-based DGGE fingerprinting and PLFAs analysis were performed on seawater and sediment samples from six stations on two transects. Higher diversity and variability among stations was detected by DGGE in sediment than in water samples although seawater revealed higher diversity of culturable hydrocarbon-degrading bacteria. The most polluted sediment hosted higher total bacterial diversity and higher abundance and diversity of culturable HC degraders. Alkane- and PAH-degrading bacteria were isolated from all stations and assigned to Alcanivorax, Marinobacter, Thalassospira, Alteromonas and Oleibacter (first isolation from the Mediterranean area). High total microbial diversity associated to a large selection of HC degraders is believed to contribute to natural attenuation of the area, provided that new contaminant contributions are avoided.

Recent Progress in Monoaromatic Pollutants Removal from Groundwater through Bioremediation

Monoaromatic pollutants such as benzene, toluene, ethylbenzene and mixture of xylenes are now considered as widespread contaminants of groundwater. In situ bioremediation under natural attenuation or enhanced remediation has been successfully used for removal of organic pollutants, including monoaromatic compounds, from groundwater. Results published indicate that in some sites, intrinsic bioremediation can reduce the monoaromatic compounds content of contaminated water to reach standard levels of potable water. However, engineering bioremediation is faster and more efficient. Also, studies have shown that enhanced anaerobic bioremediation can be applied for many BTEX contaminated groundwaters, as it is simple, applicable and economical. This paper reviews microbiology and metabolism of monoaromatic biodegradation and in situ bioremediation for BTEX removal from groundwater under aerobic and anaerobic conditions. It also discusses the factors affecting and limiting bioremediation processes and interactions between monoaromatic pollutants and other compounds during the remediation processes.