Slurry Bioreactor Research Articles

Bioaugmentation of Bio-Slurry Reactor Containing Pyrene Contaminated Soil by Engineered Pseudomonas putida KT2440

Bioaugmentation of Bio-Slurry Reactor Containing Pyrene Contaminated Soil by Engineered Pseudomonas putida KT2440

Simulated bio-slurry reactor for bioremediation of highly contaminated soils by 2,4,6-trinitrotoluene (TNT)

The widespread use of 2,4,6-trinitrotoluene (TNT) in military sites causes serious soil contamination problems. In this study, various additions of glucose, glycerol, and activated sludge were tested under laboratory conditions in a simulated bio-slurry reactor for bioremediation of soil from highly TNT-contaminated sites. The results showed that the addition of both glucose and glycerol as electron donors could efficiently promote microbial degradation of TNT. The co-addition of glycerol and sludge resulted in 65.2% total removal of TNT in the soil (2.76 × 102 mg/kg) and 79.8% total removal of TNT in the soil (1.35 × 102 mg/kg), respectively. After 39 days of incubation with glucose and sludge, the removal of TNT reached 86.3% in the most seriously polluted soil (2.83 × 103 mg/kg). 16S rRNA sequencing for bacteria showed that the addition of glucose and glycerol significantly stimulated the growth of Enterobacteriaceae and Pseudomonas populations, respectively, which dominated the post-degradation soil microbial community. The bioavailability concentration of TNT extracted with (2-Hydroxypropyl)-β-cyclodextrin (HPβCD) rapidly decreased to very low levels during remediation seems to provide an explanation for complete degradation of TNT could not be achieved even in soils with relatively lower contamination. In addition, adequate electron donors are necessary to ensure the sustainable bioremediation of TNT-contaminated soil with high concentrations compared to surfactant. This work suggests that co-addition of glycerol (or glucose) and sludge is a desirable strategy for aerobic bioremediation of sites contaminated with high concentrations of TNT.

Bioremediation of Soil Contaminated with 2,4-D Herbicide Using Bioslurry Reactor

Ex-situ bioremediation of 2,4-D herbicide-contaminated soil was studied using a slurry bioreactor operate at aerobic conditions. The performance of the slurry bioreactor was tested for three types of soil (sand, sandy loam and clay) contaminated with different concentration of 2,4-D, 200,300and500mg/kg soil. Sewage sludge was used as an inexpensive source of microorganisms which is available in large quantities in wastewater treatment plants. The results show that all biodegradation experiments demonstrated a significant decreases in 2,4-D concentration in the tested soils. The degradation efficiency in the slurry bioreactor decreases as the initial concentration of 2,4-D in the soils increases.A 100 % removal was achieved at initial concentration of 200mg 2,4-D/kg of sandy soil after 12 days and 92 % at 500mg 2,4-D/kg sandy soil after 14 days.Clay soil represented minimum removal efficiency among the three soils, 82 % at initial concentration of 200mg 2,4-D/kg clay soil after 12 days and 72 % for 500mg 2,4-D/kg clay soil after 14 days. Abiotic conditions were performed to investigate the desorption efficiency of the contaminant from soil to liquid phase through the three soils. In abiotic reactor the results showed that the rate of desorption for sand and sandy loam soils were nearly the same, it varied between0.102-0.135 day-1 at different initial concentration of 2,4-D. While for clay soil the desorption rate varied between 0.042- 0.031 day-1 at different initial concentration of 2,4-D. The decrease in desorption rate in clay soil refers to the characteristic of clay soil, (fine texture, high organic matter and high cation exchange capacity compared with the other soils) that may retain the 2,4-D in the organic matter and the clay minerals.

Assessment of oily sludge biodegradation in lab scale composting and slurry bioreactor by bacterial consortium

The present study aimed to investigate biodegradability of oily sludge in lab scale composting and slurry bioreactor using a potential bacterial consortium isolated from petroleum-contaminated sites. The consortium used in the study consisted of bacterial genera, including Enterobacter, Bacillus, Microbacterium, Alcaligenes Pseudomonas, Ochrobactrum, Micrococcus, and Shinella which were obtained after rigorous screening using different hydrocarbons. The meticulously designed lab scale composting experiments were carried out and showed that the combination of 10% oily sludge (A1) exhibited the highest total carbon (TC) removal, which was 40.33% within 90 days. To assess the composting experiments' efficiency, the first (k1) and second (k2) order rate constants were evaluated and was found to be 0.0004–0.0067 per day and second (k2) 0.0000008–0.00005 g/kg. day respectively. To further enhance the biodegradation rate of A1 combination, a slurry bioreactor was used. The maximum total petroleum hydrocarbon (TPH) removals in a slurry bioreactor for cycle-I and –II were 48.8% and 46.5%, respectively, on the 78th and 140th days of the treatment. The results obtained in the study will be a technological platform for the development of slurry phase treatment of petroleum waste in a sustainable and eco-friendly manner.

Influencing factors of bioaugmentation treatment of PAH-contaminated soils in slurry bioreactors

Polycyclic aromatic hydrocarbons (PAHs) are a group of contaminants with low bioavailability and biodegradability. As a result, removing PAHs from contaminated soils is often inefficient. In this study, soils spiked with fluoranthene and pyrene were inoculated with Aeromonas sp. BCP-3, a newly isolated strain from coke-plant sludge, and treated in slurry bioreactors. The removal of PAHs was significantly affected by aeration rate, slurry water-soil mass ratio, stirring rate, temperature, and the concentration of Tween-80. Such effects were attributed to changes in BCP-3 growth, PAHs solid-liquid mass transfer, and slurry particle size. Notably, under optimal conditions (i.e., aeration rate of 1.5 L/min, temperature of 30 °C, stirring rate of 200 rpm, water-soil mass ratio of 1.5:1, and Tween-80 concentration of 1.3 %), 96.3 % and 97.2 % of initially spiked fluoranthene and pyrene were removed within 12 days, respectively. A PAH-contaminated soil was collected from a local coking plant and treated under the same conditions, except for the Tween-80 concentration. For the real soil, the Tween-80 concentration was 4 % to ensure a significant proportion of PAHs released into the liquid phase. Twenty-one days after inoculation of BCP-3, the removal efficiencies of low molecular weight PAHs and high molecular weight PAHs were 82.2 % and 51.8 %, respectively. The removal efficiencies of PAHs were significantly higher than the slurry without BCP-3 or HgCl2-sterilized slurry. BCP-3 improved the bioavailability and biodegradability of PAHs, resulting in effective PAH removal in slurry bioreactors. Overall, successful bioaugmentation was achieved with the addition of Tween-80 and the optimization of operating conditions.

Enhanced bioremediation of oil-contaminated soil in a slurry bioreactor by H2O2-stimulation of oil-degrading/biosurfactant-generating bacteria: performance optimization and bacterial metagenomics.

Oil-contaminated soil is the main challenge for oil-rich countries, and this study aimed to investigate the performance of the H2O2-stimulated slurry bioreactor for the bioremediation of real oil-contaminated soil. The effect of biomass concentration, soil to water (S/W) ratio, slurry temperature, pH, and H2O2 concentration were optimized for the removal of total petroleum hydrocarbons (TPH) from oil-contaminated soil. TPH removal efficiency, biosurfactants production, and peroxidase and dehydrogenase activities were measured. The optimum conditions for the complete biodegradation of 32 [Formula: see text] in the slurry bioreactor during 6days were biomass of 2250mg/L, S/W ratio of 20%, the temperature of 30°C, pH of 7, and an H2O2 concentration of 120mg/L. The highest peroxidase, dehydrogenase, surfactin, and rhamnolipid formation were also obtained under optimum conditions. The results pointed out that complete biodegradation of 32g/kg of TPH in oil-contaminated soil at a short reaction time of 6days is achievable in the developed process operated under optimum conditions. The GC/FID analysis of solid and liquid phases showed that the bioprocess completely biodegraded the different TPH fractions. H2O2 efficiently stimulated the biosurfactant-generating bacteria to produce peroxidase and thereby accelerating the bioremediation rate. Accordingly, an H2O2-mediated slurry bioreactor inoculated with biosurfactant/peroxidase-generating bacteria is a promising technique for cleaning up oil-contaminated soils.

Modelling of n-Hexadecane bioremediation from soil by slurry bioreactors using artificial neural network method

Diesel oil is known to be one of the major petroleum products that can pollute water and soil. Soil pollution caused by petroleum hydrocarbons has substantially impacted the environment, especially in the Middle East. In this study, modeling and optimization of hexadecane removal from soil was performed using two pure cultures of Acinetobacter and Acromobacter and consortium culture of both bacterial species using artificial neural network (ANN) method. Then the best ANN structure was proposed based on mean square error (MSE) as well as correlation coefficient (R) for pure cultures of Acinetobacter and Acromobacter as well as their consortium. The results showed that the correlations between the actual data and the data predicted by ANN (R2) in Acromobacter, Acinetobacter and consortium of both cultures were 0.50, 0.47 and 0.63, respectively. Despite the low correlation between the experimental data and the data predicted by the ANN, the correlation coefficient and the precision of ANN for the consortium was higher. As a result, ANN had desirable precision to predict hexadecan removal by the cobsertium culture of Ochromobater and Acintobacter.

Ex-situ bioremediation of petroleum hydrocarbon contaminated soil using mixed stimulants: Response and dynamics of bacterial community and phytotoxicity

Pollution of agricultural soils by excessive petroleum hydrocarbons (PHs) has recently become a severe worldwide environmental issue. Various approaches have been recently employed to biodegrade PHs and detoxify soils. In the present study, an experimental mesocosm was developed in a bioslurry reactor. Six treatments were applied to degrade PHs-and detoxify contaminated soil by adding external stimulants such as nutrients, activated sludge, synthetic surfactant, and long-chain rhamnolipids. The comparative analysis revealed that the combination of activated sludge, nutrients, and biosurfactant showed a 79.4% reduction in TPHs after 10 days in the mesocosm experiment. The lowest reduction in total PHs (48.5 %) was attained in the nutrient-supplied mesocosms. The consortia’s kinetic analyses of PHs revealed the lowest half-life time (t1/2 = 4.1 days), the highest biodegradation rate constants (k = 0.17 day1), and the reaction rate data from each bioremediation method was fitted with a first-order reaction rate model. The 16S rRNA gene amplicon and sequencing revealed that Streptomyces, Nocardioides, Arthrobacter, Pseudomonas, and Bacillus were the main oxidative species as PHs degraders. The highest relative abundances were in Arthrobacter, Pseudomonas, and Bacillus. The phytotoxicity studies proved that there was a significant decrease in the toxicity of soil after the biotreatment. According to the findings of this study, adding external stimulants such as activated sludge, nutrients, and biosurfactants enhanced the degradation of PHs in the soil in bioslurry enhancement as a promising approach to pilot scale.

Strategy to Promote the Biodegradation of Phenanthrene in Contaminated Soil by a Novel Bacterial Consortium in Slurry Bioreactors.

Polycyclic aromatic hydrocarbons (PAHs) are typical high-risk, persistent organic pollutants. Biological slurry reactors are widely used for enhanced bioremediation. In this experiment, a highly efficient phenanthrene-degrading bacteria group was obtained through screening and domestication, and the community was named MZJ_21. After the addition of MZJ_21 to the aerobic slurry bioreactor, with the optimum conditions of the temperature, stirring speed, and aeration rate of 30 °C, 120 rpm, and 1 L/min, respectively, the phenanthrene degradation ratio reached 95.41% within 48 h. The exploration of the degradation of phenanthrene by MZJ_21 indicated that most MZJ_21 communities adsorbed on the soil particle, mainly because MZI_21 could secrete extracellular polymers, which could stably adhere MZJ_21 on the solid phase. At the same time, the distribution ratio of phenanthrene in the solid phase is increased, so that the efficient phenanthrene degradation reaction takes place in the solid phase.

Surfactant Utilization In Oil Sludge Biode Gradation Using Slurry Bioreactor

Oil sludge from petroleum industry effluent is classified as hazardous waste and requiredspecial treatment before discharge to the environment. Biodegradation using bacterialactivities is a general treatment for oil sludge processing. However, the bacterial abilityin oil sludge biodegradation is blocked by non-aqueous phase liquid of oil sludge. Twopossible ways of enhancing the bioavailability of oil sludge are surfactants application and slurry bioreactors system. The objective of this study is to obtain the surfactant which can increase oil sludge biodegradation using simple slurry bioreactor. The surfactant selection obtained Emulsogen LP (58% effectiveness) which was examined based on HLB value, nonionic character, and surfactant effectiveness. Emulsogen LP is readily biodegradable which reached 93% biodegradability in 15 days. The biodegradation test showed that Emulsogen LP addition on its Critical Micelle Concentration (10 mg/L) enhanced oil sludge biodegradation in 3 bacterial cultures of Pseudomonas aeruginosa, Bacillus subtilis, and Actinobacter baumanni after 48 hours. By surfactant addition, oil sludge biodegradation reached 37-49% whereas without surfactant addition it only reached 28-33%. The highest oil sludge biodegradation was obtained in P. aeruginosa cultures with Emulsogen LP addition (49%). The surfactant addition had no effect on microbial growth. Moreover, P. aeruginosa population was increased by surfactant addition.

Bioremediation of soil contaminated with toxic mixed reactive azo dyes by co-cultured cells of Enterobacter cloacae and Bacillus subtilis.

Azo dyes, known for its toxicity and mutagenicity, are used by textile industries. Bioremediation serves the best alternative treatment process due to its eco-friendly nature and cost-effectiveness. Degradation using individual bacteria promotes azo dye removal, while the degradation is enhanced using the immobilization method. Bio-carrier promotes the attachment of the bacterial strains and increases azo dye degradation. The present study focuses on the biodegradation of Reactive Red (RR), Reactive Brown (RB), Reactive Black dye (RBL), and mixed dyes in a soil slurry bioreactor containing free cells, co-culture, and immobilized cells. The physico-chemical analysis and soil characteristics were determined. The free cells of Bacillus cereus showed degradation of azo dyes - 79.42±0.03% RR, 78.78±0.02% RBL; 70.76±0.03% RB, and 84.89±0.05% of mixed dyes respectively. Enterobacter cloacae free cells resulted in degradation of 72.87±0.01% RR, 75.21±0.01% RBL, 74.50±0.02% RB, and 73.39±0.04% mixed dyes respectively. Co-cultured bacterial strains resulted in 77.18±0.03% RR, 80.27±0.02% RBL, 76.97±0.02% RB and 86.29±0.05% mixed dyes respectively. The immobilization of Bacillus cereus and Enterobacter cloacae on 2% corn starch resulted in 98.4±0.01% degradation of RR, 89.8±0.09% degradation of RB, 99.4±0.05% of RBL, and 98.1±0.08% of mixed reactive dyes respectively.

Investigating the effects of combined bio-enhancement and bio-stimulation on the cleaning of hexadecane-contaminated soils

IntroductionPetroleum hydrocarbons are among the most important soil pollutants. The main purpose of this study was to investigate hexadecane removal as a representative of petroleum hydrocarbons in slurry bioreactors with the help of bio-enhancement and bio-stimulation. MethodIn this study, hexadecane degrading bacteria were first isolated from soil and compost and were identified by Polymerase Chain Reaction (PCR). After that, using the Taguchi test, the effects of such parameters as salinity, pH, bacteria type, inoculated bacteria number, C:N:P ratio, micronutrient content, soil-to-water ratio, and the initial concentration of hexadecane on hexadecane removal rate were assessed using a Gas Chromatography-Flame Ionization Detector (FID-GC). ResultsThe results indicated that the two bacterial species (Ochrobactrum oryzae and Acinetobacter radioresistence) resulted in the highest removal of hexadecane. Salt had an inhibitory effect on the biodegradation of hexadecane, and microbial consortium was more effective in removing hexadecane compared to pure bacteria. Due to the presence of sufficient amounts of phosphorus and nitrogen in the primary soil, addition of these compounds had no effects on hexadecane removal. Nevertheless, addition of micronutrients enhanced the removal of contaminants. As the water-to-soil ratio increased, the bacteria’s access to food increased, as well, which resulted in a higher biodegradation rate. The initial concentration of hexadecane was the most important factor in its removal. DiscussionThe isolated bacteria from compost removed hexadecane from soil more efficiently compared to the bacteria isolated from soil. Furthermore, increase in the variety of bacteria types in the consortium resulted in an increase in the removal efficiency and a decrease in the retention time for bioremediation. Overall, hexadecane was removed by biological processes, ultrasound waves, soil adsorption, and chemical processes where evaporation had no effects. The initial concentration of hexadecane and bio-enhancement were among the important factors influencing the removal of hexadecane from the soil.

Preliminary insights about the treatment of contaminated marine sediments by means of bioslurry reactor: Process evaluation and microbiological characterization

Contaminated marine sediments represent a critical threat towards human health and ecosystems, since they constitute a potential reservoir of toxic compounds release. In the present study, a bioslurry reactor was studied for the treatment of real marine sediments contaminated by petroleum hydrocarbons. The experimental campaign was divided in two periods: in the first period, microcosm trials were carried out to achieve useful indicators for biological hydrocarbon removal from sediments. The microcosm trials highlighted that the inoculum of halotolerant allochthonous bacteria provided the highest performance followed by autochthonous biomass. Based on the achieved results, in the second experimental period a bioslurry reactor was started up, based on a semisolid stirred tank reactor (STR) operated in batch mode. The process performances have been evaluated in terms of total petroleum hydrocarbon (TPH) removal, coupled with the characterization of microbial community through a Next Generation Sequencing (NGS) and phytotoxicity tests through the Germination Index (GI) with Lepidium Sativum seeds. The achieved results showed good hydrocarbons removal, equal to 40%, with a maximum removal rate of 220 mgTPH kg-1 d-1, but highlighting that high contaminant concentrations might affect negatively the overall removal performance. In general, the observed results were encouraging towards the feasibility of biological treatment of marine sediments contaminated by hydrocarbons. The microbiological analysis allowed the identification of taxa most involved in the degradation of TPH, highlighting after the treatment a shift in the microbial community from that of the raw sediment.

Salt selected for hydrocarbon-degrading bacteria and enhanced hydrocarbon biodegradation in slurry bioreactors

Hydrocarbon and salt contamination of surface and groundwater resources often co-occur from oil production activities. However, salt is often considered as a potential inhibitor of microbial activity. The feasibility of microbiome-based biotechnologies to treat the hydrocarbon contamination is contingent on the ability of the indigenous community to adapt to saline conditions. Here, we demonstrate enhanced hydrocarbon biodegradation in soil slurries under saline conditions of up to ~1 M (5%) compared to non-saline systems and the underlying causes. The mineralization extent of hexadecane was enhanced by salinity in the absence of nutrients. Salinity, similar to nutrients, enhanced the mineralization but through ecological selection. Microbial community analysis indicated a significant enrichment of Actinobacteria phylum and an increase in the absolute abundance of the hydrocarbon-degrading Dietzia genus, but a decrease in the total population size with salinity. Moreover, the in situ expression of alkane hydroxylases genes of Dietzia was generally increased with salinity. The data demonstrate that indigenous halotolerant hydrocarbon degraders were enriched, and their hydrocarbon degradation genes upregulated under saline conditions. These findings have positive implications for engineered biotreatment approaches for hydrocarbons in saline environments such as those affected with produced waters and oil sands tailing ponds.

Bioaugmentation treatment of polycyclic aromatic hydrocarbon-polluted soil in a slurry bioreactor with a bacterial consortium and hydroxypropyl-β-cyclodextrin

ABSTRACT The aim of the study was to verify the effect of bioaugmentation by the bacterial consortium YS with hydroxypropyl-β-cyclodextrin (HPCD) in a soil slurry. The bacterial consortium YS was enriched from a petroleum-polluted soil using pyrene as sole carbon resource. After 3 weeks, the degradation rate of phenanthrene in CK increased from 22.58% to 55.23 and 78.21% in bioaugmentation (B) and HPCD + bioaugmentation (MB) respectively. The degradation rate of pyrene in CK increased from 17.33% to 51.10% and 60.32% in B and MB respectively in the slurry. The augmented YS persisted in the slurry as monitored by 16S rRNA gene high-throughput sequencing and outcompeted some indigenous bacteria. Enhanced polycyclic aromatic hydrocarbon (PAH) degradation was observed in the addition of HPCD due to the enhanced bioavailability of phenanthrene and pyrene. Additionally, the amount of PAH-degrading bacteria and enzymatic activity in bioaugmentation with HPCD were higher than that in the CK group. The results indicated that bioaugmentation with a bacterial consortium and HPCD is an environmentally friendly method for the bioremediation of PAH-polluted soil.

Bovine Manure as a Rich Source for Isolation of Halo-Tolerant Bacterial Strains Capable of PAHs Biodegradation in Slurry Bioreactor

This study aimed to isolate a bacterial consortium that capable of decomposing PAHs. Three halo-tolerant bacterial strains of Microbacterium paraoxydans B3F (S1), Stenotrophomonas N3 (S2), and Citrobacter NB2 (S3) were isolated from bovine manure. The isolate Microbacterium paraoxydans B3F showed the least resistance to salinity and growth not observed at 2 and 2.5% of NaCl, while isolate Citrobacter NB2 indicated growth in all salinity levels. The PHE biodegradation was more efficient in bacterial consortium compared to pure culture. At the end of the 35th day, the removal efficiency of PHE with an initial concentration of 100 mg/kg for seed volumes of 2, 10, and 20 mL was 33%, 50%, 52%, respectively. The TPHs biodegradation efficiencies at different soil/water ratios of 25%, 50% and 100% were 12%, 28.7 % and 60.8%, respectively. Three halo-tolerant bacteria were isolated from Bovine manure were efficiently used for bioremediation of phenanthrene.

An efficient lab-scale soil bioreactor for the removal of chromium (Cr) and arsenic (As) contaminated soil using co-culture

ABSTRACT Heavy metal pollution has become a serious global threat in recent times which are mostly caused by anthropogenic activities. Bioremediation is cost-effective and eco-friendly technique. In the present study, bioremediation of the co-metal was performed by isolating chromium (Cr) and arsenic (As) resistant bacterial strains and its optimisation of different environmental parameters such as pH, temperature, carbon sources, nitrogen sources and vari+ous concentrations of chromium and arsenic were studied. The isolated co-culture bacterial strains were identified with biochemical and molecular identification using 16s RNA sequencing. Further, a lab-scale soil bioreactor was set up and mineralisation of chromium and arsenic was observed using different heavy metal contaminated soil samples. About 51.1% Chromium was mineralised by the co-culture, 26.7% in cycle 2, 22% in cycle 3 and 34.2% in cycle 4 respectively. The Arsenic mineralisation was 16.7%,23.7%,35.4% and 35.8% at the end of 4 cycles. The final mineralised concentration was analysed by Inductively coupled plasma optical emission Mass spectrometry (ICP-MS) resulting in 29.9 of Chromium and Arsenic 0.083 mg/L respectively. The physico-chemical parameters, such as pH, temperature, TS, TDS, BOD and COD were monitored for the mineralisation study in the soil slurry bioreactor. The study proved that there was effective mineralisation of the co-metals with the cocultures of the isolated bacterial strains from the metal contaminated site.

A rhamnolipid biosurfactant increased bacterial population size but hindered hydrocarbon biodegradation in weathered contaminated soils.

Surfactants are used to enhance the bioavailability of recalcitrant residual petroleum contamination during bioremediation. However, surfactants in some cases inhibit biodegradation, which is often attributed to their toxicity. Herein, we show that a rhamnolipid biosurfactant likely served as a carbon source and exhibited physiological inhibition on petroleum biodegradation. The addition of biosurfactants in mixed, batch, slurry bioreactors with soils from a petroleum-contaminated site led to a dose-dependent shift in the microbial community with a decrease in diversity and increase in population size and delayed biodegradation. Microbial community analysis indicated the enrichment of Alphaproteobacteria affiliated taxa such as Sphingomonadaceae in systems amended with biosurfactant. The diversity was significantly lower in systems with higher doses of biosurfactants compared to systems without biosurfactant. Droplet Digital PCR indicated a 30-90 fold increase in 16S rRNA copy numbers in systems with higher doses of biosurfactant than control systems without surfactant and nutrients, whereas the nutrient amendment alone led to a two-fold increase in population size. Total petroleum hydrocarbon analysis showed that the biodegradation extent was negatively impacted by rhamnolipid at the highest dose compared to lower doses (23% vs. 40%) or without the biosurfactant. Indigenous isolates cultivated from the oil-amended soil exhibited growth on rhamnolipid as a sole carbon source. A novel insight gained is how dose-dependent responses of microbial communities to biosurfactants alter the biodegradation time profile of hydrocarbons. The study highlights the significance of microbial assessment prior to surfactant-mediated bioremediation practices.

A coupled UV photolysis-biodegradation process for the treatment of decabrominated diphenyl ethers in an aerobic novel bioslurry reactor.

The commercial flame retardant is an emerging contaminant (EC) commonly found in soils and sediments. A coupled UV-photolysis-biodegradation process was used to decompose decabromodiphenyl ether (BDE-209) in clay slurries. A novel bioslurry bioreactor (NBB) was employed in which BDE-209 degradation was maximized by the simultaneous application of LED UVA irradiation and biodegradation by a mixed bacterial culture. The rate of BDE-209 degradation decreased in the order: coupled UV photolysis-biodegradation (1.31 × 10-2 day-1) > UV photolysis alone (1.10 × 10-2 day-1) > biodegradation alone (1.00 × 10-2 day-1). Degradation intermediates detected included hydroxylated polybrominated diphenylethers, partially debrominated PBDE congeners and polybrominated dibenzofuran. The UV-resistant bacterial strains isolated that could utilize BDE-209 as a sole carbon source included Stenotrophomonas sp., Pseudomonas sp., and Microbacterium sp. These strains encoded important functional genes such as dioxygenase and reductive dehalogenases. Continuous UV irradiation during the NBB process affected various biochemical oxidative reactions during PBDEs biodegradation. Simultaneous photolysis and biodegradation in the NBB system described reduces operational time, energy, expense, and maintenance-demands required for the remediation of BDE-209 when compared to sequential UV-biodegradation process or to biodegradation alone.Electronic supplementary materialThe online version of this article (10.1007/s11356-020-10753-9) contains supplementary material, which is available to authorized users.

Bioaugmentation Treatment of a PAH-Polluted Soil in a Slurry Bioreactor

A bioslurry reactor was designed and used to treat loamy clay soil polluted with polycyclic aromatic hydrocarbons (PAHs). To this end, biostimulation alone, or combined with bioaugmentation with two bacterial strains (Rhodocccus erythropolis and Pseudomonas stuzeri) previously isolated from the polluted site, was applied. The PAH concentrations decreased notably after 15 days in all of the treatments. The concentrations of the two- and three-ring compounds fell by >80%, and, remarkably, the four- to six-ring PAHs also showed a marked decrease (>70%). These results thus indicate the capacity of bioslurry treatments to improve, notably, the degradation yields obtained in a previous real-scale remediation carried out using biopiles. In this sense, the remarkable results for recalcitrant PAHs can be attributed to the increase pollutants’ bioavailability achieves in the slurry bioreactors. Regarding bioaugmentation, although treatment with R. erythropolis led to a somewhat greater reduction of lighter PAHs at 15 days, the most time-effective treatment was achieved using P. stutzeri, which led to an 84% depletion of total PAHs in only three days. The effects of microbial degradation of other organic compounds were also monitored by means of combined qualitative and quantitative gas chromatography mass spectrometry (GC–MS) tools, as was the evolution of microbial populations, which was analyzed by culture and molecular fingerprinting experiments. On the basis of our findings, bioslurry technology emerges as a rapid and operative option for the remediation of polluted sites, especially for fine soil fractions with a high load of recalcitrant pollutants.