Soil Slurry Bioreactor Research Articles

Combination of slurry-bioreactors and actinobacteria consortia as strategy to bioremediate chlordane-contaminated soils

Soil contamination caused by pesticides poses a significant environmental challenge, and addressing it requires effective solutions. Bioremediation, combining the utilization of slurry-bioreactors and microbial consortia, emerges as an appropiated strategy to tackle this issue. Therefore, this research evaluated the chlordane (CLD) removal efficiency by a Streptomyces consortium through bioaugmentation of polluted soils, and slurry-bioreactors. For that, a Streptomyces defined consortium with CLD removal abilities was inoculated in soil microcosms and soil-slurry bioreactors (SB), with (SB-TSB) and without stimulation (SB-water). In soil, CLD presence has no negative effect on consortium growth. This was supported by comparing its duplication time (7.48 ± 0.14 h) with the obtained in the biotic control (7.45 ± 0.04 h). Furthermore, 17% of pesticide removal by microbial action was detected in the treated microcosms. In SB, the microbial development was not affected by the pesticide presence. In SB-TSB, the microbial growth was higher than in SB-water. This was supported by its lesser duplication time (7.27 ± 0.17 h) with respect to the non-stimulated systems (10.88 ± 0.29 h). However, SB-water showed the highest CLD removal ability (34.8%), with a concomitant increase in the chloride ion release. In the phytotoxicity test, the vigor index showed that the bioremediation in SB-water did not exert adverse effects greater than those generated by the CLD. Indeed, the root length increased after the treatment. These findings demonstrate the versatility of the Streptomyces consortium to remediate solid and semi-solid matrices impacted with pesticides, and the advantage of using bioaugmented SB to enhance the pollutants removal and accelerating the clean-up time required.

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.

Pilot-scale bioaugmentation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil using an indigenous bacterial consortium in soil-slurry bioreactors

Soil-slurry bioreactor based bioremediation of polycyclic aromatic hydrocarbons (PAHs) contaminated soil was studied through laboratory and pilot-scale trials, in which the degradation mechanism was explored. Indigenous PAH-degrading consortium was firstly screened out and it degraded 80.5% of total PAHs in lab-scale bioreactors. Then a pilot-scale trial lasting 410 days was conducted in two bioreactors of 1.5 m3 to examine the operating parameters and validate the optimum running conditions. During the initial 200 days, the crucial running parameters affecting PAH removal were evaluated and selected. Subsequently, an average PAH removal rate of 93.4% was achieved during 15 consecutive batches (210 days) under the optimum running conditions. The kinetic analysis showed that the reactor under optimum conditions achieved the highest PAH degradation rate of 0.1795 day−1 and the shortest half-life of 3.86 days. Notably, efficient mass transfer of PAHs and high biodegradation capability by bioaugmented consortia in soil-slurry bioreactors were two key mechanisms for appreciable PAH removal performance. Under the optimal operating conditions, the degradation rate of low-molecular-weight (LMW) PAHs was significantly higher than high-molecular-weight (HMW) PAHs; when the mass transfer was limited, there was no significant difference between their degradation behaviors. Both microbial co-metabolism and collaborative metabolism might occur when all PAHs demonstrated low degradation rates. The findings provide insightful guidance on the future assessment and remediation practices of PAH-contaminated sites.

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.

Ex situ remediation of polluted soils by absorptive polymers, and a comparison of slurry and two-phase partitioning bioreactors for ultimate contaminant degradation

The present study has provided a comparison between a conventional ex situ method for the treatment of contaminated soil, a soil slurry bioreactor, with a novel technology in which a contaminant is rapidly and effectively removed from the soil by means of absorptive polymer beads, which are then added to a two-phase partitioning bioreactor (TPPB) for biodegradation of the target molecule. 4-nitrophenol (4NP) was selected as a model contaminant, being representative of a large class of xenobiotics, and the DuPont thermoplastic Hytrel™ 8206 was utilized for its extraction from soil over ranges of soil contamination level, soil moisture content, and polymer:soil ratios. Since the polymers were able to rapidly (up to 77% and 85% in 4 and 24h respectively) and selectively remove the contaminant, the soil retained its nutrient and microflora content, which is in contrast to soil washing which can remove these valuable soil resources. After 4h of reaction time, the TPPB system demonstrated removal efficiency four times higher (77% vs 20%) than the slurry system, with expected concomitant savings in time and energy. A volumetric removal rate of 75mg4NPh−1L−1 was obtained in the TPPB, significantly greater than the value of 1.7 obtained in the slurry bioreactor. The polymers were readily regenerated for subsequent reuse, demonstrating the versatility of the polymer-based soil treatment technology.

Simultaneous analysis of endosulfan, chlorpyrifos, and their metabolites in natural soil and water samples using gas chromatography-tandem mass spectrometry

Analysis of endosulfan, chlorpyrifos, and their nonpolar metabolites in extracts from environmental aqueous and soil samples was performed using a gas chromatography-tandem mass spectrometry (GC-MS/MS) technique. Full-scan GC-MS analysis showed poor sensitivity for some of the metabolites (endodiol and endosulfan ether). A multisegment MS/MS method was developed and MS/MS parameter isolation time, excitation time, excitation voltage, and maximum excitation energy were optimized for chosen precursor ions to enhance selectivity and sensitivity of the analysis. The use of MS/MS with optimized parameters quantified analytes with significantly higher accuracy, and detection limits were lowered to ~1/6th compared with the full-scan method. Co-eluting compounds, chlorpyrifos and chlorpyrifos oxon, were also analyzed successfully in the MS/MS mode by choosing exclusive precursor ions. Analysis of soil and water phase samples from contaminated soil slurry bioreactors showed that the MS/MS method could provide more reliable estimates of these pesticide and metabolites (especially those present in low concentrations) by annulling interferences from soil organic matter.

Optimisation of Pyrene Removal by a Mixed Culture in a Soil-Slurry Bioreactor using Response Surface Methodology (RSM)

Bioremediation of pyrene by a mixed culture enriched from hydrocarbon-polluted soil was performed in a soil-slurry bioreactor. A Munchong series, a Malaysian soil with the following properties: silty clay, organic carbon content of 4.7% and pH 7.22 was used. An experiment was designed using response surface methodology (RSM) with treatment combinations of soil-water ratio of (0.1-0.2 w/v), concentration of pyrene to soil ratio (500-1000mg/Kg) and different pH (5-8) combinations. The result shows that with higher ratio of pyrene concentration 1000mg/Kg of soil and minimum pH of 5 at the beginning produced highest percentage of pyrene removal from the bioreactor soil. The analysis of factors shows that biomass growth in the reactor depends only on contaminant concentration and initial pH and not soil/water ratio. This is a promising method for optimising ex-situ remediation of soil before scaling up and, with highly acclimatised mixed culture; significant concentration of pollutant will be removed.

Enzymatic Treatment of Soils Contaminated with Phenol and Chlorophenols Using Soybean Seed Hulls

This study presents the application of soybean seed hulls for the decontamination and/or detoxification of phenol and chlorophenol polluted soils. The effect of soil was examined on both catalytic activity of soybean seed hull peroxidase (SBP) and enzymatic transformation of phenol, 2-chlorophenol, and 2,4-dichlorophenol through the polymerization reaction. The sorption of the enzyme to soil organic matter was found to account for the loss of partial catalytic activity of soybean seed hulls in a soil slurry environment. The organic matter present in loamy soils, rather than other soluble soil constituents and soil micro-organisms, is a factor in SBP inhibition by soil and the corresponding decline in treatment efficiency of phenol and chlorophenols. Under improved conditions, however, soybean seed hulls demonstrated a satisfactory ability to catalyze the polymerization reaction. Over 96% of total phenols were removed using soybean seed hulls in a soil slurry bioreactor, which demonstrates a great potential in use of soybean seed hulls, a readily available and inexpensive source of SBP, for bioremediation of soils contaminated with phenolic compounds.

Initial characterization of new bacteria degrading high-molecular weight polycyclic aromatic hydrocarbons isolated from a 2-year enrichment in a two-liquid-phase culture system.

To characterize some polycyclic aromatic hydrocarbons (PAH)-degrading microorganisms isolated from an enriched consortium degrading high molecular weight (HMW) PAHs in a two-liquid-phase (TLP) soil slurry bioreactor, and to determine the effect of low molecular weight (LMW) PAH on their growth and HMW PAH-degrading activity. Several microorganisms were isolated from a HMW-PAH (pyrene, chrysene, benzo[a]pyrene and perylene) degrading consortium enriched in TLP cultures using silicone oil as the organic phase. From 16S rRNA analysis, four isolates were identified as Mycobacterium gilvum B1 (99% identity),Bacillus pumilus B44 (99% identity), Microbacterium esteraromaticum B21 (98% identity), and to the genus Porphyrobacter B51 (96% identity). The two latter isolates have not previously been associated with PAH degradation. Isolate B51 grew strongly in the interfacial fraction in the presence of naphthalene vapours and phenanthrene compared with cultures without LMW PAHs. Benzo[a]pyrene was degraded in cultures containing a HMW PAH mixture but pyrene had no effect on its degradation. The growth of isolates B1 and B21 was improved in the aqueous phase than in the interfacial fraction for cultures with naphthalene vapours. Pyrene was required for benzo[a]pyrene degradation by isolate B1. For isolate B21, pyrene and chrysene were degraded only in cultures without naphthalene vapours. Consortium enriched in a TLP culture is composed of microorganisms with different abilities to grow at the interface or in the aqueous phase according to the culture conditions and the PAH that are present. Naphthalene vapours increased the growth of the microorganisms in TLP cultures but did not stimulate the HMW PAH degradation. New HMW PAH-degrading microorganisms and a better understanding of the mechanisms involved in HMW PAH degradation in TLP cultures.

Bioremediation of pentachlorophenol-contaminated soil by bioaugmentation using activated soil.

The use of an indigenous microbial consortium, pollutant-acclimated and attached to soil particles (activated soil), was studied as a bioaugmentation method for the aerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil. A 125-l completely mixed soil slurry (10% soil) bioreactor was used to produce the activated soil biomass. Results showed that the bioreactor was very effective in producing a PCP-acclimated biomass. Within 30 days, PCP-degrading bacteria increased from 10(5) cfu/g to 10(8) cfu/g soil. Mineralization of the PCP added to the reactor was demonstrated by chloride accumulation in solution. The soil-attached consortium produced in the reactor was inhibited by PCP concentrations exceeding 250 mg/l. This high level of tolerance was attributed to the beneficial effect of the soil particles. Once produced, the activated soil biomass remained active for 5 weeks at 20 degrees C and for up to 3 months when kept at 4 degrees C. The activated attached soil biomass produced in the completely mixed soil slurry bioreactor, as well as a PCP-acclimated flocculent biomass obtained from an air-lift immobilized-soil bioreactor, were used to stimulate the bioremediation of a PCP-impacted sandy soil, which had no indigenous PCP-degrading microorganisms. Bioaugmentation of this soil by the acclimated biomass resulted in a 99% reduction (from 400 mg/kg to 5 mg/kg in 130 days) in PCP concentration. The PCP degradation rates obtained with the activated soil biomass, produced either as a biomass attached to soil particles or as a flocculent biomass, were similar.

Aniline degradation in a soil slurry bioreactor

This research was designed to determine the feasibility of the biodegradation of aniline in a soil slurry system. Microorganisms isolated from an aniline‐contaminated site were classified to be Achromobacter xylosoxidans and a Pseudomonas species. A mixed culture of bacteria was observed to grow on aniline as the only source of carbon. Studies conducted in liquid media demonstrated simultaneous oxygen uptake and aniline removal at a concentration of 700 mg/L. The optimum pH for the biodegradation of aniline by the classified microorganisms in liquid media at a concentration of 700 ppm was determined to be between pH 7 and pH 8. Biodegradation studies were conducted in soil slurry system using soil similar to that at the aniline‐contaminated site. These studies investigated the role of abiotic processes in the removal of aniline, the ability of indigenous microorganisms to degrade aniline, and the effect of amendment with an acclimated bacterial population and the addition of nutrients. The ability of aniline to serve as a sole source of nitrogen and carbon was also investigated.

Estimation of oxygen transfer in soil slurry bioreactor

The apparent volumetric O transfer coefficient in a soil slurry bioreactor was significantly affected by the particle size of the soil and its clay content but less affected by the concentration of organic matter. The k L a values in the slurry of 40% (w/v) soil content ranged from 60% to 80% of that in water. O requirement was estimated for a bio-remediation: O was limiting in heavily contaminated soil and in soil with high clay content.

Reductive microbial dechlorination of indigenous polychlorinated biphenyls in soil using a sediment-free inoculum.

In laboratory experiments, unagitated soil slurry bioreactors inoculated with micro-organisms extracted from polychlorinated biphenyl-contaminated (PCBs) sediments from the Hudson River were used to anaerobically dechlorinate PCBs. The onset of dechlorination activity was accelerated by the addition of certain organic acids (pyruvate and maleate) and single congeners (2,3,6-trichlorobiphenyl). Dechlorination was observed under several working conditions after 19 weeks of incubation with PCB-contaminated soil and nutrient solution. Best results showed a drop in average chlorine content from 4.3 to 3.6 chlorines per biphenyl due to a loss of m-chlorines. Soil used for these experiments was obtained from a PCB-contaminated (weathered Aroclor 1248) site at an electric power substation. Dechlorination was observed with no sediment particles or other matrix being added.