Degradation of phenanthrene and fluoranthene in a slurry bioreactor using free and Ca-alginate-immobilized Sphingomonas pseudosanguinis and Pseudomonas stutzeri bacteria

Effect of hydraulic residence time on nitrogen removal from a synthetic mariculture wastewater using a bench-scale recirculating bioreactor embedded with aerobic denitrifying bacteria Marinobacter alkaliphilus strain JY28

Beads loaded with tea dregs powder and immobilized aerobic denitrifying bacteria (Marinobacter alkaliphilus strain JY28) were prepared by cross-linking sodium alginate and polyvinyl alcohol. The beads were subsequently utilized for nitrogen removal in treatment of wastewater from a marine recirculating aquaculture system (MRAS). The effects of hydraulic residence time (HRT) on nitrogen removal efficiency, microbial community succession, and the physicochemical properties and kinetic behaviors of the immobilized bacterial beads were investigated. The results indicated that the highest NO3--N removal rate was 99.4 ± 0.6 % at an HRT of 10 h, while the cumulative NO2--N concentration remained at its lowest level (0.04 ± 0.05 mg L-1). Furthermore, the peak maximum specific nitrogen removal rates (μmax) for NO3--N and NO2--N were found to be 16.12 mg L-1·h-1 and 8.61 mg L-1·h-1, respectively. The surface of the immobilized bacterial beads was rough and effectively bound Marinobacter alkaliphilus strain JY28. The interior of the beads possessed an irregular honeycomb-like and porous structure, favorable for the immobilization and proliferation of Marinobacter alkaliphilus strain JY28. The presence of the ring structure in the functional bonds enhanced both the mechanical strength and the immobilized bacterial beads stability. Marinobacter alkaliphilus strain JY28 was retained in the bacterial beads and consistently maintained its dominance during the whole experimental process. The results lay a theoretical foundation for application of immobilized bacterial beads for highly efficient nitrogen removal in MRAS wastewater treatment.

Characterization of a novel 1,2-dichloroethane degrader Ancylobacter sp. J3 and use of its immobilized cells in the treatment of polluted groundwater

A novel 1,2-dichloroethane (1,2-DCA) degrading bacteria strain J3 was isolated from 1,2-DCA contaminated groundwater and identified as Ancylobacter sp. The strain J3 was associated with self-flocculation during the growth process, and the degradation pathway study showed that the bacteria could completely mineralize 1,2-DCA. The microorganism was immobilized and the optimum preparation conditions were obtained by orthogonal experiment: 6 % polyvinyl alcohol, 2 % sodium alginate, 1 % biochar, and 2 % CaCl2, and the immobilized cells were named J3C. The degradation rates of J3C at low pH, temperature, and high concentration NaCl were higher than that of free J3. The fitting results of the pseudo-first-order degradation kinetics model showed that for above 200 mg/L 1,2-DCA, the degradation rate of J3C was higher than that of free J3. The adsorption process of the sterile J3C aligns with the pseudo-first-order kinetic model and the intraparticle diffusion model. The internal mass transfer kinetics analysis revealed that the beads with biochar and a small diameter (0.34 cm) were more conducive to mass transfer. Finally, remediation of real polluted groundwater by J3C shows that for groundwater with a pH value of about 7, 1,2-DCA concentrations of about 100, 200 mg/L, 1,2-DCA can be completely degraded by J3C, while for groundwater with a pH value of 12, 250 mg/L 1,2-DCA, the degradation rate was 83.15 % by J3C, 66.91 % higher than that of free J3. The changes in microbial communities in groundwater showed that J3C disturbed the groundwater microbial little for the immobilized cells in J3C originated from the groundwater.

Enhanced phoxim biodegradation by immobilizing Novosphingobium sp. RL4 on attapulgite-sodium alginate

Background

Residual phoxim pollution presents a potential threat to natural ecosystems and human health. The immobilization of degrading strains on natural adsorbent materials is a common strategy to enhance the degradation of target compounds in the environment by the strains.

Methods

A phoxim-degrading bacterial strain was isolated from the rhizosphere soil of rhubarb (Rheum palmatum L.), which had been exposed to long-term phoxim contamination. To enhance its stability and practical applicability, sodium alginate (SA) was utilized as a carrier material, while biochar (BC) and attapulgite (ATP) served as adsorption materials. These components were used to immobilize the strain, forming three distinct bacterial bead formulations: SA-RL4, SA + BC-RL4, and SA + ATP-RL4.

Results

The isolated phoxim-degrading strain was identified as Novosphingobium sp. RL4. Furthermore, the degradation products of phoxim by strain RL4 were analyzed and characterized. Based on the specific surface area, mass-transfer performance results, adsorption isotherms, and degradation efficiency, the addition of ATP or BC to SA has an equally positive impact on the degradation of phoxim by immobilized microspheres. ATP can replace BC as an adsorbent carrier material for embedding bacteria to a certain extent. At 20 mg/L, SA + ATP-RL4 degraded 89.37% of phoxim in 72 h. Importantly, SA + ATP-RL4 can be reused, and the degradation efficiency remained above 80% after 5 cycles. Furthermore, it exhibits high tolerance and better degradation ability compared to free cells of RL4 when used in treating agricultural wastewater containing phoxim.

Conclusion

SA + ATP-RL4 shows potential for in situ remediation of phoxim-contaminated environments.

Immobilization of Peniophora incarnata F1 in PVA-SA-biochar matrix and its degradation performance and mechanism for erythromycin degradation

Erythromycin is becoming one of the most common contaminants detected in surface water and wastewater, which poses a potential risk to ecological systems and human health. Until now, there is still no effective way to eliminate it. Herein, a novel and efficient erythromycin-degrading fungus Peniophora incarnata F1, capable of utilizing erythromycin as its sole source of carbon and energy, was isolated from contaminated sludge. Moreover, a fungal immobilization system was developed using polyvinyl alcohol (PVA), sodium alginate (SA) and rape straw biochar (RB) to enhance the removal ability of erythromycin. Under optimal conditions of 30 °C and pH 6.0, the removal rate of erythromycin with PVA-SA-RB@F1 within 5 d reached 89.90%, which is 31.43% higher than that of free strain F1 (58.47%). Furthermore, eight biodegradation products of erythromycin were identified, and five compounds were firstly reported. Based on these metabolites, we inferred erythromycin was transformed to simple products mainly by dehydration, desugar, dehydrogenation, ester bond hydrolysis and carbon chain cleavage reactions. Finally, PVA-SA-RB@F1 were applied to wastewater contained 10 mg/L and 50 mg/L erythromycin, with the removal rates of 100% and 64.97%, respectively. These results show that PVA-SA-RB@F1 can be used as an effective tool to remove erythromycin in water environment. Therefore, this study provides a feasible strategy for bioremediation of erythromycin polluted environment.

Deep-sea microorganisms-driven V5+ and Cd2+ removal from vanadium smelting wastewater: Bacterial screening, performance and mechanism

The disorderly discharge of industrial wastewater containing heavy metals has caused serious water pollution and ecological environmental risks, ultimately threatening human life and health. Biological treatment methods have obvious advantages, but the existing microorganisms exhibit issues such as poor resistance, adaptability, colonization ability, and low activity. However, a wide variety of microorganisms in deep-sea hydrothermal vent areas are tolerant to heavy metals, possessing the potential for efficient treatment of heavy metal wastewater. Based on this, the study obtained a group of deep-sea microbial communities dominated by Burkholderia-Caballeronia-Paraburkholderia through shake flask experiments from the sediments of deep-sea hydrothermal vents, which can simultaneously achieve the synchronous removal of vanadium and cadmium heavy metals through bioreduction, biosorption, and biomineralization. Through SEM-EDS, XRD, XPS, and FT-IR analyses, it was found that V(V) was reduced to V(IV) through a reduction process and subsequently precipitated. Glucose oxidation accelerated this process. Cd(II) underwent biomineralization to form precipitates such as cadmium hydroxide and cadmium carbonate. Functional groups on the microbial cell surface, such as -CH2, C=O, N-H, -COOH, phosphate groups, amino groups, and M-O moieties, participated in the bioadsorption processes of V(V) and Cd(II) heavy metals. Under optimal conditions, namely a temperature of 40 °C, pH value of 7.5, inoculation amount of 10%, salinity of 4%, COD concentration of 600 mg/L, V5+ concentration of 300 mg/L, and Cd2+ concentration of 40 mg/L, the OD600 can reach its highest at 72 h, with the removal efficiency of V5+, Cd2+, and COD in simulated vanadium smelting wastewater reaching 86.32%, 59.13%, and 61.63%, respectively. This study provides theoretical insights and practical evidence for understanding the dynamic changes in microbial community structure under heavy metal stress, as well as the resistance mechanisms of microbial treatment of industrial heavy metal wastewater.

Immobilization of Coprinus comatus with magnetic alginate hydrogel microsphere for improving the antioxidant activity of fermentation products

Coprinus comatus is an edible mushroom and its fermented product possesses antioxidant activity. In this study, to further enhance the antioxidant activity and improve the reusability of the strain, calcium alginate hydrogel was used as the carrier for embedding and immobilizing Coprinus comatus. The effects of CaCl2 concentration, sodium alginate concentration, microsphere diameter, and the amount of magnetic particle on the antioxidant activity of fermented products were investigated. The results showed that the magnetic immobilized microsphere prepared by 2.50% CaCl2, 2.00% sodium alginate and 0.50% Fe3O4 had the best fermentation antioxidant activity (EC50 was 0.43 ± 0.01 mg/mL) when the diameter was 5 mm, which increased by 24.56% compared to the initial activity. Besides, the microsphere showed strong reusability, the antioxidant activity was still better than the free strain after being used five times. This study not only enhanced the antioxidant activity of Coprinus comatus fermented product through immobilization, but also provided an effective method for microbial fermentation.

Phenanthrene removal from soil washing eluent by Bacillus subtilis embedded in alginate-carboxymethyl cellulose-diatomite beads

The processes of surfactant-enhanced soil washing have been widely applied to the remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil, accompanied by the production of soil washing eluent. In this study, novel composite materials of beads containing alginate, carboxymethyl cellulose and diatomite (SCD) were used to encapsulate Bacillus subtilis to remove phenanthrene (PHE) from simulated soil washing eluent with rhamnolipid. The effects of dosage, pH and temperature on the PHE removal performance were explored, and the optimal PHE removal conditions [SCD bead dose 16.2% (w:v), pH 7.1 and 30.6°C] were determined using response surface methodology. After incubation in simulated soil washing eluent for 7 d, SCD beads removed 84.92% of PHE, which was 49.18% higher than by free bacteria. In addition, SCD beads mainly removed PHE through biodegradation processes, and the degradation rate (1.38 mg L-1 d-1) was higher than that of free bacteria (0.64 mg L-1 d-1). Characterization results revealed that the immobilized substrate provided the micro-environment for bacteria and reduced the intense effect of high rhamnolipid concentration. Reusability results showed that SCD beads could be recycled four times to remove 80.05% of PHE. Collectively, SCD beads have great prospects for the decontamination of soil-washing eluent containing complex components.

Optimization of liquid fermentation conditions for Coprinus comatus to enhance antioxidant activity

Coprinus comatus is an edible and medicinal fungus. In this study, the antioxidant activity of the fermentation product of C. comatus was investigated through optimization of fermentation process. The results indicated that the fermentation product of C. comatus had obvious scavenging ability for 2,2'-Azino-bis(3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) free radical. The EC50 of the n-butanol extract from the fermentation product on ABTS·+ was 0.65 ± 0.02 mg/mL. On this basis, the liquid fermentation conditions of C. comatus were optimized through single factor and response surface optimization experiments according to the scavenging ability of ABTS·+ to improve the antioxidant capacity of the fermentation product. The results showed that when the 14% of C. comatus was fermented in a culture medium with a C/N ratio of 48:1 for 6 days, the ABTS·+ scavenging ability was the strongest, and the EC50 of n-butanol extract was 0.57 ± 0.01 mg/mL, which was 12.31% higher than the initial activity. This study laid the foundation for the development of C. comatus.

PAH bioremediation with Rhodococcus rhodochrous ATCC 21198: Impact of cell immobilization and surfactant use on PAH treatment and post-remediation toxicity

Polycyclic aromatic hydrocarbons (PAHs) are prevalent environmental contaminants that are harmful to ecological and human health. Bioremediation is a promising technique for remediating PAHs in the environment, however bioremediation often results in the accumulation of toxic PAH metabolites. The objectives of this research were to demonstrate the cometabolic treatment of a mixture of PAHs by a pure bacterial culture, Rhodococcus rhodochrous ATCC 21198, and investigate PAH metabolites and toxicity. Additionally, the surfactant Tween ® 80 and cell immobilization techniques were used to enhance bioremediation. Total PAH removal ranged from 70-95% for fluorene, 44-89% for phenanthrene, 86-97% for anthracene, and 6.5-78% for pyrene. Maximum removal was achieved with immobilized cells in the presence of Tween ® 80. Investigation of PAH metabolites produced by 21198 revealed a complex mixture of hydroxylated compounds, quinones, and ring-fission products. Toxicity appeared to increase after bioremediation, manifesting as mortality and developmental effects in embryonic zebrafish. 21198's ability to rapidly transform PAHs of a variety of molecular structures and sizes suggests that 21198 can be a valuable microorganism for catalyzing PAH remediation. However, implementing further treatment processes to address toxic PAH metabolites should be pursued to help lower post-remediation toxicity in future studies.

Biodegradation of phenolic pollutants and bioaugmentation strategies: A review of current knowledge and future perspectives

The widespread use of phenolic compounds renders their occurrence in various environmental matrices, posing ecological risks especially the endocrine disruption effects. Biodegradation-based techniques are efficient and cost-effective in degrading phenolic pollutants with less production of secondary pollution. This review focuses on phenol, 4-nonylphenol, 4-nitrophenol, bisphenol A and tetrabromobisphenol A as the representatives, and summarizes the current knowledge and future perspectives of their biodegradation and the enhancement strategy of bioaugmentation. Biodegradation and isolation of degrading microorganisms were mainly investigated under oxic conditions, where phenolic pollutants are typically hydroxylated to 4-hydroxybenzoate or hydroquinone prior to ring opening. Bioaugmentation efficiencies of phenolic pollutants significantly vary under different application conditions (e.g., increased degradation by 10-95% in soil and sediment). To optimize degradation of phenolic pollutants in different matrices, the factors that influence biodegradation capacity of microorganisms and performance of bioaugmentation are discussed. The use of immobilization strategy, indigenous degrading bacteria, and highly competent exogenous bacteria are proposed to facilitate the bioaugmentation process. Further studies are suggested to illustrate 1) biodegradation of phenolic pollutants under anoxic conditions, 2) application of microbial consortia with synergistic effects for phenolic pollutant degradation, and 3) assessment on the uncertain ecological risks associated with bioaugmentation, resulting from changes in degradation pathway of phenolic pollutants and alterations in structure and function of indigenous microbial community.

A novel alginate-embedded magnetic biochar-anoxygenic photosynthetic bacteria composite microspheres for multipollutant removal: Mechanisms of photo-bioelectrochemical enhancement and excellent reusability performance

Existing wastewater treatment technologies face the key challenge of simultaneously removing emerging contaminants and nutrients from wastewater efficiently, with a simplified technological process and minimized operational costs. In this study, a novel alginate-embedded magnetic biochar-anoxygenic photosynthetic bacteria composite microspheres (CA-MBC-PSB microspheres) was prepared for efficient, cost-effective and one-step removal of antibiotics and NH4+-N from wastewater. Our results demonstrated that the CA-MBC-PSB microspheres removed 97.23% of sulfadiazine (SDZ) within 7 h and 91% of NH4+-N within 12 h, which were 21.23% and 38% higher than those achieved by pure calcium alginate-Rhodopseudomonas palustris microspheres (53% and 45.7%), respectively. The enhanced SDZ and NH4+-N removal were attributed to the enhanced photoheterotrophic metabolism and excretion of extracellular photosensitive active substances from R. Palustris through the photo-bioelectrochemical interaction between R. Palustris and magnetic biochar. The long-term pollutants removal performance of the CA-MBC-PSB microspheres was not deteriorated but continuously improved with increasing ruse cycles with a simultaneous removal efficiency of 99% for SDZ and 92% for NH4+-N after three cycles. The excellent stability and reusability were due to the fact that calcium alginate acts as an encapsulating agent preventing the loss and contamination of R. palustris biomass. The CA-MBC-PSB microspheres also exhibited excellent performance for simultaneous removal of SDZ (89% in 7 h) and NH4+-N (90.7% in 12 h) from the secondary effluent of wastewater treatment plant, indicating the stable and efficient performance of CA-MBC-PSB microspheres in practical wastewater treatment.

Exploration of the biodegradation pathway and enhanced removal of imazethapyr from soil by immobilized Bacillus marcorestinctum YN1

Excessive or inappropriate applications of imazethapyr cause severe ecological deteriorations and health risks in human. A novel bacterial strain, i.e., Bacillus marcorestinctum YN1, was isolated to efficiently degrade imazethapyr, with the degradation pathways and intermediates predicted. Protein mass spectrometry analysis identified enzymes in strain YN1 potentially involved in imazethapyr biodegradation, including methylenetetrahydrofolate dehydrogenase, carbon-nitrogen family hydrolase, heme degrading monooxygenase, and cytochrome P450. The strain YN1 was further immobilized with biochar (BC600) prepared from mushroom waste (i.e., spent mushroom substrate) by pyrolysis at 600 °C to evaluate its degrading characteristics of imazethapyr. Scanning electron microscope observation showed that strain YN1 was adsorbed in the rich pore structure of BC600 and the adsorption efficiency reached the maximum level of 88.02% in 6 h. Both energy dispersive X-ray and Fourier transform infrared spectroscopy analyses showed that BC600 contained many elements and functional groups. The results of liquid chromatography showed that biochar-immobilized strain YN1 (IBC-YN1) improved the degradation rate of imazethapyr from 79.2% to 87.4%. The degradation rate of imazethapyr by IBC-YN1 could still reach 81.0% in the third recycle, while the bacterial survival rate was 67.73% after 180 d storage at 4 °C. The treatment of IBC-YN1 significantly shortened the half-life of imazethapyr in non-sterilized soil from 35.51 to 11.36 d, and the vegetative growth of imazethapyr sensitive crop plant (i.e., Cucumis sativus L.) was significantly increased in soil remediated, showing that the inhibition rate of root length and fresh weight were decreased by 12.45% and 38.49% respectively. This study exhanced our understanding of microbial catabolism of imazethapyr, and provided a potential in situ remediation strategy for improving the soil environment polluted by imazethapyr.

Co-culture of Acinetobacter sp. and Scedosporium sp. immobilized beads for optimized biosurfactant production and degradation of crude oil

The widespread exploration and exploitation of crude oil has increased the prevalence of petroleum hydrocarbon pollution in the marine and coastal environment. Bioremediation of petroleum hydrocarbons using cell immobilization techniques is gaining increasing attention. In this study, the crude oil degradation performance of bacterial and fungal co-culture was optimized by entrapping both cells in sodium-alginate and polyvinyl alcohol composite beads. Results indicate that fungal cells remained active after entrapment and throughout the experiment, while bacterial cells were non-viable at the end of the experimental period in treatments with the bacterial-fungal ratio of 1:2. A remarkable decrease in surface tension from 72 mN/m to 36.51 mN/m was achieved in treatments with the bacterial-fungal ratio of 3:1. This resulted in a significant (P < 0.05) total petroleum hydrocarbon (TPH) removal rate of 89.4%, and the highest degradation of n-alkanes fractions (from 2129.01 mg/L to 118.53 mg/L), compared to the other treatments. Whereas PAHs removal was highest in treatments with the most fungal abundance (from 980.96 μg/L to 177.3 μg/L). Furthermore, enzymes analysis test revealed that catalase had the most effect on microbial degradation of the target substrate, while protease had no significant impact on the degradation process. High expression of almA and PAH-RHDa genes was achieved in the co-culture treatments, which correlated significantly (P < 0.05) with n-alkanes and PAHs removal, respectively. These results indicate that the application of immobilized bacterial and fungal cells in defined co-culture systems is an effective strategy for enhanced biodegradation of petroleum hydrocarbons in aqueous systems.

Enhanced simultaneous removal of sulfamethoxazole and zinc (II) in the biochar-immobilized bioreactor: Performance, microbial structures and gene functions

Biochar-immobilized functional bacteria Bacillus SDB4 was applied for sulfamethoxazole (SMX) and zinc (Zn2+) simultaneous removal in the bioreactor. Under the optimal operating conditions of HRT of 10 h, pH of 7.0, SMX concentration of 10 mg L-1 and Zn2+ concentration of 50 mg L-1, the removal efficiencies of SMX and Zn2+ by the immobilized reactor (IR) were 97.42% and 96.14%, respectively, 20.39% and 30.15% higher than those by free bioreactor (FR). SEM-EDS and FTIR results revealed that the functional groups and light metals on the carrier promoted the biosorption and biotransformation of SMX and Zn2+ in IR. Moreover, the improvement of SMX and Zn2+ removal might be related to the abundance enhancement of functional bacteria and genes. Bacillus SDB4 responsible for SMX and Zn2+ removal was the main strain in IR and FR. Biochar increased the relative abundance of Bacillus from 32.12% in FR to 38.73% in IR and improved the abundances of functional genes (such as carbohydrate metabolism, replication and repair and membrane transport) by 1.82%-11.04%. The correlations among the physicochemical properties, microbial communities, functional genes and SMX-Zn2+ co-contaminant removal proposed new insights into the mechanisms of biochar enhanced microbial removal of antibiotics and heavy metals in biochar-immobilized bioreactors.

Enhanced bioremediation performance of diesel-contaminated soil by immobilized composite fungi on rice husk biochar

In response to the low removal capacity and poor tolerance of fungi to diesel-contaminated soil, a novel immobilization system using biochar to enhance composite fungi was proposed. Rice husk biochar (RHB) and sodium alginate (SA) were used as immobilization matrices for composite fungi, and the adsorption system (CFI-RHB) and the encapsulation system (CFI-RHB/SA) were obtained. CFI-RHB/SA exhibited the highest diesel removal efficiency (64.10%) in high diesel-contaminated soil over a 60-day remediation period compared to the free composite fungi (42.70%) and CFI-RHB (49.13%). SEM demonstrated that the composite fungi were confirmed to be well attached to the matrix in both CFI-RHB and CFI-RHB/SA. FTIR analysis revealed the appearance of new vibration peaks in diesel-contaminated soil remediated by immobilized microorganisms, demonstrating changes in the molecular structure of diesel before and after degradation. Furthermore, CFI-RHB/SA maintains a stable removal efficiency (>60%) in higher concentrations of diesel-contaminated soil. High-throughput sequencing results indicated that Fusarium and Penicillium played a key role in the removal of diesel contaminants. Meanwhile, both dominant genera were negatively correlated with diesel concentration. The addition of exogenous fungi stimulated the enrichment of functional fungi. The insights gained from experiment and theory help to provide a new understanding of immobilization techniques of composite fungi and the evolution of fungal community structure.

Determining the degradation mechanism and application potential of benzopyrene-degrading bacterium Acinetobacter XS-4 by screening

In industrial wastewater treatment, organic pollutants are usually removed by in-situ microorganisms and exogenous bactericides. Benzo [a] pyrene (BaP) is a typical persistent organic pollutant and difficult to be removed. In this study, a new strain of BaP degrading bacteria Acinetobacter XS-4 was obtained and the degradation rate was optimized by response surface method. The results showed that the degradation rate of BaP was 62.73% when pH= 8, substrate concentration was 10 mg/L, temperature was 25 °C, inoculation amount was 15% and culture rate was 180 r/min. Its degradation rate was better than that of the reported degrading bacteria. XS-4 is active in the degradation of BaP. BaP is degraded into phenanthrene by 3, 4-dioxygenase (α subunit and β subunit) in pathway Ⅰ and rapidly forms aldehydes, esters and alkanes. The pathway Ⅱ is realized by the action of salicylic acid hydroxylase. When sodium alginate and polyvinyl alcohol were added to the actual coking wastewater to immobilize XS-4, the degradation rate of BaP was 72.68% after 7 days, and the removal effect was better than that of single BaP wastewater (62.36%), which has the application potential. This study provides theoretical and technical support for microbial degradation of BaP in industrial wastewater.

Surfactant-enhanced bioremediation of petroleum-contaminated soil and microbial community response: A field study

Surfactant-enhanced bioremediation (SEBR) is frequently employed to clean up soil polluted with petroleum hydrocarbons, but few studies have focused on how surfactants affect microbial communities and different fractions of petroleum hydrocarbons, particularly in the field. Here, the surfactants sodium dodecyl benzene sulfonate (SDBS), alpha olefin sulfonate (AOS), Triton X-100 (TX-100), Tween80, and rhamnolipid were combined with the oil-degrading bacterium Pseudomonas sp. SB to remediate oil-contaminated soil in the laboratory. AOS gave the highest removal efficiency (65.1%) of total petroleum hydrocarbons (TPHs). Therefore, AOS was used in a field experiment with Pseudomonas sp. SB and the removal efficiency of TPHs and long-chain hydrocarbons C21-C40 reached 57.4 and 53.0%, respectively, significantly higher than the other treatments. During bioremediation the addition of Pseudomonas sp. SB significantly stimulated the growth of bacterial genera such as Alcanivorax, Luteimonas, Parvibaculum, Stenotrophomonas, and Pseudomonas and AOS further stimulated the growth of Sphingobacterium, Pseudomonas and Alcanivorax. This study validates the feasibility of surfactant-enhanced bioremediation in the field and partly reveals the mechanism of surfactant-enhanced bioremediation from the perspective of changes in different fractions of petroleum and microbial community dynamics.

Research progress of bio-slurry remediation technology for organic contaminated soil

Bio-slurry remediation technology, as a controllable bioremediation method, has the significant advantage of high remediation efficiency and can effectively solve the problems of high energy consumption and secondary pollution of traditional organic pollution site remediation technology. To further promote the application of this technology in the remediation of organically polluted soil, this paper summarizes the importance and advantages of bio-slurry remediation technology compared with traditional soil remediation technologies (physical, chemical, and biological). It introduces the technical infrastructure and its technological processes. Then, various factors that may affect its remediation performance are discussed. By analyzing the applications of this technology to the remediation of typical organic pollutant-(polycyclic aromatic hydrocarbons(PAHs), polychlorinated biphenyls(PCBs), total petroleum hydrocarbons(TPH), and pesticide) contaminated sites, the following key features of this remediation technology are summarised: (1) the technology has a wide range of applications and can be used in a versatile way in the remediation projects of various types of organic-contaminated soil sites such as in clay, sand, and high organic matter content soil; (2) the technology is highly controllable. Adjusting environmental parameters and operational conditions, such as nutrients, organic carbon sources (bio-stimulation), inoculants (bio-augmentation), water-to-soil ratio, etc., can control the remediation process, thus improving the restoration performance. To sum up, this bio-slurry remediation technology is an efficient, controllable and green soil remediation technology that has broad application prospects.

A novel chitosan-biochar immobilized microorganism strategy to enhance bioremediation of crude oil in soil

The chitosan-biochar composite is a clean and environmentally friendly immobilized microorganisms carrier. In this study, the chitosan-biochar composite as a carrier to immobilize a compound microbial agent contained Pseudomonas aeruginosa and Bacillus licheniformis, and investigated its role in the remediation of oil-contaminated soil. When using 1% (v/v) acetic acid, 3% (m/v) chitosan solution, 0.1% biochar, 4% (v/v) NaOH solution, freeze-drying 6 h, the optimal chitosan-biochar composite material could be obtained. The specific surfacearea of the material increased to 1.725 m²/g and the average pore size also increased from 130.2260 nm to 165.2980 nm after the addition of biochar through the analysis of specific surface area and pore size, which enlarged the contact area of microorganisms and crude oil with the material. SEM showed that the bacterial successfully adhered to the surface and internal of the material. Using FTIR, the results showed that the synthesis of composite carrier material was the covalent combination of -NH₂ on chitosan and -COOH on biochar, forming a new chemical bond -NH-CO-. After 60 days of remediation of oil-contaminated soil, the removal rate of crude oil by chitosan-biochar composite immobilized microorganism method was 45.82%, which was 21.26% higher than that of natural remediation. Simultaneously, several oil-degrading bacteria increased at genus level, including Nocardioides (26.79%-33.09%), Bacillus (3.01%-4.10%), Dietzia (1.84%-5.56%), Pseudomonas (0-0.78%), among which Pseudomonas belongs to exogenous bacteria. The results indicated that the chitosan-biochar composite material has high application value in removing crude oil, and further provides a new strategy for bioremediation of oil-contaminated soil.

Biotransformation as a tool for remediation of polycyclic aromatic hydrocarbons from polluted environment - review on toxicity and treatment technologies

Polycyclic aromatic hydrocarbons, a prominent family of persistent organic molecules produced by both anthropogenic and natural processes, are widespread in terrestrial and aquatic environments owing to their hydrophobicity, electrochemical stability and low aqueous solubility. Phenanthrene and naphthalene belong to the group of polycyclic aromatic hydrocarbons whose occurrence are reported to be relatively higher. The bioremediation mode of removing the toxicities of these two compounds has been reported to be promising than other methods. Most of the microbial classes of bacterial, fungal and algal origin are reported to degrade the target pollutants into non-toxic compounds effectively. The review aims to give an overview on toxicological studies, identification and enrichment techniques of phenanthrene and naphthalene degrading microbes and the bioremediation technologies (microbial assisted reactors, microbial fuel cells and microbial assisted constructed wetlands) reported by various researchers. All the three modes of bioremediation techniques were proved to be promising on different perspectives. In the treatment of phenanthrene, a maximum recovery of 96% and 98% was achieved in an aerobic membrane reactor with Bacillus species and single chamber air cathode microbial fuel cell with Acidovorax and Aquamicrobium respectively were reported. With the constructed wetland configuration, 95.5% of removal was attained with manganese oxide based microbial constructed wetland. The maximum degradation efficiency reported for naphthalene are 99% in a reverse membrane bioreactor, 98.5% in a marine sediment microbial fuel cell and 92.8% with a low-cost sandy soil constructed wetland.

Improving mass transfer rates in microbial cell immobilization system for environmental applications: Synergistic interaction of cells on crude oil biodegradation

Among the various techniques used to clean up polluted environments, bioremediation is the most cost-effective and eco-friendly option. The diversity of microbial communities in a consortium can significantly affect the biodegradability of hazardous organic pollutants, particularly for in situ bioremediation processes. This is largely attributed to interactions between members of a consortium. In this study, the effect of internal diffusion limitations in substrate model biodegradation was firstly examined by immobilized bacterial cells at different particle sizes produced by the electrospray technique. According to the obtained results, for particles with large size, the effectiveness factors (η) were about 0.58-0.67, and the resistance to diffusive on the biodegradation rate was significant, while with decreasing the particle size, η increases and approaches about 1. After selection of suitable bead size, heavy crude oil biodegradation was investigated using a consortium consisting of three oil-degrading bacterial strains at different treatment systems. The removal rate in the suspended co-culture system stands at minimum value of 38% with all three strains which is an indicator of negative interactions among consortium members. Independent immobilization of microorganisms minimizes the competition and antagonistic interactions between strains and leads to more crude oil removal, so that, the biodegradation rate reached 60%.

Immobilization of Biomass Materials for Removal of Refractory Organic Pollutants from Wastewater

In the field of environmental science and engineering, microorganisms, enzymes and algae are promising biomass materials that can effectively degrade pollutants. However, problems such as poor environmental adaptability, recycling difficulties, and secondary pollution exist in the practical application of non-immobilized biomass materials. Biomass immobilization is a novel environmental remediation technology that can effectively solve these problems. Compared with non-immobilized biomass, immobilized biomass materials have the advantages of reusability and stability in terms of pH, temperature, handling, and storage. Many researchers have studied immobilization technology (i.e., methods, carriers, and biomass types) and its applications for removing refractory organic pollutants. Based on this, this paper reviews biomass immobilization technology, outlines the mechanisms and factors affecting the removal of refractory organic pollutants, and introduces the application of immobilized biomass materials as fillers for reactors in water purification. This review provides some practical references for the preparation and application of immobilized biomass materials and promotes further research and development to expand the application range of this material for water purification.

Coupling of desorption of phenanthrene from marine sediments and biodegradation of the sediment washing solution in a novel biochar immobilized-cell reactor

The recurrent dredging of marine sediments needs the use of ex-situ technologies such as sediment washing (SW) to effectively remove polycyclic aromatic hydrocarbons. Notwithstanding, the large volumes of generated spent SW effluents require adequate treatment by employing highly-efficient, inexpensive and environmentally-friendly solutions. This study proposes the phenanthrene (PHE) desorption from sediments using Tween® 80 (TW80) as extracting agent and the treatment of the resulting spent SW solution in a biochar (BC) immobilized-cell bioreactor. The SW process reached the highest PHE removal of about 91% using a surfactant solution containing 10,800 mg L^-1 of TW80. The generated amount of spent PHE-polluted SW solution can be controlled by keeping a solid to liquid ratio of 1:4. A PHE degradation of up to 96% was subsequently achieved after 43 days of continuous reactor operation, aerobically treating the TW80 solution in the BC immobilized-cell bioreactor with a hydraulic retention time of 3.5 days. Brevundimonas, Chryseobacterium, Dysgonomonas, Nubsella, and both uncultured Weeksellaceae and Xanthobacteraceae genera were mainly involved in PHE biodegradation. A rough economic study showed a total cost of 342.60 € ton^-1 of sediment, including the SW operations, TW80 and BC supply and the biological treatment of the SW solution.

Synergetic effects of microbial-phytoremediation reshape microbial communities and improve degradation of petroleum contaminants

Microbial-phytoremediation is an effective bioremediation technology that introduces petroleum-degrading bacteria and oil-tolerant plants into oil-contaminated soils in order to achieve effective degradation of total petroleum hydrocarbons (TPH). In this work, natural attenuation (NA), microbial remediation (MR, using Acinetobacter sp. Tust-DM21), phytoremediation (PR, using Suaeda glauca), and microbial-phytoremediation (MPR, using both species) were utilized to degrade petroleum hydrocarbons. We evaluated four different biological treatments, assessing TPH degradation rates, soil enzyme activities, and the structure of microbial community in the petroleum-contaminated soil. This finding revealed that the roots of Suaeda glauca adsorbed small amounts of polycyclic aromatic hydrocarbons, causing the structure of soil microbiota community to reshape. The abundance of petroleum-degrading bacteria and plant growth-promoting rhizobacteria (PGPR) has increased, as has microbial diversity. According to correlation research, these genera increased soil enzyme activity, boosted the number of degradation-functional genes in the petroleum hydrocarbon degradation pathway, and accelerated the dissipation and degradation of TPH in petroleum-contaminated soil. This evidence contributes to a better understanding of the mechanisms involved in the combined microbial-phytoremediation strategies for contaminated soil, specifically the interaction between microflora and plants in co-remediation and the effects on the structural reshaping of rhizosphere microbial communities.

Phenanthrene biodegradation in a fed-batch reactor treating a spent sediment washing solution: Techno-economic implications for the recovery of ethanol as extracting agent

The continuous dredging of sediments contaminated by polycyclic aromatic hydrocarbons such as phenanthrene (PHE) has required the employment of high-efficiency technologies, including sediment washing (SW). However, the large amount of generated spent SW effluents requires the development of effective, eco-friendly and cost-saving approaches, which can tackle the waste formation in favor of the recovery of chemicals. This study proposes the treatment of a spent SW solution containing ethanol (EtOH) as extracting agent, by testing different initial PHE concentrations (i.e. 20-140 mg L^-1) within six consecutive cycles in a fed-batch bioreactor under aerobic conditions. The biological process achieved a PHE removal of 63-91% after the enrichment of PHE-degrading bacteria and the proper supplementation of nutrients, and was mainly affected by the initial PHE concentration value and the excessive decrease of pH and dissolved oxygen. Achromobacter, Sphingobacterium and Dysgonomonas genera were mainly involved in PHE degradation, which followed a first-order kinetic model (R² = 0.652-0.928) with a degradation rate and half-life time of 0.127-1.177 d^-1 and 0.589-2.912 d, respectively. A techno-economic assessment revealed that a virtuous operation of SW, EtOH recovery and biodegradation of the SW solution can allow the recovery of up to 1.35 tons of EtOH per ton of remediated sediment and the decrease of the overall costs by 50%.

PAHs biodegradation in soil washing effluent by native mixed bacteria embedded in polyvinyl alcohol-sodium alginate-nano alumina gel beads

In this study, the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in soil washing solution containing Tween 80 was conducted using native mixed bacteria (Pseudomonas sp. Z1, Sphingobacterium sp. Z2, and Klebsiella sp. K) embedded in polyvinyl alcohol-sodium alginate-nano alumina (PVA-SA-ALNPs) gel beads. The optimal dosage of immobilized beads and embedded biomass for the biodegradation of phenanthrene (PHE), fluoranthene (FLU), and pyrene (PYR) were 10 % (v/v) and 20 % (v/v), respectively. SEM analysis showed that the porous structure of the immobilized beads was a cross-linked network with abundant pores that provided many potential adhesion sites for microorganisms. The beads with the immobilized mixed bacteria maintained a high activity during batch experiments and could even be reused for 3 cycles (90 d). Compared with the beads containing individual immobilized strain, the immobilized mixed bacteria showed a more efficient biodegradation of PHE (91.67 %), FLU (88.6 %), and PYR (88.5 %) in synthetic soil washing effluent within 30 d. The first-order kinetic model suitably described the degradation process of the three target PAHs. By adding Tween 80 to the synthetic eluent, the degradation of PHE, FLU, and PYR increased by 16.39 %, 22.25 %, and 21.29 %, respectively, indicating that Tween 80 promoted PAHs biodegradation, even though it was also rapidly degraded during the reaction cycle. These findings suggest that the developed mixed bacteria embedded in PVA-SA-ALNPs gel beads has great potential for PAHs remediation.

Sustainable ex-situ remediation of contaminated sediment: A review

Routine waterway dredging activities generate huge volumes of dredged sediment. The remediation of dredged contaminated sediment is a worldwide challenge. Novel and sustainable ex-situ remediation technologies for contaminated sediment have been developed and adopted in recent years. In this review paper, the state-of-art ex-situ treatment technologies and resource utilisation methods for contaminated sediment were critically reviewed. By applying different techniques, sediment could been successfully transformed into sustainable construction materials, such as ceramsite, supplementary cementitious materials, fill materials, paving blocks, partition blocks, ready-mixed concrete, and foamed concrete. We highlighted that proper remediation technologies should be cleverly selected and designed according to the physical and chemical characteristics of sediment, without neglecting important aspects, such as cost, safety, environmental impacts, readiness level of the technology and social acceptability. The combination of different assessment methods (e.g., environmental impact assessment, cost-benefit analysis, multi-criteria decision analysis and life cycle assessment) should be employed to comprehensively evaluate the feasibility of different sustainable remediation technologies. We call on the scientific community in a multidisciplinary fashion to evaluate the sustainability of various remediation technologies for contaminated sediment.

Enhanced bioremediation of 2,3',4,4',5-pentachlorodiphenyl by consortium GYB1 immobilized on sodium alginate-biochar

2,3',4,4',5-pentachlorodiphenyl (PCB 118), a dioxin-like PCB, is often detected in the environment and is difficult to be aerobically biodegraded. In this study, a novel polychlorinated biphenyl degrading consortium GYB1 that can metabolize PCB 118 was successfully obtained by acclimatization process. To enhance the application performance of free bacterial cells, consortium GYB1 was immobilized with sodium alginate and biochar to prepare SC-GYB1 beads. Orthogonal experiments indicated that the optimal composition of the beads (0.2 g) was 2.0% sodium alginate (SA) content, 2.0% wet weight of cells and 1.5% biochar content, which can degrade 50.50% PCB 118 in 5 d. Immobilization shortened the degradation half-life of 1 mg/L PCB 118 by consortium GYB1 from 8.14 d to 3.79 d and made the beads more robust to respond to environmental stress. The SC-GYB1 beads could even keep considerable PCB degradation ability under 200 mg/L Cd²⁺ stress. According to 16S rRNA gene analysis, Pseudomonas and Stenotrophomonas played the dominant role in consortium GYB1. And embedding obviously altered the community structure and the key bacterial genera during the PCB removal process. Therefore, the immobilization of bacteria consortium by sodium alginate-biochar enhanced the biodegradation of PCB 118, which will provide new insights into functional microorganisms' actual application for PCB restoration.

Enhanced biodegradation of light crude oil by immobilized Bacillus licheniformis in fabricated alginate beads through electrospray technique

Petroleum contamination of marine environments due to exploitation and accidental spills causes serious harm to ecosystems. Bioremediation with immobilized microorganisms is an environmentally friendly and cost-effective emerging technology for treating oil-polluted environments. In this study, Bacillus licheniformis was entrapped in Ca alginate beads using the electrospray technique for light crude oil biodegradation. Three important process variables, including inoculum size (5-15% v/v), initial oil concentration (1500-3500 ppm), and NaCl concentration (0-30 g/L), were optimized to obtain the best response of crude oil removal using response surface methodology (RSM) and Box-Behnken design (BBD). The highest crude oil removal of 79.58% was obtained for 1500 ppm of crude oil after 14 days using immobilized cells, and it was lower for freely suspended cells (64.77%). Our result showed similar trends in the effect of variables on the oil biodegradation rate in both free cell (FC) and immobilized cell (IC) systems. However, according to the analysis of variance (ANOVA) results, the extent of the variables' effectiveness was different in FC and IC systems. In the immobilized cell system, all variables had a greater effect on the rate of light crude oil degradation. Moreover, to evaluate the effectiveness of free and immobilized B. licheniformis in bioremediation of an actual polluted site, the crude oil spill in natural seawater was investigated. The results suggested the stability of beads in the seawater, as well as high degradation of petroleum hydrocarbons by free and immobilized cells in the presence of indigenous microorganisms.

Enhanced biodegradation of organophosphorus insecticides in industrial wastewater via immobilized Cupriavidus nantongensis X1T

Chlorpyrifos is an important organophosphorus insecticide. It is highly toxic to mammals and can pollute the environment. Cupriavidus nantongensis X1^T can efficiently degrade chlorpyrifos. Immobilization technology can also improve the viability, stability and catalytic ability of bacteria. In this study, strain X1^T was, therefore, captured on various composite immobilized carriers, sodium alginate (SA), diatomite (KLG), chitosan (CTS) and polyvinyl alcohol (PVA). The four types of immobilized beads (SA, SA + KLG, SA + CTS and SA + PVA) could form a slice and honeycomb structure to capture strain X1^T. The results showed that SA + CTS (SC) was an optimal material combination for the immobilization of strain X1^T to degrade chlorpyrifos. Compared with SA-X1^T, after adding CTS, the specific surface area and adsorption capacity for chlorpyrifos were increased 3.4 and 1.7 fold, respectively. SC-X1^T could degrade 96.6% of chlorpyrifos at 20 mg/L within 24 h and the degradation rate constant was 4.8 fold greater than immobilized strain LLBD2, a well-studied chlorpyrifos-degrading strain. The immobilized beads SC-X1^T also showed a more stable and greater degradation ability than X1^T free cells for chlorpyrifos in industrial wastewater. The synergy of adsorption and degradation of immobilized strain X1^T is suitable for in-situ remediation of chlorpyrifos contaminated environment.

Exploration of the biotransformation processes in the biodegradation of phenanthrene by a facultative anaerobe, strain PheF2, with Fe(III) or O2 as an electron acceptor

The study of biodegradation of polycyclic aromatic hydrocarbons (PAHs) with metal ions as electron acceptors is still in its infancy. Here, a pure culture of PheF2 sharing 99.79% 16S rRNA-sequence similarity with Trichococcus alkaliphilus, which was recently reported to degrade PAHs, was isolated and found to degrade PAHs with Fe (III) or O₂ reduction. Phenanthrene was selected as a model of PAH to study the biodegradation process by PheF2 with Fe (III) or O₂ as an electron acceptor. PheF2 exhibited nearly 100%, 37.1%, and 28.5% anaerobic biodegradation of phenanthrene at initial concentrations of 280.7 μM, 280.6 μM, and 281.3 μM, respectively, within 10 days under anaerobic conditions with XAD-7 as a carrier, heptamethylnonane (HMN) as a solution, and nothing, respectively. PheF2 could degrade nearly 100% of the initial phenanthrene concentration of 283.4 μM under aerobic conditions within three days. The initial step of phenanthrene biodegradation by PheF2 involved carboxylation and dioxygenation under anaerobic and aerobic conditions, respectively. The biotransformation processes of phenanthrene degradation by PheF2 with Fe(III) or O₂ as an electron acceptor were explored by metabolite and genome analysis. These findings provide an important theoretical support for evaluation of PAHs fate and for PAHs pollution control or remediation in anaerobic and aerobic environments.

Microbial vanadate reduction coupled to co-metabolic phenanthrene biodegradation in groundwater

Vanadate [V(V)] and phenanthrene (PHE) commonly coexist in groundwater aquifer, posing potential threats to ecological environment and public health. However, little is known about the complicated biogeochemical processes involving microbial V(V) reduction coupled with co-metabolic PHE biodegradation. Herein we demonstrated that synchronous removal of V(V) and PHE could be realized under anaerobic condition. Complete V(V) removal and PHE degradation efficiency of 82.0 ± 0.8% were achieved in 7-d operation in batch experiment. 250-d continuous column experiment implied that hydrochemical condition affected V(V) and PHE removals. V(V) was reduced to insoluble vanadium (IV) and PHE was degraded into small molecule organics (e.g. salicylic acid). Geobacter and Acetobacterium used methanol and intermediates from PHE degradation as electron donors for V(V) reduction. PHE was decomposed by Mycobacterium and Clostridium with methanol as co-metabolic substrate and V(V) as electron acceptor. Genes encoding proteins for V(V) reduction (omcA, omcB and mtrC) and PHE degradation (phnAc) were upregulated. Cytochrome c and nicotinamide adenine dinucleotide promoted electron transfer for V(V) and PHE detoxification. Extracellular polymeric substances could bind V(V) and improve the bioavailability of PHE. Our findings provide a robust strategy for remediation of V(V) and PHE co-contaminated groundwater.

Bacterial ecotoxicity and shifts in bacterial communities associated with the removal of ibuprofen, diclofenac and triclosan in biopurification systems

The proliferation and possible adverse effects of emerging contaminants such as pharmaceutical and personal care products (PPCPs) in waters and the environment is a cause for increasing concern. We investigated the dissipation of three PPCPs: ibuprofen (IBP), diclofenac (DCF) and triclosan (TCS), separately and in mixtures, in the ppm range in biopurification system (BPS) microcosms, paying special attention to their effect on bacterial ecotoxicity, as well as bacterial community structure and composition. The results reveal that BPS microcosms efficiently dissipate IBP and DCF with 90% removed after 45 and 84 days of incubation, respectively. However, removal of TCS required a longer incubation period of 127 days for 90% removal. Furthermore, dissipation of the PPCPs was slower when a mixture of all three was applied to BPS microcosms. TCS had an initial negative effect on bacterial viability by a decrease of 34-43% as measured by live bacterial cell counts using LIVE/DEAD® microscopy; however, this effect was mitigated when the three PPCPs were present simultaneously. The bacterial communities in BPS microcosms were more affected by incubation time than by the PPCPs used. Nonetheless, the PPCPs differentially affected the composition and relative abundance of bacterial taxa. IBP and DCF initially increased bacterial diversity and richness, while exposure to TCS generally provoked an opposite effect without full recovery at the end of the incubation period. TCS, which negatively affected the relative abundance of Acidobacteria, Methylophilales, and Legionellales, had the largest impact on bacterial groups. Biomarker OTUs were identified in the BPS microcosms which were constrained to higher concentrations of the PPCPs and thus are likely to harbour degradation and/or detoxification mechanisms. This study reveals for the first time the effect of PPCPs on bacterial ecotoxicity and diversity in biopurification system microcosms and also facilitates the design of further applications of biomixtures to eliminate PPCPs.

Hazardous wastes treatment technologies

A review of the literature published in 2019 on topics related to hazardous waste management in water, soils, sediments, and air. The review covered treatment technologies applying physical, chemical, and biological principles for the remediation of contaminated water, soils, sediments, and air. PRACTICAL POINTS: This report provides a review of technologies for the management of waters, wastewaters, air, sediments, and soils contaminated by various hazardous chemicals including inorganic (e.g., oxyanions, salts, and heavy metals), organic (e.g., halogenated, pharmaceuticals and personal care products, pesticides, and persistent organic chemicals) in three scientific areas of physical, chemical, and biological methods. Physical methods for the management of hazardous wastes including general adsorption, sand filtration, coagulation/flocculation, electrodialysis, electrokinetics, electro-sorption ( capacitive deionization, CDI), membrane (RO, NF, MF), photocatalysis, photoelectrochemical oxidation, sonochemical, non-thermal plasma, supercritical fluid, electrochemical oxidation, and electrochemical reduction processes were reviewed. Chemical methods including ozone-based, hydrogen peroxide-based, potassium permanganate processes, and Fenton and Fenton-like process were reviewed. Biological methods such as aerobic, anoxic, anaerobic, bioreactors, constructed wetlands, soil bioremediation and biofilter processes for the management of hazardous wastes, in mode of consortium and pure culture were reviewed. Case histories were reviewed in four areas including contaminated sediments, contaminated soils, mixed industrial solid wastes and radioactive wastes.

Quantification of Naphthalene Dioxygenase (NahAC) and Catechol Dioxygenase (C23O) Catabolic Genes Produced by Phenanthrene-Degrading Pseudomonas fluorescens AH-40

Background

Petroleum polycyclic aromatic hydrocarbons (PAHs) are known to be toxic and carcinogenic for humans and their contamination of soils and water is of great environmental concern. Identification of the key microorganisms that play a role in pollutant degradation processes is relevant to the development of optimal in situ bioremediation strategies.

Objective

Detection of the ability of Pseudomonas fluorescens AH-40 to consume phenanthrene as a sole carbon source and determining the variation in the concentration of both nahAC and C23O catabolic genes during 15 days of the incubation period.

Methods

In the current study, a bacterial strain AH-40 was isolated from crude oil polluted soil by enrichment technique in mineral basal salts (MBS) medium supplemented with phenanthrene (PAH) as a sole carbon and energy source. The isolated strain was genetically identified based on 16S rDNA sequence analysis. The degradation of PAHs by this strain was confirmed by HPLC analysis. The detection and quantification of naphthalene dioxygenase (nahAc) and catechol 2,3-dioxygenase (C23O) genes, which play a critical role during the mineralization of PAHs in the liquid bacterial culture were achieved by quantitative PCR.

Results

Strain AH-40 was identified as pseudomonas fluorescens. It degraded 97% of 150 mg phenanthrene L^-1 within 15 days, which is faster than previously reported pure cultures. The copy numbers of chromosomal encoding catabolic genes nahAc and C23O increased during the process of phenanthrene degradation.

Conclusion

nahAc and C23O genes are the main marker genes for phenanthrene degradation by strain AH-40. P. fluorescence AH-40 could be recommended for bioremediation of phenanthrene contaminated site.

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.

Removal of phosphate from wastewater by modified bentonite entrapped in Ca-alginate beads

Methods of removing phosphate from wastewater with a low phosphate concentration are of great environmental significance. In this study, immobilized beads were prepared by entrapping modified bentonite powder in calcium-alginate (Al-NaBT-CA), and the potential of the beads for phosphate removal from wastewater was investigated. The effects of pH (1-10) and initial phosphate concentration (0.5-50 mg/L) were also examined in batch experiments with Al-NaBT-CA beads. The optimum pH value for phosphate removal by Al-NaBT-CA beads was pH 3. In addition, a high initial phosphate concentration promoted phosphate adsorption. Adsorption kinetics showed that the adsorption of phosphate using beads followed a pseudo-second-order kinetic model (R² = 0.98-0.99). The adsorption isotherm data was well fitted by the Sips adsorption model. The maximum phosphate adsorption capacity of the Al-NaBT-CA beads was 15.77 mg/g, which was slightly less than that of the modified powder. The specific surface area of the Al-NaBT-CA beads was 17.01 m²/g, and their average pore size was 13.41 nm. Scanning electron microscopy suggested that the high inner porosity and rough outer surface of the beads facilitated phosphate transfer.