Biodegradation of perchloroethylene and chlorophenol co-contamination and toxic effect on activated sludge performance

Boosting biodegradation and mineralization efficiencies of chlorinated VOCs: The synergy of H2O2 and biotrickling filtration

This study explores a new biodegradation process of H2O2-stimulated BTFs to remove perchloroethylene (PCE) from the contaminated air stream. BTF stimulated with H2O2 significantly boosted PCE biodegradation compared to conventional methods. Optimal parameters for H2O2-assisted PCE biodegradation were also identified (nominal inlet concentration = 150 ppm, EBCT = 30 s, H2O2/PCE molar ratio = 0.2). Under these optimum conditions, the BTF achieved a maximum PCE removal efficiency of around 95 %, a mineralization rate of 65 %, and an elimination capacity of 117 g/m3.h, demonstrating its effectiveness. The BTF maintained stable performance under various PCE loads, suggesting its applicability for industrial cases. Moreover, the study revealed a positive correlation between increasing H2O2/PCE ratios and the activities of key enzymes responsible for biodegradation including dehydrogenase)increased from 1.3 to 26.1 mg-TF/gbiomass), peroxidase (increased from 0 to 251 U/gbiomass), and catalase (increased from 0 to 7.8 U/gbiomass) when the ratio was increased from 0 to 0.2. The H2O2-stimulated BTF performed efficiently for biodegradation (>90 %) and mineralization (>60 %) of PCE at empty bed contact times between 20 and 60 s. Finally, the absence of PCE and toxic intermediates in the recycled liquid supports the efficient biodegradation of PCE in the developed system. In conclusion, H2O2-stimulated BTF shows promise as a sustainable and cost-effective approach for biodegradation of chlorinated organic compounds in contaminated air streams.

Evaluation of a mixture of livestock wastewater and food waste as a substrate in a continuous-flow microbial electrolysis cell

While the efficiency of microbial electrolysis cell (MEC) systems has improved remarkably, their application in continuous reactors and wastewater treatment remains poorly understood. This study evaluated the performance of a continuous-flow MEC using livestock wastewater and food waste as substrates. The MEC system achieved a hydrogen production rate of 5.2 L/L/day using acetate as a substrate, and a rate of 2.9-4.6 L/L/day when real wastewater mixtures were used. In terms of chemical oxygen demand (COD) removal, the system demonstrated high efficiency, with values ranging from 42.3 % to 62.2 % depending on the wastewater composition. Volatile fatty acid (VFA) removal reached up to 72.8 %. The current density averaged 9.9 A/m2 with acetate and decreased to 7.0 and 6.1 A/m2 in phases using wastewater, reflecting the adaptation of the microbial community to the more complex substrates. The microbial community was dominated by Firmicutes, Bacteroidetes, Proteobacteria, and Synergistetes, with Proteobacteria showing a particularly high abundance near the anion exchange membrane (AEM) on the anode. The MEC process demonstrates substantial promise as a sustainable technology for both biohydrogen production and wastewater treatment. With further optimization and scaling, MECs could play a crucial role in the circular economy by converting waste into clean energy while simultaneously treating wastewater, offering a pathway toward more sustainable industrial and environmental practices.

Effect of weak electrical stimulation on m-dichlorobenzene biodegradation in biotrickling filters: Insights from performance and microbial community analysis

The microbial electrolysis cell coupled with the biotrickling filters (MEC-BTF) was developed for enhancing the biodegradation of gaseous m-dichlorobenzene (m-DCB) through weak electrical stimulation. The maximum removal efficiency and elimination capacity in MEC-BTF were 1.48 and 1.65 times higher than those in open-circuit BTF (OC-BTF), respectively. Weak electrical stimulation had a positive impact on the characteristics of the biofilm. Additionally, microbial community analysis revealed that weak electrical stimulation increased the abundance of key functional genera (e.g., Rhodanobacter and Bacillus) and genes (e.g., catA/E and E1.3.1.32), thereby accelerating reductive dechlorination and ring-opening of m-DCB. Macrogenomic sequencing further revealed that electron transfer pathway in MEC-BTF might be mediated through extracellular electroactive mediators and cytochromes.

Effects of co-occurrence of PFASs and chlorinated aliphatic hydrocarbons on microbial communities in groundwater: A field study

The effects of per- and polyfluoroalkyl substances (PFASs) and chlorinated aliphatic hydrocarbons (CAHs) co-contamination on the microbial community in the field have not been studied. In this study, we evaluated the presence of PFASs and CAHs in groundwater collected from a fluorochemical plant (FCP), and carried out Illumina MiSeq sequencing to understand the impact of mixed PFASs and CAHs on the indigenous microbial community. The sum concentrations of 20 PFASs in FCP groundwater ranged from 2.05 to 317.40 μg/L, and the highest PFOA concentration was observed in the deep aquifer (60 m below ground surface), co-contaminated by dense non-aqueous-phase liquid (DNAPL). The existence of PFASs and CAHs co-contamination in groundwater resulted in a considerable decrease in the diversity of microbial communities, while the abundance of metabolisms associated with contaminants biodegradation has increased significantly compared to the background wells. Furthermore, Acinetobacter, Pseudomonas and Arthrobacter were the dominant genera in PFASs and CAHs co-contaminated groundwater. The presence of high concentrations of PFASs and CAHs has been positively associated with the genus of Citreitalea. Finally, geochemical parameters, such as ORP, sulfate and nitrate were the key factors to shape up the structure of the microbial community and sources to rich the abundance of the potential functional bacteria.

Response of 2,4,6-trichlorophenol-reducing biocathode to burial depth in constructed wetland sediments

Biocathode systems could be used for in-situ bioremediation of chlorophenols (CPs) in constructed wetland (CW) sediments. However, little is known regarding whether or how cathode burial depths affect the dechlorination of CPs in sediments. Here, 2,4,6-trichlorophenol (2,4,6-TCP)-dechlorinating biocathode systems were constructed under a cathode potential of - 0.7 V (vs. a saturated calomel electrode, SCE) at three different cathode burial depths (5, 10, and 15 cm). The 2,4,6-TCP removal efficiency and average transformation rate with the biocathode increased by 21.46-36.86% and 14.63-34.88% compared to those in the non-electrode groups. Deeper cathode burial depths enhanced the 2,4,6-TCP dechlorination performance. Furthermore, the oxidation-reduction potential (ORP) of the sediment decreased with sediment depth and the applied potential created a more favorable redox environment for the enrichment of functional bacteria. Deeper cathode burial depths also promoted the selective enrichment of electro-active and dechlorinating bacteria (e.g., Bacillus and Dehalobacter, respectively). The biocathode thus served as the carrier, electron source, and regulator of functional bacteria to accelerate the transformation of 2,4,6-TCP (2,4,6-TCP → 2,4-dichlorophenol → 4-chlorophenol → phenol) in sediments. These results offer insights into the effects of cathode burial depth on 2,4,6-TCP dechlorination in sediments from a redox environment and microbial community structure standpoint.

Shotgun metagenomic analysis reveals the prevalence of antibiotic resistance genes and mobile genetic elements in full scale hospital wastewater treatment plants

Wastewater treatment plants are considered as hotspots of emerging antimicrobial genes and mobile genetic elements. We used a shotgun metagenomic approach to examine the wide-spectrum profiles of ARGs (antibiotic resistance genes) and MGEs (mobile genetic elements) in activated sludge samples from two different hospital trains at the wastewater treatment plants (WWTPs) in Daegu, South Korea. The influent activated sludge and effluent of two trains (six samples in total) at WWTPs receiving domestic sewage wastewater (SWW) and hospital wastewater (HWW) samples collected at multiple periods were subjected to high throughput 16S rRNA metagenome sequencing for microbial community diversity. Cloacibacterium caeni and Lewinella nigricans were predominant in SWW effluents, while Bacillus subtilis and Staphylococcus epidermidis were predominant in HWW effluents based on the Miseq platform. Totally, 20,011 reads and 28,545 metagenomic sequence reads were assigned to 25 known ARG types in the SWW2 and HWW5 samples, respectively. The higher abundance of ARGs, including multidrug resistance (>53%, MDR), macrolide-lincosamide-streptogramin (>9%, MLS), beta-lactam (>3.3%), bacitracin (>4.4%), and tetracycline (>3.4%), confirmed the use of these antibiotics in human medicine. In total, 190 subtypes belonging to 23 antibiotic classes were detected in both SWW2 and HWW5 samples. RpoB2, MacB, and multidrug (MDR) ABC transporter shared the maximum matched genes in both activated sludge samples. The high abundance of MGEs, such as a gene transfer agent (GTA) (four times higher), transposable elements (1.6 times higher), plasmid related functions (3.8 times higher), and phages (two times higher) in HWW5 than in SWW2, revealed a risk of horizontal gene transfer in HWW. Domestic wastewater from hospital patients also influenced the abundance of ARGs and MGEs in the activated sludge process.

Metagenomic analysis of microbial community and its role in bioelectrokinetic remediation of tannery contaminated soil

Tanneries create a serious threat to the environment by generating a significant amount of toxic metal-containing solid waste. This study deals with the application of bio-electrokinetic remediation (Bio-EK) of tannery effluent contaminated soil (TECS). Metagenomes representing the TECS sample were sequenced using the Illumina HiSeq platform. The bioreduction of hexavalent chromium Cr(VI)to trivalent chromium Cr (III) was achieved by BIO-EK techniques. NGS-data (Next Generation Sequencing) analysis was revealed that Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Planctomycetes were identified in the bio-electrokinetic system. Proteobacteria are responsible for the bioreduction of chromium hexavalent by the formation of FeS particles. The bio-generated FeS particles can be reduced the toxic chromium (VI) to non-toxic chromium (III) in soil. Simultaneously total chromium and organic content were significantly removed in BIO-EK (40 and 290 mg kg^-1) when compared to control soil (182 and 240 mg kg^-1). The presence of pollutant degrading microbes such as Desulfovibrio, Pseudomonas, Bacillus, Clostridium, Halanaerobium enhanced the bioreduction of the chromium during the electrokinetic remediation. This study can be claimed that the microbial cultures assisted electrokinetic remediation of total chromium, organic and iron in the tannery effluent contaminated soil was one of the suitable efficient techniques. In addition, the viability of the new combination technology developed (Electrokinetic + Bio) to treat low-permeability polluted soils was demonstrated.

Alkylphenols and Chlorophenols Remediation in Vertical Flow Constructed Wetlands: Removal Efficiency and Microbial Community Response

This study aims to investigate the effect of two different groups of phenolic compounds (the alkylphenols nonylphenol (NP) and octylphenol (OP), and the chlorophenol pentachlorophenol (PCP)) on constructed wetlands (CWs) performance, including on organic matter, nutrients and contaminants removal efficiency, and on microbial community structure in the plant bed substrate. CWs were assembled at lab scale simulating a vertical flow configuration and irrigated along eight weeks with Ribeira de Joane (an urban stream) water not doped (control) or doped with a mixture of NP and OP or with PCP (at a 100 μg·L−1 concentration each). The presence of the phenolic contaminants did not interfere in the removal of organic matter or nutrients in CWs in the long term. Removals of NP and OP were >99%, whereas PCP removals varied between 87% and 98%, mainly due to biodegradation. Microbial richness, diversity and dominance in CWs substrate were generally not affected by phenolic compounds, with only PCP decreasing diversity. Microbial community structure, however, showed that there was an adaptation of the microbial community to the presence of each contaminant, with several specialist genera being enriched following exposure. The three more abundant specialist genera were Methylotenera and Methylophilus (methylophilaceae family) and Hyphomicrobium (hyphomicrobiaceae family) when the systems were exposed to a mixture of NP and OP. When exposed to PCP, the three more abundant genera were Denitromonas (Rhodocyclaceae family), Xenococcus_PCC_7305 (Xenococcaceae family) and Rhodocyclaceae_uncultured (Rhodocyclaceae family). To increase CWs efficiency in the elimination of phenolic compounds, namely PCP which was not totally removed, strategies to stimulate (namely biostimulation) or increase (namely bioaugmentation) the presence of these bacteria should be explore. This study clearly shows the potential of vertical flow CWs for the removal of phenolic compounds, a still little explored subject, contributing to promote the use of CWs as nature-based solutions to remediate water contaminated with different families of persistent and/or emergent contaminants.

Moving average convergence and divergence indexes based online intelligent expert diagnosis system for anaerobic wastewater treatment process

Anaerobic wastewater treatment process is efficient but unstable due to various disturbances, such as refractory organics and influent organic overloading. Therefore, sensitive and accurate status diagnosis is important for reasonable control to improve the stability of anaerobic process. In this study, an online intelligent expert diagnosis system for anaerobic process was established based on moving average convergence and divergence (MACD) indexes of gas- and liquid-phase parameters, combined with online monitoring system and expert diagnosis database. The effect of this diagnosis system was verified through refractory organics and organic overloading shock experiments. Results showed that this diagnosis system could make rapid, accurate and comprehensive diagnosis, predictions and early-warning. MACD algorithm could enhance pattern recognition capacity of status parameters, overcome the lagging of anaerobic process and filter irregular noisy fluctuations of status parameters. MACD index of H₂ partial pressure is suitable as sensitive early-warning indicator in the initial shock stage.

Effects of substrate type on enhancing pollutant removal performance and reducing greenhouse gas emission in vertical subsurface flow constructed wetland

Constructed wetlands (CWs), known as an alternative clean technology, have been widely used for sewage treatment. However, greenhouse gas (N₂O, CH₄ and CO₂) emissions are the accompanying problem in CWs. To mitigate the net global warming potential (GWP) with the constant removal efficiency for contaminants is attracting wide attention recently. In this study, four CWs were established to explore the effects of substrate types (gravel, walnut shell, manganese ore and activated alumina) on contaminant removal and greenhouse gas emissions. CWs using manganese ore substrate with function of electronic exchange showed high removal efficiencies on COD (90.1%), TN (65.1%), TP (97.1%) and low greenhouse gas flux. The emission fluxes of N₂O, CH₄ and CO₂ were 0.07-0.20, 2.00-252.30 and 337.54-782.57 mg m^-2 h^-1, respectively. Especially, the lowest average CH₄ emission flux in the manganese ore CW was only 2.00 mg m^-2 h^-1 while those of N₂O in walnut shell CW was only 0.07 mg m^-2 h^-1, which will make a significant contribution on the mitigation of GWP of CWs. High-throughput sequencing results indicated that microbial community diversity and richness changed significantly among different substrates. The high pmoA and low mcrA, caused by the introduction of manganese ore as substrate, also explained why there was little CH₄ emission in CWs. Our study provided new insights into GWP mitigation and contaminant removal enhancement in CWs using optimal substrate.

Metagenomics survey unravels diversity of biogas microbiomes with potential to enhance productivity in Kenya

The obstacle to optimal utilization of biogas technology is poor understanding of biogas microbiomes diversities over a wide geographical coverage. We performed random shotgun sequencing on twelve environmental samples. Randomized complete block design was utilized to assign the twelve treatments to four blocks, within eastern and central regions of Kenya. We obtained 42 million paired-end reads that were annotated against sixteen reference databases using two ENVO ontologies, prior to β-diversity studies. We identified 37 phyla, 65 classes and 132 orders. Bacteria dominated and comprised 28 phyla, 42 classes and 92 orders, conveying substrate's versatility in the treatments. Though, Fungi and Archaea comprised 5 phyla, the Fungi were richer; suggesting the importance of hydrolysis and fermentation in biogas production. High β-diversity within the taxa was largely linked to communities' metabolic capabilities. Clostridiales and Bacteroidales, the most prevalent guilds, metabolize organic macromolecules. The identified Cytophagales, Alteromonadales, Flavobacteriales, Fusobacteriales, Deferribacterales, Elusimicrobiales, Chlamydiales, Synergistales to mention but few, also catabolize macromolecules into smaller substrates to conserve energy. Furthermore, δ-Proteobacteria, Gloeobacteria and Clostridia affiliates syntrophically regulate PH2 and reduce metal to provide reducing equivalents. Methanomicrobiales and other Methanomicrobia species were the most prevalence Archaea, converting formate, CO2(g), acetate and methylated substrates into CH4(g). Thermococci, Thermoplasmata and Thermoprotei were among the sulfur and other metal reducing Archaea that contributed to redox balancing and other metabolism within treatments. Eukaryotes, mainly fungi were the least abundant guild, comprising largely Ascomycota and Basidiomycota species. Chytridiomycetes, Blastocladiomycetes and Mortierellomycetes were among the rare species, suggesting their metabolic and substrates limitations. Generally, we observed that environmental and treatment perturbations influenced communities' abundance, β-diversity and reactor performance largely through stochastic effect. Understanding diversity of biogas microbiomes over wide environmental variables and its' productivity provided insights into better management strategies that ameliorate biochemical limitations to effective biogas production.

Aerobic biodegradation of p-nitrophenol in a nitrifying sludge bioreactor: System performance, sludge property and microbial community shift

The system performance, sludge property and microbial community shift were evaluated in a nitrifying sludge (NS) bioreactor for simultaneous treating p-Nitrophenol (PNP) and high ammonia wastewater. After long-term acclimation for 80 days, the removal efficiencies of PNP and NH₄⁺-N reached to 99.9% and 99.5%, respectively. Meanwhile, the effluent PNP gradually decreased from 7.9 to 0.1 mg/L by acclimation of sludge. The particle size of NS increased from 115.2 μm to 226.3 μm accompanied by the decreased zeta potential as a self-protection strategy. The presence of PNP exposure altered the effluent soluble microbial products (SMP) fluorescent components and molecular composition. The increase in the relative abundance of Thauera, Nitrospiraceae and Nitrosomonas indicated the nitrification and denitrification capacities of NS increased, which maybe the PNP cometabolic biodegradation effect. Moreover, Ignavibacteria and Aeromonas were responsible as the dominant bacteria for degrading PNP in the nitrifying system.

NGS-based characterization of microbial diversity and functional profiling of solid tannery waste metagenomes

Tanneries pose a serious threat to the environment by generating large amount of solid tannery waste (STW). Two metagenomes representing tannery waste dumpsites Jajmau (JJK) and Unnao (UNK) were sequenced using Illumina HiSeq platform. Microbial diversity analysis revealed domination of Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Planctomycetes in both metagenomes. Presence of pollutant degrading microbes such as Bacillus, Clostridium, Halanaerobium and Pseudomonas strongly indicated their bioremediation ability. KEGG and SEED annotated main functional categories included carbohydrate metabolism, amino acids metabolism, and protein metabolism. KEGG displayed 5848 and 9633 proteases encoding ORFs compared to 5159 and 8044 ORFs displayed by SEED classification in JJK and UNK metagenomes, respectively. Abundantly present serine- and metallo-proteases belonging to Bacillaceae, Clostridiaceae, Xanthomonadaceae, Flavobacteriaceae and Chitinophagaceae families exhibited proteinaceous waste degrading ability of these metagenomes. Further structural and functional analysis of metagenome encoded enzymes may facilitate the discovery of novel proteases useful in bioremediation of STW.

How the bacterial community of a tannery effluent responds to bioaugmentation with the consortium SFC 500-1. Impact of environmental variables

Bioaugmentation with the consortium SFC 500-1 is a promising alternative to remediate wastewaters, such as tannery effluents. With the aim of assessing the changes produced in response to bioaugmentation, bacterial 16S rDNA genes were sequenced with Illumina MiSeq Platform. Additionally, bacterial and fungal groups were analyzed through standard culture dependent methods. The impact of diverse physico-chemical and microbiological parameters on the prokaryotic diversity was also evaluated throughout. Bacteroidetes, Firmicutes and Proteobacteria, represented together up to 91% of the total number of sequences obtained from the tannery effluent. Diversity decreased immediately after inoculation, due to an increase in the representation of the taxa to which the added consortium belongs. However, bioaugmentation produced no greater variations since only a 10% of unique operational taxonomic units were found in the inoculated treatment. An increase in the abundance of Myroides and a reduction in the representation of Proteiniclasticum and Halomonas were major observed variations. On the other hand, pH and dissolved oxygen constituted main environmental factors affecting the structure of the prokaryotic communities. In all treatments yeasts increased over time, to the detriment of filamentous fungi. Together, data from this report may contribute to the development of improved bioremediation strategies of industrial wastewaters.

Enhancement of facultative anaerobic denitrifying communities by oxygen release from roots of the macrophyte in constructed wetlands

The radial oxygen loss (ROL) of wetland plants is a crucial factor that can influence the efficiency required for nitrogen (N) removal and microbial activities responsible for N removal in constructed wetlands (CWs). However, the shift of microbial community in different niches in response to ROL has been rarely studied. This study aims to unravel the link between the ROL and microbial response in sediment, water and rhizoplane by a surface flow CW planted with Myriophyllum aquaticum for treating high-strength swine wastewater. Ti³⁺-citrate colorimetric method demonstrated that M. aquaticum was a wetland species with a ROL of 0.019 mg/h/plant. Using quantitative polymerase chain reactions (qPCR) and high-throughput sequencing of microbial 16S rRNA gene, we demonstrated that the abundance of facultative anaerobic denitrifiers in the rhizoplane was the most of the three niches, that in the water (5-10 cm) was the less and that in the sediment was the least. Acinetobacter was enriched and dominated amongst denitrifiers in the water. Denitrifiers in the rhizoplane were mainly dominated by enriched Pseudomonas, Aeromonas, and Acinetobacter. The theoretical calculation of oxygen sources and consumptions indicated that water reaeration should support the oxygen demands for nitrification in the aerobic layer (0-5 cm), and the ROL could stimulate the growth of facultative anaerobic denitrifiers in the rhizoplane and water (5-10 cm) to achieve denitrification within CW systems.

Formation of odorant haloanisoles and variation of microorganisms during microbial O-methylation in annular reactors equipped with different coupon materials

Taste and odor (T & O) issues in drinking water have become serious problems which cannot be ignored by customers. Several studies have confirmed that microbes in water can biotransform halophenols (HPs) to haloanisoles (HAs) with earthy and musty flavors via microbial O-methylation. In this paper, the formation of 2-chloroanisole (2-CA), 2,4-dichloroanisole (2,4-DCA), 2,4,6-trichloroanisole (2,4,6-TCA), 2,3,6-trichloroanisole (2,3,6-TCA) and 2,4,6-tribromoanisole (2,4,6-TBA), and the microbial variation during the microbial O-methylation were investigated in annular reactors (ARs) with three coupon materials. For precursors, 42.5% of 2-CP and 68.9% of 2,4-DCP decayed during the reaction. Among the five HAs, the formation rate constant followed an order of 2,4,6-TCA > 2-CA > 2,4,6-TBA > 2,4-DCA ~ 2,3,6-TCA, while [HA]_max followed a totally opposite one. The simulated flow velocity had no significant effect (p > 0.05) on HA formation. Ductile iron (DI) AR could produce more HAs than stainless steel (SS) and polyvinyl chloride (PVC) ARs. The final HA molar concentration followed an order of 2,3,6-TCA > 2,4-DCA > 2,4,6-TBA ~ 2,4,6-TCA > 2-CA, which might be explained by multiple factors including HP's dissociation degree, halogen atom's steric hindrance and specificity of HP O-methyltransferases. During the reaction, the microbial biomass dramatically increased 6.8-9.0 times in bulk water but dropped significantly on coupon biofilms. The effect of HPs significantly changed the bacterial communities on coupon in terms of composition and diversity, and declined the relative abundance of HA-producing bacteria, while fungi and their HA-producing genus showed better resistance ability towards HPs. By using Pearson correlation analysis, a significant correlation (p = 0.0003) was found between [HA]_max and initial coupon biofilm biomass. Finally, a linear relationship was established between initial total biomass and HA formation potential.

Evaluation of anionic surfactant removal by anaerobic degradation of commercial laundry wastewater and domestic sewage

An expanded granular sludge bed reactor was evaluated for the anaerobic digestion of commercial laundry wastewater and domestic sewage focused on the removal of linear alkylbenzene sulfonate (LAS). The reactor was operated in three stages, all under mesophilic conditions and with a hydraulic retention time of 36 h. At stage I, the laundry wastewater was diluted with tap water (influent: 15.3 ± 4.9 mg LAS/L); at stage II, 50% of the feed volume was domestic sewage and 50% was a mixture of tap water and laundry wastewater (influent: 15.8 ± 4.9 mg LAS/L); and at stage III, only domestic sewage was used as a diluent of the laundry wastewater (influent: 24.1 ± 4.1 mg LAS/L). Due to the addition of domestic sewage the organic compounds content and LAS in the influent increased. Under such conditions, it was observed that LAS removal rate decreased from 77.2 ± 14.9% (stage I) to 55.3 ± 18.4% (stage III). Statistical tests indicated that the decrease of the LAS removal rate was significant and indicated a correlation between the removal of LAS and specific organic loading rate. The analysis of 16S rRNA gene sequencing revealed genera similar to Geobacter, Desulfovibrio, Syntrophomonas, Syntrophus, Desulfobulbus, Desulfomonile, and Desulfomicrobium, which were related to the degradation of LAS.

Effects of 4-chlorophenol toxicity on sludge performance and microbial community in sequencing batch reactors

In this study, the effects of 4-chlorophenol (4-CP) influent concentrations ranging from 10 to 100 mg L^-1 on sludge toxicity, enzymatic activity and microbial community, along with their correlations, were investigated in a sequencing batch bioreactor (SBR), which was defined as the acclimated SBR. Another SBR was set as a control group that did not receive the influent 4-CP. The results showed that the sludge toxicity increased as the influent 4-CP increased, exhibiting a positive correlation with 4-CP loads. The enzymatic activity was stimulated after long-term acclimation with 4-CP and was positively related to the 4-CP loads and sludge toxicity. During the stable operational stages of the acclimated SBR, the microbial diversity first increased and then decreased as the 4-CP loads increased, while the similarity of the microbial community between the acclimated and control SBRs decreased with increasing 4-CP loads. The aim of this study is to provide theoretical support for reducing sludge toxicity in industrial wastewater treatment.

Enhanced triclosan and nutrient removal performance in vertical up-flow constructed wetlands with manganese oxides

Limited concentrations of oxygen in constructed wetlands (CWs) have inhibited their ability to remove emerging organic contaminants (EOCs) at μg/L or ng/L levels. Manganese (Mn) oxides were proposed as a solution, as they are powerful oxidants with strong adsorptive capabilities. In the present study, triclosan (TCS) was selected as a typical EOC, and CW microcosms with Mn oxides (birnessite) coated sand (B-CWs) and without (C-CWs) were developed to test the removal capacities of TCS and common nutrients. We found that the addition of Mn oxides coated sand significantly improved removal efficiencies of TCS, NH₄-N, COD, NO₃-N and TP (P < 0.05). The average concentration of Mn(II) effluent was 0.036 mg L^-1, mostly lower than the drinking water limit. To gain insight into the mechanisms of pollution removal, Mn transformation, dissolved oxygen (DO) distribution, bacterial abundance, and microbial community composition were also investigated. Maximum Mn(II) was detected at 20 cm height of the B-CWs in anoxic zone. Although Mn-oxidizing bacteria existed in the layer of 30-50 cm with 10³-10⁴ CFU g^-1 dry substate, Mn oxides were only detected at height from 40 to 50 cm with rich oxygen in B-CW. The quantities of bacterial 16S rRNA, amoA, narG and nosZ were not significantly different between two systems (P > 0.05), while Illumina high-throughput sequencing analysis revealed that the abundance of denitrifying bacteria was significant higher in B-CWs, and the abundance of Gammaproteobacteria that have a recognized role in Mn transformation were significantly increased. The results indicated that Mn oxides could enhance TCS and common pollutants removal in both anoxic and aerobic areas through the recycling of Mn between Mn(II) and biogenic Mn oxides.

Degradation of 2,4,6-trichlorophenol and determination of bacterial community structure by micro-electrical stimulation with or without external organic carbon source

This study aimed to investigate the degradation efficiency of 2,4,6-trichlorophenol through a batch of potentiostatic experiments (0.2 V vs. Ag/AgCl). Efficiencies in the presence and absence of acetate and glucose were compared through open-circuit reference experiments. Significant differences in degradation efficiency were observed in six reactors. The highest and lowest degradation efficiencies were observed in the closed-circuit reactor fed with glucose and in the open-circuit reactor, respectively. This finding was due to the enhanced bacterial metabolism caused by the application of micro-electrical field and degradable organics as co-substrates. The different treatment efficiencies were also caused by the distinct bacterial communities. The composition of bacterial community was affected by adding different organics as co-substrates. At the phylum level, the most dominant bacteria in the reactor with the added acetate and glucose were Proteobacteria and Firmicutes, respectively.

Degradation of 4-chlorophenol and microbial diversity in soil inoculated with single Pseudomonas sp. CF600 and Stenotrophomonas maltophilia KB2

Soil contamination with chlorophenols is a serious problem all over the world due to their common use in different branches of industry and agriculture. The objective of this study was to determine whether bioaugmenting soil with single Pseudomonas sp. CF600 and Stenotrophomonas maltophilia KB2 and additional carbon sources such as phenol (P) and sodium benzoate (SB) could enhance the degradation of 4-chlorophenol (4-CP). During the degradation experiment, the number of bacteria as well as the structural and functional diversity of the soil microbial communities were determined. It was found that the most effective degradation of 4-CP in the soil was observed after it was inoculated with CF600 and the addition of SB. The biodegradation of five doses of 4-CP in this soil proceeded within 100 days. At the same time, the rate of the disappearance of 4-CP in the soil that had been bioaugmented with CF600 and contaminated with 4-CP and P was 5-6.5 times lower compared to its rate of disappearance in the soil that had been contaminated with 4-CP. The biodegradation of 4-CP in all of the treated and untreated soils was accompanied by a systematic decrease in the number of heterotrophic bacteria (THB) ranging between 13 and 40%. It was also proven that the tested aromatic compounds affected the soil microbial community structure through an increase in the marker fatty acids for Gram-negative bacteria (BG-) and fungi (F). The essential changes in the patterns of the fatty acid methyl esters (FAMEs) for the polluted soil included an increase in the fatty acid saturation and hydroxy fatty acid abundance. The obtained results also indicated that the introduction of CF600 into the soil contaminated with 4-CP and SB or P caused an increase in the functional diversity of the soil microorganisms. In contrast, in the soil that had been inoculated with KB2 and in the non-inoculated soil, the addition of 4-CP and P decreased the microbial activity. In conclusion, the inoculation of both strains into contaminated soil with aromatic compounds caused irreversible changes in the functional and structural diversity of the soil microbial communities.

A new screened microbial consortium OEM2 for lignocellulosic biomass deconstruction and chlorophenols detoxification

Recalcitrance limits biomass application in biorefinery. It is even more so when toxic chlorophenols are present. In this study, we screened a microbial consortium, OEM2, for lignocellulose deconstruction and chlorophenols detoxification through a short-term and efficient screening process. Microbial consortium OEM2 had a good buffer capability in the cultivation process and exhibited a high xylanase activity, with over 85% hemicellulose degradation within 12 days. Throughout the treatment process, 41.5% rice straw decomposition on day 12 and around 75% chlorophenols (MCP, 2,4-DCP, 2,4,6-TCP) removal on day 9, were recorded. Moreover, Fourier translation infrared spectroscopy (FTIR) analysis indicated that chemical bonds and groups (eg. hydrogen-bond, β-1,4 glycosidic bond, lignin-carbohydrate cross-linking) in the rice straw were broken. Cuticle and silica layer destruction and subsequent exposed cellulose fibers were observed by scanning electron microscopy (SEM). Microbial consortium OEM2 diversity analysis by 16S rRNA gene sequencing indicated that Proteobacteria (41.3%) was the most abundant phylum and the genera Paenibacillus and Pseudomonas played an important role in the lignocellulose decomposition and chlorophenols detoxification. This study developed a faster and more efficient strategy to screen a specific microbial consortium. And the new microbial consortium, OEM2, makes lignocellulose more accessible and complex pollutants unproblematic in the further biorefinery process.

Impact of mild alkali dosage on immobilized Exiguobacterium spp. mediated cost and energy efficient sludge disintegration

Approaches to (extracellular polymeric substance) EPS removal were studied with major aim to enhance the biodegradability and sludge solubilization. In this study, a novel approach of entrapment of bacterial strain was carried out to achieve long term activity of protease secreting bacteria Exiguobacterium sp. A mild treatment of potassium hydroxide (KOH) was applied to remove EPS which was followed by entrapment under the biological pretreatment. The efficiency of Exiguobacterium was predicted through dissolvable organic and suspended solids (SS) reduction. The maximum dissolvable organic matter released was 2300mg/L with the solubilization of 23% which was obtained for sludge without EPS (SWOE). For dissolvable organic release, SWOE showed higher final methane production of 232mL/g COD at the production rate of 16.2mL/g COD.d. The SWOE pretreatment was found to be cost effective and less energy intensive beneficial in terms of energy and cost (43.9KWh and -8.2USD) when compared to sludge with EPS (SWE) pretreatment (-177.6KWh and -91.23USD).

Effect of sudden addition of PCE and bioreactor coupling to ZVI filters on performance of fluidized bed bioreactors operated in simultaneous electron acceptor modes

The present work evaluated the effects of (i) feeding a water contaminated with 80 mg/L PCE to bioreactors seeded with inoculum not acclimated to PCE, (ii) coupling ZVI side filters to bioreactors, and (iii) working in different biological regimes, i.e., simultaneous methanogenic aeration and simultaneous methanogenic-denitrifying regimes, on fluidized bed bioreactor performance. Simultaneous electron acceptors refer to the simultaneous presence of two compounds operating as final electron acceptors in the biological respiratory chain (e.g., use of either O₂ or NO₃^- in combination with a methanogenic environment) in a bioreactor or environmental niche. Four lab-scale, mesophilic, fluidized bed bioreactors (bioreactors) were implemented. Two bioreactors were operated as simultaneous methanogenic-denitrifying (MD) units, whereas the other two were operated in partially aerated methanogenic (PAM) mode. In the first period, all bioreactors received a wastewater with 1 g chemical oxygen demand of methanol per liter (COD-methanol/L). In a second period, all the bioreactors received the wastewater plus 80 mg perchloroethylene (PCE)/L; at the start of period 2, one MD and one PAM were coupled to side sand-zero valent iron filters (ZVI). All bioreactors were inoculated with a microbial consortium not acclimated to PCE. In this work, the performance of the full period 1 and the first 60 days of period 2 is reported and discussed. The COD removal efficiency and the nitrate removal efficiency of the bioreactors essentially did not change between period 1 and period 2, i.e., upon PCE addition. On the contrary, specific methanogenic activity in PAM bioreactors (both with and without coupled ZVI filter) significantly decreased. This was consistent with a sharp fall of methane productivity in those bioreactors in period 2. During period 2, PCE removals in the range 86 to 97 % were generally observed; the highest removal corresponded to PAM bioreactors along with the highest dehalogenation efficiency (94 %). Principal component analysis as well as cluster analysis confirmed the trends mentioned above, i.e., the better performance of PAM over MD, and the unexpected no effect of the ZVI side filters on PCE removal and dehalogenation efficiencies. To the best of our knowledge, this is the first report on the combined treatment ZVI-biological of a water polluted with PCE, where the biological operation relied on simultaneous electron acceptors.

Potential of wheat bran to promote indigenous microbial enhanced oil recovery

Microbial enhanced oil recovery (MEOR) is an emerging oil extraction technology that utilizes microorganisms to facilitate recovery of crude oil in depleted petroleum reservoirs. In the present study, effects of wheat bran utilization were investigated on stimulation of indigenous MEOR. Biostimulation conditions were optimized with the response surface methodology. The co-application of wheat bran with KNO₃ and NH₄H₂PO₄ significantly promoted indigenous MEOR (IMEOR) and exhibited sequential aerobic (O-), facultative (A_n-) and anaerobic (A₀-) metabolic stages. The surface tension of fermented broth decreased by approximately 35%, and the crude oil was highly emulsified. Microbial community structure varied largely among and in different IMEOR metabolic stages. Pseudomonas sp., Citrobacter sp., and uncultured Burkholderia sp. dominated the O-, A_n- and early A₀-stages. Bacillus sp., Achromobacter sp., Rhizobiales sp., Alcaligenes sp. and Clostridium sp. dominated the later A₀-stage. This study illustrated occurrences of microbial community succession driven by wheat bran stimulation and its industrial potential.

Changes in fatty acid composition of Stenotrophomonas maltophilia KB2 during co-metabolic degradation of monochlorophenols

The changes in the cellular fatty acid composition of Stenotrophomonas maltophilia KB2 during co-metabolic degradation of monochlorophenols in the presence of phenol as well as its adaptive mechanisms to these compounds were studied. It was found that bacteria were capable of degrading 4-chlorophenol (4-CP) completely in the presence of phenol, while 2-chlorophenol (2-CP) and 3-chlorophenol (3-CP) they degraded partially. The analysis of the fatty acid profiles indicated that adaptive mechanisms of bacteria depended on earlier exposure to phenol, which isomer they degraded, and on incubation time. In bacteria unexposed to phenol the permeability and structure of their membranes could be modified through the increase of hydroxylated and cyclopropane fatty acids, and straight-chain and hydroxylated fatty acids under 2-CP, 3-CP and 4-CP exposure, respectively. In the exposed cells, regardless of the isomer they degraded, the most important changes were connected with the increase of the contribution of branched fatty acid on day 4 and the content of hydroxylated fatty acids on day 7. The changes, particularly in the proportion of branched fatty acids, could be a good indicator for assessing the progress of the degradation of monochlorophenols by S. maltophilia KB2. In comparison, in phenol-degrading cells the increase of cyclopropane and straight-chain fatty acid content was established. These findings indicated the degradative potential of the tested strain towards the co-metabolic degradation of persistent chlorophenols, and extended the current knowledge about the adaptive mechanisms of these bacteria to such chemicals.

Biological mechanisms associated with triazophos (TAP) removal by horizontal subsurface flow constructed wetlands (HSFCW)

Triazophos (TAP) is a widely used pesticide that is easily accumulated in the environment due to its relatively high stability: this accumulation from agricultural runoff results in potential hazards to aquatic ecosystems. Constructed wetlands are generally considered to be an effective technology for treating TAP polluted surface water. However, knowledge about the biological mechanisms of TAP removal is still lacking. This study investigates the responses of a wetland plant (Canna indica), substrate enzymes and microbial communities in bench-scale horizontal subsurface-flow constructed wetlands (HSCWs) loaded with different TAP concentrations (0, 0.1, 0.5 and 5 mg · L(-1)). The results indicate that TAP stimulated the activities of superoxide dismutase (SOD) and peroxidase (POD) in the roots of C. indica. The highest TAP concentrations significantly inhibited photosynthetic activities, as shown by a reduced effective quantum yield of PS II (ΦPS II) and lower electron transport rates (ETR). However, interestingly, the lower TAP loadings exhibited some favorable effects on these two variables, suggesting that C. indica is a suitable species for use in wetlands designed for treatment of low TAP concentrations. Urease and alkaline phosphatase (ALP) in the wetland substrate were activated by TAP. Two-way ANOVA demonstrated that urease activity was influenced by both the TAP concentrations and season, while acidphosphatase (ACP) only responded to seasonal variations. Analysis of high throughput sequencing of 16S rRNA revealed seasonal variations in the microbial community structure of the wetland substrate at the phylum and family levels. In addition, urease activity had a greater correlation with the relative abundance of some functional microbial groups, such as the Bacillaceae family, and the ALP and ACP may be influenced by the plant more than substrate microbial communities.

Natural attenuation model and biodegradation for 1,1,1-trichloroethane contaminant in shallow groundwater

Natural attenuation is an effective and feasible technology for controlling groundwater contamination. This study investigated the potential effectiveness and mechanisms of natural attenuation of 1,1,1-trichloroethane (TCA) contaminants in shallow groundwater in Shanghai by using a column simulation experiment, reactive transport model, and 16S rRNA gene clone library. The results indicated that the majority of the contaminant mass was present at 2–6 m in depth, the contaminated area was approximately 1000 m × 1000 m, and natural attenuation processes were occurring at the site. The effluent breakthrough curves from the column experiments demonstrated that the effectiveness of TCA natural attenuation in the groundwater accorded with the advection-dispersion-reaction equation. The kinetic parameter of adsorption and biotic dehydrochlorination of TCA was 0.068 m³/kg and 0.0045 d^–1. The contamination plume was predicted to diminish and the maximum concentration of TCA decreased to 280 μg/L. The bacterial community during TCA degradation in groundwater belonged to Trichococcus, Geobacteraceae, Geobacter, Mucilaginibacter, and Arthrobacter.

Microbial community structure and diversity in an integrated system of anaerobic-aerobic reactors and a constructed wetland for the treatment of tannery wastewater in Modjo, Ethiopia

A culture-independent approach was used to elucidate the microbial diversity and structure in the anaerobic-aerobic reactors integrated with a constructed wetland for the treatment of tannery wastewater in Modjo town, Ethiopia. The system has been running with removal efficiencies ranging from 94%-96% for COD, 91%-100% for SO4(2-) and S(2-), 92%-94% for BOD, 56%-82% for total Nitrogen and 2%-90% for NH3-N. 16S rRNA gene clone libraries were constructed and microbial community assemblies were determined by analysis of a total of 801 unique clone sequences from all the sites. Operational Taxonomic Unit (OTU)--based analysis of the sequences revealed highly diverse communities in each of the reactors and the constructed wetland. A total of 32 phylotypes were identified with the dominant members affiliated to Clostridia (33%), Betaproteobacteria (10%), Bacteroidia (10%), Deltaproteobacteria (9%) and Gammaproteobacteria (6%). Sequences affiliated to the class Clostridia were the most abundant across all sites. The 801 sequences were assigned to 255 OTUs, of which 3 OTUs were shared among the clone libraries from all sites. The shared OTUs comprised 80 sequences belonging to Clostridiales Family XIII Incertae Sedis, Bacteroidetes and unclassified bacterial group. Significantly different communities were harbored by the anaerobic, aerobic and rhizosphere sites of the constructed wetland. Numerous representative genera of the dominant bacterial classes obtained from the different sample sites of the integrated system have been implicated in the removal of various carbon- containing pollutants of natural and synthetic origins. To our knowledge, this is the first report of microbial community structure in tannery wastewater treatment plant from Ethiopia.

Shifts in microbial community in response to dissolved oxygen levels in activated sludge

This study evaluates the degradative efficiency of activated biomass collected from a Common Effluent Treatment Plant (CETP) under three different dissolved oxygen (DO) levels, 1, 2 and 4mgl(-1). The change in bacterial diversity with reference to DO levels was also analyzed. Results demonstrate that degradative efficiency was the highest, when the reactor was maintained at 4mgl(-1) DO, but amplicon library analysis showed a greater diversity of bacteria in the reactor maintained at 2mgl(-1) DO. Bacteria belonging to the order Desulfuromonadales, Entomoplasmatales, Pasteurellales, Thermales and Chloroflexales have only been detected in this reactor. Ammonia and nitrate levels in all three reactors indicated efficient nitrification process. Results of this study offer new insights into understanding the performance of activated biomass vis-à-vis microbial diversity and degradative efficiency with reference to DO. This information would be useful in improving the efficiency of any wastewater treatment plant.

Impacts of sludge retention time on sludge characteristics and membrane fouling in a submerged osmotic membrane bioreactor

Sludge retention time (SRT) is a feasible method to alleviate the salt accumulation in the osmotic membrane bioreactor (OMBR) by discharging the waste activated sludge. In this study, effects of SRT on sludge characteristics and membrane fouling were investigated using a submerged OMBR under two SRTs of 10 and 15d. The results showed that the lower SRT was helpful for alleviating the salt accumulation and flux decline. Besides that, the removal of NH3-N was significantly influenced by SRT. SRT also had a strong effect on soluble microbial products (SMP) and microbial activity due to the variation of salinity. Microbial diversity analysis indicated that the high salinity environment in the OMBR significantly affected the microbial communities. The flux decline in the OMBR was mainly attributed to the reduced driving force resulting from the salt accumulation, and the reversible fouling was the dominant forward osmosis (FO) membrane fouling in the OMBR.

Effect of enzyme secreting bacterial pretreatment on enhancement of aerobic digestion potential of waste activated sludge interceded through EDTA

In this study, the effect of Ethylene diamine tetra acetic acid (EDTA) on Extracellular polymeric substance (EPS) removal tailed with bacterial enzymatic pretreatment on aerobic digestion of activated sludge was studied. In order to enhance the accessibility of sludge to the enzyme secreting bacteria; the extracellular polymeric substances were removed using EDTA. EDTA efficiently removed the EPS with limited cell lysis and enhanced the sludge enzyme activity at its lower concentration of 0.2 g/g SS. The sludge was then subjected to bacterial pretreatment to enhance the aerobic digestion. In aerobic digestion the best results in terms of Suspended solids (SS) reduction (48.5%) and COD (Chemical oxygen demand) solubilization (47.3%) was obtained in experimental reactor than in control. These results imply that aerobic digestion can be enhanced efficiently through bacterial pretreatment of EPS removed sludge.