Analysis Of Microbial Community Structure Research Articles

Assessing the efficiency and microbial diversity of H2S-removing biotrickling filters at various pH conditions

This study aimed to investigate the operation of three parallel biotrickling filters (BTFs) in removing H2S at different pH conditions (haloalkaliphilic, neutrophilic, and acidophilic) and their associated microbial population in the biodesulfurization process. BTF columns were inoculated with enriched inoculum and experiments were performed by gradually reducing Empty Bed Retention Time (EBRT) and increasing inlet concentration in which the maximum removal efficiency and maximum elimination capacity in EBRT 60 s reached their maximum level in haloalkaline condition (91% and 179.5 g S-H2S m−3 h−1). For visualizing the attached microbial biofilms on pall rings, Scanning Electron Microscopy (SEM) was used and microbial community structure analysis by NGS showed that the most abundant phyla in haBTF, nBTF, and aBTF belong to Gammaproteobacteria, Betaproteobacteria, and Acidithiobacillia, respectively. Shannon and Simpson indexes evaluation showed a lower diversity of bacteria in the aBTF reactor than that of nBTF and haBTF and beta analysis indicated a different composition of bacteria in haBTF compared to the other two filters. These results indicated that the proper performance of BTF under haloalkaliphilic conditions is the most effective way for H2S removal from air pollutants of different industries.Graphical

Transcriptome Analysis: A Powerful Tool to Understand Individual Microbial Behaviors and Interactions in Ecosystems.

Transcriptome analysis is a powerful tool for studying microbial ecology, especially individual microbial functions in an ecosystem and their interactions. With the development of high-throughput sequencing technology, great progress had been made in analytical methods for microbial communities in natural environments. 16S rRNA gene amplicon sequencing (i.e., microbial community structure analysis) and shotgun metagenome analysis have been widely used to determine the composition and potential metabolic capability of microorganisms in target environments without requiring culture. However, even if the types of microorganisms present and their genes are known, it is difficult to determine what they are doing in an ecosystem. Gene expression analysis (transcriptome analysis; RNA-seq) is a powerful tool to address these issues. The history and basic information of gene expression analysis, as well as examples of studies using this method to analyze microbial ecosystems, are presented.

Rumen fluid pretreatment promotes anaerobic methane production: revealing microbial dynamics driving increased acid yield from different concentrations of corn straw.

In this work, the corn straw (CS) with concentrations of 3%, 6%, and 9% (w/v) were pretreated by rumen fluid (RF) and then used for batched mesophilic biogas production. The results showed that after a 6-day pretreatment, volatile fatty acid (VFAs) production of 3.78, 8.27, and 10.4 g/L could be found in 3%, 6%, and 9%, respectively. When concerning with biogas production, the highest accumulative methane production of 149.1 mL CH4/g volatile solid was achieved by 6% pretreated CS, which was 22% and 45% higher than 3% and 9%, respectively. Also, it was 3.6 times higher than the same concentration of unpretreated CS. The results of the microbial community structure analysis revealed that the 6% CS pretreatment not only maintained a microbial community with the highest richness and diversity, but also exhibited the highest relative abundance of Firmicutes (45%) and Euryarchaeota (3.9%). This high abundance was conducive to its elevated production of VFAs and methane. These findings provide scientific reference for the utilization of CS and support the development of agricultural waste resource utilization and environmental protection.

Response of the Endophytic Microbial Composition in Amaranthus Roots to Different Fertilization Treatments

To explore how endophytic microbial compositions in amaranth roots are influenced by various fertilization methods and to determine whether these microbes are associated with amaranthin formation, we conducted an analysis of the endophytic microbial community structure. The roots of amaranth plants subjected to different fertilization treatments—conventional fertilization without potassium (NP), conventional fertilization without phosphorus (NK), conventional fertilization without nitrogen (PK), and balanced fertilization (NPK)—were examined. The results showed that the proportions of Streptomyces, Actinospica, and Burkholderia-Caballeronia-Paraburkholderia in the amaranth roots under the balanced fertilization (NPK) treatment were all greater than those in the amaranth roots under the nitrogen (PK), phosphorus (NK), and potassium (NP) deficiency fertilization treatments. In contrast, the proportions of Phenylobacterium, Acrocalymma, Neocosmospora, Fusarium, Acidovorax, Gibellulopsis, Cladosporium, Dactylonectria, and Gibberella in the amaranth roots under the nutrient deficiency fertilization (NP, NK, and PK) treatments were higher than those in the amaranth roots under the balanced fertilization treatment. Additionally, a significantly positive correlation was found between Streptomyces and the amaranthin content. Furthermore, Acrocalymma, Neocosmospora, and Fusarium exhibited significantly negative correlations with the amaranthin content. The above results suggested that endophytes could easily colonize in amaranth roots as beneficial microorganisms under balanced fertilization conditions. In other words, the balanced fertilization (N, P and K fertilizers are 188.0, 53.0 and 50.0 kg·hm−2, respectively) could recruit more beneficial endogenous microorganisms in amaranth roots for improving their growth and quality.

New insights into microbial community for simultaneous removal of carbon and nitrogen via heterotrophic nitrification aerobic denitrification process

Heterotrophic nitrification aerobic denitrification (HNAD) process is considered to be a promising strategy for efficient removal of nitrogen and refractory organic pollutants from aquatic environments. However, isolated single strains or microbial communities of HNAD in most studies suffer from severe inadaptability in the face of complex aquatic environments. Therefore, the existence of fundamental microbial communities that is able to adapt to contaminants through shaping its structure and then remove the pollutants is a promising solution to this deficiency. Herein, we introduced three aromatic compounds (ACs) (2,4,6-Trinitrotoluene, Aniline, and Phenanthrene), and established HNAD microcosms containing the different ACs and nitrogen through aeration. Impressively, the removal efficiencies of aerobic microcosms were nearly 94.5%, 99.4% and 100% for 2,4,6-Trinitrotoluene, Aniline and Phenanthrene, respectively, and above 90% for total nitrogen (TN), demonstrating superior ACs and nitrogen elimination capabilities. Meanwhile, analysis of microbial community structure and symbiont networks exhibited that there are eight commonly dominant genera in different microcosms, namely Arthrobacter, Bacillus, Sphingobium, Massilia, Novosphingobium, Noviherbaspinrillum, Lysobacter and Azohydromonas. Notably, these core bacteria changed only in relative abundance with the microcosms, and had been proven that they all have laudable carbon and nitrogen conversion capabilities. This finding confirmed the existence of basic microbial communities whose dominant species coordinate with each other to adapt to different water environments for the purpose of water purification. Finally, the mechanism of nitrogen transformation at both gene and enzyme levels was revealed by KEGG enrichment analysis. Summarily, this study will provide valuable references for future development of water treatment technologies.

Metagenomic landscape of sediments of river Ganga reveals microbial diversity, potential plastic and xenobiotic degradation enzymes

The Ganga is the largest river in India, serves as a lifeline for agriculture, drinking water, and religious rites. However, it became highly polluted due to the influx of industrial wastes and untreated sewages, leading to the decline of aquatic biodiversity. This study investigated the microbial diversity and plastic-xenobiotic degrading enzymes of six sediment metagenomes of river Ganga at Prayagraj (RDG, TSG, SDG) and Devprayag (KRG, BNG, BRG). The water quality parameters, higher values of BOD (1.8–3.7 ppm), COD (23–29.2 ppm) and organic carbon (0.18–0.51%) were recorded at Prayagraj. Comparative analysis of microbial community structure between Prayagraj and Devprayag revealed significant differences between Bacteroidetes and Firmicutes, which emerging as the predominant bacterial phyla across six sediment samples. Notably, their prevalence was highest in the BRG samples. Furthermore, 25 OTUs at genus level were consistent across all six samples. Alpha diversity exhibited minimal variation among samples, while beta diversity indicated an inverse relationship between species richness and diversity. Co-occurrence network analysis established that genera from the same and different groups of phyla show positive co-relations with each other. Thirteen plastic degrading enzymes, including Laccase, Alkane-1 monooxygenase and Alkane monooxygenase, were identified from six sediment metagenomes of river Ganga, which can degrade non-biodegradable plastic viz. Polyethylene, Polystyrene and Low-density Polyethelene. Further, 18 xenobiotic degradation enzymes were identified for the degradation of Bisphenol, Xylene, Toluene, Polycyclic aromatic hydrocarbon, Styrene, Atrazene and Dioxin etc. This is the first report on the identification of non-biodegradable plastic degrading enzymes from sediment metagenomes of river Ganga, India. The findings of this study would help in pollution abatement and sustainable management of riverine ecosystem.

Combined metagenomics and metabolomic analysis of microbial community structure and metabolic function in continuous soybean cropping soils of Songnen Plain, China

Continuous cropping has a negative effect on soybean yield. In this study, a positioning experiment was conducted starting in 2015, with three treatments: maize–soybean rotation (SMR), 2-year maize, 2-year soybean rotation cropping (SC2), and 8-year soybean continuous cropping (SC8). We determined soybean yields (2015–2022) and analyzed soil microbial communities, functions, and metabolites composition in the 0–20 cm tillage layer using metagenomics technology and GC–MS technology during soybean flowering in 2022. Results indicated that continuous cropping (SC8) significantly reduced soybean yield compared to crop rotation (SMR) during the experimental period, while SC8 showed higher yield than SC2 in 2022. Compared to SMR, SC8 significantly increased soil N content and significantly decreased pH and TP, AP, and AK content. However, the pH and AK contents of SC8 were significantly higher than those of SC2. LeFSe analysis showed that Friedmanniella, Microlunatus, Nitrososphaera, Rubrobacter, Geodermatophilus, Nitriliruptor were enriched in SC8. Gaiella, Sphaerobacter, Methyloceanibacter were enriched in SC2. Sphingomonas, Cryobacterium, Marmoricola, Haliangium, Arthrobacter, Ramlibacter, Rhizobacter, Pseudolabrys, Methylibium, Variovorax were enriched in SMR. And the relative abundance of Cryobacterium, Marmoricola, Haliangium, Arthrobacter, Ramlibacter, Rhizobacter, Methylibium, Variovorax was significantly positively correlated with yield, while the relative abundance of Gaiella and Sphaerobacter was significantly negatively correlated with yield. SC8 significantly increased the abundance of genes in nitrogen metabolism and significantly decreased the abundance of genes related to phosphorus and potassium metabolism compared with SMR. However, the abundance of genes in potassium metabolism was significantly higher in SC8 than in SC2. Metabolomic analysis showed that compared to SMR, SC8 decreased the abundance of carbohydrates, ketones, and lipid. However, the abundance of carbohydrates, ketones, and lipid was significantly higher in SC8 than in SC2. Mantel test showed that soil pH and AK significantly affected soil microbial community, function, and metabolite composition. Correlation analysis showed significant correlation between soil metabolites and microorganisms, metabolic functions.Graphical

Induced domestication of humic reduction-denitrification coupled bacteria improved treatment of sediment: Performance, remediation effect, and metabolic mechanisms

The high organic matter in river sediment primarily induces black and odorous rebound. Traditional humic-reducing bacteria demonstrate relatively single metabolic functions and restrain the remediation within complex sediment environments. In addition, Ca(NO3)2 is commonly utilized in synergistic with bioremediation to improve the reducing environment of sediments. In this study, a multifunctional bacterial community with humic reduction-denitrification coupled bacteria was domesticated by the step-feeding strategy in an anaerobic baffle reactor (ABR). The performance, remediation effect, and metabolic mechanisms were analyzed. The results indicated that humic-reducing bacteria (HRB) and denitrifying-humic-reducing bacteria (DF/HRB) have quinone-reduction and denitrification capabilities. The synergistic effect of DF/HRBs and Ca(NO3)2 was superior to HRBs and Ca(NO3)2 on the removal of total organic matter(TOM). Microbial community structure analysis revealed an enhanced relative abundance of denitrification and humic-reducing bacteria (e.g., Thauera, Pseudomonas, Sulfurospirillum, Desulfovibrio, Geobacter) in the DF/HRB, resulting in a superior synergistic effect of DF/HRBs with Ca(NO3)2. This work helps to present an innovative approach to domesticate humic-reducing bacteria suited for the remediation environment effectively. It also expands the application of humic-reducing bacteria for in-situ anaerobic remediation of river sediments.

Analysis of Microbial Diversity and Community Structure of Rhizosphere Soil of Three Astragalus Species Grown in Special High-Cold Environment of Northwestern Yunnan, China.

Astragalus is a medicinal plant with obvious rhizosphere effects. At present, there are many Astragalus plants with high application value but low recognition and resource reserves in the northwestern area of Yunnan province, China. In this study, metagenomics was used to analyze the microbial diversity and community structure of rhizosphere soil of A. forrestii, A. acaulis, and A. ernestii plants grown in a special high-cold environment of northwestern Yunnan, China, at different altitudes ranging from 3225 to 4353 m. These microbes were taxonomically annotated to obtain 24 phyla and 501 genera for A. forrestii, 30 phyla and 504 genera for A. acaulis, as well as 39 phyla and 533 genera for A. ernestii. Overall, the dominant bacterial phyla included Proteobacteria, Actinobacteria, and Acidobacteria, while the dominant fungal ones were Ascomycota and Basidiomycota. At the genus level, Bradyrhizobium, Afipia, and Paraburkholderia were the most prevalent bacteria, and Hyaloscypha, Pseudogymnoascus, and Russula were the dominant fungal genera. Some of them are considered biocontrol microbes that could sustain the growth and health of host Astragalus plants. Redundancy analysis revealed that pH, TN, and SOM had a significant impact on the microbial community structures (p < 0.05). Finally, triterpene, flavonoid, polysaccharide, and amino acid metabolisms accounted for a high proportion of the enriched KEGG pathways, which possibly contributed to the synthesis of bioactive constituents in the Astragalus plants.

Medium optimization and dust suppression performance analysis of microbial-based dust suppressant compound by response surface curve method.

At present, microbial dust suppressants based on microbial communities lack necessary systematic analysis of factors affecting dust suppression performance. Therefore, in this study, the response surface curve method was used to optimize the culture conditions for enrichment of urease-producing microorganisms from activated sludge. The results indicated that when urea = 9.67gL-1, NH4Cl = 5.21gL-1, and pH = 9.57, the maximum urease activity of urease-producing microbial community (UPMC) was 8.22mMmin-1. The UPMC under optimized culture conditions reached a mineralization rate of 98.8% on the 1st day of mineralization. Ureolysis is one of the biological mechanisms that trigger microbial mineralization with the consequent effect of dust suppression. The analysis of microbial community structure indicated that the urease-producing bacteria Sporosarcina sp. had the highest abundance at the genus level in the microbial-based dust suppressant compound. Jeotgalicoccus sp. plays an important role in improving and maintaining the stability of urease. In addition, the optimal UPMC had low pathogenicity, which is extremely attractive for the safe application of microbial dust suppressants.

Magnetic porous microspheres enhancing the anaerobic digestion of sewage sludge: Synergistic free and attached methanogenic consortia

The addition of exogenous materials is a commonly reported method for promoting the anaerobic digestion (AD) of sludge. However, most exogenous materials are nano-sized and their use encounters problems relating to a need for continuous replenishment, uncontrollability and non-recyclability. Here, magnetic porous microspheres (MPMs), which can be controlled by magnetic forces, were prepared and used to enhance the methanogenesis of sludge. It was observed that the MPMs were spherical particles with diameters of approximately 100 µm and had a stable macroporous hybrid structure of magnetic cores and polymeric shells. Furthermore, the MPMs had good magnetic properties and a strong solid–liquid interfacial electron transfer ability, suggesting that MPMs are excellent carriers for methanogenic consortia. Experimental results showed that the addition of MPMs increased methane production and the proportion of methane in biogas from AD by 100.0 % and 21.2 %, respectively, indicating the MPMs notably enhanced the methanogenesis of sludge. Analyses of variations in key enzyme activities and electron transfer in sludge samples with and without MPMs in AD revealed that the MPMs significantly enhanced the activities of key enzymes involved in hydrolysis, acidification and methanation. This was achieved mainly by enhancing the extracellular electron transfer to strengthen the proton motive force on the cell membrane, which provides more energy generation for methanogenic metabolism. A careful examination of the variations in the morphology, pore structure and magnetism of the MPMs before and after AD revealed that the MPMs increased the prevalence of many highly active anaerobes, and that this did not weaken the magnetic performance. The microbial community structure and metatranscriptomic analysis further indicated that the acetotrophic methanogens (i.e., Methanosaeta) were mainly in a free state and that CO2-reducing methanogens (i.e., Methanolinea and Methanobacterium) mainly adhered to the MPMs. The above synergistic metabolism led to efficient methanogenesis, which indicates that the MPMs optimised the spatial ecological niche of methanogenic consortia. These findings provide an important reference for the development of magnetic porous materials promoting AD.

A comparative analysis of soil physicochemical properties and microbial community structure among four shelterbelt species in the northeast China plain.

The focal point of this study lies in the implementation of a controlled experiment conducted under field conditions. In this experiment, we deliberately selected four shelterbelts within the same field, characterized by identical planting density, and planting year. This deliberate selection effectively mitigated the potential impact of extraneous factors on the three microbiomes, thereby enhancing the reliability and validity of our findings.

Advanced electrolysis sulfur-based biofiltration for simultaneous total nitrogen removal and estrogen toxicity reduction from low carbon-to-nitrogen ratio wastewater

A sulfur-based biofilter enhanced by phosphate modified activated carbon as particle electrodes was constructed to simultaneously remove total nitrogen (TN) and estrogen from low carbon-to-nitrogen ratio (C/N) wastewater containing 1 mg/L 17-alpha-ethinylestradiol (EE2). Results showed that the enhanced biofilter achieved outstanding performance in EE2 removal (93.2 %) and TN reduction (effluent < 5 mg/L), demonstrating robustness against C/N fluctuations. It was noteworthy that it successfully reduced both acute toxicity (59.5 %) and estrogenic activity (88.6 %). Comprehensive characterization investigations and microbial community structure analysis revealed that enhanced electron transfer and increased microbial abundance likely contributed to improved biofilter performance. Core microorganisms, such as Pseudomonas and Chryseobacterium were identified as key contributors to synergistic estrogen degradation and denitrification. This study presented a feasible and promising strategy of combined process with three-dimensional electrodes and sulfur-based biofilter, highlighting substantial potential for advanced purification and safe reuse of wastewater.

Pyrrhotite-dependent microbial reduction and magnetic separation for efficient vanadium detoxification and recovery in contaminated aquifer

Microbial reduction under anaerobic condition is a promising method for remediating vanadate [V(V)] contamination in aquifers, while V(V) may be re-generated with redox fluctuations. The inability to remove vanadium after remediation has become a key issue limiting bioremediation. In this study, we proposed the use of pyrrhotite, a natural mineral with magnetic properties, to immobilize V(V) to insoluble V(IV) under microbial action and remove vanadium from the aquifer using a magnetic field, which could avoid the problem of V(V) recontamination under redox fluctuating conditions. Up to 49.0 ± 4.7 % of vanadium could be removed from the aquifer by the applied magnetic field, and the vanadium in the aquifer after the reaction was mainly in the acid-extractable and reducible states. pH had a strong effect on the magnetic recovery of V(V), while the influence of initial V(V) concentration was weak. Microbial community structure analysis showed that Thiobacillus, Proteiniphilum, Fermentimonas, and Desulfurivibrio played key roles for V(V) reduction and pyrrhotite oxidation. Structural equation model indicated the positive correlation between these genera with the magnetic recovery of vanadium. Real time-qPCR confirmed the roles of functional genes of V(V) reduction (napA and nirK) and SO42− reduction (dsrA) in such biological processes. This study provides a novel route to sustainable V(V) remediation in aquifers, with synchronous recovery of vanadium resources without rebound.

Comparative analysis of microbial community structure in the peel and core of Houhuo low-temperature Daqu

The varying degrees of browning due to the Maillard reaction result in distinct characteristics across different parts within the cross-section of Houhuo low-temperature Daqu (LTD). However, the microbial community structure of the peel and core of Daqu is still poorly understood. In this study, using a combination of high-throughput sequencing and pure culture techniques, the microbial communities present in the peel and core of Houhuo LTD were compared and analyzed. Bacillus (58.84%) and Saccharomycopsis (87.61%) were the main bacterial and fungal genera present in Houhuo LTD. The abundance and diversity of fungi were significantly lower in peel samples (P < 0.01). At the bacterial genus level, Sphingobium, Staphylococcus, and Streptomyces were significantly enriched in peel samples, while Saccharopolyspora was significantly enriched in core samples (P < 0.05). At the fungal genus level, Saccharomycopsis and Clavispora were significantly enriched in peel samples, while Monascus and Aspergillus were significantly enriched in core samples (P < 0.05). Differences in the layers of LTD block had a greater effect on the correlation between bacterial genera, and the microbial networks in the peel samples were more compact. Some microbial groups were common to the two groups, including the main bacterial genera Bacillus, Saccharopolyspora, Streptomyces, and Staphylococcus and the main fungal genera Saccharomycopsis and Monascus. Pure culture techniques revealed that B. paralicheniformis, Pediococcus pentosaceus, and S. fibuligera were the most abundant strains of Bacillus, lactic acid bacteria, and yeast in all samples, respectively. The findings could support the optimization of the Daqu-making processes and the screening of microbial strains for brewing.

Rainfall-induced changes in aquatic microbial communities and stability of dissolved organic matter: Insight from a Fen river analysis

Microbial communities are pivotal in aquatic ecosystems, as they affect water quality, energy dynamics, nutrient cycling, and hydrological stability. This study explored the effects of rainfall on hydrological and photosynthetic parameters, microbial composition, and functional gene profiles in the Fen River. Our results demonstrated that rainfall-induced decreases in stream temperature, dissolved oxygen, pH, total phosphorus, chemical oxygen demand, and dissolved organic carbon concentrations. In contrast, rainfall increased total dissolved solids, salinity, and ammonia-nitrogen concentrations. A detailed microbial community structure analysis revealed that Cyanobacteria was the dominant microbial taxon in the Fen River, accounting for approximately 75% and 25% of the microalgal and bacterial communities, respectively. The abundance of Chlorophyta and Bacillariophyta increased by 47.66% and 29.92%, respectively, whereas the relative abundance of Bacteroidetes decreased by 37.55% under rainfall conditions. Stochastic processes predominantly affected the assembly of the bacterial community on rainy days. Functional gene analysis revealed variations in bacterial functions between sunny (Sun) and rainy (Rain) conditions, particularly in genes associated with the carbon cycle. The 3-oxoacyl-[acyl-carrier-protein] reductase gene was more abundant in the Fen River bacterial community. Particular genes involved in metabolism and environmental information processing, including the acetyl-CoA C-acetyltransferase (atoB), enoyl-CoA hydratase (paaF), and branched-chain amino acid transport system gene (livK), which are integral to environmental information processing, were more abundant in Sun than the Rain conditions. In contrast, the phosphate transport system gene, the galactose metabolic gene, and the pyruvate metabolic gene were more abundant in Rain. The excitation-emission matrix analysis with parallel factor analysis identified four fluorescence components (C1–C4) in the river, which were predominantly protein- (C1) and humic-like (C2–C4) substances. Rainfall affected organic matter production and transport, leading to changes in the degradation and stability of dissolved organic matter. Overall, this study offers insight into how rainfall affects aquatic ecosystems.

Synergistic Combination of Plants and Microbial-Rich Substrates Improves Water Quality in an Integrated Plant-Substrate System

Nutrient enrichment is one of the main reasons causing water quality deterioration and eutrophication in aquaculture systems, such as tanks, ponds, and natural water bodies where cage aquaculture is located. The integration of aquatic plants and substrates synergistically utilises nutrients for the development of biofilm and plant growth, thus improving the water quality in tanks. The experiment was performed in three trials to assess the use of commercial plants integrated with substrates in enhancing nutrient removal in nutrient-enriched mesocosms. Among the plants, the combination of water spinach and lemon basil exhibited significantly higher (P &lt; 0.05) nutrient removal without causing adverse effects on plant growth when compared to the other treatments. For the substrates, the lava rock and bamboo showed the highest (P &lt; 0.05) periphyton development and productivity. The integration of water spinach and lava rock resulted in the highest (P &lt; 0.05) nutrient removal and plant relative growth rates indicating the positive effects of synergistic interaction between plants and microbial-periphyton colonised substrates. A total of 27 bacterial phyla (mainly non-pathogenic) were identified in the integrated water spinach and lava rock substrate treatment. Microbial community structure analysis showed that Proteobacteria, Planctomycetota, Verrucomicrobiota and Bacteroidota were the main groups found in water, roots of water spinach, and substrates. The highest (P &lt; 0.05) bacterial diversity was observed in the substrates, followed by plant roots and water. This study illustrated that the water quality could be significantly improved by integrating suitable plants and microbial-periphyton colonised substrates in tanks.

Fe controls the reproduction of zoogloea and sludge bulking in oil-in-iron wastewater

Following the final biological treatment, the oil wastewater is intended for reuse in factory floor cleaning. However, the presence of varying concentrations of oil-in-iron characteristic wastewater has led to a sudden surge in sludge SV to 90%, adversely affecting water treatment efficiency. In this study, we conducted an analysis of microbial community structure and selected pepA and 16S rRNA primers to assess the proportions of zoogloea and total bacteria in sludge bulking. Iron concentration plays a pivotal role, and it should be maintained at or 0.6 mgL−1. By selective discharging of sludge to maintain 1,700 mgL−1, we minimized iron enrichment, thereby enhancing the sludge settling performance. Maintaining dissolved oxygen (DO) at 3.5 mgL−1 supports the aerobic sludge's ability to replenish iron in its system, while the oil content should be controlled at 145.33 mgL−1 to reduce the release of iron into the water. The order of significance is as follows: sludge concentration &amp;gt; Fe amount &amp;gt; DO &amp;gt; oil content. Implementing this approach was applied in the field for 1 week and effectively reduced the SV from 90% to approximately 43%. The interaction between quorum sensing molecules related to sludge bulking and iron, leading to the formation of complexes, underscores the significance of controlling iron levels. This study offers a valuable case for practical application of quorum quenching technology in oil wastewater, presenting a rapid, efficient, and cost-effective solution to address the issue of sludge bulking.

Microbial coalbed gas and its geological formation process in the Jimsar region of the southern Junggar Basin, NW China

The southern Junggar Basin is abundant in coalbed gas (CBG) resources, with the Jimsar region in the southern part of the basin emerging as a potential CBG development demonstration area. However, further development of the CBG in this region is restricted by the lack of understanding of the genesis and gas reservoir formation mechanisms of the CBG. This study systematically collected CBG samples and associated water samples from the Jimsar region. Stable isotope, hydrogeochemical, and 16S ribosomal ribonucleic acid (rRNA) sequencing studies were carried out. The results demonstrate that the CBG is the primary microbial gas, and CO2 reduction is its formation pathway. Hydrogeochemical analysis shows that the coalbed water receives recharge from meteoric or surface water. The water environment is relatively active (open system). The total dissolved organic carbon (TDOC) in the coalbed water is primarily from coal, and the supply and consumption of the total dissolved nitrogen (TDN) may be relatively balanced. The dissolution of CO2 is the main source of the dissolved inorganic carbon (DIC). Furthermore, the positive δ13CDIC values and high alkalinity indicate microbial methanogenesis. Microbial community structure analysis revealed that the archaea are hydrogenotrophic methanogens in the Jimsar region. The microbial basis for the production of microbial gas is provided by the existence of hydrolytic, acidogenic, and hydrogen-producing acetogenic bacteria as well as methanogenic archaea. Natural gas genetic identification diagrams and detection of methane-oxidizing bacteria (Methylomicrobium) reveal that the CBG may be affected by slight oxidation. In addition, the methanogenic effect is much greater than the methane oxidation. Finally, based on these results and the regional tectonic background, the CBG enrichment and accumulation mode in the Jimsar region was established. This mode can be divided into three geological stages: burial and coalification, surface water recharge and microbial gas generation after uplift and denudation, and CBG accumulation controlled by reverse faults and hydrodynamic sealing. This study enriches the geological theory of CBG accumulation in the Jimsar region and provides guidance for the subsequent exploration and development of the CBG.

Comparative study of high-solid anaerobic digestion at laboratory and industrial scale – Process performance and microbial community structure

High-solid anaerobic digestion (HSD) for biogas production, compared with wet digestion, is attracting interest due to advantages such as reduced fresh water usage, improved digestate quality and potential for high organic loading rates. However, the underlying processes are not well described and evaluated for HSD. In this study, two laboratory-scale reactors (46 L) of plug-flow type were designed to simulate an industrial-scale HSD process co-digesting food waste, agricultural waste and garden residues under thermophilic conditions. Performance of the laboratory-scale HSD process under stable and disturbed conditions was compared with that in industrial-scale reactors. The results showed that the laboratory- and industrial-scale processes had similar efficiency (93 %) and VS-reduction (43 % and 41 %, respectively) and relatively similar specific methane production (339 and 366 NL CH4/kg VS, respectively). Results from tracer studies combined with chemical analyses showed no phase-separation or plug-flow behaviour along the horizontal axis in either laboratory- or industrial-scale reactors, indicating a need for further process optimisation. Analyses of microbial community structure showed high similarity between laboratory- and industrial-scale, but with some differences caused by downscaling. During the experiment, the laboratory- and industrial-scale processes both showed signs of disturbance, i.e. VFA accumulation at NH4+-N levels > 4 g/L, accompanied by a shift in microbial community structure at both scales, with significant increases in relative abundance of e.g. genera Defluviitoga and Methanothermobacter. In conclusion, this study confirmed the validity of simulating HSD at laboratory scale, thus providing valuable insights into biogas production from high-solid substrates, both in laboratory- and industrial-scale processes.