Bacterial community structure within an activated sludge reactor added with phenolic compounds

Effects of Hydraulic Retention Time on Removal of Cr (VI) and p-Chlorophenol and Electricity Generation in L. hexandra-Planted Constructed Wetland-Microbial Fuel Cell

Hexavalent chromium (Cr (VI)) and para-chlorophenol (4-CP) are prevalent industrial wastewater contaminants that are recalcitrant to natural degradation and prone to migration in aquatic systems, thereby harming biological health and destabilizing ecosystems. Consequently, their removal is imperative. Compared to conventional chemical treatment methods, CW-MFC technology offers broader application potential. Leersia hexandra Swartz can enhance Cr (VI) and 4-CP absorption, thereby improving wastewater purification and electricity generation in CW-MFC systems. In this study, three CW-MFC reactors were designed with L. hexandra Swartz in distinct configurations, namely, stacked, multistage, and modular, to optimize the removal of Cr (VI) and 4-CP. By evaluating wastewater purification, electrochemical performance, and plant growth, the optimal influent hydraulic retention time (HRT) was determined. The results indicated that the modular configuration at an HRT of 5 days achieved superior removal rates and power generation. The modular configuration also supported the best growth of L. hexandra, with optimal photosynthetic parameters, and physiological and biochemical responses. These results underscore the potential of modular CW-MFC technology for effective detoxification of complex wastewater mixtures while concurrently generating electricity. Further research could significantly advance wastewater treatment and sustainable energy production, addressing water pollution, restoring aquatic ecosystems, and mitigating the hazards posed by Cr (VI) and 4-CP to water and human health.

Structures and diversities of bacterial communities in oil-contaminated soil at shale gas well site assessed by high-throughput sequencing

Currently, there is limited understanding of the structures and variabilities of bacterial communities in oil-contaminated soil within shale gas development. The Changning shale gas well site in Sichuan province was focused, and high-throughput sequencing was used to investigate the structures of bacterial communities and functions of bacteria in soil with different degrees of oil pollution. Furthermore, the influences of the environmental factors including pH, moisture content, organic matter, total nitrogen, total phosphorus, oil, and the biological toxicity of the soil on the structures of bacterial communities were analyzed. The results revealed that Proteobacteria and Firmicutes predominated in the oil-contaminated soil. α-Proteobacteria and γ-Proteobacteria were the main classes under the Proteobacteria phylum. Bacilli was the main class in the Firmicutes phylum. Notably, more bacteria were only found in CN-5 which was the soil near the storage pond for abandoned drilling mud, including Marinobacter, Balneola, Novispirillum, Castellaniella, and Alishewanella. These bacteria exhibited resilience to higher toxicity and demonstrated proficiency in oil degradation. The functions including carbohydrate transport and metabolism, energy metabolism, replication, recombination and repair replication, signal transduction mechanisms, and amino acid transport and metabolism responded differently to varying concentrations of oil. The disparities in bacterial genus composition across samples stemmed from a complex play of pH, moisture content, organic matter, total nitrogen, total phosphorus, oil concentration, and biological toxicity. Notably, bacterial richness correlated positively with moisture content, while bacterial diversity showed a significant positive correlation with pH. Acidobacteria exhibited a significant positive correlation with moisture content. Litorivivens and Luteimonas displayed a significant negative correlation with pH, while Rhizobium exhibited a significant negative correlation with moisture content. Pseudomonas, Proteiniphilum, and Halomonas exhibited positive correlations not only with organic matter but also with oil concentration. Total nitrogen exhibited a significant positive correlation with Taonella and Sideroxydans. On the other hand, total phosphorus showed a significant negative correlation with Sphingomonas. Furthermore, Sphingomonas, Gp6, and Ramlibacter displayed significant negative correlations with biological toxicity. The differential functions exhibited no significant correlation with environmental factors but displayed a significant positive correlation with the Proteobacteria phylum. Aridibacter demonstrated a significant positive correlation with cell motility and cellular processes and signaling. Conversely, Pseudomonas, Proteiniphilum, and Halomonas were negatively correlated with differential functions, particularly in amino acid metabolism, carbohydrate metabolism, and membrane transport. Compared with previous research, more factors were considered in this research when studying structural changes in bacterial communities, such as physicochemical properties and biological toxicity of soil. In addition, the correlations of differential functions of communities with environmental factors, bacterial phyla, and genera were investigated.

Degradation and metagenomic analysis of 4-chlorophenol utilizing multiple metal tolerant bacterial consortium

Chlorophenols are persistent environmental pollutants used in synthesizing dyes, drugs, pesticides, and other industrial products. The chlorophenols released from these processes seriously threaten the environment and human health. The present study describes 4-chlorophenol (4-CP) degradation activity and metagenome structure of a bacterial consortium enriched in a 4-CP-containing medium. The consortium utilized 4-CP as a single carbon source at a wide pH range, temperature, and in the presence of heavy metals. The immobilized consortium retained its degradation capacity for an extended period. The 4-aminoantipyrine colorimetric analysis revealed complete mineralization of 4-CP up to 200 mg/L concentration and followed the zero-order kinetics. The addition of glycerol and yeast extract enhanced the degradation efficiency. The consortium showed both ortho- and meta-cleavage activity of catechol dioxygenase. Whole genome sequence (WGS) analysis revealed the microbial compositions and functional genes related to xenobiotic degradation pathways. The identified genes were mapped on the KEGG database to construct the 4-CP degradation pathway. The results exhibited the high potential of the consortium for bioremediation of 4-CP contaminated sites. To our knowledge, this is the first report on WGS analysis of a 4-CP degrading bacterial consortium.

Elucidating the roles of Cr(VI)-Cu(II) Co-pollution in the stress of aniline degradation stress: Insights into metabolic pathways and functional genes

In order to examine the impact of Cu(II)-Cr(VI) co-pollution in printing and dyeing wastewater on the aniline biodegradation system (ABS), loading experiments were conducted on ABS at varying concentrations of Cu(II)-Cr(VI). The synergistic stress imposed by Cu(II)-Cr(VI) accelerated the deterioration of the systems, with only the C2-3 (2 mg/L Cr(VI)-3 mg/L Cu(II)) sustaining stable operation for 42 days. However, its nitrogen removal performance remained significantly impaired, resulting in a total nitrogen (TN) removal rate below 40%. High-throughput sequencing analysis revealed a stronger correlation between Cr(VI) and microbial diversity compared to Cu(II). Metagenomic sequencing results demonstrated that Cu(II) emerged as the dominant factor influencing the distribution of dominant bacteria in C2-3, as well as its contribution to contaminant degradation. The complex co-pollution systems hindered aniline degradation and nitrogen metabolism through the combined bio-toxicity of heavy metals and aniline, thereby disrupting the transport chain within the systems matrix.

Unraveling the nexus of Cr (Ⅵ), Aniline, and Microbial Ecology on aniline-degrading biosystem: Removal efficiency, sludge type, microbial ecology

In order to explore the stress principle of Cr (Ⅵ) on aniline biodegradation system, a control group and experimental groups with the concentration of Cr (Ⅵ) at 2, 5, 8 mg/L were set up. The results demonstrated that Cr (Ⅵ) had minimal effects on the degradation efficiency of aniline but significantly inhibited nitrogen removal function. When Cr (Ⅵ) concentration was below 5 mg/L, the nitrification performance recovered spontaneously, while denitrification performance was severely impaired. Furthermore, the secretion of extracellular polymeric substances (EPS) and its fluorescence substance concentration were strongly inhibited with increasing Cr (Ⅵ) concentration. High-throughput sequencing revealed that the experimental groups were enriched with Leucobacter and Cr (Ⅵ)-reducing bacteria, but the abundance of nitrifiers and denitrifiers was significantly decreased compared to the control group. Overall, the effects of Cr (Ⅵ) stress at different concentrations on nitrogen removal performance were more significant than those on aniline degradation.

Fate and removal of iodinated X-ray contrast media in membrane bioreactor: Microbial dynamics and effects of different operational parameters

Iodinated X-ray contrast media (ICM) are mainly used in medical sector, and their presence in environmental waters is a cause of concern as they are capable of forming highly toxic iodinated disinfection byproducts. In the present study, the removal mechanisms of the three ICM- iohexol, iopromide, and iopamidol were elucidated in a lab-scale aerobic membrane bioreactor (MBR). At steady-state operation (solids retention time (SRT)- 70 days, organic loading rate (OLR)- 0.80 KgCOD/m³-day, nitrogen loading rate (NLR)- 0.08 KgNH₄-N/m³-day, hydraulic retention time (HRT)- 12 h), the average removal of iohexol and iopromide was found to be 34.9 and 45.2 %, respectively, whereas iopamidol proved to be highly recalcitrant in aerobic conditions of the MBR (removal <10 % in all phases of the MBR operation). Further, through batch kinetic studies and mass balance analysis, it was observed that ICM were primarily biotransformed in the MBR system and biosorption (K_d < 10 L/Kg) was negligible. The biodegradation rate coefficient values (K_biol) of the ICM were found to be <0.65 L/g-d which indicate that biotransformation rate of ICM was slow. Increased OLR (1.60 KgCOD/m³-day) and reduced SRT (20 days) were found to negatively affect the removal of the ICM. Further, the removal of ICM was found to depend on its initial concentration, and the increment in the ammonium loading (0.16 KgNH₄-N/m³-day) did not favor its removal. The dosing of ICM altered the microbial dynamics of the mixed liquor and reduced the microbial diversity and richness. Bdellovibrio, Zoogloea, and bacteria belonging to TM7-3 class, Cryomorphaceae and Hyphomonadaceae families may contribute in ICM biotransformation.

New insights for tracking bacterial community structures in industrial wastewater from textile factories to surface water using phenotypic, 16S rRNA isolates identifications and high-throughput sequencing

Industrial wastewater can possibly change the microbial ecological environment. There are few studies that focus on the bacterial variety in textile wastewater effluents and after combination with domestic wastewater. Thus, this study aimed to determine dye degrading bacteria from textile wastewater and environmental water samples using cultural method followed by phenotypic using BIOLOG and genotypic identification (16S rRNA) for dye degrading isolates identifications. Moreover, the bacterial communities in three textile and four environmental samples using Illumina MiSeq high-throughput sequencing were investigated. The findings revealed that in textile water samples, the ratio of dye-degrading bacteria (DDB) to total bacterial counts (TBC) was 27%. The identified DDB genera by 16S rRNA based on the cultural approach were Citrobacter spp., Klebsiella spp., Enterobacter spp., Pseudomonas spp., and Aeromonas spp. Regarding to the metagenomics analyses, the environmental samples had 5,598 Operational Toxanomic Units (OTUs) more than textile wastewater samples (1,463 OTUs). Additionally, the most abundant phyla in the textile wastewater were Proteobacteria (24.45-94.83%), Bacteriodetes (0.5-44.84%) and Firmicutes (3.72-67.40%), while, Proteobacteria (30.8-76.3%), bacteroidetes (8.5-50%) and Acentobacteria (0.5-23.12%) were the most abundant phyla in the environmental samples. The maximum abundant bacteria at species level in environmental samples were Aquabacterium parvum (36.71%), Delftia tsuruhatensis (17.61%), Parabacteriodes chartae (15.39%) and Methylorubrum populi (7.51%) in El-Rahawy Drain water (RDW), River Nile water (RNW), wastewater (RWW) from WWTP in Zennin and El-Rahawy Drain sediment (RDS), respectively, whereas the maximum abundant bacteria at species level in textile wastewater were Alkalibacterium pelagium (34.11%), Enterobacter kobei (26.09%) and Chryseobacterium montanum (16.93%) in factory 1 (HBT) sample, SHB sample (before mixing with domestic wastewater) and SHB sample (after mixing with domestic wastewater), respectively. In conclusion, the microbial communities in textile wastewaters are similar to those in environmental samples at the phylum level but distinct at the genus and species levels because they are exposed to a wider range of environmental circumstances.

The in-depth revelation of the mechanism by which a downflow Leersia hexandra Swartz constructed wetland-microbial fuel cell synchronously removes Cr(VI) and p-chlorophenol and generates electricity

The composite pollution by Cr(VI) and p-chlorophenol (4-CP) has high toxicity and harms water safety. However, research on the effective removal of Cr(VI) and 4-CP composite-polluted wastewater (C&P) and efficient synchronous electricity generation with reclaimed resources is limited. In this study, a downflow Leersia hexandra constructed wetland-microbial fuel cell (DLCW-MFC) was builded to treat C&P, as well as wastewater singularly polluted by Cr(VI) (SC) and 4-CP (SP), respectively, to reveal the mechanism by which DLCW-MFC treats C&P and synchronously generates electricity. The results demonstrate that the cathode layer had a stronger removal effect on pollutants than the middle layer and anode zone layer. Moreover, SC and SP had stronger pollutant removal effects than C&P. Cr(VI) had more competitive with electrons than 4-CP, and they had a synergistic effect on efficient electricity generation. The L.hexandra in SC and SP had a better growth state and lower Cr enrichment concentration than that in C&P. Cr existed in the DLCW-MFC mainly in the form of Cr(III). Gas chromatography-mass spectrometry was used to investigate the degradation pathway of 4-CP in C&P, and indicated that Phenol, 2,4-bis(1,1-dimethylethyl)- and benzoic acid compounds were the main intermediates formed at the cathode, and further mineralized to form medium-long-chain organic compounds to form CO₂. The microbial community distribution results revealed that Simplicispira, Cloacibacterium, and Rhizobium are associated with Cr(VI) removal and 4-CP degradation, and were found to be rich in the cathode of C&P. The anode of C&P was found to have more Acinetobacter (1.34%) and Spirochaeta (4.83%) than SC and SP, and the total relative abundance of electricigens at the anode of C&P (7.46%) was higher than that at the anodes of SC and SP. This study can provide a theoretical foundation for the DLCW-MFC to treat heavy metal and chlorophenol composite-polluted wastewater and synchronously generate electricity.

Wood vinegar facilitated growth and Cd/Zn phytoextraction of Sedum alfredii Hance by improving rhizosphere chemical properties and regulating bacterial community

Soil Cd and Zn contamination has become a serious environmental problem. This work explored the performance of wood vinegar (WV) in enhancing the phytoextraction of Cd/Zn by hyperaccumulator Sedum alfredii Hance. Rhizosphere chemical properties, enzyme activities and bacterial community were analyzed to determine the mechanisms of metal accumulation in this process. Results demonstrated that, after 120 days growth, different times dilution of WV increased the shoot biomass of S. alfredii by 85.2%-148%. In addition, WV application significantly increased soil available Cd and Zn by lowing soil pH, which facilitated plant uptake. The optimal Cd and Zn phytoextraction occurred from the 100 times diluted WV (D100), which increased the Cd and Zn extraction by 188% and 164%, compared to CK. The 100 and 50 times diluted WV significantly increased soil total and available carbon, nitrogen and phosphorus, and enhancing enzyme activities of urease, acid phosphatase, invertase and protease by 10.1-21.4%, 29.1-42.7%,12.2-38.3% and 26.8-85.7%, respectively, compared to CK. High-throughput sequencing revealed that the D 100 significantly increased the bacterial diversity compared to CK. Soil bacterial compositions at phylum, family and genera level were changed by WV addition. Compared to CK, WV application increased the relative abundances of genus with plant growth promotion and metal mobilization function such as, Bacillus, Gemmatimonas, Streptomyces, Sphingomonas and Polycyclovorans, which was positively correlated to biomass, Cd/Zn concentrations and extractions by S. alfredii. Structural equation modeling analysis showed that, soil chemical properties, enzyme activities and bacterial abundance directly or indirectly contributed to the biomass promotion, Cd, and Zn extraction by S. alfredii. To sum up, WV improved phytoextraction efficiency by enhancing plant growth, Cd and Zn extraction and increasing soil nutrients, enzyme activities, and modifying bacterial community.

Insights into the microbial community of treated wastewater, its year-round variability and impact on the receiver, using cultivation, microscopy and amplicon-based methods

Apart from chemical constituents, wastewater treatment plant (WWTP) effluents also release microorganisms that can be important to the receiving water bodies either from a sanitary point of view, or taking to the account the biogeochemical potential of the recipients. However, little is known about the treated wastewater microbial community, its composition, seasonal changes, functions and fate in the waters of the receiver. Thus, this study presents a synergistic approach coupling new and traditional methods: analytical chemistry, classical microbiology (cultivation- and microscopy-based methods), as well as Next Generation Sequencing and a quantitative real-time polymerase chain reaction (qPCR). The results show that in terms of bacterial community composition, treated wastewater differed from the environmental samples, irrespectively if they were related or unrelated to the WWTP effluent discharge. The canonical correspondence analysis (CCA) taking into account chemical parameters and taxonomical biodiversity indirectly confirmed the seasonal deterioration of the treated wastewater quality as a result of temperature-driven change of activated sludge community structure and biomass washout (observed also by DAPI staining). Despite seasonal fluctuations of total suspended solids and inter-related parameters (such as COD, BOD, TN, TP), the treated wastewater quality remained within current discharge limits. It was due to treatment processes intensively adjusted by WWTP operators, particularly those necessary to maintain an appropriate rate of autotrophic processes of nitrification and to support biological phosphorus removal. This can explain the observed microbiome composition similarity among WWTP effluents at high taxonomic levels. Obtained data also suggest that besides wastewater treatment efficiency, WWTP effluents are still sources of both human-related microorganisms as well as bacteria equipped in genes involved in N-cycling. Their potential of participation in nutrients cycling in the receivers is widely unknown and require critical attention and better understanding.

An attempt to stimulate aniline degrading bioreactor by exogenous auto-inducer: Decontamination performance, sludge characteristics, and microbial community structure response

To break the contradiction between aniline and nitrogen metabolism in activated sludge reactor by influencing microbial interspecific communication, Auto-inducer C6-HSL and 3-oxo-C8-HSL were selected in this study to interfere with aniline degradation system. The two Auto-inducers enhanced the aniline degradation rate and ammonia removal efficiency of the systems, especially C6-HSL. Meanwhile, the main ammonia removal way was assimilation. Exogenous Auto-inducer effectively stabilized the sludge structure and activity from the destruction of aniline, and promoted EPS secretion. Microbial diversity analysis showed that most of functional microflora of seed sludge gradually deactivated with the operation of the reactor, while Rhodococcus, Leucobacter, g_norank_f_Saprospiraceae proliferated wildly under the action of Auto-inducer. Additionally, the interspecific relationship also demonstrated a different trend. Exogenous Auto-inducer was proved to exert positive effects on aniline degradation system to a certain extent, providing new insights in the field of aniline wastewater bio-degradation.

Shifts in structure and function of bacterial community in river and fish pond sediments after a phenol spill

Phenol is widely used in industrial processes and has microbial toxicity. However, the effects of a phenol spill on the microbial community are not clear. The present study explored the changes of bacterial communities in river and fish pond sediments after a phenol spill. The bacterial richness and diversity in river sediments were lower on day 30 (36 days after the spill) than on day 0, while they increased in fish pond sediments. The structures and functions of bacterial communities in both river and fish pond sediments were changed, and a more dramatical variation was detected in fish pond sediments. In river sediments, Proteobacteria, Chloroflexi, Acidobacteria, Bacteroidetes, and Nitrospirae were the major bacterial phyla, and Chloroflexi was enriched. In fish pond sediments, genera Brevibacillus dominated bacterial communities initially, and bacterial composition showed a dramatic change on day 30. Most predicted metabolism functions, as well as genetic information processing functions of translation, replication, and repair, were enhanced in both river and fish pond sediments, while they showed an opposite change trend for xenobiotic degradation function. This work could strengthen our understanding of the effects of phenol spills on sediment bacterial communities in both lotic and lentic ecosystems.

Effect of prolonged sludge retention times on the performance of membrane bioreactor and microbial community for leachate treatment under restricted aeration

Leachate treatment is challenging owing to the complex composition of pollutants. This study investigated the treatment performance of a membrane bioreactor (MBR) and the microbial community structure corresponding to the effect of prolonged sludge retention times (SRTs) under restricted aeration. In the present study, a pilot-scale MBR was designed to treat leachate after being pretreated with an anaerobic filter for continuous operation for 240 days. The experimental results showed that removal performance of over 90% was achieved for biochemical oxygen demand, total Kjeldahl nitrogen, ammonia-nitrogen, and suspended solids when the MBR was operated at SRTs of 150-300 days. The results on microbial communities revealed that Proteobacteria, Bacteroidetes, Firmicutes, Planctomycetes, Chloroflexi, and Actinobacteria were the major phyla. Furthermore, ammonia-oxidizing bacteria belonging to Nitrosomonadaceae were considered to play a vital role in the ammonia-nitrogen removal. A high abundance of Rhizobiales was detected on the biofilm of the membrane, which could be the key driver of bio-fouling. The dynamic changes in the microbial community indicate steady performance of MBR and can act as an indicator of membrane bio-fouling. The results of our study highlight that MBR can be viably operated in long SRTs under restricted aeration for leachate treatment with technical, economic, and environmental feasibility for resource recovery.

Insights into the relevance between bacterial endophytic communities and resistance of rice cultivars infected by Xanthomonas oryzae pv. oryzicola

Bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc), impacts the production of rice. However, several rice cultivars displayed resistance to Xoc in the field, but scarce information is available about the role of endophytic microbiota in disease resistance. In the present study, the endophytic bacterial communities of resistant and susceptible rice cultivars "CG2" and "IR24", respectively, were analyzed using high throughput 16S rRNA gene amplified sequencing and culture dependent method was further used for bacterial isolation. A total of 452,716 high-quality sequences representing 132 distinct OTUs (Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes) and 46 isolates of 16 genera were explored from rice leaves infected with Xoc. Community diversity of endophytic bacteria were higher in the leaves of the resistant cultivars compared to susceptible cultivars upon Xoc infection. Strikingly, this diversity might contribute to natural defense of the resistant cultivar against pathogen. Pantoea, which is pathogen antagonist, was frequently detected in two cultivars and higher abundance were recorded in resistant cultivars. Different abundance genus includes endophytic isolates with marked antagonistic activity to Xoc. The increased proportions of antagonistic bacteria, may contribute to resistance of rice cultivar against Xoc and the Pantoea genus was recruited by Xoc infection play a key role in suppressing the development of BLS disease in rice. Taken together, this work reveals the association between endophytic bacteria and BLS resistance in rice and identification of antagonism-Xoc bacterial communities in rice.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02979-2.

Influence of bisphenol A occurrence in wastewaters on biomass characteristics and activated sludge process performance

In this work, the influence of bisphenol A (BPA) on biological wastewater treatment was studied. For it, two sequencing batch reactors (SBRs) were operated for three months. Both SBRs were fed with synthetic wastewater (SW), adding 1 mg·L^-1 of BPA into the feed of reactor SBR-BPA, while the other one operated without BPA as a control reactor (SBR-B). In addition, batch experiments were performed with adapted and non-adapted activated sludge, simulating the reaction step of SBR-BPA, to determine the pathways for BPA removal. Results of batch experiments showed that adsorption and biodegradation were the only significant BPA removal routes. BPA removal by biodegradation was more efficient when adapted biomass was used in the tests (32.2% and 8.2% with adapted and non-adapted biomass, respectively), while BPA adsorption removal route was similar in both types of activated sludge (around 40%). Regarding the SBRs experiments, after 16 days no BPA concentration was detected in SBR-BPA effluent. In the adaptation process, SBR-BPA biomass was more sensitive to low temperatures resulting in higher effluent turbidity, COD and soluble microbial products concentrations than in SBR-B. However, once temperature increased, adapted biomass from SBR-BPA presented higher activity than SBR-B biomass, showing higher values of sludge production, microbial hydrolytic enzymatic activities and specific dynamic respiration rate. The bacterial community study revealed the increase of abundance of Proteobacteria (especially Thiothrix species) and Actinobacteria (especially Nocardioides species) phyla at the expense of Bacteroidetes and Chloroflexi phyla in SBR-BPA during its operation.

Influence of particle size distribution on anaerobic degradation of phenol and analysis of methanogenic microbial community

Sludge morphology considerably affects the mechanism underlying microbial anaerobic degradation of phenol. Here, we assessed the phenol degradation rate, specific methanogenic activity, electron transport activity, coenzyme F₄₂₀ concentration, and microbial community structure of five phenol-degrading sludge of varying particle sizes (i.e., < 20, 20-50, 50-100, 100-200, and > 200 μm). The results indicated an increase in phenol degradation rate and microbial community structure that distinctly correlated with an increase in sludge particle size. Although the sludge with the smallest particle size (< 20 μm) showed the lowest phenol degradation rate (9.3 mg COD·gVSS^-1 day^-1), its methanogenic activity with propionic acid, butyric acid, and H₂/CO₂ as substrates was the best, and the concentration of coenzyme F₄₂₀ was the highest. The small particle size sludge did not contain abundant syntrophic bacteria or hydrogenotrophic methanogens, but contained abundant acetoclastic methanogens. Moreover, the floc sizes of the different sludge varied in important phenol-degrading bacteria and archaea, which may dominate the synergistic mechanism. This study provides a new perspective on the role of sludge floc size on the anaerobic digestion of phenol.

Assessing the feasibility of sequential aerobic respiration and heterotrophic denitrification of a high-strength mixture of phenol and its derivatives in the field single-well-drift test

Biological degradation of high strength phenol and its derivatives in groundwater is problematic because these compounds are toxic to human and microbes. To evaluate the feasibility of in situ bioremediation using sequential aerobic respiration and heterotrophic denitrification, a field single-well-drift test (SWDT) was conducted in groundwater contaminated with coal tar distillates. To stimulate indigenous phenol degrading microorganisms, a 1400 L of oxygen-saturated test solution containing bromide (3.96 ± 0.179 mmol-Br/L) and nitrate (5.34 ± 0.187 mmol NO₃^--N/L) was injected into an aquifer. After injection of the test solution, significant consumption of dissolved oxygen (DO) was immediately observed; then, degradation of the methyl derivatives o-cresol and m,p-cresol was observed with average zero-order rate coefficients of 0.047 mmol/L/d and 0.23 mmol/L^/d, respectively. After 73% of the injected DO was consumed, significant NO₃^- consumption was observed along with degradation of phenol and the dimethyl derivatives 2,4-xylenol and 3,5-xylenol, which had average zero-order rate coefficients of 0.17 mmol/L/d, 0.060 mmol/L/d, and 0.018 mmol/L/d, respectively. The production of CO₂, NO₂^-, and N₂O along with significant consumption of DO and NO₃^- suggest that phenolic compounds were biologically degraded by sequential aerobic respiration and heterotrophic denitrification. The results of 16s RNA analysis revealed that, after injection of the test solution, a bacterium that shared a 99% 16s rRNA sequence similarity with an uncultured bacterium revealed to be Pseudomonas stutzeri, a facultative heterotrophic denitrifier, was found in the aquifer. Thus, these results suggest that simultaneous injection of DO and NO₃^- is an appropriate in situ bioremediation strategy for degrading mixtures of high-strength phenolic compounds in an aquifer.

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.

Effects of biomass pyrolysis derived wood vinegar on microbial activity and communities of activated sludge

The effects of wood vinegar (WVG) on microbial activity and communities of activated sludge were investigated in a sequencing batch reactor (SBR) process. Results showed that the optimal WVG concentration was 4 μL/L when the pollutants removal efficiency and microbial activity were promoted by a WVG dilution factor of 1000. WVG could reduce the increase in microbial species richness, which led to a more notable variety of microbial species diversity. The enhanced microbial activity and communities were addressed to the promotion of 7 main classes of microbes in Proteobacteria, Bacteroidetes, Acidobacteria, and Nitrospirae phyla. The growth of ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and main genera of denitrifying bacteria (DNB), phosphorus-accumulating organisms (PAOs), and glycogen-accumulating organisms (GAOs) could be promoted by WVG, which improved the sewage treatment effectiveness in a SBR.

Resuscitation of functional bacterial community for enhancing biodegradation of phenol under high salinity conditions based on Rpf

This study assumed that key degraders of functional bacterial community were prone to enter into the viable but non-culturable (VBNC) state under high saline phenolic conditions, and resuscitation-promoting factor (Rpf) could strengthen these degraders for better performances. Based on these assumptions, Rpf was used to enhance salt-tolerant phenol-degrading capability of functional populations in activated sludge. Results suggested that Rpf accelerated the start-up process during sludge domestication, and significantly enhanced salt-tolerant phenol-degrading capability. High-throughput sequencing showed that the resuscitation and stimulation functions of Rpf linked mainly to the genus Corynebacterium within the phylum Actinobacteria, and the genera Proteiniphilum and Petrimonas within the phylum Bacteroidete. These key functional populations contributed to better phenol-degrading capabilities under high salinity conditions. This study indicated that Rpf is a promising additive for improving biological treatment performance of saline phenolic wastewater.

Enhanced phenol removal in an innovative lignite activated coke-assisted biological process

In this study, a lignite activated coke (LAC)-assisted activated sludge (AS) process was developed for enhancing biodegradation of phenol, while the effects of LAC on sludge properties and microbial community structure were investigated. It was found that more than 90% of phenol was removed within 1 h in the LAC/AS, which was 3 times higher than the conventional AS process. Moreover, the floc size and settleability were also significantly improved in the LAC/AS. These results suggested that LAC could serve as the nucleating agent to promote the formation of compact floc, which was beneficial for toxicity mitigation and system stability. The microbial community analysis by 16S high-throughput pyrosequencing technology further revealed a more abundant bacterial richness and diversity in the LAC/AS process loaded with phenol, while some phenol degraders, such as Propionibacteriaceae were enriched. Engineering implications further suggests the LAC-assisted AS process is technically sound and economically viable.

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.

Microbial community structure in aerobic and fluffy granules formed in a sequencing batch reactor supplied with 4-chlorophenol at different settling times

Toxic compounds, such as 4-chlorophenol (4-CP), which is a common pollutant in wastewater, are removed efficiently from sequencing batch reactors (SBRs) by microorganisms. The bacterial community in aerobic granules formed during the removal of 4-CP in a SBR was monitored for 63days. The SBR reactor was operated with a constant filling and withdrawal time of 7 and 8min and decreasing settling time (30, 5, 3 and 2min) to induce the formation of aerobic granules. During the acclimation period lasting 15days (30min settling time) had a strong effect on the bacterial community. From day 18 onwards, Sphingobium and Comamonadaceae were detected. Rhizobiaceae were dominant from day 24 to day 28 when stable aerobic granules were formed. At day 35, fluffy granules were formed, but the bacterial community structure did not change, despite the changes in the reactor operation to inhibit filamentous bacteria growth. This is the first report on changes in the bacterial community structure of aerobic and fluffy granules during granulation process in a reactor fed with 4-CP and the prediction of its metabolic pathways.

Performance and microbial community dynamics of electricity-assisted sequencing batch reactor (SBR) for treatment of saline petrochemical wastewater

High-salinity wastewater is often difficult to treat by common biological technologies due to salinity stress on the bacterial community. Electricity-assisted anaerobic technologies have significantly enhanced the treatment performance by alleviating the impact of salinity stress on the bacterial community, but electricity-assisted aerobic technologies have less been reported. Herein, a novel bio-electrochemistry system has been designed and operated in which a pair of stainless iron mesh-graphite plate electrodes were installed into a sequencing batch reactor (SBR, designated as S1) to strengthen the performance of saline petrochemical wastewater under aerobic conditions. The removal efficiency of phenol and chemical oxygen demand (COD) in S1 were 94.1 and 91.2%, respectively, on day 45, which was clearly higher than the removal efficiency of a single SBR (S2) and an electrochemical reactor (S3), indicating that a coupling effect existed between the electrochemical process and biodegradation. A certain amount of salinity (≤8000 mg/L) could enhance the treatment performance in S1 but weaken that in S2. Illumina sequencing revealed that microbial communities in S1 on days 45 and 91 were richer and more diverse than in S2, which suggests that electrical stimulation could enhance the diversity and richness of the microbial community, and reduce the negative effect of salinity on the microorganisms and enrich some salt-adapted microorganisms, thus improve the ability of S1 to respond to salinity stress. This novel bio-electrochemistry system was shown to be an alternative technology for the high saline petrochemical wastewater.

Exploring the Bioelectrochemical Characteristics of Activated Sludge Using Cyclic Voltammetry

Due to the potential interest, bioelectrochemical responses of activated sludge using the three-electrode system are tested. From the cyclic voltammograms, the oxidation current output is increasing due to incubation time increase, whereas 5, 25 and 39.33 μA are obtained after 3, 72 and 96 h, respectively. Changing the working electrode from glassy carbon to carbon paste led to the increase in the electrochemical signal from 0.3 to be 3.72 μA. On the other hand, the use of the lipophilic redox mediator (2,6-dichlorophenolindophenol (DCIP)) amplified the oxidation current to reach 19.9 μA instead of 2.1 μA. Based on these findings, the mixed microbial community of the activated sludge is exploited as a catalyst for the bio-oxidation of the degradable organic substrates, while DCIP is used as a mobile electron carrier from the intracellular matrix of the metabolically active cells to the carbon paste electrode which served as the final electron acceptor. Therefore, the extracellular electron transfer from the formed active biofilm at the electrode surface is assisted by the existence of DCIP.