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Persulfate oxidation (PS) is widely employed as a promising alternative for waste activated sludge pretreatment due to the capability of generating free radicals. The product differences and microbiological mechanisms by which PS activation triggers WAS digestion through multiple modes need to be further investigated. This study comprehensively investigated the effects of persulfate oxidation activated through multiple modes, i.e., ferrous, zero-valent iron (ZVI), ultraviolet (UV) and heat, on the performance of sludge digestion. Results showed that PS_ZVI significantly accelerated the methane production rate to 12.02 mL/g VSS. By contrast, PS_Heat promoted the sludge acidification and gained the maximum short-chain fatty acids (SCFAs) yield (277.11 ± 7.81 mg COD/g VSS), which was 3.41-fold compared to that in PS_ZVI. Moreover, ferrous and ZVI activated PS achieved the oriented conversion of acetate, the proportions of which took 73% and 78%, respectively. MiSeq sequencing results revealed that PS_Heat and PS_UV evidently enriched anaerobic fermentation bacteria (AFB) (i.e., Macellibacteroides and Clostridium XlVa). However, PS_Ferrous and PS_ZVI facilitated the enrichment of Woesearchaeota and methanogens. Furthermore, molecular ecological network and mantel test revealed the intrinsic interactions among the multiple functional microbes and environmental variables. The homo-acetogens and sulfate-reducing bacterial had potential cooperative and symbiotic relationships with AFB, while the nitrate-reducing bacteria displayed distinguishing ecological niches. Suitable activation modes for PS pretreatments resulted in an upregulation of genes expression responsible for digestion. This study established a scientific foundation for the application of sulfate radical-based oxidation on energy or high value-added chemicals recovery from waste residues. [Display omitted] • Effect of multiple activated persulfate oxidation on sludge digestion was studied. • Heat and UV activated persulfate effectively promoted the accumulation of SCFAs. • ZVI and Ferrous activated persulfate were beneficial for methane production. • Microbial community structures were altered by multiple persulfate activation modes. • Suitable activation modes for persulfate upregulated the critical genes expression. [ABSTRACT FROM AUTHOR]

Most studies have employed aeration-biofiltration process for the simultaneous removal of iron, manganese and ammonia in groundwater. However, what's inside the 'black box', i.e., the potential contribution of functional microorganisms behavior and interactions have seldom been investigated. Moreover, little attention has been paid to the correlations between environmental variables and functional microorganisms. In this study, the performance of industrial-scale biofilters for the contaminated groundwater treatment was studied. The effluent were all far below the permitted concentration level in the current drinking water standard. Pyrosequencing illustrated that shifts in microbial community structure were observed in the microbial samples from different depths of filter. Microbial networks showed that the microbial community structure in the middle- and deep-layer samples was similar, in which a wide range of manganese-oxidizing bacteria was identified. By contrast, canonical correlation analysis showed that the bacteria capable of ammonia-oxidizing and nitrification was enriched in the upper-layer, i.e., Propionibacterium, Nitrosomonas, Nitrosomonas and Candidatus Nitrotoga. The stable biofilm on the biofilter media, created by certain microorganisms from the groundwater microflora, played a crucial role in the simultaneous removal of the three pollutants. [ABSTRACT FROM AUTHOR]

Antibiotics in waste activated sludge (WAS) has drawn increasing attention because of their persistent and bioaccumulation characteristics. Most study illustrated the role of antibiotics in anaerobic fermentation from WAS, but lacking the analysis at microbial level as well as the possible interaction between them. This study investigated the effect of three sulfonamide antibiotics (sulfamethoxazole (SMX), sulfaquinoxaline (SQX), and sulfadiazine (SD)) on WAS fermentation and explored its microbiological mechanism. Results indicated that the production of short-chain fatty acids (SCFAs) was significantly improved by 1.9 folds with a peak value at 4626.1 mg COD L−1 in the existence of SD. This was attributed to the promoted release of soluble proteins and polysaccharides with the existence of sulfonamide antibiotics (SAs) as revealed by the excitation-emission matrix (EEM) spectrum. Analysis of microbial community structure showed that the total abundance of the fermenters in groups with SAs was1.2–1.6 times of that in Control. Specifically, the acid-forming genus Tissierella in SMX and SQX increased by 12.1%–15.0% compared with the Control, while the proteolytic genus Proteinivorax dominated in SD with 39.5%. Molecular ecological networks (MENs) analysis further revealed the potential cooperative relationships among different fermenters. This study was anticipated to provide some valuable information for the behavior of antibiotics in WAS fermentation. [Display omitted] • The existence of SMX, SQX and SD facilitated SCFAs production from WAS anaerobic fermentation. • The presence of SMX, SQX and SD enhanced the solubility and biodegradability of proteins and polysaccharides. • The abundance of fermenters was increased in fermentation systems containing SMX, SQX and SD. • The potential cooperative relationships were established among the key microbial community. [ABSTRACT FROM AUTHOR]

Graphical Abstract Highlights • First investigated the high COD/NO 3 −-N ratio of indole wastewater in mixed culture. • Through nitrate to observe the denitrification and methanogenesis co-existence. • Nitrate was found to facilitate indole degradation and inhibit methane formation. • The metabolites were identified based on 13C-indole isotope analysis. • A dynamic community analysis was presented to study the microbial structures. Abstract Batch experiments were conducted to investigate the effect of nitrate on indole degradation characteristics and methanogenesis under mixed denitrification and methanogenesis culture for the first time. The degradation characteristics were studied under various nitrate concentrations. Nitrate was found to facilitate indole degradation and inhibit methane formation, and the optimum concentration was 50 mg L−1 (COD/NO 3 −-N = 12). Balance analyses showed that nitrate mainly affected indole-C, which generated a higher degree of indole mineralization under NO 3 −-N treatment than in the control. Furthermore, GC–MS combined with 13C-isotope analyses conclusively identified the intermediate metabolites, which included the hydroxylated compounds oxindole and isatin, and the methylated compound 3-methylindole. The results indicated that oxindole did not accumulate and was quickly reduced when nitrate was added, but 3-methylinole, as a recalcitrant material, accumulated without reduction. High-throughput sequencing technology was used to analyse the dynamic microbial community. Results showed that the denitrifying bacterial genera Acinetobacter , Candidimonas and Longilinea accumulated in denitrification stage and decreased in methanogenesis stage, whereas the fermentation genera Alcaligenes and Thermogutta increased in methanogenesis stage. The genera Methanosphaerula and Methanothrix constituted the dominant archaeal communities. The findings obtained in this work may provide a theoretical basis for treatment with N-heterocyclic compounds under mixed culture. [ABSTRACT FROM AUTHOR]

Constructed wetlands have been widely employed as a cost-effective and environmentally friendly alternative for treating primary and secondary sewage effluents. In this study, biochar and pyrite were utilized as electron donor substrates in intermittent-aerated vertical flow constructed wetlands to strengthen the nutrient and heavy metals removal simultaneously, and the response of nutrient reduction and microbial community to heavy metals stress was also explored. The results indicated that biochar addition exhibited a better nitrogen removal, while pyrite addition greatly promoted the phosphorus removal. Moreover, the high removal efficiencies of Cu2+, Pb2+ and Cd2+ (above 90%) except for Zn2+ were obtained in each system. However, the exposure of heavy metals decreased phosphorus removal while had little effect on nitrogen removal. The influent load and intermittent aeration implementation led to a significant shift in microbial community structures, but microbial biodiversity and abundance decreased under the exposure of heavy metals. Particularly, Thiobacillus and Ferritrophicum , associated with sulfur autotrophic denitrification and iron autotrophic denitrification, were more abundant in pyrite-based wetland systems. • Biochar and pyrite addition was beneficial to nitrogen and phosphorus removal. • Biochar-mediated heterotrophic denitrification played significant role in enhancing total nitrogen removal. • Exposure to heavy metals had little impact on denitrification but hindered phosphorus removal. [ABSTRACT FROM AUTHOR]

Sulfadiazine (SDZ) is widely used in clinical treatment, livestock husbandry and aquaculture as an antibacterial agent, resulting in environmental risks. In this work, batch experiments were conducted to investigate the characteristics of SDZ biodegradation and reaction mechanisms in a nitrate anaerobic denitrifying system for the first time. The results showed that 98.52% of the SDZ, which had an initial concentration of 50 mg L−1, was degraded after 70 h, indicating that the removal efficiency of SDZ in anaerobic denitrifying system was 55.27% higher than that in anaerobic system. Furthermore, LC-MS-MS analysis confirmed that SDZ could be degraded into 16 byproducts via 3 main degradation pathways that contained 6 different reactions. After analyzing the microbial communities of the reactor, the denitrifying bacteria and desulfurizing bacteria Desulforhabdus , Ignavibacterium , SBR1031_norank , Nocardioides , etc. were highly associated with the removal of SDZ in the system. The biological toxicity test of the effluent indicated that the remaining organic matter and inorganic matter of the effluent could provide nutrients for E. coli and promote its growth. In other words, anaerobic denitrifying systems are highly efficient, simple and environmentally friendly, and have an impressive prospect in the biodegradation of sulfonamide antibiotics. Image 1 • Mixed microbes were first cultivated to remove SDZ in anaerobic denitrifying system. • Nitrate system could promote SDZ degradation and eliminate the biotoxicity of SDZ. • 3 metabolic pathways of SDZ that based on 6 chemical reactions were speculated. • Denitrification and desulfurization bacteria could promote SDZ degradation together. [ABSTRACT FROM AUTHOR]

• The quinoline wastewater treatment was first investigated in the MEC-AD system. • The performance of quinoline degradation was strengthened at a voltage of 1.0 V. • CH 4 production was increased to 1.5-fold in MEC-AD compared to the AD. • Simultaneous quinoline-C and quinoline-N removal were achieved in MEC-AD. • Exoelectrogens, methanogens, anammox and degradation bacteria have coexisted. In this study, the feasibility of quinoline-wastewater treatment was investigated in a coupled microbial electrolysis cell and anaerobic digestion system (MEC-AD). Improved degradation and enhanced mineralization of quinoline were obtained, and the optimal voltage was determined to be 1.0 V. Effective removal of quinoline at relative high concentration, and a 1.5-fold increase in methane production were achieved. The results indicated that the MEC-AD could simultaneously remove carbon and nitrogen from quinoline. Gas chromatography-mass spectrometry analysis identified 2-hydroxyquinoline and 8-hydroxycoumarin as the intermediates of quinoline. The formation and degradation of metabolites were rapid, and they did not accumulate in the MEC-AD. The results of microbial community structure analysis demonstrated that the functional species were enriched and coexisted, and that the dominant bacterial genera were SM1A02 , Comamonas , Desulfovibrio , Geobacter, and Actinomarinales_norank ; the dominant archaeal genera were Methanocorpusculum and Nitrosoarchaeum. Furthermore, the applied current played a selective role in the enrichment of microorganisms. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel up-flow microaerobic granular sludge reactor was constructed. • NH 4 +-N and TN removal averaged 92.35% and 90.41%, respectively, at a low C/N ratio. • Nitrifiers, denitrifiers, and anammox bacteria thrived in the microaerobic system. • An ecological nitrogen conversion model of granule sludge was proposed. Abstract In this study, a novel upflow microaerobic sludge reactor (UMSR) was constructed to conduct anaerobic digestion of municipal wastewater with low carbon and nitrogen ratio (C/N). Oxygen in the UMSR was supplied by falling water and external recirculation. Excellent nitrogen removal performance was obtained in the UMSR for treating wastewater with low C/N ratio at a temperature of 25 °C and a hydraulic retention time of 24 h. Ammonium and total nitrogen removal efficiencies averaged 92.35% and 90.41%, respectively, and sludge granulation occurred during acclimation. The inferred metabolism of nitrogen removal and ecological positions of functional microbe were integrated into a granule model by scanning electron microscopy. Additionally, the analysis of microbial community indicated that aerobic nitrifying bacteria and heterotrophic bacteria survived on the surface of sludge floc and granules while the anaerobic autotrophic, heterotrophic denitrifying, and anaerobic ammonia oxidation bacteria were present in the inner layer. [ABSTRACT FROM AUTHOR]

The investigation into the degradation of alkylphenol pollutants (APs) has become a hotspot due to their harmful effects on the environment and human health. In this study, microbial electrolysis cells (MECs) were used to degrade nonylphenol (NP) and 4- tert -octylphenol (4- tert -OP). The study found that the degradation rates of NP and 4- tert -OP for a 6-day period were 83.6% and 96.3%, respectively, which were 30.53% and 26.7% higher than those of the group without applied voltage. The double layer area in the degradation of 4- tert -OP was larger than that of NP, and the resistance exhibited by 4- tert -OP (87.47 Ω) in MEC was lower than that of NP (99.42 Ω). Meanwhile, NP had a greater effect on the bioenzyme activity than 4- tert -OP. GC-MS analysis showed that the degradation pathways of both pollutants mainly included oxidation and hydroxylation reactions. Furthermore, the microbial community analysis indicated that the main functional bacteria in NP degradation were Citrobacter , Desulfovibrio and Advenella , and those in 4- tert -OP degradation were Stenotrophomonas , Chryseobacterium , Dokdonella , and the key microbiomes underlying the cooperative relationship. The biotoxicity test indicated that the toxicity of residual substances was significantly reduced. Therefore, the MEC system is efficient and environmentally friendly and has broad application prospects in phenol refractory organics. [Display omitted] • Degradation ability of NP/4- tert -OP as the sole carbon source in MECs was first evaluated. • The degradation rate of NP and 4- tert -OP was effectively improved by weak electrical stimulation. • 4- tert -OP showed superior electrochemical performance and low impact on bioenzyme activity. • The main metabolic pathways of NP and 4- tert -OP were oxidation and hydroxylation reactions. • The correlation between aromatic compounds degrading bacteria and exoelectrogens was existed. [ABSTRACT FROM AUTHOR]

Electro-fermentation (EF) is an attractive way to implement the chain elongation (CE) process, by controlling the fermentation environment and reducing the dosage of external electron donors (EDs). However, besides the coexistence performance of external EDs and electrode, applications of EF technology on the fermentation broth containing both EDs and electron acceptors during CE process, are all still limited. The current study investigated the contribution of EF to caproate production, under different acetate: ethanol ratios (R A/E). The effect of multiple EDs, both from ethanol and the bio-cathode, on caproate production, was also assessed. A proof-of-concept, based on experimental data, was presented for the EF-mediated ethanol-driven CE process. Experimental results showed that ethanol, together with the additional electron donors from the bio-cathode, was beneficial for the stable caproate production. The caproate concentration increased with the decrease of R A/E , while the bio-cathode further contributed to 10.7%–26.1 % increase of caproate concentration. Meanwhile, the hydrogen partial pressure tended to 0.10 ± 0.01 bar in all controlled EF reactors, thus favoring caproate production. This was attributed to the increased availability EDs, i.e., hydrogen and ethanol, generated by the electrode and electrochemically active bacteria (EAB), which might create multiple additional pathways to achieve caproate production. Molecular ecological networks analysis of the key microbiomes further revealed underlying cooperative relationships, beneficial to the chain elongation process. The genus Clostridium_sensu_stricto , as the dominant microbial community, was positively related to acetogens, EAB and fermenters. [Display omitted] • The coexistence performance of external EDs and electrode was firstly elucidated. •External ethanol addition was conducive to the stable caproate production. •Caproate concentration showed rising trend with the increase of ethanol. •The introduction of bio-cathode contributed to 10.7%-26.1% increase. •Synergistic relationship of Clostridium sensu stricto and other microbes was revealed. [ABSTRACT FROM AUTHOR]