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•Bioaugmentation mechanism based on microbial community structure are analyzed.•Operation regulation and immobilization are proposed to overcome possible failures.•Feasible approaches ...for the scale-up application of bioaugmentation are summarized.•Research gaps and future challenges from micro to macro level are proposed.
Bioaugmentation is an optimization method with great potential to improve the treatment effect by introducing specific strains into the biological treatment system. In this study, a comprehensive review of the mechanism of bioaugmentation from the aspect of microbial community structure, the optimization methods facilitating application as well as feasible approaches of scale-up application has been provided. The different contribution of indigenous and exogenous strains was critically analyzed, the relationship between microbial community variation and system performance was clarified. Operation regulation and immobilization technologies are effective methods to deal with the possible failure of bioaugmentation. The gradual expansion from lab-scale, pilot scale to full-scale, the transformation and upgrading of wastewater treatment plants through the combination of direct dosing and biofilm, and the application of side-stream reactors are feasible ways to realize the full-scale application. The future challenges and prospects in this field were also proposed.
Electrochemical chlorination is promising for direct potable reuse (DPR) with zero-chemical-input and was investigated in this study for its application potential in reverse osmosis (RO)-based and ...non-RO-based DPR processes. Treatment of the simulated reclaimed water from non-RO-based trains showed satisfactory chlorine evolution compared to that from the RO-based trains. Under an applied current of 100 mA, a desired free chlorine concentration of 2 mg Cl2 L−1 was obtained within a short reaction time of 3.5 s. Consistent chlorine evolution performance was achieved in continuous experiments for 500 cycles, and the effluent pH was within the range of potable water guidelines (6.5 – 8.5). Electrochemical chlorination showed competitive disinfection performance compared to conventional chemical chlorination (7 log inactivation of E. coli within 60 s) at a low energy demand of ∼ 0.05 kWh m−3. The results of this preliminary investigation encourage the further exploration of electrochemical chlorination for DPR through the use of noble-metal-free anodes, utilization of renewable energy sources, removing persistent organic contaminants, and examining the synergy with RO-based DPR.
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•Electrochemical chlorination can achieve desired chlorine level for DPR.•Both chloride and total dissolved solids are important to chlorination.•Consistent performance is obtained in the continuous experiment for > 500 HRT.•Electrochemical chlorination disinfection is competitive with chemical chlorination.
Microbial electrochemical system (MES) technology has been widely investigated for organic degradation. However, the removal of recalcitrant organic contaminants containing halogen-, nitro-, or ...azo-groups remains a great challenge. Integrating the cathodic and anodic processes in an MES is able to improve or complete the mineralization of the target halogen-, nitro- and azo-organics via a sequential reductive and oxidative process. In this way, a cathode is used to reduce the toxic target organics, while an anode is to oxidize the residual organics from the reduction process and at the same time generate electrons to support the reduction process. This paper has provided a concise review about the sequential cathode-anode contaminant degradation in an MES and its specific mechanisms. Potential strategies to improve the MES degradation performance were discussed, mainly including the application and development of the biocatalyzed cathode as well as the optimization of the anodic operating condition and the improvement of anodic bacteria and electrode material. Perspectives on future directions were proposed and the key challenges were identified as the competitive or inhibitive influence of other compounds that could coexist in real wastewater on the target contaminants.
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Microbial electrochemical systems (MES) are studied to degrade organic contaminants with a lower energy demand, but degradation of recalcitrant compounds tends to be challenging. To enhance ...contaminant degradation in MES, advanced oxidation processes (AOPs) are synergistically linked to create cooperative processes such as bio-electro-Fenton (BEF) and enhanced bioanodes. BEF can achieve a high contaminant degradation efficiency with a low energy consumption due to the ability for energy recovery from the anodic organic wastes. Modifying a bioanode with catalytic oxidation materials, e.g., photocatalyst and MnO2, will achieve organic removal via the cooperation of catalysis and biodegradation. This paper has provided a concise review on the integration of AOPs with MES and identified and discussed the challenges such as deeper understanding of the electron transfer mechanisms, development of low-cost membrane, and the synergetic effects between functional materials and bacteria that are important to develop AOP-MES treatment systems.
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•Integrating AOPs with MES enhances recalcitrant organic contaminant degradation.•Bio-electro-Fenton can be energy-efficient with satisfactory degradation performance.•Critical challenges (e.g., require membrane and different water source) exist in BEF.•Enhanced bioanode with catalysts improves MES bioanode degradation ability.•Electron transfer mechanism and stability of the enhanced bioanode need investigation.
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) infections of the central nervous system are deadly and have vague symptoms. Traditional cerebro spinal fluid culture has a low positive rate, and because antibiotic use is common following ...therapy, it is more challenging to assess the response from pathogen content. In this case, a 66-year-old man who had a fever, a headache, and vomit was admitted to the hospital. He had diabetes, decline in thyroid function, and a history of pituitary tumor removal surgery. His initial treatment with ribavirin, ceftriaxone antibiotic, and moxifloxacin did not go well. Using two etiological tests (culture and metagenomic next-generation sequencing mNGS), his cerebrospinal fluid tested positively for
. Ampicillin-sulbactam and meropenem were used as treatments once
meningitis was identified. After treatment, his cerebrospinal fluid was assessed once more. Culture: negative; targeted next-generation sequencing (tNGS): positive and shows changes in the copy number of the
. After 44 days of treatment, the patient finally stopped taking antibiotics, and the prognosis was good. Our study showed that mNGS and tNGS, as novel approaches for pathogen detection, are capable of identifying pathogens quickly, sensitively, and accurately, especially when there are few infections present (such as after antibiotic treatment). The two methods can be a powerful assistance for helping clinicians to choose the best course of action.
Maternal gut microbiota play an important role in the modulation of offspring disease susceptibility and gut microbiota dysbiosis has been proposed as a mechanism through which toxic environmental ...chemicals exert their adverse impacts on health. The brominated flame retardants polybrominated diphenyl ethers (PBDEs) are developmental toxicants and induce dysbiotic gut microbiota in offspring. Yet, whether and how PBDEs impact the maternal gut microbiota remain unclear. Here, we sought to investigate the effect of 2,2′,4,4′-tetrabromodiphenyl ether (PBDE-47) exposure from preconception through lactation cessation on maternal gut microbiota and its link to host serum metabolic consequences. Female Sprague-Dawley rats were daily exposed to 10 mg/kg PBDE-47 via oral gavage from ten days before conception until offspring were weaned on postnatal day 21, then maternal fecal and blood samples were collected for microbiome and metabolome analyses by using 16S ribosomal RNA gene sequencing and gas chromatography-mass spectrometry, respectively. Maternal exposure to PBDE-47 showed a distinct profile in gut microbiota compared to control dams, as evidenced by increased Actinobacteria phylum and genera Blautia, Gemella and Phascolarctobacterium, and decreased genera AF12 and Oscillospira. Additionally, global metabolomics analysis identified 26 differential serum metabolites to distinguish PBDE-47 from controls, which were mainly involved in amino acid, lipid, carbohydrate and energy metabolism, further confirmed by pathway analysis. Importantly, the differential serum metabolites are closely correlated with the disturbed gut microbiota in response to PBDE-47. Collectively, our results suggest that maternal gut microbial dysbiosis may serve as a potential mechanism underlying PBDE-47-elicited health hazards to mothers or even offspring.
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•Maternal rats were exposed to PBDE-47 before, during and after pregnancy.•16s rRNA sequencing showed that PBDE-47 induced maternal gut microbiota dysbiosis.•Metabolomics revealed PBDE-47 elicited obvious changes in maternal serum metabolites.•Altered metabolites were involved in amino acid, lipid, sugar and energy metabolism.•The disturbed metabolites are potentially linked to the disrupted gut microbiota.
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•Bioelectrochemical degradation of monoaromatic compounds (MACs) was summarized.•MACs include phenol, BTEX, chlorophenol, nitrobenzene and chloramphenicol.•Reactor configuration, ...electrode material, electroactive microbe are key factors.•Mediators, sulfur/hydrogen cycle, system parameters also affect the process.•MACs bioelectrodegradation advantages are efficiency, selectivity and stability.
Monoaromatic compounds (MACs) are typical refractory organic pollutants which are existing widely in various environments. Biodegradation strategies are benign while the key issue is the sustainable supply of electron acceptors/donors. Bioelectrochemical system (BES) shows great potential in this field for providing continuous electrons for MACs degradation. Phenol and BTEX (Benzene, Toluene, Ethylbenzene and Xylenes) can utilize anode to enhance oxidative degradation, while chlorophenols, nitrobenzene and antibiotic chloramphenicol (CAP) can be efficiently reduced to less-toxic products by the cathode. However, there still have several aspects need to be improved including the scale, electricity output and MACs degradation efficiency of BES. This review provides a comprehensive summary on the BES degradation of MACs, and discusses the advantages, future challenges and perspectives for BES development. Instead of traditional expensive dual-chamber configurations for MACs degradation, new single-chamber membrane-less reactors are cost-effective and the hydrogen generated from cathodes may promote the anode degradation. Electrode materials are the key to improve BES performance, approaches to increase the biofilm enrichment and conductivity of materials have been discussed, including surface modification as well as composition of carbon and metal-based materials. Besides, the development and introduction of functional microbes and redox mediators, participation of sulfur/hydrogen cycling may further enhance the BES versatility. Some critical parameters, such as the applied voltage and conductivity, can also affect the BES performance, which shouldn’t be overlooked. Moreover, sequential cathode-anode cascaded mode is a promising strategy for MACs complete mineralization.
•Aerobic/anaerobic degrader, enzyme, pathway of chlorophenols (CPs) are summarized•Challenges and difficulties still exist in CPs dechlorination and ring-cleavage•The application of functional ...materials/bacteria/operating modes need be innovated•Sequential anaerobic-aerobic and bioelectrochemical system are promising strategies•The development of novel biotechnology toward efficient CPs degradation is critical
Chlorophenols (CPs) are highly toxic and refractory contaminants which widely exist in various environments and cause serious harm to human and environment health and safety. This review provides comprehensive information on typical CPs biodegradation technologies, the most green and benign ones for CPs removal. The known aerobic and anaerobic degradative bacteria, functional enzymes, and metabolic pathways of CPs as well as several improving methods and critical parameters affecting the overall degradation efficiency are systematically summarized and clarified. The challenges for CPs mineralization are also discussed, mainly including the dechlorination of polychlorophenols (poly-CPs) under aerobic condition and the ring-cleavage of monochlorophenols (MCPs) under anaerobic condition. The coupling of functional materials and degraders as well as the operation of sequential anaerobic-aerobic bioreactors and bioelectrochemical system (BES) are promising strategies to overcome some current limitations. Future perspective and research gaps in this field are also proposed, including the further understanding of microbial information and the specific role of materials in CPs biodegradation, the potential application of innovative biotechnologies and new operating modes to optimize and maximize the function of the system, and the scale-up of bioreactors towards the efficient biodegradation of CPs.
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Electrochemical treatment can be an effective approach for degrading recalcitrant organic contaminants because its anode/cathode produces powerful oxidizing/reducing conditions. Herein, through the ...cooperation of the cathodic reductive and anodic oxidative processes, 4-chlorophenol (4-CP) was successfully degraded in an electrochemical system. TiO2 nanotube arrays (TNTAs)/Sb-SnO2 and TNTAs/Pd were successfully prepared and served as the anode and cathode electrodes, respectively, to generate oxidative (hydroxyl radical, ·OH) and reductive (chemically adsorbed hydrogen, Hads) agents. The sequential reduction-oxidation (SRO) process provided a reasonable degradation pathway that accomplished reductive detoxification in the cathode and oxidative mineralization in the anode. The SRO mode achieved dechlorination efficiency (DE) of 86.9 ± 3.9% and TOC removal efficiency of 64.8 ± 4.2% within 3 h and under a current density of 8 mA cm−2, both of which were significantly higher than those obtained in the sequential oxidation-reduction or the simultaneous redox modes. The increment of current density and reaction time could improve 4-CP degradation performance, but a high current density would decrease the cathode stability and a longer reaction time led to the generation of ClO4-. This study has demonstrated that sequential reduction-oxidation can be an effective and tunable process for degrading recalcitrant organic contaminants.
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•4-CP removal is achieved via cooperative cathodic reduction and anodic oxidation.•Sequential reduction-oxidation results in the best detoxification and mineralization.•Both current density and reaction time are the key factors and optimized.•Potential problems like electrode stability & ClO4- generation warrant attention.•Specific degradation mechanism of 4-CP is analyzed and discussed.
Electrochemical oxidation (EO) can effectively remove recalcitrant organic contaminants from produced water (PW) but the formation of toxic oxidation byproducts (OBPs) is an unintended consequence. ...This study has rigorously investigated the OBPs formation during the EO treatment of a simulated PW containing phenol - a common organic contaminant existing in PW, as a model contaminant. In the absence of ammonia, free chlorine was generated from Cl- oxidation to serve as the main oxidant for phenol oxidation. During the EO process, 2,4,6-trichlorophenol and 2,6-dichlorobenzoquinone were identified as the critical intermediates that led to the formation of carbonaceous OBPs (C-OBPs). Some C-OBPs like chloroform (TCM), chloral hydrate (CH), and trichloroacetic acid (TCAA) reached their peak concentrations of 15 – 180 μM that were then reduced to 1 – 115 μM via volatilization and/or electrochemical reduction. When ammonia was present, nitrogenous OBPs (N-OBPs) were formed with the peak levels of 1 – 10 μM at the chlorination breakpoint (when ammonia was completely removed) that were subsequently reduced below 1 uM via volatilization and/or hydrolysis. It was observed that ammonia significantly decreased the formation of both C-OBPs and chlorate due to the consumption of free chlorine. A higher current density accelerated OBPs formation rates with different effects on volatile and non-volatile OBPs. The results of this study will enhance our understanding of OBPs formation precursors and mechanisms during electrochemical process and help develop strategies for proper control of OBPs to achieve safer electrochemical wastewater treatment.
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•Oxidation byproducts are formed during electrochemical treatment of produced water.•Trichlorophenol and dichlorobenzoquinone serve as intermediates for C-OBPs formation.•N-OBPs are formed in ammonia-containing produced water due to chloramine production.•Ammonia reduces C-OBPs and chlorate production by consuming free chlorine.•Higher salinity and current density accelerate OBPs formation rates.
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