Xinbai Jiang

Coupling of a bioelectrochemical system for p-nitrophenol removal in an upflow anaerobic sludge blanket reactor.

Coupling of a bioelectrochemical system (BES) into the upflow anaerobic sludge blanket (UASB) was developed for enhanced p-nitrophenol (PNP) removal in this study. Compared to the control UASB reactor, both PNP removal and the formation of its final reductive product p-aminophenol (PAP) were notably improved in the UASB-BES system. With the increase of current density from 0 to 4.71 A m(-3), the rates of PNP removal and PAP formation increased from 6.16 ± 0.11 and 4.21 ± 0.29 to 6.77 ± 0.00 and 6.11 ± 0.28 mol m(-3) d(-1), respectively. More importantly, the required dosage of organic cosubstrate was significantly reduced in the UASB-BES system than that in the UASB reactor. Organic carbon flux analysis suggested that biogas production from organic cosubstrate was seriously suppressed while direct anaerobic reduction of PNP was not remarkably affected by current input in the UASB-BES system. This study demonstrated that the UASB-BES coupling system had a promising potential for the removal of nitrophenol-containing wastewaters especially without adequate organic cosubstrates inside.

Comprehensive comparison of bacterial communities in a membrane-free bioelectrochemical system for removing different mononitrophenols from wastewater.

Membrane-free bioelectrochemical systems (MFBESs) have been developed for the degradation of nitro-aromatic contaminants, but the microbial communities that are involved have not been comprehensively investigated. In this study, the microbial communities were evaluated and compared for treating different structures of nitrophenols (NPs), i.e., o-nitrophenol (ONP), m-nitrophenol (MNP) and p-nitrophenol (PNP), in the MFBES. The results demonstrated that NPs reduction in the MFBES decreased in efficiency in the following order: ONP>MNP>PNP. Illumina MiSeq sequencing results showed that richness and diversity of bacterial species in the anodic and cathodic communities decreased when fed different NPs. Though remarkable differences in community composition were found between anodic and cathodic biofilms in the MFBES, three core genera-Treponema, Desulfovibrio and Geobacter-were dominant in the anodic or cathodic biofilm, regardless of various NPs. Other functional genera in the anodic or cathodic biofilm were selectively enriched in the MFBES treating the three NPs with different structures.

Aerobic granulation strategy for bioaugmentation of a sequencing batch reactor (SBR) treating high strength pyridine wastewater.

Aerobic granules were successfully cultivated in a sequencing batch reactor (SBR), using a single bacterial strain Rhizobium sp. NJUST18 as the inoculum. NJUST18 presented as both a good pyridine degrader and an efficient autoaggregator. Stable granules with diameter of 0.5-1 mm, sludge volume index of 25.6 ± 3.6 mL g(-1) and settling velocity of 37.2 ± 2.7 m h(-1), were formed in SBR following 120-day cultivation. These granules exhibited excellent pyridine degradation performance, with maximum volumetric degradation rate (Vmax) varied between 1164.5 mg L(-1) h(-1) and 1867.4 mg L(-1) h(-1). High-throughput sequencing analysis exhibited a large shift in microbial community structure, since the SBR was operated under open condition. Paracoccus and Comamonas were found to be the most predominant species in the aerobic granule system after the system had stabilized. The initially inoculated Rhizobium sp. lost its dominance during aerobic granulation. However, the inoculation of Rhizobium sp. played a key role in the start-up process of this bioaugmentation system. This study demonstrated that, in addition to the hydraulic selection pressure during settling and effluent discharge, the selection of aggregating bacterial inocula is equally important for the formation of the aerobic granule.

Enhanced bioelectrochemical reduction of p -nitrophenols in the cathode of self-driven microbial fuel cells

Reduction from p-nitrophenol (PNP) to p-aminophenol (PAP) was studied in the cathodes of self-driven microbial fuel cells (MFCs), and the influence of electron donor (CH3COONa) & acceptor concentration, external resistance and electrolyte conductivity were investigated. The results showed that PNP reduction efficiencies reached 100% when initial concentrations were lower than 50 mg L−1. PAP formation efficiencies were promoted from 31.7 ± 2.1% to 76.4 ± 4.1%, by increasing CH3COONa concentration from 2000 mg L−1 to 4000 mg L−1. Decreasing the external resistance from 1000 Ω to 240 Ω improved the PAP formation by 4–5 times for higher currents. Increasing the electrolyte conductivity (controlled by total dissolved solids, TDS) could accelerate the PNP degradation process within 24 h. Illumina high-throughput sequencing showed the dominating bacteria on the biocathodes were: Ignavibacterium 14.37%, Ottowia 4.04%, Pseudomonas 3.66%, Proteiniphilum 2.50%, Chlorobaculum 1.67%, Nitrospira 1.62% (at the genera level). The bacteria might play vital roles in more efficient nitrophenol degradation in biocathode MFCs. Compared to the abiotic control, the main advantages of PNP degradation in biocathodes are higher PNP reduction & PAP formation efficiencies, less electron donor consumption and higher system efficiency. The self-driven MFC system could be a promising way to deal with nitroaromatic pollutants.

Enhanced p-nitrophenol removal in a membrane-free bio-contact coupled bioelectrochemical system

In this study, a membrane-free bio-contact coupled bioelectrochemical system (BC-BES) was established for the enhanced reductive transformation of p-nitrophenol (PNP). The results showed that the electric field played a key role in both PNP reduction and p-aminophenol (PAP) formation. The vast majority of PNP was reductively transformed to PAP in the biocathode of BC-BES. At a cathode potential of −1000 mV vs. Ag/AgCl and hydraulic retention time (HRT) of 8.9 h, PNP removal rate as high as 18.95 ± 0.10 mol per m3 per day could be achieved in the BC-BES with acetate as the electron donor. High PNP removal and PAP formation could be achieved at low acetate dosage, high initial PNP concentration and short HRT, indicating the strong ability of the BC-BES to resist shock loading. Furthermore, partial mineralization of PAP was observed in the anode of the BC-BES, which was beneficial for the further polishing of the BC-BES effluent. Considering the advantages of high loading rate, low acetate consumption and high system stability, it is hoped that the application of this BC-BES will enhance the reductive removal of nitrophenols from wastewaters.

Synthesis of Cu2O–CuFe2O4 microparticles from Fenton sludge and its application in the Fenton process: the key role of Cu2O in the catalytic degradation of phenol

This paper presents the key role of Cu2O in Fenton catalysis using Cu2O–CuFe2O4 magnetic microparticles, which were prepared using Fenton sludge as an iron source. The catalytic activity of the as-prepared Cu2O–CuFe2O4 and CuFe2O4 microparticles was evaluated in a heterogeneous Fenton system for the degradation of recalcitrant phenol. The Cu2O–CuFe2O4 microparticles demonstrated relatively superior catalytic performance as compared to CuFe2O4 microparticles when used as a Fenton catalyst. The relatively higher catalytic activity of Cu2O–CuFe2O4 for phenol degradation during the Fenton process could be attributed to the availability of both monovalent [Cu(I)] and divalent [Cu(II)] as well as Fe(II)/Fe(III) redox pairs, which could react quickly with H2O2 to generate hydroxyl radicals (HO˙). An electron bridge was formed between Cu(I) and Fe(III), which accelerates the formation of Fe(II) species in order to boost the reaction rate. Highly reactive and excessively available Cu(I) species for as prepared Cu2O–CuFe2O4 microparticles could be considered to be rather crucial for the generation of highly reactive HO˙ radical species. In addition, the as-prepared Cu2O–CuFe2O4 magnetic microparticles exhibited sound stability and reusability.

Biochar supported sulfide-modified nanoscale zero-valent iron for the reduction of nitrobenzene

Sulfide-modified nanoscale zerovalent iron (S-nZVI) was effectively utilized for the reduction of various contaminants, despite its applicability being limited due to agglomeration, oxidation and electron loss. In this study, biochar (BC)-supported S-nZVI was prepared to enhance the reactivity of S-nZVI for nitrobenzene (NB) reduction. Scanning electron microscopy images showed that the S-nZVI particles were well-dispersed on the BC surface as well as in the channels. NB removal and aniline formation could be significantly enhanced by using S-nZVI@BC, as compared to S-nZVI and blank BC. NB removal by S-nZVI@BC followed the pseudo second-order kinetics model and Langmuir isotherm model, suggesting hybrid chemical reaction-sorption was involved. Furthermore, a possible reaction mechanism for enhanced NB removal by S-nZVI@BC was proposed, including chemical adsorption of NB onto S-nZVI@BC, direct reduction by S-nZVI and enhanced electron transfer. The high reducibility of S-nZVI@BC as well as its excellent antioxidation ability and reusability demonstrated its promising prospects in remediation applications.

Bioelectrodegradation of Hazardous Organic Contaminants from Industrial Wastewater

Hazardous organic contaminants tend to accumulate in the industrial effluents due to their recalcitrant properties. Approaches used for the hazardous contaminants removal always encounter conflicts between treatment efficiency and economic efficiency. Bioelectrochemical system (BES) is an attractive new type of wastewater treatment technology, which is versatile with the advantages of low energy demand, less sludge production, and synchronous resource recovery. Electrons microbially generated from the anode of BES enable bioremediation processes for removing persistent pollutants in wastewater. Highly oxidized hazardous organic contaminants could be efficiently reduced at abiotic/biocathode driven by bioanodes. This review summarized a series of typical hazardous organic pollutants transformation or degradation in BESs from the views of process operation, functional bacteria, and mechanisms. In addition, as an extent of anaerobic technology, BES coupling with traditional anaerobic process is considered as a promising way to achieve energy-efficient wastewater treatment and deliver scaled-up applications of BESs. Moreover, the main hurdles and future perspectives as well as potential future research are discussed.

Co-metabolic enhancement of 1H-1,2,4-triazole biodegradation through nitrification

Due to highly recalcitrant nature of 1H-1,2,4-triazole (TZ), the conventional biological process is quite ineffective for TZ removal from wastewater. In this study, co-metabolic enhancement of TZ biodegradation through nitrification was investigated in an activated sludge reactor. The link between enhanced TZ degradation and nitrification was established through highly efficient removal of TZ, TOC as well as dissolved organic matter with the supplement of NH4+. A new co-metabolic degradation pathway of TZ was proposed based on the identification of five co-metabolic intermediates, including 2,4-dihydro-[1,2,4]triazol-3-one and [1,2,4]triazolidine-3,5-dione. High-throughput sequencing analysis suggested the significant improvement of microbial community in the co-metabolic system in terms of richness, abundance and uniformity. Functional species related to nitrification and biodegradation was enriched with the supplement of NH4+, confirming the key role of nitrification. This study demonstrated that nitrification-assisted co-metabolism had a promising potential for the removal of recalcitrant contaminants such as TZ from wastewater.

Promotion of Para-Chlorophenol Reduction and Extracellular Electron Transfer in an Anaerobic System at the Presence of Iron-Oxides

Anaerobic dechlorination of chlorophenols often subjects to their toxicity and recalcitrance, presenting low loading rate and poor degradation efficiency. In this study, in order to accelerate p-chlorophenol (p-CP) reduction and extracellular electron transfer in an anaerobic system, three iron-oxide nanoparticles, namely hematite, magnetite and ferrihydrite, were coupled into an anaerobic system, with the performance and underlying role of iron-oxide nanoparticles elucidated. The reductive dechlorination of p-CP was notably improved in the anaerobic systems coupled by hematite and magnetite, although ferrihydrite did not plays a positive role. Enhanced dechlorination of p-CP in hematite or magnetite coupled anaerobic system was linked to the obvious accumulation of acetate, lower oxidation–reduction potential and pH, which were beneficial for reductive dechlorination. Electron transfer could be enhanced by Fe2+/Fe3+ redox couple on the iron oxides surface formed through dissimilatory iron-reduction. This study demonstrated that the coupling of iron-oxide nanoparticles such as hematite and magnetite could be a promising alternative to the conventional anaerobic reduction process for the removal of CPs from wastewater.