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Membrane aerated biofilm reactor （MABR） effectively combines biofilm technology and membrane separation technology，which has great potential in wastewater denitrification. This paper focuses on the stability and nitrogen removal performance of MABR，which is used to treat soybean processing wastewater and simulated domestic wastewater. The results showed that when HRT was 12 h，aeration pressure was 10 kPa and C/N ratio was 5，MABR had the best treatment effect on simulated domestic sewage，and the average removal rates of COD，ammonia nitrogen and TN were 92.0%，86.5% and 83.3% respectively. When HRT was 8 h and aeration pressure was 10 kPa，MABR had the best treatment effect on soybean processing wastewater. The volume loads of COD，ammonia nitrogen， TN were 1 320，125.5，184 g/（m3·d） respectively，and the average removal rate had reached 84.2%，81.5%， 79.7% respectively，which was superior to the traditional biofilm method for nitrogen removal.

Selective electrochemical reduction of nitrate (NO3-) into ammonia (NH_3) is critical for environmental remediation and resource recovery. This review comprehensively summarizes the recent advances in electrochemical conversion of NO3- into NH_3. Mechanisms of NO3- reduction are discussed. The conversion of NO3- into NO_2 and formation of N—H is the key for achieving high selectivity of NH3. The technologies and strategies for enhancing the performance of electrode are summarized and compared. The crystal structure, morphology and charge density of materials are the key factors affecting the properties of electrode materials. The influence of electrochemical reactor on NO3- conversion and NH_3 formation is described. The core of electrolytic cell is to avoid anode interference and in-situ realize NH_3 separation and recovery. With these facts, it is proposed that the strategies for NO3- electrochemical selective reduction synthesis of NH_3 are the development of low-cost, stable, and efficient electrode materials and electrochemical synthesis and in-situ separation of NH_3 reactor. Besides, the long-term large-scale research on the electrochemical synthesis of NH_3 from actual NO3- wastewater is critical for promoting the industrialization of this technology.

Electrocatalytic nitrate reduction into ammonia is promising for its restricted activity and selectivity in wastewater treatment, however, it remains challenging. In this work, Co3O4 nanosheet electrodes with rich oxygen vacancies (OVs) (Co3O4−x/NF) are prepared and then applied as efficient catalysts for selective electrocatalytic reduction of nitrate to ammonia. The resulting Co3O4−x/NF electrodes exhibit high NO3−-N removal efficiency and NH4+-N selectivity, at 93.7% and 85.4%, respectively. X-Ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectra (EPR) results clearly reveal the formation of OVs in Co3O4−x/NF. The electrochemical characterization results confirm that OVs can effectively improve electron transfer as well as the electrochemically active area. The Co2+/Co3+ ratio of Co3O4−x/NF increases after the electrocatalytic reduction of nitrate, highlighting the crucial role played by Co2+ in mediating ammonia production via the Co2+/Co3+ cycle. These findings offer valuable guidelines for the development of more efficient and sustainable approaches for nitrate-contaminated wastewater treatment and ammonia synthesis. [ABSTRACT FROM AUTHOR]

Abstract Background Lignin materials are abundant and among the most important potential sources for biofuel production. Development of an efficient lignin degradation process has considerable potential for the production of a variety of chemicals, including bioethanol. However, lignin degradation using current methods is inefficient. Given their immense environmental adaptability and biochemical versatility, bacterial could be used as a valuable tool for the rapid degradation of lignin. Kraft lignin (KL) is a polymer by-product of the pulp and paper industry resulting from alkaline sulfide treatment of lignocellulose, and it has been widely used for lignin-related studies. Results Beta-proteobacterium Cupriavidus basilensis B-8 isolated from erosive bamboo slips displayed substantial KL degradation capability. With initial concentrations of 0.5–6 g L-1, at least 31.3% KL could be degraded in 7 days. The maximum degradation rate was 44.4% at the initial concentration of 2 g L-1. The optimum pH and temperature for KL degradation were 7.0 and 30°C, respectively. Manganese peroxidase (MnP) and laccase (Lac) demonstrated their greatest level of activity, 1685.3 U L-1 and 815.6 U L-1, at the third and fourth days, respectively. Many small molecule intermediates were formed during the process of KL degradation, as determined using GC-MS analysis. In order to perform metabolic reconstruction of lignin degradation in this bacterium, a draft genome sequence for C. basilensis B-8 was generated. Genomic analysis focused on the catabolic potential of this bacterium against several lignin-derived compounds. These analyses together with sequence comparisons predicted the existence of three major metabolic pathways: β-ketoadipate, phenol degradation, and gentisate pathways. Conclusion These results confirmed the capability of C. basilensis B-8 to promote KL degradation. Whole genomic sequencing and systematic analysis of the C. basilensis B-8 genome identified degradation steps and intermediates from this bacterial-mediated KL degradation method. Our findings provide a theoretical basis for research into the mechanisms of lignin degradation as well as a practical basis for biofuel production using lignin materials.

Guilin, a famous tourist city, is located in northeast Guangxi Province of Southwest China. However, recently, abnormal haze events occurred frequently in the winter. To characterize inorganic elements in PM2.5 and associated sources during a winter haze episode, 30 samples were collected from 6 sites in Guilin from December 16 to 20, 2016, and 24 inorganic elements were measured using an inductively coupled plasma mass spectrometer. The results showed that the sum of 24 inorganic elements varied from 5.47 ± 0.45 to 9.26 ± 0.73 μg m−3, and accounting for 6.81% ± 13.35% to 8.63% ± 15.05% of PM2.5 at all sites. Among them, crustal elements, including K, Ca, Na, Mg, Al, Fe, and Ti contributed approximately 82% ± 6%–90% ± 3%. Cluster results combined the coefficient of divergence and hierarchical cluster for inorganic elements and the sites showed that YS designated as the background site had obvious spatial heterogeneity, specially, mass concentration, and Igeo (index of geoaccumulation) values of Ni, Cr, Mo, and Ba were higher than those at the other five sites, which indicating that PM2.5 in Guilin was significantly affected by interregional transport. The results of source apportionment showed that Al, Ti, B, Fe, Ca, Mg, and Cr were derived from road and building dust, whereas Sb, As, and Hg originated from coal combustion, Co and V from vehicle emission (such as diesel and gasoline combustion), and other metals (Zn, Pb, Mn, Ba, Cu, Ni, Se, Cd, Mo, Tl, K, and Na) from coal combustion and industrial processes. [ABSTRACT FROM AUTHOR]

Perfluorooctanoic acid (PFOA) as an emerging persistent organic pollutant is hard to be degraded by conventional methods because of its stable physical and chemical properties. Microbial transformation is an attractive remediation approach to prevent and clean up PFOA contamination. To date, several strains of wild microbes have been reported to have limited capacity to degrade PFOA, selection of superior strains degrading PFOA become urgently necessary. Here, we report the application of genome shuffling to improve the PFOA-degrading bacterium Pseudomonas Parafulva YAB-1. The initial mutant populations of strain YAB1 were generated by nitrosoguanidine and ultraviolet irradiation mutagenesis respectively, resulting in mutants YM-9 and YM-19 with slightly improved PFOA-degrading ability. YM-9 and YM-19 were used as the starting strains for three rounds of recursive protoplast fusion. The positive mutants were screened on inorganic salt medium plates containing different concentrations of PFOA and selected based on their PFOA degradability in shake-flask fermentation test. The best performing recombinant F3-52 was isolated after three rounds of genome shuffling. In batch fermentation, the PFOA degradation rate of mutant F3-52 was up to 58.6%, which was 1.8-fold higher than that of the parent strain YAB1, and 1.6-fold higher than the initial mutants YM-9 and YM-19. Pass-generation test indicated that the heredity character of F3-52 was stable. The results demonstrated that genome shuffling was an efficient method for improving PFOA degradation of Pseudomonas Parafulva YAB1. The bred mutant F3-52 with 58.6% PFOA-degrading rate could be used for the environmental control of PFOA pollutant. [ABSTRACT FROM AUTHOR]

Here, Pannonibacter phragmitetus BB was investigated at genomic, genetic and protein levels to explore molecular mechanisms of chromium biotransformation, respectively. The results of Miseq sequencing uncovered that a high-qualified bacterial genome draft was achieved with 5.07 Mb in length. Three novel genes involved in chromate reduce and transport, named nitR, chrA1 and chrA2 , were identified by alignment, annotation and phylogenetic tree analyses, which encode a chromate reductase (NitR) and two chromate transporters (ChrA1 and ChrA2). Reverse transcription real-time polymerase chain reaction (RT-qPCR) analyses showed that the relative quantitative transcription of the three genes as the maximum reduction rate of Cr(VI) were significantly up-regulated with the increasing initial Cr(VI) concentrations. However, at the maximum cell growth points nitR was in a low transcription level, while the transcription of chrA1 and chrA2 were hold at a relatively high level and decreased with the increasing initial Cr(VI) concentrations. The ex-situ chromate reducing activity of NitR was revealed a V max of 34.46 µmol/min/mg enzyme and K m of 14.55 µmol/L, suggesting feasibility of the reaction with Cr(VI) as substrate. The multiple alignment demonstrates that NitR is potentially a nicotinamide adenine dinucleotide phosphate (NADPH) dependent flavin mononucleotide (FMN) reductase of Class I chromate reductases. Our results will prompt a large-scaled bioremediation on the contaminated soils and water by Pannonibacter phragmitetus BB, taking advantage of uncovering its molecular mechanisms of chromium biotransformation. [ABSTRACT FROM AUTHOR]

Ficus tikoua(F. tikoua) was a potential species for antimony (Sb) phytoremediation due to its wide growth in the mining area. However, little was known about its tolerance mechanisms toward Sb. The determination of the distribution and chemical speciation of Sb inF. tikouais essential for understanding the mechanisms involved in Sb accumulation, transportation, and detoxification. The present study investigated the subcellular distribution and chemical forms of Sb inF. tikoua. The plant was exposed to different Sb concentrations (0, 30, 90, and 180 μmol/L) for 30 days. The results showed thatF. tikouapossessed a marked ability to tolerate and accumulate Sb. The proportional Sb increased with increasing Sb concentration in the solution, and the highest Sb concentration occurred in roots (1274.5–1580.9 mg/kg), followed by stems (133.5–498.9 mg/kg) and leaves (4.1–15.7 mg/kg). In the subcellular sequestration of Sb inF. tikoua, the largest accumulation of Sb occurred in cell walls (72.4–87.5%) followed by cytoplasmic organelles (8.2–18.6%) and cytoplasmic supernatant. The results suggested that cell walls act as important protective barriers against Sb toxicity inF. tikoua. Although Sb in all plant tissues found primarily in the fractions extracted by ethanol and distilled water, the current study found that the Sb amounts in the HAc-extractable fraction, HCl-extractable fraction, and residue fraction increased at the highest Sb level (180 μmol/L) compared to that under lower Sb levels. These results indicate that excessive Sb accumulated inF. tikouaunder Sb stress is bound to non-dissolved or low-bioavailable compounds, a biochemical mechanism that benefitsF. tikouabecause it helps alleviate Sb toxicity. [ABSTRACT FROM PUBLISHER]

Culture-independent and -dependent methods were used to evaluate the genetic diversity of hexavalent chromium-resistant bacteria in contaminated soils. Denaturing gradient gel electrophoresis (DGGE) showed that hexavalent chromium-resistant bacteria in contaminated soils had significant structural diversity that was not related to the concentration of hexavalent chromium, while the diversity of soil bacterial communities was correlated with soil pH. Twenty-two chromium-resistant bacterial strains were isolated from contaminated soil, including members ofBrevundimonas,Micrococcus,Exiguobacterium,AlcaligenesandPannonibacter. Repetitive sequence-based polymerase chain reaction showed that the BOX- primer produced the more complex banding patterns than the ERIC- and REP- primers, indicating a high degree of genotypic diversity. These bacterial strains varied in ability to reduce hexavalent chromium.Pannonibacterreduced 300 mg·L−1of hexavalent chromium in solution within 24 h. X-ray photoelectron spectra (XPS) analysis revealed that Cr(OH)3, Cr2O3, and CrCl3composed approximately 83.51% of the total chromium in the reduction product. [ABSTRACT FROM AUTHOR]

Plastic pollution, particularly non-degradable residual plastic films and microplastics (MPs), is a serious environmental problem that continues to worsen each year. Numerous studies have characterized the degradation of plastic fragments; however, there is known a lack of about the state of current physicochemical biodegradation methods used for plastics treatment and their degradation efficiency. Therefore, this review explores the effects of different physicochemical factors on plastics/MPs degradation, including mechanical comminution, ultraviolet radiation, high temperature, and pH value. Further, this review discusses different mechanisms of physicochemical degradation and summarizes the degradation efficiency of these factors under various conditions. Additionally, the important role of enzymes in the biodegradation mechanism of plastics/MPs is also discussed. Collectively, the topics discussed in this review provide a solid basis for future research on plastics/MPs degradation methods and their effects. [Display omitted] • UV could disrupt the molecular structure of MPs to produce –C O−, C–OH, and –CHOOH groups. • Physicochemical degradation of MPs was caused by many factors. • The degradation efficiency of MPs mainly depends on the type of microorganism. • Microorganisms have selective degradation effect on different polymers. • The biodegradation mechanism of MPs is conducted by the participation of enzymes. [ABSTRACT FROM AUTHOR]

Kraft lignin (KL) is the major pollutant in black liquor. The bacterial strain Pandoraea sp. B-6 was able to degrade KL without any co-substrate under high alkaline conditions. At least 38.2 % of chemical oxygen demand and 41.6 % of color were removed in 7 days at concentrations from 1 to 6 g L −1. The optimum pH for KL degradation was 10 and the optimum temperature was 30 °C. The greatest activities of 2,249.2 U L −1 for manganese peroxidase and 1,120.6 U L −1 for laccase were detected on the third and fifth day at pH 10, respectively. Many small molecules, such as cinnamic acid, ferulic acid, 2-hydroxy benzyl alcohol, and vanillyl methyl ketone, were formed during the period of KL degradation based on GC–MS analysis. These results indicate that this strain has great potential for biotreatment of black liquor. [ABSTRACT FROM AUTHOR]

Oxygen catalysts are notorious for their high overpotential and sluggish kinetics. Both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) consist of four proton‐coupled/decoupled electron‐transfer steps with a bond‐breaking (ORR) or of a bond‐forming (OER) step. The rate‐determining steps and intermediates for OER and ORR are different, and the binding energy between the active sites and intermediates are not identical; thus, it is tough to achieve identical oxygen binding energies of the intermediates close to the theoretical equilibrium potential. A good bifunctional oxygen catalyst should have multiple redox centers that could be responsible for OER and ORR. Composites with multiactive centers and conductive supports could offer new opportunities for bifunctional air electrode. For more details see the Review by S. Wang, Y. Cheng et al. on page 3906 ff. [ABSTRACT FROM AUTHOR]

Heavy metals and ammonia are difficult to remove from wastewater, as they easily combine into refractory complexes. The struvite formation method (SFM) was applied for the complex decomposition and simultaneous removal of heavy metal and ammonia. The results indicated that ammonia deprivation by SFM was the key factor leading to the decomposition of the copper–ammonia complex ion. Ammonia was separated from solution as crystalline struvite, and the copper mainly co-precipitated as copper hydroxide together with struvite. Hydrogen bonding and electrostatic attraction were considered to be the main surface interactions between struvite and copper hydroxide. Hydrogen bonding was concluded to be the key factor leading to the co-precipitation. In addition, incorporation of copper ions into the struvite crystal also occurred during the treatment process. [ABSTRACT FROM AUTHOR]

Abstract: This study focused on the biodegradation of kraft lignin (KL) by Novosphingobium sp. B-7 using KL as sole carbon source. Results revealed that Novosphingobium sp. B-7 reduced the chemical oxygen demand (COD) by 34.7% in KL mineral salt medium after 7days of incubation. Additionally, the maximum activities of manganese peroxidase (MnP) of 3229.8Ul−1 and laccase (Lac) of 1275Ul−1 were observed at 4th and 5th day, respectively. GC–MS analysis indicated that after incubated with Novosphingobium sp. B-7, low molecular weight alcohols and lignin-related monomer compounds such as ethanediol, p-hydroxy benzoic acid and vanillic acid were formed in the system, which strongly confirmed the degradation of KL by Novosphingobium sp. B-7. [Copyright &y& Elsevier]

Abstract: The nitrogen pollution has caused serious environmental problems. The main aims of the present study were to remove the nitrogen from wastewater through ANAMMOX (ANaerobic AMMonium OXidation) process, and let the effluent meet the discharge standard which was significant and advance in the field of ANAMMOX application which was also very important to the environmental protection and water recycling. This study reports the performance of ANAMMOX-EGSB (Expanded Granular Sludge Bed) reactor after feeding with synthetic wastewater. The results showed that the effluent ammonium concentration was 11.90mgN/L and the nitrogen remove efficiency (NRE) reached up to 94.68% when the volumetric nitrogen loading rate (NLR) and volumetric nitrogen removal rate (NRR) were as high as 27.31 and 25.86kgN/(m3·d), respectively. The effluent ammonium concentration meets the Chinese integrated wastewater discharge standard (GB8978-1996) in which the ammonium concentration should be lower than 15mgN/L. The maximum ammonium, nitrite and nitrogen conversion rates (q max ) by the ANAMMOX granular sludge in the reactor were 907.13, 841.76, 1810.10mgN/(g VSS·d) and half saturation constants (K S ) were 2.69, 0.44, 3.11mgN/L, respectively. [Copyright &y& Elsevier]

• Cemented paste backfill exhibited effective immobilization for arsenic waste. • AsO 4 3 - substituted SeO 4 2 - inside the ettringite in the form of HAsO 4 2 -. • The As-ettringite solid phase was formed as the primary retention phase for As (Ⅴ). Although cemented paste backfill (CPB) method has been proposed as a resource disposal technology for arsenic waste, the immobilization potential and immobilization mechanism of arsenic in CPB remain unclear. In this study, lead-zinc slag, gypsum, and sodium arsenate were used to simulate the disposal of arsenic waste in CPB. Toxicity characteristic leaching procedure (TCLP) and compressive strength tests were used to determine the immobilization potential of arsenic in CPB. The immobilization mechanisms of arsenic in CPB were studied by X-ray diffraction (XRD), scanning electronic microscopy-energy dispersive spectrometry (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR). The high compressive strength and low leaching toxicity showed that CPB had better immobilization potential of arsenic. SEM and XRD analyses showed that the formation of As-ettringite is an important immobilization mechanism of arsenic in CPB. FTIR analysis showed that AsO 4 3 - substituted SeO 4 2 - inside the ettringite in the form of HAsO 4 2 -. In the hydration process from 0 to 3 days, physical encapsulation and Ca-As precipitates were the main immobilization mechanism of arsenic. In the hydration process from 3 to 28 days, the immobilization efficiency of As-ettringite on arsenic was significantly higher than that of physical encapsulation and Ca-As precipitation. This study demonstrated that CPB is suitable for the immobilization of arsenic waste. [ABSTRACT FROM AUTHOR]

Sulfidation roasting followed by flotation is widely known as a possible generic technology for enriching valuable metals in low-grade Zn-Pb oxide ores. Zn 2 SiO 4 is the primary Zn phase in willemite. Zn 4 Si 2 O 7 (OH) 2 (H 2 O), the main Zn phase in hemimorphite, transforms into Zn 2 SiO 4 at temperatures above 600 °C. To enrich the Zn in willemite and hemimorphite, the Zn species should first be converted to ZnS. Therefore, a thorough understanding of the sulfidation reaction of Zn 2 SiO 4 during roasting with pyrite is of vital important. In this study, the sulfidation behavior and reaction mechanisms of a Zn 2 SiO 4 -pyrite roasting system were determined using HSC 5.0 software, TG-FTIR spectroscopy, XRD, XPS and SEM-EDS. The results indicate that the sulfidation process can be divided into three steps: the decomposition of pyrite and formation of a sulfur-rich environment, the sulfur-induced migration of O 2− and transformation of sulfur vapor, and the sulfidation reaction via oxygen-sulfur exchange. During the sulfidation roasting process, pyrite was converted to loose and porous Fe 3 O 4 , whereas Zn 2 SiO 4 was transformed into ZnS and SiO 2 in situ. These findings provide theoretical support for controlling the sulfidation roasting process of willemite and hemimorphite. [ABSTRACT FROM AUTHOR]

Abstract: Partial nitrification (PN) process is an essential pre-treatment to Anammox process for nitrogen removal from ammonium-rich wastewaters. High activity nitrifiers (HANs) are considered as the key to high-rate PN process. The HANs could be successfully enriched at free ammonia (FA) concentrations of 10–20mgNH3–NL−1, which differed significantly from those enriched at FA concentrations of 1–3mgNH3–NL−1. The maximum specific ammonium conversion rate, half saturation constant, half inhibition constant, cell yield and decay rate were 2.87gNg−1 VSSd−1, 5.82mgNL−1, 8218.8mgNL−1, 0.15gVSSg−1 –N and 0.09d−1 for HANs at 30°C, respectively, which endowed the PN process a volumetric conversion rate (VCR) as high as 2.22±0.33kgNm−3 d−1. The cultivation mode of HANs was workable and the HANs were promising as inoculum for the PN process. [Copyright &y& Elsevier]

Abstract: The anaerobic ammonium oxidation (Anammox) was successfully started up in an upflow biofilm (UBF) reactor and operated for 435days at 35°C. The process development could be divided into four phases, i.e. endogenous denitrification without Anammox reaction (P1), functional biomass enrichment under relatively low nitrogen loading rate (NLR) (P2), specific Anammox activity (SAA) enhancement with high NLR (P3) and the final stable stage (P4). The maximal NLR was as high as 34.5kgN/m3d. Nitrogen mass balance showed that 88.84% of input nitrogen converted to dinitrogen gas, 1.74% was used for cellular synthesis and the rest was converted to nitrate. The final produced biomass was fast-growing with SAA of 1.8gN/gVSSd and doubling time of 4.3–7.4d. Granulation and biofilm formation contributed to the biomass enrichment, while appropriate recirculation as well as relatively high temperature (35°C) helped to promote SAA. Effective retention time and promoted sludge activity were considered as the key factors for bacterial growth and efficient Anammox process. [Copyright &y& Elsevier]