•Phragmites australis can accumulate Cd in the roots with a short treatment time.•AM fungus alleviates Cd induced phytotoxicity in roots of P. australis.•AM fungus increased enzyme activities and levels of thiolic compounds in roots.•PCA could be used to evaluate role of AM fungus in alleviation of Cd phytotoxicity.The positive effects of arbuscular mycorrhizal (AM) fungi on host plants under heavy metal (HM) stress conditions have been widely recognized. HMs are known to induce phytotoxicity through 1) the production of reactive oxygen species (ROS), 2) the direct interaction with thiol groups or 3) the competition with essential elements. However, how AM fungus inoculation can affect defense mechanisms against cadmium (Cd) stress, which can regulate and alleviate the phytotoxicity via different pathways, is still unclear. We hypothesized that one or some factors in each pathway of phytotoxicity were involved in detoxifying Cd by inoculating with AM fungus. In this study, the involvements of enzymes, thiolic compounds, and divalent essential elements in the roots of Phragmites australis (Cav.) Trin. ex Steud. were assessed. In addition, we also worked to elucidate the significant factors among three possible pathways involved in biosynthesis with AM fungus inoculation, using principal component analysis (PCA). The results presented here indicate that AM symbiosis can result in a marked tolerance to Cd via accumulating Cd with a shorter exposure treatment time, and obvious fluorescence in the roots was also observed. The decrease in phytotoxicity was mainly accomplished by changes in superoxide dismutase (SOD), catalase (CAT), non-protein thiols (NPT), calcium (Ca), manganese (Mn), and copper (Cu). These results provide comprehensive insights for elucidating the defense mechanisms by which inoculation with AM fungus has beneficial roles in helping P. australis cope with the deleterious effects of Cd.

The increasing salinity in aquatic environments has had a negative impact on the biodegradation of atrazine, an extensively used herbicide which has been proven to pollute soil and water ecosystems. In the present study, a novel atrazine-degrading strain (ZXY-2) was isolated from industrial wastewater and identified as the Arthrobacter genus with the 16S rRNA gene. Results indicated that the strain showed a high salinity tolerance, and was able to tolerate NaCl concentrations up to 10% (w/w). Plackett–Burman (PB) multifactorial design and response surface methodology (RSM) were then employed to optimize the culturing conditions. Results showed that among the selected fifteen factors, six contributing factors were obtained. Subsequently, by employing the RSM to model and optimize atrazine degradation, a biodegradation efficiency of 12.73 mg L−1 h−1 was reached under optimal conditions (34.04 °C, pH 9.0, inoculum size 10% (v/v), 2.212 g L−1 of sucrose, 6 g L−1 of Na2HPO4·12H2O, and 50 mg L−1 of atrazine). In addition, a statistically quadratic polynomial mathematical model was suggested (R2 = 0.9873). In contrast to other atrazine-degrading bacteria, ZXY-2 appears to be adapted to life under high salinity conditions and sustains excellent atrazine degradation performance. Therefore it could potentially be applied in atrazine bioremediation.

The aim of this study is to investigate the effect of a novel iron oxide–zeolite system on the anaerobic digestion of cow manure and rice straw. The results showed that the cumulative methane yield during the 40 days of digestion with the supplementation of the newly formed additive reached as high as 394.38 mL/g of VSadd, which was 74.11% higher than that with the mixture of iron oxide and zeolite as the additive (226.51 mL/g of VSadd) and 372.85% higher than the control (83.05 mL/g of VSadd). The introduction of the iron oxide–zeolite system also brought a more stable pH condition, higher total VFA, and lower ammonia concentration. In terms of the substrate degradation, a better bioavailability of the lignocellulosic biomass has been obtained. The coenzyme F420 assay demonstrated a significantly strengthened methanogen activity by the addition of the iron oxide–zeolite system. Considering its high efficiency and good performance, the iron oxide–zeolite system can be extended to practical engineering application for biomethane production.

•Mutant strains from Chlorella pyrenoidosa were primarily screened from mutant library after mutagenizing by ARTP.•The OD680 of the optimum mutant strain in stationary phase were increased by 32.08%.•Dry weight and lipid productivity of the optimum mutant strain were increased by 22.07% and 16.85%.In this study, an efficient screening program was established with ARTP. Five strains from oleaginous microalgae Chlorella pyrenoidosa were screened from mutant library after mutagenizing by ARTP. Among them, the optimal mutant strain was named as II-H6. In the BG11 medium, the OD680 of II-H6 in stationary phase were increased by 32.08% than the original strain. Meanwhile, compared with the original strain, the dry weight and lipid productivity of II-H6 were increased by 22.07% and 16.85%, respectively. II-H6 showed a good genetic stability in BG11 medium and the optimum growth temperature and pH were 33 °C and 9.0. 18S gene fragment length of II-H6 strain were 1886 bp. Analysis of the gene fragment showed that the II-H6 strain had a close relationship to the original strain, and it belonged to the mutation within the genus Chlorella.Download high-res image (131KB)Download full-size image

In order to assess the capacity of Aquabacterium parvum sp. strain B6 for nitrate-dependent Fe(II) oxidation, batch cultivation was conducted, and its ability to oxidize Fe(II) coupled to nitrate reduction in the presence of diverse organic substrates was studied. Meanwhile, the nitrate-removal rate of B6 with various impact factors was further optimized by the response surface methodology (RSM). The results show that strain B6 is capable of utilizing different organic compounds as substrates for nitrate reduction. Compared with yeast extract, B6 showed a greater potential of chemical oxygen demand (COD) degradation and cell proliferation with acetate and glucose mediums, respectively, while citrate was not beneficial for this process due to its low consumption rate. RSM analysis demonstrated that the maximum nitrate-reduction rate of 30.64% could be achieved with an initial pH of 7.4, incubation temperature of 25.0 °C, and carbon source concentration of 266.10 mg/L.

Cyanobacterial blooms generated by nutrient addition into aquatic systems pose serious risks to ecosystems and human health. Though there are established chemical, physical, and biological means of eradication, more efficient and environmentally friendly measures are desired. This study investigates the effect of potassium ferrate(VI) on the growth and intracellular and extracellular organic matter accumulations of the cyanobacterium Microcystis aeruginosa. Cultures were inoculated with three separate concentrations of potassium ferrate(VI) (3, 15, 30 mg L−1) and monitored by measuring chlorophyll-a (Chl-a) and intracellular/extracellular dissolved organic carbon. Results show that ferrate(VI) addition effectively removed the microalgae from the medium, as indicated by the reduction of Chl-a. Organic matter accumulation of the microalgae was also affected by ferrate(VI) treatment; fluorescence EEM spectra show details of changing intracellular dissolved organic matter (IDOM) and extracellular dissolved organic matter (EDOM). A new peak appeared in the EDOM indicating altered humic and proteinaceous compounds. This study demonstrates that ferrate(VI) is a potential treatment for the water contaminated with the toxic microalgae M. aeruginosa.

Arbuscular mycorrhizal (AM) fungi have been used to alleviate heavy metal stress on plant growth and uptake of micro- and macroelements. A greenhouse pot experiment was conducted to verify the effects of AM fungus Rhizophagus irregularis on the growth, physiological characteristics, total Cd, and element uptake of Phragmites australis under different Cd stress (in the range of 0–20 mg L−1). The results showed that the symbiosis could effectively alleviate Cd toxicity with greater root biomass, higher photosynthesis rate, and lower levels of malonaldehyde (MDA) and proline than non-mycorrhizal plants could. However, reduced transpiration rate (Tr) and stomatal conductance (gs) indicated R. irregularis protected host plants from Cd stress (≥5 mg L−1) via the stomatal closure. Although micro- and macroelements displayed differently in the presence of Cd, higher concentrations were still detected in mycorrhizal plants in contrast to non-mycorrhizal plants. Moreover, step multiple regression significantly demonstrated Pnmax, stem diameter (Sd), and gs were the important factors with regard to total Cd uptake in the symbiosis, but Mn affected to non-mycorrhizal plants. These results suggested R. irregularis could alleviate the competition between Mn and Cd by altering plant physiology. This work clearly demonstrated that R. irregularis can be able to support P. australis growth better even though under high Cd stress (>1 mg L−1), suggesting its good potential for practical use in high Cd-contaminated areas.

•A bioaugmented constructed wetland was used for environmental impact assessment.•An in-depth perspective on aquatic environmental improvement of bioaugmentation was provided by e-Balance.•A comprehensive perspective on environmental burden of bioaugmentation was provided by CML.•Results of each LCA method are associated with specific implications.Bioaugmentation is a promising technology to enhance the removal of specific pollutants; however, environmental impacts of implementing bioaugmentation have not been considered in most studies. Appropriate methodology is required for the evaluation from both in-depth and comprehensive perspectives, which leads to this study initiating the application of life cycle assessment (LCA) of bioaugmentation. Two LCA methods (CML and e-Balance) were applied to a bioaugmentation case with the aim of illustrating how to evaluate the environmental impacts of bioaugmentation from different perspectives based on the selection of different LCA methods. The results of the case study demonstrated that the LCA methods with different methodology emphasis produced different outcomes, which could lead to differentiated optimization strategies depending on the associated perspectives. Furthermore, three important aspects are discussed, including coverage of impact categories, the selection of characterization modeling for specific pollutants, and the requirement of including economic indicators for future investigation.Download high-res image (233KB)Download full-size image

An aerobic denitrification system, initially bioaugmented with Pseudomonas strain T13, was established to treat coal-based ethylene glycol industry wastewater, which contained 3219 ± 86 mg/L total nitrogen (TN) and 1978 ± 14 mg/L NO3−-N. In the current study, a stable denitrification efficiency of 53.7 ± 4.7% and nitrite removal efficiency of 40.1 ± 2.7% were achieved at different diluted influent concentrations. Toxicity evaluation showed that a lower toxicity of effluent was achieved when industry wastewater was treated by stuffing biofilm communities compared to suspended communities. Relatively high TN removal (~50%) and chemical oxygen demand removal percentages (>65%) were obtained when the influent concentration was controlled at below 50% of the raw industry wastewater. However, a further increased concentration led to a 20–30% decrease in nitrate and nitrite removal. Microbial network evaluation showed that a reduction in Pseudomonas abundance was induced during the succession of the microbial community. The napA gene analysis indicated that the decrease in nitrate and nitrite removal happened when abundance of Pseudomonas was reduced to less than 10% of the overall stuffing biofilm communities. Meanwhile, other denitrifying bacteria, such as Paracoccus, Brevundimonas, and Brucella, were subsequently enriched through symbiosis in the whole microbial network.

For the first time, we demonstrate chromate (Cr(VI)) bioreduction using methane (CH4) as the sole electron donor in a membrane biofilm reactor (MBfR). The experiments were divided into five stages lasting a total of 90 days, and each stage achieved a steady state for at least 15 days. Due to continued acclimation of the microbial community, the Cr(VI)-reducing capacity of the biofilm kept increasing. Cr(VI) removal at the end of the 90-day test reached 95% at an influent Cr(VI) concentration of 3 mg Cr/L and a surface loading of 0.37g of Cr m–2 day–1. Meiothermus (Deinococci), a potential Cr(VI)-reducing bacterium, was negligible in the inoculum but dominated the MBfR biofilm after Cr(VI) was added to the reactor, while Methylosinus, a type II methanotrophs, represented 11%–21% of the total bacterial DNA in the biofilm. Synergy within a microbial consortia likely was responsible for Cr(VI) reduction based on CH4 oxidation. In the synergy, methanotrophs fermented CH4 to produce metabolic intermediates that were used by the Cr(VI)-reducing bacteria as electron donors. Solid Cr(III) was the main product, accounting for more than 88% of the reduced Cr in most cases. Transmission electron microscope (TEM) and energy dispersive X-ray (EDS) analysis showed that Cr(III) accumulated inside and outside of some bacterial cells, implying that different Cr(VI)-reducing mechanisms were involved.

Atrazine residues in water pose a serious threat to the environment and to human health. One method to reduce levels of atrazine in the environment is phytoremediation, a potential technology for in situ remediation. However, as atrazine is a herbicide, it damages the growth of plants and weakens the effect of phytoremediation. In this work, a pot culture experiment was conducted to investigate the effect of Funnelliformis mosseae inoculation on the phytoremediation of atrazine by Canna indica L. var. flava Roxb. The results demonstrated that C. indica was found as a novel tolerant species, and that inoculation with F. mosseae can alleviate the physiological inhibition of atrazine in the growth of plants and promote photosynthesis. Furthermore, C. indica inoculated with F. mosseae exhibited a greater efficiency to remove atrazine and to lower atrazine residue concentrations than plants without inoculation. With inoculation of F. mosseae, the maximum removal rates increased from 68.064% to 95.670%, while the concentration with the highest removal rates changed from 1.489 mg L−1 to 7.363 mg L−1. Inoculation of F. mosseae contributed 2.2–52.0% to the removal rate. This study shows that C. indica inoculated with F. mosseae may ultimately serve as a viable phytoremediation solution for in situ remediation.

Microcystins (MCs) are toxic compounds produced by cyanobacteria in eutrophicate water environment and threaten the drinking water quality which often leads to serious sicknesses. MCs are difficult to be removed in water treatment when the concentration is very low but still harmful. When the MC concentration is low (μg/L), filter or some conventional chemical does not work, but UV can keep removing it to a lower level by some active groups. Herein, 185-nm UV irradiation in an immersing mode was used to remove MCs. Compared with the normal radiation mode, the immersing mode showed a remarkable degradation rate of MCs and a greater removal efficiency than the direct radiation. Radicals of ·H and ·OH were produced and strengthened the removal rate, after H2O absorbed 185 nm photons. Three important factors of pH value, initial concentration, and aeration capacity were investigated. When pH was less than 7, a better removal rate by ·H was found, due to the main path of MC degradation and Adda strain removal. When the initial concentration increased, the MC removal ratio decreased because HO· formed near the lamp surface and degraded MC molecules fast. When the aeration capacity improved, the MC removal ratio for the presence of air enforced reaction of dissolved oxygen with hydrated electrons and hydrogen atoms produced in the radiolysis.

The waterborne polyurethane/doped TiO2 nanoparticle hybrid films were prepared. Nd, I doped TiO2 was prepared with a 50 nm particle size firstly. The hybrid film was prepared by mixing doped TiO2 with waterborne polyurethane, followed by heat treatment. The presence and nanometric distribution of doped TiO2 nanoparticles in prepared membranes is evident according to SEM images. The photocatalytic activities of doped TiO2 were significantly enhanced compared with pure TiO2 powders. After the hybrid film fabrication, the photocatalytic activities were almost the same as the pure catalysts with kMB of 0.046. In the antibacterial testing, the hybrid films can inhibit E. coli growth. A significant decrease in membrane fluidity and increase of permeability of E. coli were observed.

Arbuscular mycorrhizal fungi (AMF) can alter the dynamics of soluble nitrogen in paddy field soils by promoting nitrogen assimilation by rice. However, it is unknown whether this affects N2O emissions from rice paddies. This study was designed to assess the effects of AMF on N2O emissions by analyzing the relationships between AMF and the parameters affecting N2O emissions. Path analysis was used to quantitatively partition the direct and indirect effects of different parameters on N2O emissions. Results showed that N2O emissions were controlled by environmental pathways (transpiration, evaporation, and precipitation affecting soil water content) and biotic pathways (soluble nitrogen assimilation by the rice, which varies according to rice biomass). Under different water conditions, the contributions of the two pathways to N2O emissions varied strongly. During the flooding stage, the environmental pathways were dominant, but inoculation with AMF promoted the contribution of the biotic pathway to the reduction of N2O emissions. During the draining stage, the environmental pathways were dominant in the non-inoculated treatment, but inoculation made the biotic pathways dominant by increasing the biomass of rice. During the growing stage, N2O emissions from inoculated soil (17.9–492.9 μg N2O-N m−2 h−1) were significantly lower than those in non-inoculated soil (22.1–553.1 μg N2O-N m−2 h−1; p < 0.05). Consequently, inoculating with AMF has the potential for mitigating N2O emissions from rice paddies.

Bioaugmentation is an effective method of treating municipal wastewater with high ammonia concentration in sequencing batch reactors (SBRs) at low temperature (10°C). The cold-adapted ammonia- and nitrite-oxidizing bacteria were enriched and inoculated, respectively, in the bioaugmentation systems. In synthetic wastewater treatment systems, the average NH4+ -N removal efficiency in the bioaugmented system (85%) was much higher than that in the unbioaugmented system. The effluent NH4+-N concentration of the bioaugmented system was stably below 8 mg·L−1 after 20 d operation. In municipal wastewater systems with bioaugmentation, the effluent NH4+-N concentration was below 8 mg·L−1 after 15 d operation. The average NH4+-N removal efficiency in unbioaugmentation system (about 82%) was lower compared with that in the bioaugmentation system. By inoculating the cold-adapted nitrite-oxidizing bacteria (NOB) into the SBRs after 10 d operation, the nitrite concentration decreased rapidly, reducing the NO2−-N accumulation effectively at low temperature. The functional microorganisms were identified by PCR-DGGE, including uncultured Dechloromonas sp., uncultured Nitrospira sp., Clostridium sp. and uncultured Thauera sp. The results suggested that the cold-adapted microbial agent of ammonia-oxidizing bacteria (AOB) and NOB could accelerate the start-up and promote achieving the stable operation of the low-temperature SBRs for nitrification.

The immobilizing fermentation characteristics and bioflocculant production of two bioflocculant-producing bacteria, Agrobacterium tumefaciens F2 and Bacillus sphaeicus F6 using mycelial pellets as biomass carrier were investigated. The optimal parameters of fermentation for the best flocculation efficiency were determined via response surface methodology (RSM) as follows: seed age 24 h, inoculum amount 3.6% (m/m), initial pH 7.7, temperature 29.5 °C, and rotation speed 140 rpm. Under these optimal conditions, combined mycelial pellets were transferred repeatedly for over 30 cycles for bioflocculant production. The bacterial biomass, flocculating efficiency and the bioflocculant yield were stable during the semi-continuous production process. Bioflocculant produced after 18–30 h fermentation had the highest yield. Scanning electron microscope images showed that the bioflocculant-producing bacteria were immobilized on the mycelial pellets. Using mycelial pellets as a biomass carrier for the semi-continuous fermentation of bioflocculant is feasible and promising for future industrial production applications.

To evaluate the vegetative periodic effect of rhizosphere on the patterns of metal bioaccumulation, the concentrations of Mg, K, Ca, Mn, Zn, Fe, Cu, Cr, Ni, Cd and Pb in the corresponding rhizosphere soil and tissues of Phragmites australis growing in the Sun Island wetland (Harbin, China) were compared. The concentrations of Zn, Fe, Cu, Cr, Ni, Cd and Pb in roots were higher than in shoots, suggesting that roots are the primary accumulation organs for these metals and there exists an exclusion strategy for metal tolerance. In contrast, the rest of the metals showed an opposite trend, suggesting that they were not restricted in roots. Harvesting would particularly be an effective method to remove Mn from the environment. The concentrations of metals in shoots were generally higher in autumn than in summer, suggesting that Ph. australis possesses an efficient root-to-shoot translocation system, which is activated at the end of the growing season and allows more metals into the senescent tissues. Furthermore, metal bioaccumulation of Ph. australis was affected by vegetative periodic variation through the changing of physicochemical and microbial conditions. The rhizospheric microbial characteristics were significantly related to the concentrations of Mg, K, Zn, Fe and Cu, suggesting that microbial influence on metal accumulation is specific and selective, not eurytopic.

The lauryl benzene sulfonic acid sodium (LAS)-carbon nanotube (CNT)-modified PbO2 electrode was fabricated by thermal deposition and electrodeposition methods. Its morphology and composition were compared with those of PbO2, CNT-PbO2, and LAS-PbO2 electrodes. It was found that CNT could be doped into the PbO2 film in the presence of LAS. The [Fe(CN)6]4−/3− redox couple in 0.1 M KCl was used for initial evaluation of the electro-catalytic activity of prepared electrodes. The results showed that LAS-CNT-PbO2 electrode exhibited the largest peak current and the smallest ΔEp in [Fe(CN)6]4−/3− redox process. The stability tests showed that the service life of LAS-CNT-PbO2 electrode was 1.8 times longer than that of PbO2 electrode. The electro-catalytic activity of the prepared electrodes was also examined for the electrochemical oxidation of 4-chlorophenol (4-CP) and the LAS-CNT-PbO2 electrode exhibited the highest activity for 4-CP degradation among the four PbO2-based electrodes. Besides, HPLC was employed to identify the products resulting from the electrochemical oxidation of 4-CP and the degradation mechanism of 4-CP was also discussed.Graphical abstractHighlights► Carbon nanotube (CNT) modified PbO2 electrodes were prepared. ► The CNT could be doped into the PbO2 film in the presence of surfactant-LAS. ► LAS-CNT-PbO2 electrode showed the highest 4-CP and TOC removal percentage. ► The service life of LAS-CNT-PbO2 electrode was 1.8 times longer than that of PbO2 electrode. ► The degradation mechanism of 4-CP was also discussed.

Low temperatures can result in start-up and operational problems in wastewater treatment plants. The microbial community structures of three full-scale biological processes for municipal wastewater treatment, namely, anoxic–oxic activated sludge (A/O) process, oxidation ditch, and sequencing batch reactor, in winter and spring were investigated. The performances of the three biological processes were all stable during winter and spring. Comparing all three plants, the NH4+-N removal efficiency using the A/O process was found to be the highest during both winter and spring. According to the similarity coefficient of the polymerase chain reaction and denaturing gradient gel electrophoresis analysis determined via the culture-independent method, the microbial community structure is the most stable using the A/O process at different temperatures. The dominant members primarily belonged to Proteobacteria, Nitrospira, and Bacteroidetes. In addition, Proteobacteria was the dominant member in the activated sludge utilizing peptone, glucose, and fatty acid. Compared with other biological processes, the A/O process was superior at low temperatures based on its pollution removal performance and stable microbial community sturcture.

The metal doped TiO2 was prepared with Fe(III), Co(II), Ni(II), Cu(II), Ag(I), La (III), Nd(III), Ho(III), and Y(III) as doped catalysts. These catalysts were carried by ceramic foams to enhance their photocatalytic efficiency, which was later studied with methylene blue (MB) and Escherichia coli (E. coli) as targets. The results suggested that the photocatalytic activities of TiO2 were enhanced when ceramic foams were used as catalyst carriers and that the photocatalytic efficiency could also be significantly increased by the dopants, especially by Ag(I) and rare earth. In the bactericidal activity testing, the inhibitory effect of TiO2 on E. coli was enhanced significantly when ceramic foams were used as carriers. Ag(I) doped TiO2 showed the greatest inhibition on E. coli. As to the E. coli cells treated by Ag(I) doped TiO2, the observation with a Scanning Electronic Microscope (SEM) suggested that the cells could no longer maintain their morphology and the spheroplasts were formed after the treatment.SEM image of the E. coli after 1 h of illumination with Ag(I) doped TiO2 with ceramic foam (B). The cells were almost completely deformed: the normal cells were rod-shaped while cells treated by doped TiO2 under UV light irradiation become elliptical.

A compound bioflocculant CBF-F26, produced by mixed culture of Rhizobium radiobacter F2 and Bacillus sphaeicus F6, was investigated with regard to its physicochemical and flocculating properties. It was identified as a polysaccharide bioflocculant composed of rhamnose, mannose, glucose, and galactose, respectively, in a 1.3: 2.1: 10.0: 1.0 molar ratio. The average molecular weight was determined as 4.79 × 105 Da by gel-permeation chromatography. Infrared spectrum and X-ray photoelectron spectroscopy revealed the presence of carboxyl, hydroxyl and amino groups in its structure. Thermostability test suggested that CBF-F26 was thermostable and high flocculating activity was maintained. Thermogravimetric property, intrinsic viscosity and surface morphology of CBF-F26 were also studied. CBF-F26 was effective under neutral and weak alkaline conditions (pH 7.0–9.0), and flocculating activities of higher than 90% were obtained in the concentration range of 8–24 mg l−1 at pH 8.0. The flocculation could be stimulated by cations Ca2+, Zn2+, Fe2+, Al3+, and Fe3+. In addition, the probable flocculation mechanisms were proposed.

•Nitrate reduction and Fe2+ oxidation occurred at the same time.•Stimulating denitrification with various electron donors was compared.•RSM demonstrated that initial pH and temperature produced the largest effect.A novel Anaerobic Fe(II) Oxidizing Denitrifier (AFODN) strain SZF15 was isolated from the sediment of Tang Yu reservoir. Based on phenotypic and phylogenetic characteristics, the isolated strain was identified as Pseudomonas sp. Strain SZF15 was studied for characteristics of nitrate and Fe2+ removal. Results showed the strain had the capability to completely reduce 80.86% of NO3−-N and oxidize 75.53% of Fe2+ over 72 h at the anaerobic condition. Meanwhile, the oxidation rate of Fe2+ was 0.72 mg L−1 h−1. Furthermore, the effectiveness of various electron donors with stimulating denitrification was compared in this experiment. The results indicated that the most rapid nitrate removal rate was occurred in the presence of hydrogen gas. Besides, response surface methodology (RSM) analysis demonstrated that the maximum removal rate of nitrate occurred under the conditions with an initial pH of 6.63, C/N ratio of 5.14, temperature of 32.45 °C and Fe2+ concentration of 62.45 mg L−1.

Nitrogen (N) runoff from paddy fields serves as one of the main sources of water pollution. Our aim was to reduce N runoff from paddy fields by fertilizer management and inoculation with arbuscular mycorrhizal fungi (AMF). In northeast China, Shuangcheng city in Heilongjiang province, a field experiment was conducted, using rice provided with 0%, 20%, 40%, 60%, 80%, and 100% of the local norm of fertilization (including N, phosphorus and potassium), with or without inoculation with Glomus mosseae. The volume, concentrations of total N (TN), dissolved N (DN) and particulate N (PN) of runoff water were measured. We found that the local norm of fertilization led to 18.9 kg/ha of N runoff during rice growing season, with DN accounting for 60%–70%. We also found that reduction in fertilization by 20% cut down TN runoff by 8.2% while AMF inoculation decreased N runoff at each fertilizer level and this effect was inhibited by high fertilization. The combination of inoculation with AMF and 80% of the local norm of fertilization was observed to reduce N runoff by 27.2%. Conclusively, we suggested that the contribution of AMF inoculation combined with decreasing fertilization should get more attention to slow down water eutrophication by reducing N runoff from paddy fields.Download high-res image (75KB)Download full-size image

•High loading of NO3− significantly inhibited Cr(VI) reduction in a CH4-based MBfR.•NO3− had a strong impact on the Cr-reducing microbial community in the biofilms.•Introduction of NO3− regulated the functional genes in the biofilm community.The effects of nitrate (NO3−) on chromate (Cr(VI)) reduction in a membrane biofilm reactor (MBfR) were studied when CH4 was the sole electron donor supplied with a non-limiting delivery capacity. A high surface loading of NO3− gave significant and irreversible inhibition of Cr(VI) reduction. At a surface loading of 500 mg Cr/m2-d, the Cr(VI)-removal percentage was 100% when NO3− was absent (Stage 1), but was dramatically lowered to < 25% with introduction of 280 mg N m−2-d NO3− (Stage 2). After ∼50 days operation in Stage 2, the Cr(VI) reduction recovered to only ∼70% in Stage 3, when NO3− was removed from the influent; thus, NO3− had a significant long-term inhibition effect on Cr(VI) reduction. Weighted PCoA and UniFrac analyses proved that the introduction of NO3− had a strong impact on the microbial community in the biofilms, and the changes possibly were linked to the irreversible inhibition of Cr(VI) reduction. For example, Meiothermus, the main genus involved in Cr(VI) reduction at first, declined with introduction of NO3−. The denitrifier Chitinophagaceae was enriched after the addition of NO3−, while Pelomonas became important when nitrate was removed, suggesting its potential role as a Cr(VI) reducer. Moreover, introducing NO3− led to a decrease in the number of genes predicted (by PICRUSt) to be related to chromate reduction, but genes predicted to be related to denitrification, methane oxidation, and fermentation increased.Download high-res image (241KB)Download full-size image

•Chelatococcus sp. CO-6, isolated from Shengli Oilfield, is a crude-oil-degrading bacterium.•The whole genome of Chelatococcus sp. CO-6 has been sequenced.•The relationship between genes and mechanism of crude oil biodegradation has been analyzed.Chelatococcus sp. CO-6 is a crude-oil-degrading strain, which was isolated from Shengli Oilfield. However, little genetic information is known about this species. We present the complete genome sequence analysis of Chelatococcus sp. CO-6 in this study. It could provide further insight into its genetic basis for membrane transport and immune system against bacteriophage in strain CO-6.

Our study sought to assess how much phosphorus (P) runoff from paddy fields could be cut down by fertilizer management and inoculation with arbuscular mycorrhizal fungi. A field experiment was conducted in Lalin River basin, in the northeast China: six nitrogen–phosphorus–potassium fertilizer levels were provided (0, 20%, 40%, 60%, 80%, and 100% of the recommended fertilizer supply), with or without inoculation with Glomus mosseae. The volume and concentrations of particle P (PP) and dissolved P (DP) were measured for each runoff during the rice growing season. It was found that the seasonal P runoff, including DP and PP, under the local fertilization was 3.7 kg/ha, with PP, rather than DP, being the main form of P in runoff water. Additionally, the seasonal P runoff dropped only by 8.9% when fertilization decreased by 20%; rice yields decreased with declining fertilization. We also found that inoculation increased rice yields and decreased P runoff at each fertilizer level and these effects were lower under higher fertilization. Conclusively, while rice yields were guaranteed arbuscular mycorrhizal inoculation and fertilizer management would play a key role in reducing P runoff from paddy fields.Download full-size image