Cr(VI) reduction and Cr(III) immobilization by Acinetobacter sp. HK-1 with the assistance of a novel quinone/graphene oxide composite.

Cr(VI) biotreatment has attracted a substantial amount of interest due to its cost effectiveness and environmental friendliness. However, the slow Cr(VI) bioreduction rate and the formed organo-Cr(III) in solution are bottlenecks for biotechnology application. In this study, a novel strain, Acinetobacter sp. HK-1, capable of reducing Cr(VI) and immobilizing Cr(III) was isolated. Under optimal conditions, the Cr(VI) reduction rate could reach 3.82 mg h(-1) g cell(-1). To improve the Cr(VI) reduction rate, two quinone/graphene oxide composites (Q-GOs) were first prepared via a one-step covalent chemical reaction. The results showed that 2-amino-3-chloro-1,4-naphthoquinone-GO (NQ-GO) exhibited a better catalytic performance in Cr(VI) reduction compared to 2-aminoanthraquinone-GO. Specifically, in the presence of 50 mg L(-1) NQ-GO, a Cr(VI) removal rate of 190 mg h(-1) g cell(-1), which was the highest rate obtained, was achieved. The increased Cr(VI) reduction rate is mainly the result of NQ-GO significantly increasing the Cr(VI) reduction activity of cell membrane proteins containing dominant Cr(VI) reductases. X-ray photoelectron spectroscopy analysis found that Cr(VI) was reduced to insoluble Cr(III), which was immobilized by glycolipids secreted by strain HK-1. These findings indicate that the application of strain HK-1 and NQ-GO is a promising strategy for enhancing the treatment of Cr(VI)-containing wastewater.

Enhanced-nitrogen removal through Fe(III)-triggered partial dissimilatory nitrate reduction to ammonium coupling with anammox in anammox bioreactor.

Anammox is recognized as a prospective alternative for future biological nitrogen removal technologies. However, the nitrate by-products produced by anammox bacteria limit its overall nitrogen removal efficiency below 88 %. This study introduced Fe(III) into the anammox bioreactor to enhance the nitrogen removal efficiency to approximately 95 %, surpassing the biochemical limit of 88 % imposed by anammox stoichiometry. Anammox sludge was demonstrated to utilize extracellular polymeric substances to reduce Fe(III) into Fe(II), and this process promoted the dominance of Ca. Brocadia. The iron addition improved the abundance of narGHI genes and facilitated the partial dissimilatory nitrate reduction to ammonium, with nitrite as the end product. The accumulated nitrite was then eliminated through the anammox pathway, along with the excess ammonium (30 mg/L) in the influent. Overall, this study deepens our understanding of the enhanced nitrogen removal triggered by Fe(III) in anammox sludge and offers an effective approach to boost anammox process.

Global transcriptome analysis of Escherichia coli exposed to immobilized anthraquinone-2-sulfonate and azo dye under anaerobic conditions.

The immobilization of quinone compounds is regarded as a promising strategy to accelerate anaerobic decolorization of xenobiotic compounds azo dyes in the presence of quinone-reducing microorganisms. However, little is known about the basic response of these microorganisms to immobilized quinones in the presence of azo dyes. In the present study, whole-genome DNA microarrays were used to investigate a quinone-reducing bacterium Escherichia coli K-12 transcription response to immobilized anthraquinone-2-sulfonate (AQSim) reduction and azo dye acid red 18 (AR 18) decolorization. Transcriptome analysis showed that AQSim was more accessible for the cells of E. coli K-12 than AR 18. Despite there being some differences between AQSim and soluble AQS mediated decolorization of AR 18, AQSim reduction and AR 18 decolorization, more similarity could be observed in the four processes. Among over 60 % shared genes, several groups of genes exhibited high expression levels, including those genes encoding terminal reductases, menaquinone biosynthesis, formate dehydrogenases and outer membrane proteins. Especially, nrfABCD, frdBCD and dsmABC encoding terminal reductases were significantly upregulated. Further gene deletion experiments demonstrated that the above three groups of genes were involved in AQSim-mediated AR 18 decolorization. In addition, significant upregulation of stress response genes was observed, which indicated the adaptation of E. coli K-12 to AQSim and AR 18 exposures.

Biotransformation of benzene and toluene to catechols by phenol hydroxylase from Arthrobacter sp. W1.

Phenol hydroxylase gene engineered microorganism (PHIND) was used to synthesize catechols from benzene and toluene by successive hydroxylation reaction. HPLC-MS and (1)H NMR analysis proved that the products of biotransformation were the corresponding catechols via the intermediate production of phenols. It was indicated that the main products of toluene oxidation were o-cresol and p-cresol. 3-Methylcatechol was the predominant product for m-cresol biotransformation. Formation rate of catechol (25 µM/min/g cell dry weight) was 1.43-fold higher than that of methylcatechols. It was suggested that phenol hydroxylase could be successfully used to transform both benzene and toluene to catechols by successive hydroxylation.

Metabolic characterization and genes for the conversion of biphenyl in Dyella ginsengisoli LA-4.

A complete bph gene cluster (bphLA-4) containing 12,186 bp was amplified from Dyella ginsengisoli LA-4. The bphLA-4 was composed of bphABCXD, and an additional gene encoding a meta-fission product hydrolase was located in the bphX region. BphLA-4 was independently transcribed by the two operons, bphA1A2orf1A3A4BCX0 and bphX1orf2X2X3D, and significantly differed from bphKF707. Both benzoate and catechol induced the expression of both operons. 2-Hydroxypenta-2,4-dienoate was identified as the intermediate of the biphenyl degradation by strain LA-4. This finding suggested that there existed a novel lower pathway of biphenyl degradation in strain LA-4.

Enhanced biodegradation of 4-aminobenzenesulfonate in membrane bioreactor by Pannonibacter sp. W1.

4-Aminobenzenesulfonate (4-ABS), an aromatic amine and recalcitrant toxic pollutant, is widely used in the dye and pharmaceutical industry. Pannonibactersp. W1 is a specialized microbial strain which can efficiently degrade 4-ABS. This study shows the feasibility of using the specialized strain in an MBR system to treat synthetic wastewater containing large amount of 4-ABS. Due to membrane retention, the biomass concentration is able to reach 5 g/L within two months of continuous operation. Pannonibacter sp. W1 is able to adapt to the high loading rate of 1000 mg 4-ABS/L and achieve a remarkable 4-ABS removal efficiency of 99% within 6 h. Strain W1 grows well under the MBR continuous operation and remains as the dominant bacterium at the end of 60 days continuous operation. Minor membrane fouling has been detected within 40 days of operating at 15 LMH. At a flux of 25 LMH, the system experiences the 'TMP jump'. The high organic removal rate and low membrane fouling results illustrate the excellent performance of the bioaugmented MBR system in 4-ABS wastewater treatment.

[Anaerobic Reduction Process Characteristics and Microbial Community Analysis for Sulfate and Fe(â ¡) EDTA-NO/Fe(â ¢) EDTA].

Based on biological flue gas desulfurization technology (Bio-FGD) and chelating absorption-biological regeneration technology (BioDeNOx), simultaneous desulfurization and denitrification by biological methods combined with chelating absorption technology has been proposed in this study. This technique uses an alkaline absorption liquid with Fe(Ⅱ) EDTA to absorb the SO2 and NO in the flue gas. In this study, an attempt is made to simultaneously remove sulfate (SO42-) and Fe(Ⅱ) EDTA-NO/Fe(Ⅲ) EDTA, which are the SO2 and NO absorption byproducts in an anaerobic reactor. The results indicate that average removal efficiencies for SO42- and Fe(Ⅱ) EDTA-NO of 95.16% and 96.61%, respectively, were achieved when the hydraulic residence time (HRT) and pH were controlled at 16 h and 7.0. The reduction products of SO42- were mainly in the form of S2- in the liquid phase and hydrogen sulfide (H2S) in the gas phase, while the reduction products of Fe(Ⅱ) EDTA-NO was N2. The reduction of Fe(Ⅲ) EDTA could be achieved at all stages of the operation, however, the reduction rate decreases with a reduction in the HRT. In the fifth stage, the main sulfate-reducing bacteria (SRB) in the reactor was Desulfomicrobium, a heterotrophic denitrifying bacteria, Pseudomonas, and two types of sulfur autotrophic denitrifying bacteria, Sulfurimonas and Sulfurovum, which coexisted. Two genera of bacteria that can also reduce sulfur, Thermovirga and Mesotoga, were also identified in the reactor.

[Performance and Influencing Factors of Dissimilatory Nitrate Reduction to Ammonium Process by the Strain Desulfovibrio sp. CMX].

The process of dissimilatory nitrate reduction to ammonium (DNRA) plays an important role in the presence and conversion of ammonium ions in nature. However, the influencing factors and mechanisms of DNRA process in sulfate-reducing bacteria (SRB) have not yet been identified. The ability, influencing factors and mechanisms of DNRA was investigated in Desulfovibrio sp. CMX isolated previously in our laboratory. The results showed that the production rate of ammonium reached 85.8% and 97.3% respectively with NO3- and NO2- (10 mmol·L-1) as the sole electron donor and nitrogen source. Meanwhile, there was no by-products such as N2 and N2O. Then the effects of different extra nitrogen sources and initial concentrations of sulfate and sulfide on DNRA process were also investigated. As a result, extra nitrogen, yeast extract, could promote DNRA process by improving both growth and metabolism of the strain. In another study, sulfate promoted the nitrate reduction stage while inhibited the nitrite reduction. Overall, the DNRA process by Desulfovibrio sp. CMX was inhibited by sulfate. In addition, both the growth and two stages of the DNRA process were inhibited in the presence of sulfide. Dose effect of sulfide was observed. Inhibition was enhanced with the increase of sulfide concentration. It's noticeable that the inhibition on nitrate reduction was stronger than the inhibition on nitrite reduction with 6 mmol·L-1 of sulfide, leading to the lower reduction rate of nitrate than that of nitrite. In this condition, no accumulation of nitrite was observed in the system.

Decolorization of azo dyes with high salt concentration by salt-tolerant mixed cultures under anaerobic conditions.

Because the lack of detailed study of biological decolorization in high salt dye wastewater, it is still difficult to evaluate the biological treatment on high-salinity dye wastewater. The experiments were carried out to study the salt-tolerant bacteria, which is useful in the treatment of high-salinity colored wastewater. Simulated wastewater containing 5-150 g/L salt (NaCl) and 50-2000 mg/L Reactive Brilliant Red K-2BP was treated with three salt-tolerant mixed cultures (CAS, TAS, DSAS), which were under a gradually acclimated procedure. With the increase of concentrations of salt and dye, the decolorization became low. The abilities of decolorization of dyes wastewater by three mixed cultures (CAS, TAS, DSAS) were studied, CAS and DSAS mixed cultures showed more active for the treatment of high-salinity colored wastewater than TAS mixed cultures. The results suggested that there might be a simple process for the high salt wastewater treatment, which could be incorporated into conventional activated sludge plants.

Biodegradation of azo dyes by genetically engineered azoreductase.

A azoreductase gene with 537 bp was obtained by PCR amplification from Rhodobacter sphaeroides AS1.1737. The enzyme, with a molecular weight of 18.7 kD, was efficiently expressed in Escherichia coli and its biodegradation characteristics for azo dyes were investigated. Furthermore, the reaction kinetics and mechanism of azo dyes catalyzed by the genetically engineered azoreductase were studied in detail. The presence of a hydrazo-intermediate was identified, which provided a convincing evidence for the assumption that azo dyes were degraded via an incomplete reduction stage.

Identification of the microbial community composition and structure of coal-mine wastewater treatment plants.

The wastewater from coal-mine industry varies greatly and is resistant to biodegradation for containing large quantities of inorganic and organic pollutants. Microorganisms in activated sludge are responsible for the pollutants' removal, whereas the microbial community composition and structure are far from understood. In the present study, the sludges from five coal-mine wastewater treatment plants were collected and the microbial communities were analyzed by Illumina high-throughput sequencing. The diversities of these sludges were lower than that of the municipal wastewater treatment systems. The most abundant phylum was Proteobacteria ranging from 63.64% to 96.10%, followed by Bacteroidetes (7.26%), Firmicutes (5.12%), Nitrospira (2.02%), Acidobacteria (1.31%), Actinobacteria (1.30%) and Planctomycetes (0.95%). At genus level, Thiobacillus and Comamonas were the two primary genera in all sludges, other major genera included Azoarcus, Thauera, Pseudomonas, Ohtaekwangia, Nitrosomonas and Nitrospira. Most of these core genera were closely related with aromatic hydrocarbon degradation and denitrification processes. Identification of the microbial communities in coal-mine wastewater treatment plants will be helpful for wastewater management and control.

United membrane biological reactor in the treatment of wastewater.

The united membrane biological reactor( UMBR) was studied for the treatment of some simulate and municipal wastewater. The removal efficiency for COD and turbidity are greater than 80% and 99% respectively. Effluent COD is less than 100 mg/L while turbidity less than 5. The removal of LAS in bath wastewater is greater than 70%. In treatment of dinning-hall wastewater, removal of fatty oil is greater than 90%, and its concentration in effluent is less than 5 mg/L. The match of biological reactor and the membrane separation component were calculated. The stable performance of wastewater treatment can be maintained by the optimization of operation conditions and the cleanout of membranes.

[Analyses of cell coloring matter and degradation products of anthraquinone dye decolorization bacteria XL-1 using ultraviolet absorption spectroscopy].

The species of cell coloring matter of anthraquinone dye decolorization bacteria XL-1, degradation reaction degrees, and the changes of molecule structure of degradation products were studied using ultraviolet absorption spectroscopy. The results indicate that the bacteria cells contain bacteria chlorophyll a and like-carotene. Its molecular structure changed evidently during the degradation process, the conjugate structure was destroyed, and new intermediate products were created.

Accelerating effect of bio-reduced graphene oxide on decolorization of Acid Red 18 by Shewanella algae.

In this study, the effects of bio-reduced graphene oxide (BRGO) on the bio-reduction of Acid Red 18 (AR 18) by Shewanella algae were first investigated, and a possible mechanism of BRGO-mediated AR 18 bio-decolorization was proposed. The prepared BRGO was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), infrared spectroscopy (IR), Raman spectra, and transmission electron microscope (TEM), respectively. Moreover, electrochemical experiment demonstrated that BRGO is of good electrical conductivity. AR 18 bio-decolorization could be enhanced in dose-dependent manner of BRGO. The maximum increase in AR 18 removal efficiency was observed at a dose of 0.075 g L(-1) BRGO. Under the same conditions, BRGO could also improve the decolorization rates of Acid Red 88, Acid Red 27, and Acid Red 73. During decolorization, the formation of BRGO and cells composite was observed, which is beneficial for transferring electrons from cells to BRGO. In addition, BRGO could accelerate the bio-decolorization of AR 18 under saline conditions (2-7 %). These findings indicate that BRGO can accelerate the electrons transfer from cells to azo dyes.

[Study on treatment of methylene blue wastewater by fly ash adsorption-Fenton and thermal regeneration].

The physicochemical properties of water-washed fly ash (FA) and acid modified fly ash (M-FA) were investigated. The adsorption of methylene blue by FA and M-FA were studied by batch experiments. Two methods, Fenton-drive oxidation regeneration and thermal regeneration, were used for regeneration of the used FA and M-FA. The result showed that the rate of adsorption process followed the second order kinetics and the adsorption followed Langmuir isotherms. The adsorption equilibrium time was 30 min, and the equilibrium adsorption capacity of FA and M-FA were 4.22 mg x g(-1) and 5.98 mg x g(-1) respectively. The adsorption capability of M-FA was higher than that of FA. In the range of pH 2-12, the adsorption capacity of M-FA increased with the increase of pH, whereas the adsorption capacity of FA decreased slowly until the pH 8 and then increased. Electrostatic adsorption was the major factor on the adsorption capacity. Around 61% and 55% percentage regeneration (PR) were obtained for FA and M-FA respectively when 78.4 mmol x L(-1) H2O2 and 0.72 mmol x L(-1) Fe2+ were used. When the condition of thermal regeneration was 400 degrees C and 2 h, a positive correlation can be found between the PRs of FA and regeneration times, the PRs were 102%, 104% and 107% in three cycles of adsorption-thermal regeneration process. However a negative correlation can be found between the PRs of M-FA and regeneration times, the PRs were 82%, 75% and 74% in three cycles of adsorption-thermal regeneration process. The PR of FA was higher than that of M-FA, and thermal regeneration was superior to Fenton-drive regeneration.

[Characterization and thermodynamic properties of Cu(II) imprinted chitosan crosslinked membrane].

A new type of Cu(II)-imprinted chitosan crosslinked membrane (IM Cu(II)-E-CTS) was prepared via molecular imprinting technology, chemical pre-crosslinking and crosslinking methods for treatment of wastewater containing low concentration of copper ion. IM Cu(II)-E-CTS was characterized by porosity, swelling ratio, amino group content, surface morphology, functional group and crystallinity. The thermodynamic properties of Cu (II) adsorption on the as-synthesized membrane at the low concentration (20-70 mg x L(-1)) were studied. It is found that porosity, swelling ratio and amino group contents of IM Cu(II)-E-CTS are 76.9%, 109% and 4.26 mmol x g(-1), respectively. Compared to the pristine chitosan membrane (CTS), 44.0% lower swelling ratio, 528% higher of porosity, 16.5% lower of amino group content are found with IM(Cu) (II)-E-CTS. Compared to crosslinked chitosan membranes (E-CTS), 24.6% higher amino group content is found with IM(Cu) (II)-E-CTS. Compared to CTS and E-CTS, the membrane morphology of IM Cu(II) E-CTS has undergone significant changes, and the internal structure became loose. Compared with CTS, molecular chain of IM Cu(II)-E-CTS is irregular and its crystallinity ability is lowered. IM Cu(II)-E-CTS adsorbs more Cu(II) than that of the other two metal cations [Ni(II) and Zn(II)]. The adsorption of copper ion on IM Cu(II)-E-CTS for 20-70 mg x L(-1) of initial Cu(II) concentration follows the Freundlich adsorption isotherm (R2 > 0.99). The adsorption is a spontaneous, exothermic, and entropy-decreased process.

Dynamics of augmented soil system containing biphenyl with Dyellaginsengisoli LA-4.

One high efficient biphenyl-degrading strain Dyella ginsengisoli LA-4 was inoculated into biphenyl-contaminated soil for bioaugmentation in this study. The results showed that bioaugmentation could accelerate the startup period of the biphenyl bioremediation process compared with the non-augmented one. PCR-DGGE fingerprints demonstrated that both of the diversity and pattern of microbial community were affected by the addition of strain LA-4 and biphenyl. Biphenyl-utilizing populations gradually increased and become the dominant species. The introduced strain LA-4 could be persistent and co-exist well with the indigenous populations. However, both of the strain LA-4 and indigenous microorganisms in the bioaugmented system would be partially inhibited by Zn(2+) and Ni(2+). This study suggests that it is feasible and potentially useful to remediate biphenyl-contaminated soil using bioaugmentation with D. ginsengisoli LA-4.

[Characteristics of adsorption and desorption isotherm of cresol isomers on activated carbon].

Simulated wastewater containing o-, m- and p-cresol was used respectively to study the effects of substituted position on adsorption and desorption and the feasibility of activated carbon adsorption-bioregeneration treatment. According to the isotherm, the adsorbability sequences in the order of p-cresol > o-cresol > m-cresol, which is positively correlated to pK(a) and negatively correlated to solubility and critical oxidation potential (COP); and the desorbability sequences in the order of o-cresol > m-cresol > p-cresol, which is negatively correlated to boiling point and viscosity. According to comparative analysis, irreversible adsorption is found to be the main reason for differences between adsorption and desorption isotherms. A mathematical statistics method was applied to estimate the amount of irreversible adsorption. The irreversible adsorption amounts of o, m, p-cresol are 27.9 mg/g, 28.5 mg/g and 33.4 mg/g, respectively.

[Utilizing fly ash to prepare polysilicon acid and compounded PFS and the study of its properties].

Fly ash which is a kind of solid waste of power station in Dalian was prepared as polysilicon acid, and compound polymerized ferric sulphate and its properties was studied. Fly ash was dipped in NaOH solution. The effects of temperature, concentration of NaOH solution and reactive time were examined respectively on the conversion efficiencies of silicon. Then the solution which was rich in silicon was used to compound polymerized ferric sulfate (PFS) and got compounded polymerized ferric sulphate (F-PFS), and evaluated the effects of slaking time and Fe3+/Si molar ratio on conversion efficiencies of silicon. Then used Na2SiO3 to prepare polysilicon acid compounded polymerized ferric sulphate (N-PFS) with the same silicon concentration at the best condition. The best ratio of dissolved silicon 0.207 9 g x g(-1) was attained at the condition of 4 mol x L(-1) NaOH solution, 120 degrees C for 4 h. The coagulant was attained at the condition of Fe3+/Si molar ratio of 1:0.2 and slaking time of 2 h. The reducing turbidity by F-PFS is the same as N-PFS, but F-PFS is better than N-PFS and PFS is in the stabilization, sedimentation,and the property of treating with urban sewage.

[Treatment of bromoamine acid wastewater by combined ALR-BAC process].

Combined ALR-BAC was used to treat bromoamine acid wastewater. The results showed that the ALR system could run steadily for over 1 months at the BAA concentration 650 mg x L(-1) after one-month acclimation, the decoloration rate of BAA was reached to about 90% within 12 h, and the removal rate of COD was about 50%, the precipitation performance of the suspended microorganism was good. When the influent bromoamine acid concentration was above 200 mg x L(-1), the decolorization products of BAA were easy to undergo auto-oxidation and the yellow intermediate products which were difficult to biodegrade were formed. The BAC process could inhibit the auto-oxidation of the decolorization products effectively, and the decolorization products could be biodegraded gradually. When there were no added sulphate, the concentrations of Br- and SO4(2-) were increased as the COD concentration reduced. Ultimately, the release rates of Br- and SO4(2-) were 72.2% and 66.9%, the COD removal efficiency was about 85.7%.