Dark fermentation of sewage sludge (i.e., the byproduct of biological sewage treatment process) is a promising way for renewable hydrogen production. However, low carbohydrate content and low C/N ratio essentially limited hydrogen production efficiency from sewage sludge. In this study, three raw forestry wastes with higher biodegradable carbohydrate content (fallen poplar leaves, flower waste, and sheared ryegrass) were added into a batch sludge fermentation system, aiming to explore an effective and practically feasible method to enhance hydrogen production from sludge. The results showed that the hydrogen yield from sole sewage sludge increased from 11.2 to 20.8, 32, and 51.7 mL/g-volatile solids (VS)added with the addition of poplar leaves, flower waste, and ryegrass as co-substrates, respectively, with relevant increase ratios of 0.85, 1.85, and 3.60 times, respectively. Model simulation results indicated that the lag time of sludge fermentation was also shortened through the addition of the above three raw forestry wastes as co-substrates. Meanwhile, the VS removal for sole sludge fermentation increased from 3.4% to 7.2, 12.7, and 18.6% by co-fermentation with poplar leaves, flower waste, and ryegrass, respectively. The enhancement from co-fermentation might be due to the addition of more biodegradable carbohydrate, more suitable C/N ratio of substrate, and higher carbohydrate utilization. After fermentation, the acetate-type fermentation was predominant in all four groups. Co-fermentation with these forestry wastes did not change the dominant hydrogen fermentation type. This study demonstrated that it was feasible to enhance hydrogen production and sludge reduction by co-fermentation with poplar leaves, flower waste, and ryegrass.

A series of pure Ni thin chains with particle diameters ranging from 15 to 80 nm were successfully synthesized by a wet chemical method. Magnetization measurements for the Ni chains reveal that the saturation magnetization increases and the coercivity decreases with increasing particle diameter. The magnetization reversal mechanism of both the samples with a diameter of 30 and 50 nm can be described by the model of “chain of spheres”. Using the fanning mode, the calculated coercivities and the remnant ratios agree well with the experimental results. Surprisingly, the coercivity is greatly enhanced, reaching as high as 790 Oe at T = 5 K for the Ni chains with a diameter of ∼15 nm, which are composed of single-crystal particles. Meanwhile, in the degradation of pentachlorophenol (PCP) solutions with Fe0 nanoparticles as reducing agents, Ni nanochains with a diameter of ∼80 nm were added, and the results indicate that the sample could serve as a good catalyst in dechlorination systems.

Phytoremediation of strontium contaminated soil by Sorghum bicolor (L.) Moench was investigated, and the soil microbial community-level physiological profiles (CLPPs) were examined. The growth and the stable strontium (88Sr) accumulations of the energy crop S. bicolor grown on the Sr-spiked soil at the level of 0, 50, 100, 200, and 400 mg/kg soil were characterized through pot soil system after the entire growth period (140 days). Correspondingly, the available content of strontium in soil extracted by Mehlich III extraction solution reached 42.0, 71.9, 151.8, and 242.2 mg/kg, respectively. The Sr-polluted soil microbial community was assessed by a Biolog Eco-plate method. The results showed that the spiked Sr significantly increased the height and the stem biomass weight of the plant. Sr contents in roots, stems, and leaves of the sorghum increased linearly (R2 > 0.95) with the elevation of the Sr-spiked level in soil. The average Sr concentration in roots, stems, and leaves reached 68.9, 61.3, and 132.6 mg/kg dry weight (DW) under Sr-spiked 400 mg/kg soil, respectively. Sr content in tissues decreased in the order of leaves > roots > stems. The bioconcentration factor (BCF; Sr contents in shoots to soil) values of S. bicolor in soil system was lower than 1 (0.21∼0.39) whether based on the spiked Sr level or on the available Sr level in soil. The transfer factor (TF; Sr contents in shoots to roots) values of S. bicolor in soil system usually is higher than 1 or near to 1 (0.92∼1.29). TF values increased while BCF values decreased as the soil Sr increased. The Biolog Eco-plate assay showed that Sr at the spiked level of 400 mg/kg soil enhanced the soil microbial diversity and activity.

The advanced treatment of municipal secondary effluent was performed by catalytic ozonation using Fe3O4-CeO2/MWCNTs as catalyst. The experimental results showed that in catalytic ozonation system, the removal efficiency of soluble COD was more than 46% after 30 min reaction, and about 36% of effluent organic matters (EfOMs) were mineralized, which was four times higher than that in single ozonation system. Moreover, proteins, humic acids, and UV254 decreased obviously after 30 min reaction, but polysaccharides did not significantly decrease. In catalytic ozonation system, the ozone utilization increased, which is favorable for the degradation of EfOM. The organic compounds and alkalinity were the main hydroxyl radical consumers in municipal secondary effluent. The catalytic ozonation process was also effective for the degradation of two target micropollutants (sulfamethazine and carbamazepine). The catalyst could be stable after five-time reuse for catalytic ozonation of effluent.

A MIL-100(Fe)/graphene oxide (GO) composite was prepared by a one-step hydrothermal method and utilized as a heterogeneous Fenton-like catalyst for methyl orange (MO) degradation. The obtained catalyst was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), nitrogen adsorption–desorption isotherms, thermogravimetric (TG) analysis, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The effects of H2O2 dosage, initial pH and catalyst dosage on the degradation of MO were investigated. The MIL-100(Fe)/GO presented high catalytic activity for the degradation of MO, achieving almost complete decomposition of MO after 240 min with reaction conditions of 8 mM H2O2, pH of 3.0 and 0.5 g L−1 catalyst. Kinetics analysis showed that MO removal followed a pseudo-first-order kinetic model. The catalyst showed stable catalytic activity and reusability after three successive runs. The possible catalytic mechanism of MIL-100(Fe)/GO was also proposed.

•Cobalt ions were removed from aqueous solution by forward osmosis (FO).•The effect of operation conditions on FO performance was determined.•The separation mechanism at various conditions was discussed.•FO membrane after Co(II) separation was characterized.•FO might be an alternative technology for radioactive wastewater.The performance of Co(II) removal from aqueous solution by forward osmosis (FO) was investigated. NaCl solutions were used as the draw solutions (DS). The effects of membrane characteristics, feed solutions properties, DS concentration, cross-flow rates on FO performance (water flux, Co(II) flux and retention, and reverse NaCl flux) were determined. The separation mechanisms under the various operational conditions were discussed. Changes of the FO membrane after Co(II) separation were characterized. The results show that CTA-ES featured the highest water fluxes of 15.5 ± 0.5 L m−2 h−1 at AL-FS and 23.4 ± 2.5 L m−2 h−1 at AL-DS among the three membranes. The active layer charge of the FO membrane was a main factor affecting Co(II) retention by FO. The texture of the support layer played a great role in the water permeability and reverse NaCl flux. The optimal operational conditions for Co(II) retention was NaCl concentration of 1.0 M in DS, the cross-flow rates of 11 and 5 cm s−1 at the feed and DS sides respectively. After used, the active layer of the CTA-ES membrane became more rough and hydrophobic. Co might attach to the membrane and became the membrane foulants. FO process could be an alternative technology for radioactive wastewater.

•A novel strain was isolated and identified as Clostridium butyricum INET1.•The hydrogen production performance was investigated.•The conditions for hydrogen production were optimized.•It can use various substrates (glucose, xylose, sucrose, lactose, starch and glycerol) for hydrogen production.A novel hydrogen-producing strain was isolated from gamma irradiated digested sludge and identified as Clostridium butyricum INET1. The fermentative hydrogen production performance of the newly isolated C. butyricum INET1 was characterized. Various carbon sources, including glucose, xylose, sucrose, lactose, starch and glycerol were used as substrate for hydrogen production. The operational conditions, including temperature, initial pH, substrate concentration and inoculation proportion were evaluated for their effects on hydrogen production, and the optimal condition was determined to be 35 °C, initial pH 7.0, 10 g/L glucose and 10% inoculation ratio. Cumulative hydrogen production of 218 mL/100 mL and hydrogen yield of 2.07 mol H2/mol hexose was obtained. The results showed that C. butyricum INET1 is capable of utilizing different substrates (glucose, xylose, sucrose, lactose, starch and glycerol) for efficient hydrogen production, which is a potential candidate for fermentative hydrogen production.

•Triclosan was irradiated to improve its biodegradability.•Irradiation at 1–5 kGy could enhance its mineralization and dechlorination.•Triclosan was removed by combined irradiation and biodegradation process.•The kinetics and pathway of triclosan degradation was proposed.•Irradiation can be an alternative pretreatment for recalcitrant pollutants.Triclosan is an antimicrobial agent which has been frequently detected in the environment. In this paper, the biodegradation of triclosan after radiation-induced advanced oxidation was investigated. The results show that the removal efficiency of triclosan in the combined irradiation and biological treatment process ranged from 88% to 97%, depending on the absorbed dose, while it was only 54% in the single biological treatment process. The removal efficiency of total organic carbon (TOC) was in the range of 53.1%,−59.2% at dose of 1–5 kGy in the combined irradiation and biological treatment process. In comparison, the removal efficiency of TOC in the single biological treatment process was 24.5%, suggesting that irradiation can enhance the mineralization of triclosan. The dechlorination efficiency of triclosan ranged from 48.6% to 78.4% at dose of 1–5 kGy. The intermediates of triclosan degradation were tentatively identified by LC-MS analysis and the possible degradation pathway was proposed. Based on the above results, the combined irradiation and biological treatment process could be an alternative process for treating triclosan-containing wastewater.

•Ozone is an efficient oxidant used for degrading organic pollutants.•Catalysts can improve O3 decomposition to form hydroxyl radicals.•Fe-based materials is emerging and promising catalysts for catalytic ozonation.•The preparation and characterization of Fe-based catalysts was summarized.•Their application for removing toxic organic pollutants was reviewed.Catalytic ozonation utilizes catalysts to improve the decomposition of ozone and the formation of hydroxyl radicals, which can overcome some disadvantages of ozonation. Fe-based materials are widely used as catalysts for heterogeneous catalytic ozonation due to their easy preparation, excellent catalytic performance and the abundance of Fe in nature. In this paper, the performances of various Fe-based catalysts, including Fe0-derived, FeOOH-derived, Fe2O3-derived, Fe3O4-derived and iron oxides composite, their preparation and characterization methods were briefly introduced. The catalytic ozonation using Fe-based catalysts for the degradation of various emerging contaminants, such as pesticides and herbicides, pharmaceuticals, phthalic acid esters, dyes, nitrobenzenes, phenols, as well as for the treatment of actual wastewater was summarized. The main influencing factors on catalytic ozonation of toxic organic pollutants were discussed, and their potential applications and perspectives were proposed.Download high-res image (129KB)Download full-size image

The kinetics and catalytic mechanism of sulfamethazine (SMT) degradation using Fe3O4/Mn3O4 nanocomposite as catalysts in heterogeneous Fenton-like process were investigated. The degradation process of SMT conformed to first-order kinetic model. The apparent activation energy (Ea) of the process was calculated to be 40.5 kJ/mol. The reusability and stability of the catalysts were evaluated based on the results of the successive batch experiments. The intermediates were identified and quantified by ion chromatography (IC), high-performance liquid chromatography (HPLC), and gas chromatography–mass spectrometry (GC-MS). The results suggested that the bonds of S–C, N–C, and S–N were broken mainly by ·OH attack to form the organic compounds, which were gradually decomposed into small-molecule organic acids, such as oxalic acid, propionic acid, and formic acid. The possible catalytic mechanism for SMT degradation was tentatively proposed.

In this study, Zn-CNT composites were prepared by the infiltration fusion method and characterized by TEM, XPS and N2 adsorption/desorption experiments. The reaction of Zn-CNTs and O2 in aqueous solution was performed for the in situ generation of H2O2, which was employed to react with Fe2+ for the Fenton degradation of 4-chlorophenol (4-CP). The effect of various parameters, including the initial pH, dosage of Zn-CNTs and Fe2+ concentration on 4-CP degradation was examined. The removal efficiencies of 4-CP and TOC (total organic carbon) were 98.8% and 87.4%, respectively, when the Fe2+ concentration was 20 mg L−1, initial pH was 2.0, Zn-CNT dosage was 2 g L−1, reaction time was 20 min and O2 flow rate was 400 mL min−1. When 4-CP was spiked in the secondary effluent of a municipal wastewater treatment plant, the removal efficiency of 4-CP and TOC was 47.0% and 45.6%, respectively, under the above-mentioned conditions. The intermediate products were detected by LC-MS and IC, and the possible degradation pathway of 4-CP and the reaction mechanism of the Zn-CNTs/O2/Fe2+ system were tentatively proposed.

Nitrate pollution in groundwater is a worldwide problem. This paper reports on the denitrifying performance of using the biodegradable polymer polybutylene succinate (PBS) as a biofilm medium and carbon source to remove nitrate from groundwater via a packed bed bioreactor which was operated continuously for nearly 2 years. Results showed that the effluent nitrate concentration reached 3.3–8.8 mg L−1 and 88–97% of nitrate removal was achieved. The denitrification rate range was 0.25–0.35 g N per L per d at 20–29 °C and decreased to 0.12 g N per L per d at 10–18 °C. According to microelectrode analysis, the nitrate consumption rate (1069 ± 103 μmol cm−1 h−1) was much higher than the ammonium production rate (74 ± 7 μmol cm−1 h−1), which proved that denitrification plays the major role in the system. A low level of DOC (1.7 ± 0.6 mg L−1) and ammonium (0.5 ± 0.3 mg L−1) was observed in the effluent, which was beneficial for practical application. The consumption rate of PBS was 2.75 ± 0.72 g PBS/g NO3–Nremoved. In the attached biofilm, Proteobacteria, Betaproteobacteria, Burkholderiales and Comamonadaceae were the major phyla (75.6%), classes (59.8%), orders (42.3%) and families (42.2%) in each level. In the top 20 genera accounting for 25% of total sequences, 9 genera including Simplicispira, Comamonadaceae, Hydrogenophaga and Rhodocyclaceae were affiliated with denitrifying groups with an abundance of 16%, whereas the bacteria belonging to the other 11 genera including Veillonellaceae, Propionivibrio and Bdellovibrio were reported to have the function of degradation and acidification of organic substance and might serve for degrading PBS in the system. The PBS solid-phase denitrification is promising for removing nitrate from groundwater.

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants, which are ubiquitous and pose the potential risk to ecosystem and human health. It is necessary to remove PPCPs from water and wastewater. In this study, sulfamethoxazole, a widely used antibiotic, was chosen as targeted pollutant. Fenton process and persulfate process were employed to remove sulfamethoxazole from aqueous solution. The results showed that Fenton process required less amount of Fe(II) and oxidant than persulfate process to achieve 100% removal of sulfamethoxazole in the water sample prepared with de-ionized water. The maximal mineralization reached 83% when hydrogen peroxide concentration was 1 mM and Fe(II) was 0.05 mM for Fenton process. The maximal mineralization for persulfate process was 60% with 4 mM of persulfate and 4 mM of Fe(II). The increase of Fe(II) concentration could increase the decomposition of hydrogen peroxide and persulfate, but did not increase the mineralization of sulfamethoxazole, indicating that the decomposition of hydrogen peroxide and persulfate was not positive correlation with the removal and mineralization of sulfamethoxazole. Five intermediate compounds were detected in Fenton process while eight intermediate compounds in persulfate process, suggesting that different degradation pathway occurred in the two processes. The wastewater components had negative effect on the degradation of sulfamethoxazole for both Fenton and persulfate processes. The removal efficiency of sulfamethoxazole was 52.5% and 52.3%, respectively, for Fenton and persulfate processes. Persulfate process could be an alternative for treating the real wastewater containing PPCPs.

•Sulfamethoxazole (SMX) -saturated AC was regenerated by gamma irradiation.•SMX could be removed at 5.0 kGy by gamma irradiation.•The mineralization of SMX required much higher dose (150 kGy).•Ionizing irradiation is a promising alternative for regeneration of AC.Activated carbon (AC) has been widely used for reclamation and reuse of the effluent of wastewater treatment plant to further remove the emerging contaminants, such as PPCPs in recent years. How to regenerate the exhausted AC effectively and economically is still a challenge. In the present study, the regeneration of AC exhausted with SMX was performed by gamma irradiation to simultaneously recover the spent AC and degrade the pollutants. The results showed that the adsorption of SMX onto AC can be described by the Langmuir isotherm and the adsorption capacity was about 417 mg/g. SMX can be removed rapidly when exposed to gamma irradiation, with the initial concentration of 100 mg/L, more than 99% of SMX was removed at 5.0 kGy, while an extremely high dose (150 kGy) was needed to reach 80% mineralization ratio. The regeneration efficiency was about 21–30% at 50–200 kGy. The absorbed SMX and the intermediates formed during gamma irradiation were released into aqueous solution from AC and mineralized, leading to the partial regeneration of the adsorption capacity of AC. Further studies are needed to optimize the experimental conditions to increase the regeneration efficiency.

•Separation of Cs ions was performed using vacuum membrane distillation.•Influences of operation parameters on permeate flux was examined.•Dusty gas model could simulate the mass transfer well.The separation of cesium ions (Cs+) from water solution was studied using vacuum membrane distillation (VMD) process. The removal efficiency of Cs+ was more than 99.76% and the membrane flux maintained about 6.14 L m−2 ·h−1 during the continuous operation. The dusty gas model was used to analyze the mass transfer of VMD process and it could simulate the mass transfer process well with average relative error of 4.84%. Mass transfer mechanism during cesium ions separation by VMD was investigated. Knudsen diffusion, i.e. collision between water vapor molecules, was proved to be the dominant mass transfer influence mechanism during VMD process. Anionic counterpart of Cs+ (Cl− and NO3−) had little influence on Cs removal, while high salt loading of the feed solution would decrease Cs removal efficiency of VMD due to salt crystallization on the membrane. Effects of operation factors (feed temperature: 303–343 K, vacuum side pressure: 5.05–90.9 kPa, feed flow velocity: Reynolds number 100–400 and feed salt concentration: NaCl 0–100 g/L) on the permeate flux were investigated. It was found that membrane flux was exponentially proportional to the feed temperature, directly proportional to the feed velocity and inversely proportional to the vacuum side pressure and feed salt concentration. VMD process has showed its promising prospect in cesium ions separation from water solution.

•Co-fermentation of sludge with perennial ryegrass was investigated.•The addition of ryegrass considerably enhanced sludge hydrogen fermentation.•The highest hydrogen yield achieved 60 mL/g-VS at sludge/ryegrass ratio of 30:70.•The Cone model sometimes fitted better than the modified Gompertz model.•Hydrogen yield increased exponentially with increase of dehydrogenase activity.The low C/N ratio and low carbohydrate content of sewage sludge limit its application for fermentative hydrogen production. In this study, perennial ryegrass was added as the co-substrate into sludge hydrogen fermentation with different mixing ratios for enhancing hydrogen production. The results showed that the highest hydrogen yield of 60 mL/g-volatile solids (VS)added was achieved when sludge/perennial ryegrass ratio was 30:70, which was 5 times higher than that from sole sludge. The highest VS removal of 21.8% was also achieved when sludge/perennial ryegrass ratio was 30:70, whereas VS removal from sole sludge was only 0.7%. Meanwhile, the co-fermentation system simultaneously improved hydrogen production efficiency and organics utilization of ryegrass. Kinetic analysis showed that the Cone model fitted hydrogen evolution better than the modified Gompertz model. Furthermore, hydrogen yield and VS removal increased with the increase of dehydrogenase activity.

•Radioactive graphite waste is an important issue worldwide.•The treatment and disposal of irradiated graphite was briefly reviewed.•The formation C-14, Cl-36 and H-3, in irradiated graphite was summarized.•The various methods for treating irradiated graphite were introduced.Graphite is used as a moderator and reflector in nuclear reactors. Fission products and activation of impurities in the graphite contaminated this graphite during reactor operation. Larger amount of irradiated graphite has to be considered as radioactive waste. The management of irradiated graphite waste is becoming an increasingly important issue worldwide. The objective of this paper was to briefly review the recent advances in the treatment and disposal of irradiated graphite to offer deep insight into a better understanding of the techniques for the management of irradiated graphite from nuclear reactors. The properties of irradiated graphite were briefly introduced. The formation of radionuclides, especially C-14, Cl-36 and H-3, in the irradiated graphite was summarized. The main features of Wigner treatment, thermal treatment, chemical treatment, conditioning, coating and impregnation, gasification were addressed. The final end point of the graphite and the final end point of the radionuclides were discussed and their influences on selection of treatment methods were compared.

AbstractBACKGROUNDThe presence of sulfonamide antibiotics in aquatic environments has received increasing attention. In this study, the nanocomposite Fe3O4–Mn3O4 was synthesized, characterized and used as a catalyst for the degradation of sulfamethazine (SMT) in a heterogeneous Fenton-like process.RESULTSThe composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), BET specific surface area, vibrating sample spectrometry (VSM), Raman and Fourier transform infrared (FTIR) spectroscopy before and after use. The catalytic activity was evaluated under different conditions, including pH value, H2O2 dosage, catalyst dosage, temperature and initial concentration of SMT. The removal efficiency of SMT was more than 99% in 50 min at pH=3, T = 45 °C, H2O2=6 mmol L−1, Fe3O4–Mn3O4 dosage = 0.5 g L−1, SMT=20 mg L−1.CONCLUSIONSFe3O4–Mn3O4 composite was an efficient catalyst for degradation of SMT in a Fenton-like process. © 2016 Society of Chemical Industry

•Two SnOx/MWCNT and two SnO2/MWCNT cathodes were prepared for the electrochemical reduction of CO2 to formate.•A 60% faradaic efficiency with 25% energy efficiency was obtained with the two SnOx/MWCNT cathodes.•The efficiencies were not strongly influenced by the morphology of the particle agglomeration.A comparative study is reported on the electrocatalytic reduction of CO2 to HCOOH in aqueous alkaline solution with differently prepared tin-oxide particles on multi-walled carbon nanotubes from SnCl2 or SnCl4 precursors. The highest faradaic and energy efficiencies of 64% and 27% were obtained at − 1.40 V vs. SCE with particles that were obtained by KBH4 reduction from a SnCl2 precursor. At lower potentials, competitive reduction reactions occur. A SnCl2 versus SnCl4 precursor favors retention of a Sn(II) valence state in a surface tin oxyhydroxide surface layer. Different morphologies of the particle agglomerates made little difference in the electrocatalytic selectivity and activity. The two SnOx/CNT electrodes both showed a current density retention of ~ 70% after a 20-h electrolysis.

A magnetic graphene, i.e., nanoscaled zero valent iron/graphene (0FG) composite, was prepared, characterized and applied for the removal of Co(II) from aqueous solution. The magnetic graphene (0FG) was synthesized through reduction of graphene oxide (GO) and ferrous ions by potassium borohydride. The kinetics and isotherms of Co(II) adsorption onto 0FG were investigated. The mechanism for Co(II) removal was proposed based on the Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and the X-ray absorption fine structure (XAFS) analysis. The results showed that pseudo second-order models and the Freundlich isotherm model fitted well with the data obtained. The adsorption capacity of 0FG was calculated from the Langmuir isotherm, which was 65.58, 101.60 and 134.27 mg/g at 10, 20 and 30 °C, respectively. Thermodynamic parameters suggested that the adsorption process was endothermic and spontaneous. Co2+ was stabilized by γ-FeOOH/γ-Fe2O3/Fe3O4 on the surface of graphene sheets, forming CoFe2O4-like nanocrystals. The coordination numbers and interatomic distances indicated that Co2+ mainly occupied the octahedral site, while pseudo-tetrahedral coordination may occur by dehydroxylation of Co(O,OH)6. Magnetic graphene is a potential adsorbent for Co2+ removal.

The temperature, initial pH, and substrate concentration on fermentative hydrogen production was optimized by the Box–Behnken design using γ-irradiated sludge as inoculum, and the fermentation process was analyzed at optimal conditions. The experimental results showed that the maximum cumulative hydrogen production was 3000 mL of H2/L of medium and the hydrogen yield was 1.81 mol of H2/mol of glucose, at 32.9 °C, with an initial pH of 7.92 and a glucose concentration of 17.0 g/L. The highest hydrogen production rate was accompanied by the exponential growth of microorganisms. The mixed cultures underwent the mixed-acid-type fermentation in the first 10 h and then changed to the acetate butyrate pathway until the end of fermentation. The hydrogen yield showed a positive relationship with acetate generation during the fermentation process.

The low-pressure wet oxidation was used to solubilize the waste-activated sludge for recovering the carbon source, and the treated sludge was applied for the fermentative hydrogen production. The experimental results showed that, after low-pressure oxidation treatment, the concentration of soluble chemical oxygen demand (SCOD), polysaccharides, and protein present in the liquid phase was increased by 2.0, 2.2, and 102.5 times, respectively. Bio-hydrogen production was successfully achieved using solubilized sludge as the substrate. Through comparison of the hydrogen production from glucose, the treated sludge, and the mixture of the sludge and glucose, it was found that the hydrogen yield of tests using different substrates showed a positive relation with the ratio of acetic acid/butyric acid in soluble metabolites and the ratio of polysaccharides/SCOD in substrates. It can be concluded that the waste-activated sludge treated by low-pressure wet oxidation can be used as low-cost substrate for bio-hydrogen production.

AbstractVolume concentration determination of atmospheric krypton and xenon is very important for krypton-85 and radioactive xenon isotopes monitoring. An injection set-up integrated adjustable quantity sample injection and quantitative dilution function was designed. The effects of electron impact (EI) source parameters on the sensitivity of MS detector were studied. Optimal values were as follows: ionization energy of 70 eV, emission current of 40 mA, cathode voltage of 27 mV, ion focus voltage of 85 mV and lens compensation voltage of 20 V. A GC-MS method for the determination of krypton and xenon in atmosphere without sample pretreatment was developed. Minimal detected concentrations for krypton and xenon were 3.3 × 10−8 (V/V) and 2.6 × 10−9 (V/V) respectively. Moreover, krypton and xenon concentrations in the ground level air were measured with the results of 1.1 × 10−6 (V/V) and 9.3 × 10−8 (V/V). The related combined standard uncertainties for krypton and xenon results were 2.38% and 3.15%, respectively.Direct injection mode means that air samples are not required to be pretreated, which can directly enter into GC–MS for analysis. An injection set–up integrated adjustable quantity sample injection and quantitative dilution function was designed, so that standard reference samples at lower concentration levels were obtained and the external standard curve was calibrated by only one standard reference sample.

The migration and sorption of Sr in clay-sand mixture were investigated by batch experiment, column experiments and numerical simulation. The results showed that as the clay content in clay-sand mixture increased, the effective porosity, absorption capacity and retardation factor of the mixture for Sr increased, but the dispersion coefficient and migration velocity decreased. The migration of Sr was influenced strongly when clay content was in range of 0–25 %, but influenced weakly when clay content was more than 25 %. The experimental data was consistent with the calculated results by CXTFIT program.

Fe3O4/multi-walled carbon nanotubes were prepared, characterized and used as a nanocatalyst for ozonation of p-hydroxybenzoic acid. The stability and reusability of the catalyst was evaluated. Characterization techniques including X-ray diffraction, Fourier transform infrared absorption spectroscopy, scanning electron microscope, high-resolution transmission electron microscopy and physical property measurement were used to analyze the reason for the decrease in catalyst activity. The addition of t-butanol and bicarbonate were used to explore the different process between hydroxyl radicals and ozone. The experimental results showed that the catalytic ozonation could significantly increase the degradation and mineralization of p-hydroxybenzoic acid. The initial pH value was a crucial factor influencing ozone decomposition and the surface property of catalyst or organic pollutant. The degradation of p-hydroxybenzoic acid increased by 32 % in catalyzed ozonation compared to single ozonation after 5 min reaction with unadjusted pH (about 5.4). In batch experiments, the removal efficiency of p-hydroxybenzoic acid and total organic carbon decreased 36.1 and 6.8 % after six run times. Bicarbonate significantly inhibited the mineralization of p-HBA, but it had almost no influence on the catalytic degradation of p-hydroxybenzoic acid. A possible pathway for p-hydroxybenzoic acid degradation was tentatively proposed.

•Magnetic nanoscaled Fe3O4/CeO2 composite was used to degrade TCP.•OH mechanism was determined to predominate in the process.•A possible degradation pathway of TCP was proposed.The degradation of 2,4,6-trichlorophenol (TCP) was investigated by using magnetic nanoscaled Fe3O4/CeO2 composite as a heterogeneous Fenton-like catalyst. The individual and interactive effects of four process variables, i.e. solution pH, initial TCP concentration, Fe3O4/CeO2 dosage and H2O2 concentration, on TCP removal, mineralization and dechlorination were investigated by response surface methodology (RSM) using the central composite design (CCD). The optimal regions of degradative conditions were pH 2.0–2.1, TCP 20–100 mg/L, Fe3O4/CeO2 1.5–2.5 g/L, and H2O2 17–30 mM. The removal efficiency, mineralization and dechlorination rate of TCP was 99%, 65% and 95% after 90 min, respectively under the conditions of pH 2.0, TCP 100 mg/L, Fe3O4/CeO2 2.5 g/L and H2O2 30 mM, which agreed well with the modeling prediction. Fe3O4/CeO2 showed a high catalytic ability for the removal of TCP in comparison with other processes. The recyclability of Fe3O4/CeO2 was also examined. According to the results of iron leaching, the effects of radical scavengers and intermediates determination, a possible pathway of TCP degradation was proposed based on OH mechanism (including free OH in the bulk liquid and surface-bounded OH).

The cross-linked starch/polycaprolactone (SPCL10) and starch/polycaprolactone (SPCL12) blends were prepared, characterized and used as carbon source and biofilm support for biological nitrate removal. The results showed that SPCL10 and SPCL12 had similar performance on water absorption (about 21 %) and leaching capacity. FTIR spectra confirmed the cross-linking reaction between starch and PCL. SEM displayed a thermoplastic nature of SPCL10 and SPCL12. These blends could serve as solid carbon source and biofilm support for biological denitrification, and the acclimation time of microbial biofilm on the surfaces of SPCL10, SPCL12 and PCL were about 2 days, 2 days and 16 days, respectively. The average denitrification rates were 0.0216, 0.0154 and 0.0071 mg NO3-N/(g h) for SPCL10, SPCL12 and PCL, respectively, and the effluent NO2-N concentration was below 1 mg/L at all cases. The phenomenon of ammonia formation was observed, but ammonia concentration was below 0.5 mg/L.

Di-n-butyl phthalate is widely used as plasticizer, which has been listed as priority pollutant due to its toxic and ubiquitous characteristics. It is difficult to remove by the conventional wastewater treatment processes. In this paper, the feasibility of using Micrococcus sp. to bioaugment a sequencing batch reactor for degrading di-n-butyl phthalate (DBP) was investigated. The terminal restriction fragment length polymorphisms (T-RFLP) were used to analyze the variation of microbial community in the reactor. The experimental results showed that for the bioaugmented reactor, the removal efficiency of DBP was about 85 % as compared to 25 % of the control reactor when initial DBP concentration was 100 mg/L. The bioaugmentation not only enhanced the removal efficiency of target compound, but also shortened the start-up time of the reactor. The kinetics of DBP degradation conformed to the first-order model in both reactors. The T-RFLP analysis indicated the bacterial community changes in the acclimated activated sludge and the introduced Micrococcus sp. during the operational process.

•Gamma irradiation was used for enriching H2-producing bacteria.•The optimal dose was 5.0 kGy.•Gamma irradiation was a powerful pretreatment methods.Gamma irradiation was used as a pretreatment method for enriching hydrogen-producing bacteria from digested sludge. The experimental results demonstrated that 5.0 kGy was optimal dose among the different doses (0.5–10 kGy) applied in this study. The maximum cumulative hydrogen production, hydrogen yield, hydrogen production rate and substrate degradation efficiency of the sludge irradiated at such dose were 529.4 mL, 267.7 mL/g glucose, 37.25 mL/h and 98.9%, respectively when the fermentation conditions were as follows: at 36 °C, initial pH 7.0 and 10 g/L glucose as substrate. In comparison with the conventional pretreatment methods, such as heat-shock, acid, base, aeration and chloroform, gamma irradiation was more powerful pretreatment method for enriching hydrogen-producing bacteria. The effect of Gamma irradiation on the microbial community structure of the pretreated sludge needs further study.

•Gamma irradiation was used for enriching H2-producing bacteria.•Different pretreatment methods were compared.•Gamma irradiation was a powerful pretreatment methods.The pretreatment of digested sludge by different methods, including ionizing irradiation, heat-shock, acid and base, was performed for enriching hydrogen-producing bacteria. These methods were evaluated and compared based on their suitability in the enrichment of hydrogen-producing bacteria in dark fermentation with glucose as a substrate in batch tests. The experimental results showed that the seed sludge pretreated by ionizing irradiation achieved the best hydrogen production among the different pretreatment methods, and the maximum hydrogen production potential, maximum hydrogen production rate, hydrogen yield and substrate degradation rate were 525.6 mL, 37.2 mL/h, 267.7 mL/g glucose (2.15 mol/mol glucose) and 98.9%, respectively. Ionizing irradiation can be a good optional pretreatment method for enriching hydrogen-producing bacteria from digested sludge. The effect of ionizing irradiation on the microbial community structure dynamics of the pretreated sludge deserves further study, which will help us to understand the mechanisms leading to the effect of high bio-hydrogen production.

Denitrification of groundwater was studied using a laboratory-scale reactor packed with biodegradable snack ware served as both carbon source and biofilm support for microorganisms. The complete removal of 50 mg/L of nitrate-nitrogen was achieved in a 23-day-old reactor with 2.1 h of hydraulic retention time without inoculating with any external microorganisms, which indicates that indigenous microorganisms in groundwater proliferate readily and result in stable biofilm formation onto biodegradable snack ware. Accumulation of nitrite and nitrate residue was detected when hydraulic retention time was lower than 2.1 h. The breakthrough of nitrate-nitrogen up to over 10 mg/L in the effluent water was observed with nitrate removal efficiency reducing to about 75 % when hydraulic retention time was lowered to 1.4 h. The highest rate of denitrification was observed with 1.5 h of hydraulic retention time. Dissolved organic carbon concentration in the effluent water ranged between 10 and 20 mg/L during the stable operation of the reactor, and nitrite-nitrogen concentration was never higher than 0.09 mg/L. Considering its relatively low price and high denitrification rate, biodegradable snack ware can become a good alternative for denitrification process.

Magnetic nanoscaled Fe3O4/CeO2 composite was prepared by the impregnation method and characterized as a heterogeneous Fenton-like catalyst for 4-chlorophenol (4-CP) degradation. The catalytic activity was evaluated in view of the effects of various processes, pH value, catalyst addition, hydrogen peroxide (H2O2) concentration, and temperature, and the pseudo-first-order kinetic constant of 0.11 min–1 was obtained for 4-CP degradation at 30 °C and pH 3.0 with 30 mM H2O2, 2.0 g L–1 Fe3O4/CeO2, and 0.78 mM 4-CP. The high utilization efficiency of H2O2, calculated as 79.2%, showed a promising application of the catalyst in the oxidative degradation of organic pollutants. The reusability of Fe3O4/CeO2 composite was also investigated after six successive runs. On the basis of the results of metal leaching, the effects of radical scavengers, intermediates determination, and X-ray photoelectron spectroscopic (XPS) analysis, the dissolution of Fe3O4 facilitated by CeO2 played a significant role, and 4-CP was decomposed mainly by the attack of hydroxyl radicals (•OH), including surface-bound •OHads generated by the reaction of Fe2+ and Ce3+ species with H2O2 on the catalyst surface, and •OHfree in the bulk solution mainly attributed to the leaching of Fe.

A considerable increase in nitrate concentration in groundwater has been observed in many countries. This research focuses on nitrate removal using biodegradable snack ware (BSW) as both carbon source and biofilm support for denitrifiers. The denitrification efficiency of a laboratory-scale denitrification reactor packed with BSW was examined in a low-temperature condition. The nitrate removal efficiency supported by BSW decreased to approximately 40% at 12°C from nearly 100% at 25°C with 50 mg/L of nitrate-nitrogen in the influent and 2 h of hydraulic retention time (HRT). The complete nitrate removal was obtained when nitrate-nitrogen concentration was no more than 15 mg/L at 2 h of HRT and at 12°C. If the initial concentration of nitrate-nitrogen was 50 mg/L, 5 h of HRT was needed for the complete nitrate removal. Nitrite concentration in the treated water decreased evidently as HRT was increased from 2 to 5 h, or as nitrate-nitrogen concentration in the influent decreased to 15 mg/L from 50 mg/L. It was observed that varying HRT and nitrate concentration in the influent had no noticeable effect on dissolved organic carbon content in the effluent under the experimental conditions. This study indicated that the complete nitrate removal could be achieved readily even at 12°C using BSW as carbon source by changing HRT or the initial concentration of nitrate in the influent, which has some useful implications in environmental engineering practice.

Biochemical oxygen demand (BOD) is one of the most important and widely used parameters for characterizing the organic pollution of water and wastewater. In this paper, a novel reactor-type biosensor for rapid measurement of BOD was developed, based on using immobilized microbial cell (IMC) beads as recognition bio-element in a completely mixed reactor which was used as determining chamber, replacing the traditionally used membrane as recognition bio-element. The IMC beads were freely suspended in the aqueous solution, so the mass transfer resistance for dissolved oxygen and organic compounds significantly reduced, and the quantity of the microbial cells used as recognition element can be easily adjusted, in comparison with the traditional membrane-type BOD biosensor, in which exists a unadjustable contradiction between the quantity of biomass and the thickness of the bio-membrane, thus limiting the stability and the detection limit. This novel kind of BOD biosensor significantly increased the sensitivity of the response, the detecting precision and prolonged the life time of the recognition element. The experimental data showed that the most appropriate temperature for biochemical reaction in the reactor was 30 °C, and the IMC beads could keep the bioactivity for about 70 d at the detecting frequency of 8 times every day. The standard deviation of repeatability and the reproducibility of responses were within ±6.4% and ±5.0%, respectively, which are within acceptable bias limits, and meet the requirement of BOD rapid measurement.

A central composite design was carried out to investigate the effect of temperature, initial pH and glucose concentration on fermentative hydrogen production by mixed cultures in batch test. The modeling abilities of the response surface methodology model and neural network model, as well as the optimizing abilities of response surface methodology and the genetic algorithm based on a neural network model were compared. The results showed that the root mean square error and the standard error of prediction for the neural network model were much smaller than those for the response surface methodology model, indicting that the neural network model had a much higher modeling ability than the response surface methodology model. The maximum hydrogen yield of 289.8 mL/g glucose identified by response surface methodology was a little lower than that of 360.5 mL/g glucose identified by the genetic algorithm based on a neural network model, indicating that the genetic algorithm based on a neural network model had a much higher optimizing ability than the response surface methodology. Thus, the genetic algorithm based on a neural network model is a better optimization method than response surface methodology and is recommended to be used during the optimization of fermentative hydrogen production process.

This review summarized the experimental design methods used to investigate the effects of various factors on fermentative hydrogen production processes, including one-factor-at-a-time design, full factorial design, Taguchi design, Plackett–Burman design, central composite design and Box–Behnken design. Each design method was briefly introduced, followed by the introduction of its analysis. In addition, the advantages and disadvantages of each design method were briefly discussed. Moreover, the application of each design method to the study of fermentative hydrogen production was analyzed and discussed. Based on the discussion in this review, an experimental design strategy for optimizing fermentative hydrogen production processes was proposed. In the end, the software packages that can carry out the above mentioned factorial design and analysis were briefly introduced.

This review summarized several main factors influencing fermentative hydrogen production. The reviewed factors included inoculum, substrate, reactor type, nitrogen, phosphate, metal ion, temperature and pH. In this review, the effect of each factor on fermentative hydrogen production and the advance in the research of the effect were briefly introduced and discussed, followed by some suggestions for the future work of fermentative hydrogen production. This review showed that there usually existed some disagreements on the optimal condition of a given factor for fermentative hydrogen production, thus more researches in this respect are recommended. Furthermore, most of the studies on fermentative hydrogen production were conducted in batch mode using glucose and sucrose as substrate, thus more studies on fermentative hydrogen production in continuous mode using organic wastes as substrate are recommended.

A fractional factorial design was carried out to investigate the effects of temperature, initial pH and glucose concentration on fermentative hydrogen production by mixed cultures in batch tests and then the experimental data of substrate degradation efficiency, hydrogen yield and average hydrogen production rate were described by a neural network, based on which the simultaneous optimization of the three responses was performed by the method of desirability function. The analysis showed that the neural network could successfully describe the effects of temperature, initial pH and glucose concentration on the substrate degradation efficiency, hydrogen yield and average hydrogen production rate of this study. The maximum substrate degradation efficiency of 95.3%, hydrogen yield of 305.3 mL/g glucose and average hydrogen production rate of 23.9 mL/h were all obtained at the optimal temperature of 39.0 °C, initial pH of 7.0 and glucose concentration of 24.6 g/L identified by the method of desirability function based on a neural network. In sum, the method of desirability function based on a neural network was a useful tool to optimize several responses for fermentative hydrogen production processes simultaneously.

The kinetic models were developed and applied for fermentative hydrogen production. They were used to describe the progress of a batch fermentative hydrogen production process, to investigate the effects of substrate concentration, inhibitor concentration, temperatures, pH, and dilution rates on the process of fermentative hydrogen production, and to establish the relationship among the substrate degradation rate, the hydrogen-producing bacteria growth rate and the product formation rate. This review showed that the modified Gompertz model was widely used to describe the progress of a batch fermentative hydrogen production process, while the Monod model was widely used to describe the effects of substrate concentration on the rates of substrate degradation, hydrogen-producing bacteria growth and hydrogen production. Arrhenius model was used a lot to describe the effects of temperature on fermentative hydrogen production, while modified Han–Levenspiel model was used to describe the effects of inhibitor concentration on fermentative hydrogen production. The Andrew model was used to describe the effects of H+ concentration on the specific hydrogen production rate, while the Luedeking–Piret model and its modified form were widely used to describe the relationship between the hydrogen-producing bacteria growth rate and the product formation rate. Finally, some suggestions for future work with these kinetic models were proposed.

Removal of nitrate from groundwater was investigated using biodegradable meal box (BMB) and poly(ɛ-caprolactone) (PCL) as carbon source and biofilm carrier. The experimental results show that nitrate in groundwater can be effectively removed using BMB and PCL as carbon source. Denitrification rates supported by BMB and PCL were 52.80 and 42.77 mg (NO3-N)/(m2·h), respectively, at 30°C and pH 7.5. The pH value of effluent ranged from 7 to 8, and NO2-N concentration was less than 0.1 mg/L. Compared with BMB, PCL could decrease nitrite accumulation; however, more significant influence of temperature on denitrification was observed for PCL as carbon source. Temperature constants for BMB and PCL were 0.045 and 0.068, respectively, at 10–30°C. Based on denitrification efficiency and cost, BMB is more suitable as a carbon source for denitrification of groundwater than PCL.

The effects of nitrate on fermentative hydrogen production and soluble metabolites from mixed cultures were investigated by varying nitrate concentrations from 0 to 10 g N/L at 35°C with an initial pH of 7.0. The results showed that the substrate degradation rate, hydrogen production potential, hydrogen yield, and average hydrogen production rate initially increased with increasing nitrate concentrations from 0 to 0.1 g N/L, while they decreased with increasing nitrate concentrations from 0.1 to 10 g N/L. The maximum hydrogen production potential of 305.0 mL, maximum hydrogen yield of 313.1 mL/g glucose, and maximum average hydrogen production rate of 13.3 mL/h were obtained at a nitrate concentration of 0.1 g N/L. The soluble metabolites produced by the mixed cultures contained only ethanol and acetic acid (HAc) without propionic acid (HPr) and butyric acid (HBu). This study used the Modified Logistic model to describe the progress of cumulative hydrogen production in batch tests. A concise model was proposed to describe the effects of nitrate concentration on average hydrogen production rate.

The inhibitory effect of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate. The experimental results showed that, at 35 °C and initial pH 7.0, during the fermentative hydrogen production, the substrate degradation efficiency, hydrogen production potential, hydrogen yield and hydrogen production rate all trended to decrease with increasing added ethanol, acetic acid, propionic acid and butyric acid concentration from 0 to 300 mmol/L. The inhibitory effect of added ethanol on fermentative hydrogen production was smaller than those of added acetic acid, propionic acid and butyric acid. The modified Han–Levenspiel model could describe the inhibitory effects of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production rate in this study successfully. The modified Logistic model could describe the progress of cumulative hydrogen production.

Effect of temperatures ranging from 20 °C to 55 °C on fermentative hydrogen production by mixed cultures was investigated in batch tests. The experimental results showed that, at initial pH 7.0, during the fermentative hydrogen production using glucose as substrate, the substrate degradation efficiency and hydrogen production potential increased with increasing temperatures from 20 °C to 40 °C. The maximal substrate degradation efficiency was 98.1%, the maximal hydrogen production potential was 269.9 mL, the maximal hydrogen yield was 275.1 mL/g glucose and the shortest lag time was 7.0 h. The temperature for fermentative hydrogen production by mixed cultures was optimized to be 40 °C. The expanded Ratkowsky models could be used to describe the effect of temperatures on the hydrogen production potential, maximum hydrogen production rate and the lag time during fermentative hydrogen production.

The effect of temperature, initial pH and glucose concentration on fermentative hydrogen production by mixed cultures was investigated in batch tests, and the optimization of fermentative hydrogen production process was conducted by response surface methodology with a central composite design. Experimental results showed that temperatures, initial pH and glucose concentrations had impact on fermentative hydrogen production individually and interactively. The maximum hydrogen yield of 289.8 mL/g glucose was estimated at the temperature of 38.6 °C, the initial pH of 7.2 and the glucose concentration of 23.9 g/L. The maximum hydrogen production rate of 28.2 mL/h was estimated at the temperature of 37.8 °C, the initial pH of 7.2 and the glucose concentration of 27.6 g/L. The maximum substrate degradation efficiency of 96.9% was estimated at the temperature of 39.3 °C, the initial pH of 7.0 and the glucose concentration of 26.8 g/L. Response surface methodology was a better method to optimize the fermentative hydrogen production process. Modified logistic model could describe the progress of cumulative hydrogen production in the batch tests of this study successfully.

The effect of the Fe2+Fe2+ concentrations ranging from 0 to 1500 mg/L on the fermentative hydrogen production from glucose was investigated in batch tests by mixed cultures at 35 °C and initial pH 7.0. The experimental results showed that in certain concentration range, Fe2+Fe2+ was able to enhance the hydrogen production rate, the cumulative hydrogen quantity, and the hydrogen yield by the mixed cultures. The maximum cumulative hydrogen quantity of 302.3 mL and the maximum hydrogen yield of 311.2 mL/g glucose were obtained at the Fe2+Fe2+ concentration of 300 and 350 mg/L, respectively. The major soluble metabolites produced by the mixed cultures were ethanol, acetic acid, and butyric acid, with little or no propionic acid. The glucose degradation efficiency had the trend to decrease with increasing Fe2+Fe2+ concentrations from 0 to 1500 mg/L, but when the Fe2+Fe2+ concentrations were lower than 350 mg/L, the glucose degradation efficiency was between 96.25 and 98.78%, which is relatively high and kept unchanged with increasing Fe2+Fe2+ concentrations. In certain concentration range, Fe2+Fe2+ was able to enhance the biomass production yield. When the Fe2+Fe2+ concentrations were between 100 and 750 mg/L, there was a high biomass production yield plateau ranging from 259.2 to 334.2 mg/g glucose. The final pH value had the trend to decrease with increasing Fe2+Fe2+ concentrations from 0 to 1000 mg/L, and the lowest final pH value was about 4.3 at the Fe2+Fe2+ concentration of 1000 mg/L.

The pretreatment of digested sludge by five methods (by acid, base, heat-shock, aeration and chloroform, respectively) was conducted in batch tests to evaluate and compare their suitability in the enrichment of hydrogen-producing bacteria. The experimental results showed that, at 35 °C and initial pH 7.0, the hydrogen yields of the pretreated digested sludge were higher in comparison with the control test during the fermentative hydrogen production using glucose as the substrate. In all tests, for fermentative hydrogen production from glucose, the digested sludge pretreated by heat-shock could obtain the maximal hydrogen production potential, maximum hydrogen production rate, hydrogen yield, substrate degradation efficiency and biomass concentration, which were 215.4 mL, 120.4 mL/h, 221.5 mL/g glucose, 97.2% and 2739 mg/L, respectively. The final pH values in the liquid after fermentative hydrogen production in all tests were between 3.4 and 4.1. Heat-shock is an easy and practical pretreatment method for enriching hydrogen-producing bacteria from digested sludge.

The interaction mechanism between zinc and the intact yeast cells of Saccharomyces cerevisiae was investigated by using the scanning electron microscopy with energy-dispersive X-ray analysis, as well as X-ray absorption fine structure spectroscopy (XAFS). Displacement of H+, K+, Mg2+, and Na+ during zinc uptake confirmed the existence of both covalent interactions and ionic interactions between Zn2+ and the microbe. Ion exchange mechanism played a role in zinc uptake. The local environment of Zn accumulated in the intact yeast cells was determined by XAFS, which suggests that the nearest neighboring atom of the bound zinc ion on the biomass is oxygen atom. The adsorbed zinc ion on the intact cells of S. cerevisiae is a tetrahedron structure, with the Zn–O bond length of 1.97 Å, and the coordination number is only 3.2 of Zn–O structure in the first shell.

Chlorophenols (CPs), as important contaminants in groundwater, are toxic and difficult to biodegrade. Recently nanoscale zero-valent iron received a great deal of attention because of its excellent performance in treating recalcitrant compounds. In this study, nanoscale zero-valent iron particles were prepared using chemical reduction, and the reductive transformations of three kinds of chlorinated phenols (2-CP, 3-CP, and 4-CP) by nanoscale zero-valent iron under different conditions were investigated. The transformation process of the CPs was shown to be dechlorination first, then cleavage of the benzene ring. The removal efficiency of the CPs varied as follows: 2-CP > 3-CP > 4-CP. The reactivity of CPs was associated with their energy of lowest unoccupied molecular orbit (ELUMO). With the increase in initial concentrations of CPs, removal efficiency decreased a little. But the quantities of CPs reduced increased evidently. Temperature had influence on not only the removal efficiency, but also the transformation pathway. At higher temperatures, dechlorination occurred prior to benzene ring cleavage. At lower temperatures, however, the oxidation product was formed more easily.

The effect of substrate concentration ranging from 0 to 300 g/L on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate. The experimental results showed that, at 35 and initial pH 7.0, during the fermentative hydrogen production, the hydrogen °C production potential and hydrogen production rate increased with increasing substrate concentration from 0 to 25 g/L. The maximal hydrogen production potential of 426.8 mL and maximal hydrogen production rate of 15.1 mL/h were obtained at the substrate concentration of 25 g/L. The maximal hydrogen yield and the maximal substrate degradation efficiency were respectively 384.3 mL/g glucose and 97.6%, at the substrate concentration of 2 g/L. The modified Logistic model could be used to describe the progress of cumulative hydrogen production in this study successfully. The Han-Levenspiel model could be used to describe the effect of substrate concentration on fermentative hydrogen production rate.

Nanoscale Fe0 was synthesized through a reductive method in this paper. The experiments were performed to investigate the reduction of 2,4-dichlorophenol (2,4-DCP) by nanoscale Fe0 under different conditions. The pathways for the reduction of 2,4-DCP by nanoscale Fe0 were discussed. Batch studies demonstrated that the mechanism includes adsorption, dechlorination and cleavage of the benzene ring. Dechlorination, which occurs after 2,4-DCP molecule is adsorbed on the interface of Fe particle, is an interfacial reaction. One or two chlorine atom can be removed from 2,4-DCP to form 2-chlorophenol, 4-chlorophenol or phenol. As the concentration of 2,4-DCP increased, the relative dechlorination ratio decreased. However, the reduced quantities of 2,4-DCP increased. Temperature can influence dechlorination rate and pathway. Dechlorination is prior to cleavage of the benzene ring at a higher temperature, but at a lower temperature, adsorption may be the main pathway, and cleavage of the benzene ring may be prior to dechlorination.

The reaction mechanism and pathway of the ozonation of 2,4,6-trichlorophenol (2,4,6-TCP) in aqueous solution were investigated. The removal efficiency and the variation of H2O2, Cl− formic acid, and oxalic acid were studied during the semi-batch ozonation experiments (continuous for ozone gas supply, fixed volume of water sample). The results showed that when there was no scavenger, the removal efficiency of 0.1 mmol/L 2,4,6-TCP could reach 99% within 6 min by adding 24 mg/L ozone. The reaction of molecular ozone with 2,4,6-TCP resulted in the formation of H2O2. The maximal concentration of H2O2 detected during the ozonation could reach 22.5% of the original concentration of 2,4,6-TCP. The reaction of ozone with H2O2 resulted in the generation of a lot of OH• radicals. Therefore, 2,4,6-TCP was degraded to formic acid and oxalic acid by ozone and OH• radicals together. With the inhibition of OH• radicals, ozone molecule firstly degraded 2,4,6-TCP to form chlorinated quinone, which was subsequently oxidized to formic acid and oxalic acid. Two reaction pathways of the degradation of 2,4,6-TCP by ozone and O3/OH• were proposed in this study.

•Graphene-alginate and/or PVA immobilized waste yeast was prepared.•U removal was studied using this novel biosorbent.•Graphene oxide (0.01%, w/v) could enhance the biosorbent performance.•The kinetics of U sorption followed pseudo second-order kinetic model.•The carboxyl and hydroxyl groups may involve in U sorption.To evaluate its ability to absorb dissolved uranium (VI), the waste biomass of Saccharomyces cerevisiae was immobilized using different agents, including Ca-alginate (Ca-SA), Ca-alginate with graphene oxide (GO), polyvinyl alcohol (PVA, 5% or 10%, w/v)-SA-GO in CaCl2-boric acid solution. The experimental results showed that graphene oxide at 0.01% (w/v) could enhance the performance of the immobilized cells. The yeast gel beads prepared with 5% PVA-1% SA-2% yeast-0.01% GO-2% CaCl2-saturated boric acid (4#) generally showed the better physical-chemical properties such as higher tolerance to the unfavorable environmental conditions. Moreover, the 4# gel beads exhibited more stable capacity for U(VI) sorption and desorption at various conditions, such as pH in the range of 3–9. A pseudo second-order kinetic model could describe the kinetics of U(VI) sorption onto the 4# gel beads (R2 = 0.96). The Langmuir, Freundlich, Tempkin and Sips models could be used to describe U(VI) sorption by the 4# gel beads, with the R2 being 0.90, 0.83, 0.96, 0.97, respectively. The Sips maximum capacity of 4# gel beads was 24.4 mg U/g dry weight. The desorption efficiency of U(VI) adsorbed onto the 4# gel beads was 91%, 73% and 40% by 0.1 M HNO3, 0.1 M HCl and 0.1 M NaOH, respectively. However, the 4# gel beads exhibited lower U(VI) sorption capacity than the raw yeast cell (Sips maximum capacity of 35.6 mg U/g). The immobilized Saccharomyces cerevisiae using SA, PVA and/or GO showed obvious changes in the molecular vibration of functional groups such as carboxyl, amide and hydroxyl groups compared with the raw yeast cells, according to FTIR analysis. The SEM-EDX analysis showed that U(VI) was adsorbed unevenly on the cellular surface. Carboxyl and hydroxyl groups may be involved in U(VI) binding by yeast cells.

The reductive degradation of chlorophenols (CPs), including 2-CP, 4-CP and 2,4-DCP by gamma irradiation was investigated and compared. The results showed that the most efficient degradation took place with 2,4-DCP, followed by 2-CP and then 4-CP. This confirmed that the number and position of chlorine atoms existing in the benzene ring have significant impact on dechlorination and decomposition of CPs. The G-values of decomposition of CPs, the formation of intermediate products and chloride ion, and the degradation rate (KCPs and KCl−1) were also determined.Highlights► Reductive degradation of 2-CP, 4-CP and 2,4-DCP by γ radiation was compared. ► Number and position of chlorine affect their dechlorination and decomposition. ► G-values of CPs decomposition, intermediate formation and chloride release were determined.

•The hydrophobic membrane contactor (HMC) was used to remove ammonia.•The ammonia removal efficiency could reach above 90%.•The ammonia mass transfer coefficient increased with increase of feed velocity.•The HMC is a promising way to remove ammonia from radioactive wastewater.The radioactive wastewater produced in the manufacturing process of UO2 kernel for high temperature gas-cooled reactor (HTR) contains high concentration of ammonia. The ammonia has to be removed effectively for further treatment of the wastewater. In this study, the hydrophobic membrane contactor (HMC) was adopted to remove and recover the ammonia from radioactive wastewater at room temperature. The operating parameters such as feed velocity and initial ammonia concentration were determined. In addition, the effect of wastewater composition on ammonia separation was studied. The experiment results showed that ammonia removal efficiency could reach above 90% after 120 min operation when pH was not adjusted. While the initial pH of wastewater was adjusted to 12.0, ammonia removal efficiency could reach above 95%. The ammonia mass transfer coefficient increased with increase of feed velocity and tended to an asymptotic value when the feed velocity reached 0.049 m/s. When the initial ammonia concentration was 2211.6 mg/L, 5864.6 mg/L and 23,898.7 mg/L, the ammonia removal efficiency was 95.0%, 94.2% and 94.1%, respectively after 120 min operation, i.e. the initial concentration of ammonia in wastewater had almost no effect on ammonia separation. In addition, the coexisting substances, such as urea and tetrahydrofurfuryl alcohol (THFA), also had no effect on ammonia separation. The HMC is a promising way to separate ammonia from radioactive wastewater.

A novel biosorbent, immobilized Saccharomyces cerevisiae in magnetic chitosan microspheres was prepared, characterized, and used for the removal of Sr2+ from aqueous solution. The structure and morphology of immobilized S. cerevisiae before and after Sr2+adsorption were observed using scanning electron microscopy with energy dispersive X-ray spectroscopy. The experimental results showed that the Langmuir and Freundlich isotherm models could be used to describe the Sr2+ adsorption onto immobilized S. cerevisiae microspheres. The maximal adsorption capacity (qm) was calculated to be 81.96 mg/g by the Langmuir model. Immobilized S. cerevisiae was an effective adsorbent for the Sr2+ removal from aqueous solution.

•Degradation of CHBA in the effluent was performed by gamma irradiation.•CHBA removal rate in the effluent was 1.7–3.5 times lower than in deionized water.•G values of CHBA were lower in the effluent than in deionized water.Gamma irradiation-induced degradation of a chlorinated aromatic compound, 3-chloro-4-hydroxybenzoic acid (CHBA) in biological treated effluent was studied and the results were compared with those obtained in deionized water. Gamma irradiation led to a complete decomposition of CHBA and a partial mineralization in the treated effluent. The removal of CHBA followed the pseudo first-order reaction kinetic model and the rate constant in the treated effluent was 1.7–3.5 times lower than that in deionized water. The CHBA degradation rate was higher at acidic condition than at neutral and alkaline conditions. The radiolytic yield, G-value for CHBA degradation was lower in the treated effluent, which decreased with increase in absorbed doses and increased with increase in initial concentrations of CHBA. The degradation mechanism of CHBA using gamma irradiation was proposed through the oxidation by –OH and reduction by eaq- and H– radicals. As exposed to gamma irradiation, dechlorination takes place rapidly and combines with the oxidation and cleavage of the aromatic ring, producing chloride ions, small carboxylic acids, acetaldehyde and other intermediates into the solution.

The irradiation-induced degradation of an azo dye, Alizarin Yellow GG (AY-GG), was investigated in aqueous solution under gamma irradiation using a 60Cobalt source at a dose rate of 113 Gy/min. The decolorization percentage of AY-GG reached 65% when its initial concentration was 100 mg/l and the absorbed dose was 9 kGy. The decolorization process could be described by first-order kinetic equation. In addition, specific oxygen uptake rate (SOUR, mg O2 (g MLVSS)−1 h−1) of activated sludge using the irradiated azo dye solutions was 8.1 mg O2 (g MLVSS)−1 h−1 after 9 kGy irradiation, indicating that the biodegradability of AY-GG could be enhanced by 30%. However, toxic intermediates including heterocyclic aromatic amines and cyanides were detected during the irradiation process, which inhibited the complete biological degradation of azo dye. Fortunately, the inhibition could be eliminated by further irradiation. The azo dye solution became amenable to biodegradation and can be further treated by biological treatment process.Highlights► Decolorization process by radiation conformed to first-order kinetics. ► Biodegradability of AY-GG could be enhanced 30% after 9 kGy radiation. ► Radiation can be used as a pretreatment technology for azo dye-containing wastewater. ► Combining radiation with aerobic biological treatment is a feasible strategy.

AbstractThe biological aerated filter (BAF) was used to treat the oil-field produced water. The removal efficiency for oil, COD, BOD and suspended solids (SS) was 76.3%–80.3%, 31.6%–57.9%, 86.3%–96.3% and 76.4%–82.7%, respectively when the hydraulic loading rates varied from 0.6m·h−1 to 1.4m·h−1. The greatest part of removal, for example more than 80% of COD removal, occurred on the top 100cm of the media in BAF. The kinetic performance of BAF indicated that the relationship of BOD removal efficiency with the hydraulic loading rates in biological aerated filters could be described by ci/ci=1 -exp(-2.44/L0.59). This equation could be used to predict the BOD removal efficiency at different hydraulic loading rates.

•Carbamazepine was removed by the combined gamma radiation and biodegradation.•The removal efficiency of carbamazepine increased with dose.•Irradiation could enhance the mineralization of carbamazepine significantly.•The combined irradiation and biodegradation was effective for carbamazepine removal.Carbamazepine is an emerging contaminant and resistant to biodegradation, which cannot be effectively removed by the conventional biological wastewater treatment processes. In this study, the combined gamma irradiation and biodegradation was employed to remove carbamazepine from wastewater. The effect of dose on the removal of carbamazepine was studied at different doses (300, 600 and 800 Gy). The results showed that the removal efficiency of carbamazepine increased with dose increasing during the irradiation process. The maximum removal efficiency was 99.8% at 800 Gy, while the removal efficiency of total organic carbon (TOC) was only 26.5%. The removal efficiency of TOC increased to 79.3% after the sequent biological treatment. In addition, several intermediates and organic acids were detected. The possible degradation pathway of carbamazepine during the integrated irradiation and biodegradation was proposed. Based on the overall analysis, the combined gamma irradiation and biological treatment process can be an alternative for removing the recalcitrant organic pollutants such as carbamazepine from wastewater.Download high-res image (109KB)Download full-size image

•The enrichment of hydrogen-producer is crucial for biohydrogen production.•Different methods, such as heat, acid/base, chemical inhibitor were introduced.•The principle and application of different treatment methods were presented.•The effect of pretreatment methods on microbial community was briefly discussed.Microorganisms capable of producing hydrogen are widely present in natural habitat, such as sludge, compost, soil, sediments, leachate and organic wastes and so on. A variety of pretreatment methods have been used for enriching hydrogen-producing bacteria from the mixed cultures, that is to say, eliminating the hydrogen consumers while preserving the hydrogen producers. In this paper, different pretreatment methods for enriching hydrogen-producers from mixed cultures were reviewed, including heat-shock (65–121 °C, 10 min–10 h), acid (pH 2–4, 30 min–24 h), base (pH 10–12, 30 min–24 h), chemical inhibitors (chloroform, iodopropane, BESA and fatty acids, 30 min–24 h), aeration (30 min–4 d), ultra-sonication (20–79 kJ/g TS), microwave (325–2450 W, 1.5–5 min), UV irradiation (15 min–3 h), ionizing radiation (0.5–10 kGy), freeze (−25 to 10 °C) and thaw (room temperature –30 °C), electric current (10 V, 10 min), load-shock (COD = 50–83 g/L, 2–3 d), operational parameters control (HRT, OLR and temperature control) and the combined treatment methods. The different sources of mixed cultures for enriching hydrogen-producers were introduced. The principle and application of different treatment methods were presented and compared. The effect of pretreatment methods on microbial community was briefly discussed. The results showed that heat treatment was mostly used. However there is no agreement on which method is the most effective for enriching hydrogen-producers. Since the characteristics of raw inoculum from different sources vary a lot, the selection of pretreatment method basing on the microbial distribution is recommended.

•Biodegradation made a major contribution to the degradation of MDHB.•The maximum removal efficiency of MDHB achieved 70.1% by the integrated process.•The radiation dose of 600 Gy was suitable for the mineralization of MDHB.•The dechlorination efficiency reached 77.4% during the integrated process.•The degradation pathway of MDHB by the integrated process was proposed.Chlorinated paraben, namely, methyl 3, 5-dichloro-4-hydroxybenzoate (MDHB) is the by-product of chlorination disinfection of paraben and frequently detected in the aquatic environments, which exhibited higher persistence and toxicity than paraben itself. In this paper, the combined irradiation and biological treatment process was employed to investigate the removal of MDHB from aqueous solution. The results showed that the removal efficiency of MDHB and total organic carbon (TOC) by irradiation process increased with radiation dose no matter what the initial concentration of MDHB was. The maximum removal efficiency of MDHB was 100%, 91.1%, 93%, respectively, for the initial concentration of MDHB of 1 mg/L, 5 mg/L and 10 mg/L with the radiation dose of 800 Gy. However, the maximum removal efficiency of TOC among all the experimental groups was only 15.3% obtained with the initial concentration of 1 mg/L at dose of 800 Gy. The subsequent biological treatment enhanced the mineralization of MDHB. The suitable radiation dose for the subsequent biological treatment was determined to be 600 Gy. In this case the removal efficiency of TOC increased to about 70%. Compared to the single biological treatment, the integrated irradiation and biological treatment significantly increase the degradation and mineralization of MDHB. Moreover, the dechlorination efficiency reached 77.4% during the integrated irradiation and biological treatment process. In addition, eight intermediates were identified during the combined process and the possible degradation pathway was proposed.

•Removal of sulfamethazine antibiotics was performed by advanced oxidation.•The nanocomposite of CeFe-graphene was prepared and characterized.•The removal efficiency of sulfamethazine was more than 99% at optimal condition.•The possible catalytic mechanism of CeFe-graphene was tentatively proposed.The presence of sulfonamide (SMT) antibiotics in aquatic environments has received increasing attention in recent years, and they are ubiquitous pollutants which cannot be effectively removed by conventional wastewater treatment processes. In this paper, the nanocomposites Ce0/Fe0-reduced graphene oxide (Ce0/Fe0-RGO) were synthesized through chemical reduction method, and characterized by Raman and FTIR before and after use. The addition of RGO can prevent the agglomeration of Ce0 and Fe0. The elimination of SMT can be divided into adsorption and degradation process. The adsorption of SMT onto the catalyst can enhance its degradation. The effect of pH value, concentration of H2O2, catalyst dosage, temperature and initial SMT concentration on the removal efficiency of SMT was determined. When pH = 7, T = 25 °C, H2O2 = 8 mM, Ce0/Fe0-RGO = 0.5 g/L, SMT = 20 mg/L, the removal efficiency of SMT and TOC was 99% and 73%, respectively. The stability of the catalysts was evaluated with repeated batch experiments using ethanol, water and acid as solvents to wash the used catalysts, respectively. The surface change of the catalysts after each use was characterized by Raman and FTIR analysis. The intermediates were detected by GC-MS and IC, the possible degradation pathway of SMT was tentatively proposed.Download high-res image (171KB)Download full-size image

•The removal of PPCPs from wastewater was reviewed.•Analytical methods for 87 commonly used PPCPs were summarized.•Tables summarizing the biological and chemical processes were provided.•Suggestions were made for further study.The pharmaceutical and personal care products (PPCPs) are emerging pollutants which might pose potential hazards to environment and health. These pollutants are becoming ubiquitous in the environments because they cannot be effectively removed by the conventional wastewater treatment plants due to their toxic and recalcitrant performance. The presence of PPCPs has received increasing attention in recent years, resulting in great concern on their occurrence, transformation, fate and risk in the environments. A variety of technologies, including physical, biological and chemical processes have been extensively investigated for the removal of PPCPs from wastewater. In this paper, the classes, functions and the representatives of the frequently detected PPCPs in aquatic environments were summarized. The analytic methods for PPCPs were briefly introduced. The removal efficiency of PPCPs by wastewater treatment plants was analyzed and discussed. The removal of PPCPs from wastewater by physical, chemical and biological processes was analyzed, compared and summarized. Finally, suggestions are made for future study of PPCPs. This review can provide an overview for the removal of PPCPs from wastewater.