Synthesis of iron-manganese bimetallic materials supported by activated carbon and application of activated persulfate in the degradation of soil contaminated by crude oil.

Heterogeneous catalytic processes based on zero-valent iron (ZVI) have been developed to treat soil and wastewater pollutants. However, the agglomeration of ZVI reduces its ability to activate persulfate (PS). In this study, a new Fe-Mn@AC activated material was prepared to activated PS to treat oil-contaminated soil, and using the microscopic characterization of Fe-Mn@AC materials, the electron transfer mode during the Fe-Mn@AC activation of PS was clarified. Firstly, the petroluem degradation rate was optimized. When the PS addition amount was 8%, Fe-Mn@AC addition amount was 3% and the water to soil ratio was 3:1, the petroluem degradation rate in the soil reached to the maximum of 85.69% after 96 h of reaction. Then it was illustrated that sulfate and hydroxyl radicals played major roles in crude oil degradation, while singlet oxygen contributed slightly. Finally, the indigenous microbial community structures remaining after restoring the Fe-Mn@AC/PS systems were analyzed. The proportion of petroleum degrading bacteria in soil increased by 23% after oxidation by Fe-Mn@AC/PS system. Similarly, the germination rate of wheat seeds revealed that soil toxicity was greatly reduced after applying the Fe-Mn@AC/PS system. After the treatment with Fe-Mn@AC/PS system, the germination rate, root length and bud length of wheat seed were increased by 54.05%, 7.98 mm and 6.84 mm, respectively, compared with the polluted soil group. These results showed that the advanced oxidation system of Fe-Mn@AC activates PS and can be used in crude oil-contaminated soil remediation.

Design, Synthesis and Second-Order Nonlinear Optical Properties of Azobenzene-Based Polysiloxanes.

To study the effect of polymeric structures on second-order nonlinear optical properties, polysiloxanes materials based on azobenzene as chromophore have been designed and synthesized successfully. Herein, the siloxane monomer is directly bonded to azobenzene units by palladium catalysis, which avoids the influence of flexible chains on the photoelectric properties of azobenzene. According to the different positions of azobenzene units in the polymers, it is divided into side-chain, main-chain, and alternative-type polymers. The chemical structures of obtained polysiloxanes are confirmed by nuclear magnetic resonance spectra and mass spectra. Three polymers present high thermal decomposition temperatures and the medium glass transition temperatures. The effects of polymeric structures on the second-order nonlinear properties are compared. The main-chain polysiloxane possesses the highest thermal stability because of its rigid architecture. The side-chain polysiloxane shows the fastest isomerization transformation rate due to the large free volume. Besides, the alternative polysiloxane displays the best second-order nonlinear performance with second harmonic generation coefficient (d33 ) value of 47.6 pm V-1 , which is 3 times higher than the side-chain one.

Synthesis of biochar@α-Fe2O3@Shewanella loihica complex for remediation of soil contaminated by hexavalent chromium: Optimization of conditions and mechanism.

The reduction of hexavalent chromium combined with the process of dissimilatory iron reduction is an important strategy for microbial remediation of chromium-contaminated soil. However, its applicability is limited by the slow speed of bacterial bioreduction and the toxic effect of heavy metals on bacteria. Here, biochar (BC) was used as a substrate and was loaded with iron oxide in the form of hematite and Shewanella loihica to synthesize a BC@α-Fe2O3@S. loihica complex and thus achieve combined microbial-chemical remediation. After optimization by a Box-Behnken design, the optimal dosages of the complex, humic acid (as an electron shuttle), and sodium lactate (as an electron donor) were found to be 1.38 mL/g, 33.94 mg/g, and 12.95%, respectively. The Cr(VI) reduction rate in soil contaminated with 1000 mg/kg Cr(VI) reached 98.26%, and remediation could be achieved within 7 days. Characterization of the BC@α-Fe2O3@S. loihica complex before and after it was used for remediation by energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy proved that the oxygen-containing functional groups and aromatic compounds on the surface of the BC participated in the adsorption and reduction of Cr(VI) and that the loaded hematite particles were fully utilized by microorganisms. Therefore, the BC@α-Fe2O3@S. loihica complex has great potential for the remediation of Cr(VI)-contaminated soil.

Analysis of organic matter conversion behavior and kinetics during thermal hydrolysis of sludge and its anaerobic digestion performance.

In thermal hydrolysis (TH) of waste activated sludge (WAS), the material transformation of a specific temperature heating for a set duration is generally examined. However, this study looked at the material changes of TH as the temperature rose (90-210 °C) and the kinetic derivation of soluble chemical oxygen demand (SCOD), protein, and carbohydrate using the Coats-Redfern model. It was found that the proportion of soluble protein and soluble carbohydrate in the organic components and their contents reached the maximum (17.39 and 8.10 g L-1 respectively) at 180 °C. Differently, volatile fatty acid (VFA), amino acids, and ammonia nitrogen increased with the TH temperature and reached a maximum at 210 °C. The fitting equations of non-isothermal dynamics at the medium- and low-temperature stages (90-180 °C) at n = 1, 0.5, and 2 were studied. When n = 1, the activation energies of COD, protein, and carbohydrate were 33.32, 23.34, and 36.15 kJ mol-1, respectively. And the kinetic analysis results were in good agreement with the experimental results (the maximum rate of increase in protein and carbohydrate was at 135-150 °C and 150-180 °C, respectively). Moreover, the pattern of anaerobic digestion performance of WAS was comparable to the trend of protein and carbohydrate in TH, the highest cumulative methane production was 159.68 mL·g-1VS for the TH sludge at 180 °C. This study provided a theoretical foundation for the use of thermal hydrolysis in engineering.

Enhancement of enzyme activities and VFA conversion by adding Fe/C in two-phase high-solid digestion of food waste: Performance and microbial community structure.

Two-phase high-solid digestion is conducive to the degradation of food waste. In this study, Fe/C was added in high-solid digestion in different acidification and/or methanogenic phase. The experimental results indicated that it significantly increased the cumulative yield of biomethane. When Fe/C was added to the acidification phase only and both the acidification and methanogenic phases, the biomethane yield reached 474.07 ± 7.03 and 475.47 ± 4.68 mL·g VS -1, respectively, and the biodegradation rate reached 87.30% and 87.58%, respectively, indicating that Fe/C had mainly effect on the performance of acidification phase. In a two-phase anaerobic fermentation system, the activity of dehydrogenases and the concentration of coenzyme F420 were 2.23-2.95 mg·g-1·h-1 and 0.0063-0.0294 mol·g-1 volatile solids, respectively. Additionally, the archaeal communities production pathway of methane from using acetic acid to using hydrogen as the reactant.

Optimization of Cellulase Immobilization with Sodium Alginate-Polyethylene for Enhancement of Enzymatic Hydrolysis of Microcrystalline Cellulose Using Response Surface Methodology.

A novel method of immobilizing cellulase on sodium alginate (SA)-polyethylene glycol (PEG) enabled the cellulase to be used repeatedly. The matrix of the immobilized cellulase was detected and characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. In comparison with SA-immobilized cellulase, the relative enzyme activity and immobilization rate increased by 25% and 18%, respectively. The application range of the immobilized enzyme in terms of temperature and pH was larger than that of the free enzyme, and its thermal stability increased. The immobilized enzyme was used in enzymatic hydrolysis, in which MCC was used as the substrate. The optimal conditions for enzymatic hydrolysis were as follows: the dosage of SA-PEG-immobilized cellulase was 3.55 g/g total solids of the substrate, the concentration of the substrate was 13.16%, and the pH was 5.11. In comparison with the yield of reducing sugars in the first round of hydrolysis of MCC by SA-immobilized cellulase, the yield in the hydrolysis of MCC by SA-PEG-immobilized cellulase increased by 133%. After five cycles of repeated use, the total yield of reducing sugars when MCC was hydrolyzed by SA-PEG-immobilized cellulase was similar to that achieved with free cellulase. In comparison with the free enzyme, the highest yield when the immobilized enzyme was used was 22.68%. Therefore, the immobilized cellulase exhibited high performance in enzymatic hydrolysis.

A comparison of antibiotics, antibiotic resistance genes, and bacterial community in broiler and layer manure following composting.

Animal manure is an important source of antibiotics and antibiotic resistance genes (ARGs) in the environment. However, the difference of antibiotic residues and ARG profiles in layer and broiler manure as well as their compost remains unexplored. In this study, we investigated the profiles of twelve antibiotics, seventeen ARGs, and class 1 integrase gene (intI1) in layer and broiler manure, and the corresponding compost at large-scale. Compared with layer manure, broiler manure exhibited approximately six times more residual tetracyclines, especially chlortetracycline. The relative abundances of qnrS and ermA genes in broiler manure were significantly higher than those in layer manure. The concentration of tetracyclines not only had a significantly positive correlation with tetracycline resistance genes (tetA and tetC) but was also positively correlated with quinolone resistance (qepA, qnrB, and qnrS) and macrolide resistance (ermA and ermT). Most ARGs in manure were reduced after composting. However, the relative abundance of sulfonamide resistance gene sul1 increased up to 2.41% after composting, which was significantly higher than that of broiler (0.41%) and layer (0.62%) manure. The associated bacterial community was characterized by high-throughput 16S rRNA gene sequencing. The relative abundances of thermophilic bacteria had significant positive correlations with the abundance of sul1 in compost. The composting has a significant impact on the ARG-associated gut microbes in poultry manure. Variation partitioning analysis indicated that the change of bacterial community compositions and antibiotics contributed partially to the shift in ARG profiles. The results indicate that at industry-scale production broiler manure had more antibiotics and ARGs than layer manure did, and composting decreased most ARG abundances in poultry manure except for sulfonamide resistance genes.

Immobilization of Cr(VI) in Soil Using a Montmorillonite-Supported Carboxymethyl Cellulose-Stabilized Iron Sulfide Composite: Effectiveness and Biotoxicity Assessment.

A novel composite of montmorillonite-supported carboxymethyl cellulose-stabilized nanoscale iron sulfide (CMC@MMT-FeS), prepared using the co-precipitation method, was applied to remediate hexavalent chromium (Cr(VI))-contaminated soil. Cr(VI)-removal capacity increased with increasing FeS-particle loading. We tested the efficacy of CMC@MMT-FeS at three concentrations of FeS: 0.2, 0.5, and 1 mmol/g, hereafter referred to as 0.2 CMC@MMT-FeS, 0.5 CMC@MMT-FeS, and 1.0 CMC@MMT-FeS, respectively. The soil Cr(VI) concentration decreased by 90.7% (from an initial concentration of 424.6 mg/kg to 39.4 mg/kg) after 30 days, following addition of 5% (composite-soil mass proportion) 1.0 CMC@MMT-FeS. When 2% 0.5 CMC@MMT-FeS was added to Cr(VI)-contaminated soil, the Cr(VI) removal efficiency, as measured in the leaching solution using the toxicity characteristic leaching procedure, was 90.3%, meeting the environmental protection standard for hazardous waste (5 mg/kg). The European Community Bureau of Reference (BCR) test confirmed that the main Cr fractions in the soil samples changed from acid-exchangeable fractions to oxidable fractions and residual fractions after 30 days of soil remediation by the composite. Moreover, the main complex formed during remediation was Fe(III)-Cr(III), based on BCR and X-ray photoelectron spectroscopy analyses. Biotoxicity of the remediated soils, using Vicia faba and Eisenia foetida, was analyzed and evaluated. Our results indicate that CMC@MMT-FeS effectively immobilizes Cr(VI), with widespread potential application in Cr(VI)-contaminated soil remediation.

The Immobilization Effect of Natural Mineral Materials on Cr(VI) Remediation in Water and Soil.

The effects of sepiolite, montmorillonite, and attapulgite on the removal and immobilization of Cr(VI) in water and soil were studied. X-ray diffraction (XRD) characterizations showed that the purities of these three mineral materials decreased in the following order: montmorillonite > attapulgite > sepiolite, and that their surface molecular bond types were similar. The adsorption potential of Cr(VI) in aqueous solutions of the three mineral materials was in the following order: sepiolite > attapulgite > montmorillonite. The adsorption mechanism for attapulgite was consistent with the Freundlich isotherm adsorption model, whereas that for montmorillonite was more consistent with the Langmuir model. Sepiolite had a good fitting effect for both isothermal adsorption models. For montmorillonite and attapulgite, a lower pH corresponded to a higher removal of Cr(VI). For sepiolite, however, the removal efficiency of Cr(VI) from an aqueous solution was the lowest at a pH of approximately 5.0. The results of the soil toxicity characteristic leaching procedure showed that, following the addition of 15% sepiolite, attapulgite, or montmorillonite to the contaminated soil, Cr(VI) concentrations in the leachates decreased by 16.8%, 18.9%, and 15.9%, respectively, and the total Cr concentrations in the leachates were reduced by 21.2%, 29.2%, and 17.6%. Of the three mineral materials, attapulgite demonstrated the highest Cr(VI) immobilization efficiency in soil. This study emphasizes the effect of attapulgite on the immobilization of Cr(VI) in soil and aqueous solutions, thus providing a theoretical basis for the potential application of natural mineral material remediation of Cr(VI)-contaminated aqueous solutions and soils.

Effects of adding osmoprotectant on anaerobic digestion of kitchen waste with high level of salinity.

Anaerobic digestion of kitchen waste can be inhibited by a high concentration of Na+ in the substrate. The aim of this study was to determine the extent to which the effect of salinity during KW anaerobic digestion could be reduced by adding osmoprotectant. The results show that when Na+ concentrations were increased from 0 to 20 g/L, the yield of cumulative methane production decreased from 623.97 to 0 mL/g volatile solids (VS). Adding 2.0 and 2.5 g/L glycine betaine (GB) to reactors during anaerobic digestion of KW with concentrations of 5 and 10 g Na+/L were determined to be the optimal dosages to alleviate Na+ inhibition; this resulted in 29.07% and 63.49% improvements in methane yield respectively. The maximum soluble chemical oxygen demand reductions that resulted from adding 2.0 and 2.5 g GB/L to kitchen waste anaerobic digestion with 5 and 10 g Na+/L were 90.00% and 82.92%, respectively. Adding GB was helpful to both the production and degradation of acetic and butyric acids, which enhanced the rate of conversion of raw material to methane. Archaeal community changes between the medium and high salt concentration groups were revealed by high-throughput sequencing and by adding GB. The most abundant archaeal phyla in all samples were Euryarchaeota and Crenarchaeota. The hydrogenotrophic methanogens showed more salt tolerance than acetoclastic methanogens. The hydrogenotrophic pathway was predominant for methanogenesis of high-level Na+ inhibition anaerobic digestion.

Expression of microRNA-21 in osteoporotic patients and its involvement in the regulation of osteogenic differentiation.

Expression of microRNA-21 in bone tissue and serum of patients with osteoporosis (OP) and its involvement in the regulation of osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs) were investigated. Bone tissue and serum were collected from 48 patients with OP and 48 normal subjects. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of six microRNAs. Among these microRNAs, the expression level of microRNA-21 in bone tissue and serum of OP patients was the lowest. In addition, BMSCs of SD rats were isolated and cultured. Subculture was performed 3 times, transfection of microRNA-21 was performed and osteogenic differentiation was induced. Control group [negative control (NC)] was transfected with microRNA-21 mimics followed by osteogenic induction. Experimental groups were transfected with microRNA-21 analogue (mimics) and microRNA-21 inhibitor (inhibitor) followed by osteogenic induction. Ten days after osteogenic induction, alkaline phosphatase (ALP) staining and alizarin red staining were performed to measure the mineralized stained area and the number of mineralized nodules in each treatment group. RT-qPCR was used to detect the expression of osteogenic genes in each group of cells. RT-qPCR results showed that microRNA-21 expression was lower in bone tissue and serum of patients with OP than that of normal subjects. Moreover, compared with control group, BMSCs showed increased stained mineralized areas, deeper color and increased number of mineralized nodules. In addition, increased mRNA expression of osteogenic genes was evident after microRNA-21 mimics transfection and osteogenic induction (p<0.05). Compared with control group, BMSCs showed decreased stained mineralized areas, lighter color, decreased number of mineralized nodules, and decreased mRNA expression of osteogenic genes after microRNA-21 inhibitor transfection and osteogenic induction (p<0.05). MicroRNA-21 is expressed at low level in bone tissue and serum in patients with OP, and microRNA-21 can promote osteogenic differentiation of BMSCs. Our study provided theoretical basis for drug treatment of OP.

An Insight into the Anaerobic Co-digestion of Municipal Solid Waste and Food Waste: Influence of Co-substrate Mixture Ratio and Substrate to Inoculum Ratio on Biogas Production.

The unbalanced nutrients of municipal solid waste (MSW), particularly high carbon contents, were regarded as a major limiting factor to anaerobic digestion process. In this study, the addition of MSW in food waste (FW) feedstock to have a balanced C/N ratio was studied. Different co-substrate mixtures with C/N ratio of 20 to 40 were subjected to anaerobic batch experiment at lab scale, under mesophilic conditions. The biogas production decreased with the increase in C/N ratio due to insufficient availability of organic nitrogen for anaerobic microbial growth. Specific biogas and methane yields were observed to be 827 and 474.44 mL g-1VS, respectively, with volatile solids (VS) reduction rate of 88%, at C/N ratio of 20. Furthermore, the effect of the substrate to inoculum (S/I) ratio on digester performance was also studied. The biogas production decreased with the increase in S/I ratio due to the formation of more volatile fatty acids (VFAs) which led to decrease in pH and accumulated unionized ammonia-N. Specific biogas and methane yields were recorded to be 655 and 410.20 mL g-1VS, with 64% rate of biodegradability at S/I ratio of 0.5. Kinetics and statistics study showed that the higher S/I ratio could lead to VFA accumulation and result in low methane yield.

Enhancing methane production of excess sludge and dewatered sludge with combined low frequency CaO-ultrasonic pretreatment.

Methane production of excess sludge (ES) and dewatered sludge (DS) were investigated with low frequency CaO-ultrasonic pretreatment. The results showed that the concentrations of SCOD and VFAs in pretreated ES (P-ES) and DS (P-DS) were 212.11% and 75.26%, 270.30% and 159.52% higher than those of untreated ES and DS, respectively. The contents of acetic acid and ethanol comprised 83.87%-92.88% of the total VFAs. The cumulative methane production (CMP) of P-ES and P-DS were 167.08 and 162.96 mL/g·VS, respectively, which resulted in 40.45% and 36.94% higher than those of untreated ones. The biodegradability of P-ES was 87.65%, which was close to theoretical value. Low frequency CaO-ultrasonic pretreatment could not only improve the performance of anaerobic digestion (AD), but also accelerate the decomposition rate of two kinds of sludge. Therefore, this study provided meaningful insight for exploring efficient pretreatment strategy to stabilize and enhance AD performance for practical application.

Enhancing anaerobic digestion performance and degradation of lignocellulosic components of rice straw by combined biological and chemical pretreatment.

In order to determine eco-friendly pretreatment method, the combination of different pretreatment reagents such as: CaO, ammonia solution (AS), liquid fraction of digestate (LFD), CaO-AS and CaO-LFD were used in this study. The features of physico-chemical structures and anaerobic digestion (AD) performance of rice straw were investigated using different combined biological and chemical pretreatment methods. The results showed that CaO-LFD bio-chemical pretreatment achieved the best effect among different pretreatment conditions. The removal rate of lignocellulosic components from CaO-LFD pretreated rice straw was 20.73% higher than that of the control sample. The ether and ester bonds between lignin and hemicellulose were ruptured during pretreatment. Moreover, the methane yield from CaO-LFD pretreated rice straw was 274.65 mL gVS-1, which was 57.56% more than the control. Compared with the untreated rice straw, T80 decreased by 42.86%. CaO-LFD combined pretreatment has advantages as both biological and chemical pretreatment, which complement each other to improve the degradation of the rice straw. Meantime, AD performance was improved and excellent economic viability was achieved. Therefore, this study provides sustainable insight for exploring efficient pretreatment strategy to stabilize and enhance AD performance for further application.

Bacterial community and molecular ecological network in response to Cr2O3 nanoparticles in activated sludge system.

The potential environmental risks of chromium oxide nanoparticles (Cr2O3 NPs) have caused great concerns. However, their possible impacts on activated sludge process are very limited. In this study, we carried out long-term exposure experiments to evaluate the influence of Cr2O3 NPs on wastewater nutrient removal, bacterial community and molecular ecological network (MEN) in the sequencing batch reactor (SBR). It was found that 1 mg/L Cr2O3 NPs increased the effluent concentrations of NO3--N and TP from 6.5 to 15.4 mg/L, and 0.6-2.7 mg/L, indicating the serious deterioration of denitrification and phosphorus removal. Cr2O3 NPs significantly decreased the bacterial richness in terms of the number of different OTUs (626 OTUs in Cr2O3 samples and 728 OTUs in controls). Detrended correspondence analysis (DCA) showed that the overall taxonomic structure of bacterial community was altered at Cr2O3 NPs in activated sludge systems. Further analysis revealed that three genera related to denitrification (Desulfovibrio, Pseudomonas and Hyphomicrobium) and two genera related to phosphorus removal (Accumulibacter and Rhodobacter) decreased significantly, which was consistent with the observed influences of Cr2O3 NPs on denitrification and phosphorus removal. MEN analysis showed that the overall architecture of the network under Cr2O3 NPs was substantially alerted. ß-Proteobacteria, playing an important role in nutrients removal, had less complex interactions in the presence of Cr2O3 NPs, which may be associated with the deterioration of denitrification and phosphorus removal. This study provides insights into our understanding of shifts in the bacteria community and their MEN under Cr2O3 NPs in activated sludge systems.

Serial completely stirred tank reactors for improving biogas production and substance degradation during anaerobic digestion of corn stover.

Several completely stirred tank reactors (CSTR) connected in series for anaerobic digestion of corn stover were investigated in laboratory scale. Serial anaerobic digestion systems operated at a total HRT of 40days, and distribution of HRT are 10+30days (HRT10+30d), 20+20days (HRT20+20d), and 30+10days (HRT30+10d) were compared to a conventional one-step CSTR at the same HRT of 40d. The results showed that in HRT10+30d serial system, the process became very unstable at organic load of 50gTS·L-1. The HRT20+20d and HRT30+10d serial systems improved methane production by 8.3-14.6% compared to the one-step system in all loads of 50, 70, 90gTS·L-1. The conversion rates of total solid, cellulose, and hemicellulose were increased in serial anaerobic digestion systems compared to single system. The serial systems showed more stable process performance in high organic load. HRT30+10d system showed the best biogas production and conversions among all systems.

Responses of Bacterial Communities to CuO Nanoparticles in Activated Sludge System.

The main objectives of this study were to investigate the influence of copper oxide nanoparticles (CuO NPs) on wastewater nutrient removal, bacterial community and molecular ecological network in activated sludge. The results showed that long-term exposure to 1 mg/L CuO NPs induced an increase of effluent concentrations of ammonia and total phosphorus, which was consistent with the inhibition of enzyme activities of ammonia monooxygenase, nitrite oxidoreductase, exopolyphosphatase, and polyphosphate in the presence of CuO NPs. MiSeq sequencing data indicated that CuO NPs significantly decreased the bacterial diversity and altered the overall bacterial community structure in activated sludge. Some genera involved in nitrogen and phosphorus removal, such as Nitrosomonas, Acinetobacter, and Pseudomonas decreased significantly. Molecular ecological network analysis showed that network interactions among different phylogenetic populations were markedly changed by CuO NPs. For example, ß-Proteobacteria, playing an important role in nutrients removal, had less complex interactions in the presence of CuO NPs. These shifts of the abundance of related genera, together with the network interactions may be associated with the deterioration of ammonia and phosphorus removal. This study provides insights into our understanding of shifts in the bacteria community and their molecular ecological network under CuO NPs in activated sludge systems.

Mineralization of pyrene induced by interaction between Ochrobactrum sp. PW and ryegrass in spiked soil.

This study was conducted to investigate the capability of pyrene-degrading bacterium Ochrobactrum sp. PW and ryegrass (Lolium multiflorum) grown alone and in combination on the degradation of pyrene in soil. After 60 days of ryegrass growth, plant biomass, pyrene-degrading microbial mass, soil enzyme activity (catalase activity and polyphenol oxidase activity) and residual concentration of pyrene in soils were determined. Higher dissipation rates were observed in PW inoculation treatments: ryegrass+PW rhizosphere soil (RP-r) and ryegrass+PW non-rhizosphere soil (RP-nr), than planting of ryegrass alone, rhizosphere (R-r) or non-rhizosphere (R-nr). The inoculation with PW significantly (p<0.05) increased the dry weight of ryegrass root and shoot, nearly 2.8 and 3.3 times higher than ryegrass treatment. The pyrene-degrading microbial mass indicated that a much larger mass of bacteria, actinobacteria were present in RP treatment. The catalase activity in all different treatments were significantly (p<0.05) higher than in with treatment R-nr, and the polyphenol oxidase activity was also significantly (p<0.05) increased by inoculation with PW, leading to enhanced mineralization of pyrene from soil. Our results suggest that adding of PAHs-degrading bacteria to soil can enhance remediation of PAHs contaminated soil, while improving plant growth.

Mesophilic anaerobic co-digestion of cattle manure and corn stover with biological and chemical pretreatment.

Biological and chemical pretreatment methods using liquid fraction of digestate (LFD), ammonia solution (AS), and NaOH were compared in the process of mesophilic anaerobic co-digestion of cattle manure and corn stover. The results showed that LFD pretreatment could achieve the same effect as the chemical pretreatment (AS, NaOH) at the performance of anaerobic digestion (AD). Compared with the untreated corn stover, the cumulative biomethane production (CBP) and the volatile solid (VS) removal rate of three pretreatment methods were increased by 25.40-30.12% and 14.48-16.84%, respectively, in the co-digestion of cattle manure and corn stover. T80 was 20-37.14% shorter than that of the control test (35 ± 1 days). LFD pretreatment not only achieved the same effect as chemical pretreatment, but also reduced T80 and improved buffer capacity of anaerobic digestion system. Therefore, this study provides meaningful insight for exploring efficient pretreatment strategy to stabilize and enhance AD performance for practical application.