Passive sampling of diverse pesticides in water by hydrophilic-lipophilic balance sorbent-embedded cellulose acetate membrane: Kinetics, equilibrium partitioning and field application.

Pesticides are useful products for agriculture and human life, but they are often released into surface waters and are hazardous to aquatic ecosystems. Pesticides monitoring in surface waters is challenging due to the great variety, ultratrace levels and nonpoint source pollution of pesticides; however, continuous passive sampling may be conducive to solving these problems. This work evaluated the performance of a newly developed passive sampler (hydrophilic-lipophilic balance sorbent-embedded cellulose acetate membrane, HECAM) for six types of currently used/present pesticides. The uptake kinetics and equilibrium partitioning of nineteen pesticides in different dissolved concentrations were studied by dynamic accumulation and equilibrium partitioning experiments, respectively. In the dynamic accumulation experiments, pesticides gradually accumulated in the HECAM and followed a first-order kinetic model. The same type of pesticides had roughly comparable accumulation concentrations. The estimated uptake rate constants ranged from 1.04 to 13.5 L g-1 d-1, and sampling rates ranged from 0.02 to 0.31 L d-1 for the pesticides in the HECAM (size of 2 cm × 3 cm). Pesticide accumulation concentrations in the HECAM increased linearly with increasing dissolved concentrations, which means that varying concentrations can also be monitored by the HECAM. In the equilibrium partitioning experiments, the pesticide partitioning behavior at varying dissolved concentrations can be described by the Freundlich model. The calculated equilibrium partition coefficients (log KD) for pesticides ranged from 3.32 to 4.54, and different pesticide types showed different changes with log Kow. Comparable results were found when estimating chemical equilibrium partition coefficients by the dynamic accumulation and equilibrium partitioning methods. Field deployment of the HECAM in river waters resulted in the detection of four pesticides, and the measured results were comparable to those of active sampling coupled with liquid-liquid extraction. These results suggest that the HECAM would be a promising strategy for simultaneously monitoring diverse pesticides in waters.

Transformation of dissolved organic matter at a full-scale petrochemical wastewater treatment plant.

Transformation of dissolved organic matter (DOM) in petrochemical wastewater (PCW) treatment has rarely been studied. In this work, low- and high-salinity PCW were collected from a treatment plant and the transformations of DOM at molecular level along the treatment processes of both PCW were comparatively investigated. By using Orbitrap MS, the polar DOM constituents were categorized into five molecular classes namely saturated compounds, aliphatics, highly unsaturated and phenolic compounds (Huph), polyphenols and condensed polycyclic aromatics (Cpla). Aliphatics (58.62%) with low molecular weight (150-250 Da) and O/C (0-0.2) were dominant in raw low-salinity PCW; while Huph (65.03%) with O/C at 0.2-0.8 were rich in raw high-salinity PCW. After full-scale treatment, differentiated DOM constituents in both raw PCWs were transformed into aliphatics and Huph with O/C at 0.3-0.5. Anoxic/Oxic treatment of low-salinity system (L-A/O) removed a high fraction of aliphatics (53.05%); while Huph with low O/C (0.1-0.3) (65.68%) in the effluent of L-A/O were further mineralized by ozonation of low-salinity system (L-ozonation). In comparison, anoxic/oxic treatment of high-salinity system (H-A/O) mainly removed unsaturated Huph (34.10%) and aliphatics (30.86%). This resulted in a decrease of dissolved organic carbon as indicated via Spearman correlation. Different from L-ozonation, ozonation of high-salinity system (H-ozonation) degraded aliphatics (26.09%) and Huph (41.85%) with a relatively high O/C (0.2-1.2). After L-A/O and L-ozonation treatments, remaining saturated compounds that were originated from raw low-salinity PCW, were removed by subsequent biological aerated filter. Comparatively, after H-A/O and H-ozonation treatments, residual Huph and aliphatics which were mainly bio-derivates and ozonated intermediates, were further removed by air flotation filter. Hence, DOM transformation of different PCWs along similar treatments varied significantly. This study provides in-depth insights on DOM transformation along a full-scale PCW treatment process.

Highly efficient and simultaneous magnetic solid phase extraction of heavy metal ions from water samples with l-Cysteine modified magnetic polyamidoamine dendrimers prior to high performance liquid chromatography.

Due to the strong metal-sulfur interaction between mercapto groups and metal ions, which can be used to functionalize polyamidoamine dendrimer decorated Fe3O4 nanoparticles for high enrichment of trace heavy metal ions from waters. Based on this concept, polyamidoamine dendrimer modified Fe3O4 nanomaterials were functionalized with l-Cysteine and a new magnetic solid phase extraction for rapid adsorption and separation of Hg2+, Pb2+, Co2+ and Cd2+ from waters was established. The factors affecting extraction efficiency have been optimized. Upon the optimal parameters, the established method provided good linear ranges of 0.1-200 µg L-1 for Hg2+ and 0.05-200 µg L-1 for Pb2+, Co2+ and Cd2+, and high sensitivity with limits of detection (LOD) of 0.018 µg L-1, 0.014 µg L-1, 0.013 µg L-1 and 0.025 µg L-1 for Cd2+, Pb2+, Co2+ and Hg2+, respectively. Real water samples were utilized to validate the proposed method, and achieved results revealed that the proposed method was sensitive, effective, stable and suitable for monitoring Pb2+, Cd2+, Co2+and Hg2+ in environmental waters. This work provided a novel strategy for the simultaneous analysis of target cations in waters, and a new direction for developing decoration method of nanomaterials according to specific purpose.

Comparison of short-term efficacy of MIS-TLIF and Endo-LIF in the treatment of single-segment degenerative lumbar diseases.

Background: A prospective controlled study was conducted to compare the short-term clinical results and postoperative complications of minimally invasive transforaminal lumbar decompression and fusion (minimally invasive surgery transforaminal lumbar interbody fusion, MIS-TLIF) and percutaneous endoscope-assisted transforaminal lumbar interbody fusion (endoscopic lumbar interbody fusion, Endo-LIF) in the treatment of single-segment degenerative lumbar diseases, to provide some scientific guidance for clinicians to select surgical treatment for patients with lumbar degeneration. Methods: From October 2020 to October 2021, a total of 62 patients were enrolled, with 31 patients in the MIS-TLIF group and 31 patients in the Endo-LIF group. All patients were followed up for 6 months. The following information from the two groups of patients was recorded: (1) operation time, radiation exposure time, intraoperative blood loss, bed rest time, and hospital stay; (2) ODI score (The Oswestry Disability Index), low back pain VAS score (Visual Analogue Scale), and lumbar vertebra JOA score (Japanese Orthopaedic Association Scores) 1 day before the operation; 1, 3, 6 days after operation; and 1, 3 and 6 months after operation. (3) X-ray evaluations of lumbar fusion at the last follow-up. Results: There were significant differences in operation time, intraoperative fluoroscopy time, and hospitalization cost between the two groups. The MIS-TLIF group was significantly better than the Endo-LIF group, and the intraoperative bleeding volume of the Endo-LIF group was significantly better than that of the MIS-TLIF group, but there was no significant difference in postoperative bed rest time and postoperative hospital stay. There was no significant difference in the scores of ODI, VAS, and JOA between the two groups before and after the operation. At the last follow-up, the fusion rate was 100% in the MIS-TLIF group and 100% in the Endo-LIF group. Conclusions: There was no significant difference in short-term clinical efficacy and safety between Endo-LIF and MIS-TLIF in the treatment of single-segment degenerative lumbar diseases, but MIS-TLIF was significantly better than Endo-LIF in terms of the operation time, hospitalization cost, and fluoroscopy time, and Endo-LIF was significantly better than MIS-TLIF in terms of intraoperative blood loss.

Carbon dots fabricated by solid-phase carbonization using p-toluidine and l-cysteine for sensitive detection of copper.

In this study, a label-free "turn off" fluorescent sensor has been resoundingly fabricated using carbon dots (CDs) for ultrasensitive detection of copper ions (Cu2+). CDs are prepared by solid phase carbonization method using p-toluidine and l-cysteine as the precursors. The synthesized CDs exhibited the highest fluorescence intensity with excitation and emission wavelengths set at 300 nm and 400 nm, respectively. The CDs were selective and sensitive to Cu2+ due to the static quenching mechanism. The concentration of CDs, and solution pH and incubation time were important parameters for the developed sensor. The experimental results showed that 20 mgL-1 was enough for the analysis. As the solution pH was concerned, it was apparent that the sensor was endowed with an excellent response signal to Cu2+ and provided high sensitivity at pH 12. The interaction occurred very quickly, and the incubation time could be set at 1 min. The sensor provided a two-stage calibration curve to Cu2+ in the range of 0.05-0.7 and 0.7-4 µM with a limit of detection of 47 nM. The obtained results clearly demonstrated that this facile method was fast, reliable and selective for detecting Cu2+, which would explore a prospective strategy for developing effective and low-cost sensors for monitoring metal ions in aqueous environments.

Local bone metabolism balance regulation via double-adhesive hydrogel for fixing orthopedic implants.

The effective osteointegration of orthopedic implants is a key factor for the success of orthopedic surgery. However, local metabolic imbalance around implants under osteoporosis condition could jeopardize the fixation effect. Inspired by the bone structure and the composition around implants under osteoporosis condition, alendronate (A) was grafted onto methacryloyl hyaluronic acid (H) by activating the carboxyl group of methacryloyl hyaluronic acid to be bonded to inorganic calcium phosphate on trabecular bone, which is then integrated with aminated bioactive glass (AB) modified by oxidized dextran (O) for further adhesion to organic collagen on the trabecular bone. The hybrid hydrogel could be solidified on cancellous bone in situ under UV irradiation and exhibits dual adhesion to organic collagen and inorganic apatite, promoting osteointegration of orthopedic implants, resulting in firm stabilization of the implants in cancellous bone areas. In vitro, the hydrogel was evidenced to promote osteogenic differentiation of embryonic mouse osteoblast precursor cells (MC3T3-E1) as well as inhibit the receptor activator of nuclear factor-κ B ligand (RANKL)-induced osteoclast differentiation of macrophages, leading to the upregulation of osteogenic-related gene and protein expression. In a rat osteoporosis model, the bone-implant contact (BIC) of the hybrid hydrogel group increased by 2.77, which is directly linked to improved mechanical stability of the orthopedic implants. Overall, this organic-inorganic, dual-adhesive hydrogel could be a promising candidate for enhancing the stability of orthopedic implants under osteoporotic conditions.

Influences of integrated coagulation-ozonation pretreatment on the characteristics of dissolved organic pollutants (DOPs) of heavy oil electric desalting wastewaters.

The quality of heavy oil electric desalting wastewaters (HO-EDWs) affects the effectiveness of refinery wastewater treatment plants. In this study, an integrated coagulation-ozonation (ICO) process was used to pretreat HO-EDWs and the influences on the characteristics of dissolved organic pollutants (DOPs) were investigated. Coagulation using aluminum sulfate removed 39% of soluble chemical oxygen demand (SCOD), 21% of dissolved organic carbon (DOC), 57% of petroleum hydrocarbons and 38% of polar oils from Liaohe HO-EDWs and the biodegradability was greatly improved. Ozonation removed 33% of SCOD and 88% of polar oils from the coagulated HO-EDWs. Most species of aromatic compounds, phenols, aliphatic acids, anilines and naphthenic acids with high C numbers and ring numbers were degraded and the unsaturation degrees of DOPs significantly decreased under ozonation. As a result, the biodegradability was further improved and the acute toxicity towards Vibrio fischeri was substantially reduced. Some OxS1 species and organic nitrogen compounds in HO-EDWs were penetrated through ozonation and caused the residual biotoxicity. The results demonstrate the potential of ICO pretreatment for improving the quality of refractory HO-EDWs.

Influences of humic-rich natural materials on efficiencies of UASB reactor: A comparative study.

Two humic-rich natural materials namely peat soil and lignite were supplemented in up-flow anaerobic sludge blanket (UASB) bioreactors for the treatment of phenolic wastewater. Peat soil improved phenol degradation and resistance to shock load; ultimately, contributing to higher COD removal efficiency (83.3%), methane production (4532 mL d-1), and better reactor's stability. Accordingly, the amount of extracellular polymeric substances (EPS) and coenzyme F420 in sludge were increased to 1.3-fold and 2.5-fold, respectively, as compared to the control treatment. The addition of lignite however displayed poor phenol degradation and no effects on the secretion of EPS and F420. The peat soil significantly influenced the microbial community structures, whereas the effect of lignite was inconspicuous. In the presence of peat soil, the abundance of syntrophic fermentation bacteria and methanogens was significantly increased. This study illustrates the potential use of peat soil in UASB for the treatment of phenolic wastewaters.

Rapid magnetic enrichment and sensitive detection of Sudan pollutants with nanoscale zero valent iron-based nanomaterials in combination with liquid chromatography-ultraviolet detector.

In present work, we reported a new nanomaterial nano Fe0 decorated with SiO2 and dopamine by self-assembly method (Fe@SiO2@PDA). A sensitive method for determination of Sudan pollutants in aqueous samples was developed using Fe@SiO2@PDA as magnetic solid phase extraction adsorbents prior to high-performance liquid chromatography with variable wavelength detector. The possible parameters which would affect the enrichment have been optimized. The best parameters were as follows: elutent, 4.5 mL methanol; adsorbent dosage, 30 mg; adsorption time, 20 min; elution time, 18 min; sample pH 7; sample volume, 40 mL. The experimental results demonstrated that Fe@SiO2@PDA exhibited good adsorption properties to Sudan Red dyes. The established method provided excellent linear ranges over 0.01-50 µg L-1 and detection limits ranged from 2.0 to 5.1 ng L-1 for Sudan red I-IV. The developed method was also evaluated with real water samples and the results demonstrated that it was of applicative value owing to its merits including robustness, easy operation, fastness, cheapness and high enrichment efficiency, and had great prospect in environmental fields.

Influences of coagulation pretreatment on the characteristics of crude oil electric desalting wastewaters.

Highly polluted crude oil electric desalting wastewaters (EDWs) severely affect the efficiency of refinery wastewater treatment plants (WWTPs). Coagulation is an efficient pretreatment to reduce the impacts of EDWs. In the present study, the influences of coagulation pretreatment on the characteristics of EDWs of three typical Chinese crude oils, Liaohe heavy oil (LHO), Karamay heavy oil (KHO) and Daqing light oil (DLO), were investigated. The stability of three raw EDWs was broken and the contents of organic pollutants were significantly reduced by aluminum sulfate coagulation. More soluble COD and polar oils were removed from LHO-EDW (1241 and 98 mg L-1) and KHO-EDW (779 and 57 mg L-1) compared to DLO-EDW (417 and 11 mg L-1). Coagulation significantly changed the compositions of the organic pollutants of two heavy oil EDWs; however, slightly influenced DLO-EDW, particularly the polar organic pollutants. Most types of aromatic compounds, aliphatic acids and Ox polar compounds were removed from two heavy oil EDWs, but mainly alkanes were removed from DLO-EDW. As such, the differences in the types of dominant polar compounds became insignificant among treated heavy oil and light oil EDWs. Coagulation notably decreased the acute biotoxicity and improved the biodegradability of all treated EDWs. The residual organic nitrogen compounds in treated KHO-EDW contributed to a higher residual biotoxicity compared to treated LHO-EDW. The results demonstrate that coagulation can effectively improve the qualities of heavy oil EDWs by lowering the contents of organic pollutants and removing recalcitrant compounds, thus guaranteeing the efficiency of refinery WWTPs.

Aerobic sludge granulation in shale gas flowback water treatment: Assessment of the bacterial community dynamics and modeling of bioreactor performance using artificial neural network.

Flowback water from shale gas extraction is highly saline and comprises complex organic substances, thereby posing a significant challenge for the environmental management of the unconventional natural gas industry. In this work, an aerobic granular sludge (AGS) method was successfully used for the treatment of flowback water from shale gas extraction. The formed AGS had a diameter of 0.25-2.0 mm and the total sludge volume index was 23.40 mL g-1. The AGS efficiently removed COD, NH4+-N and TN by 70.1%, 92.1%, and 59.2%, respectively. The bacterial communities responsible for the removal of nitrogen and degradation of organics were enriched in AGS. The dynamics of contaminant removal was further explained with a three-layered artificial neural network model. The results showed that the initial concentration of COD, TDS, NH4+-N and TN governed the contaminants' removal. As for operating parameters, aerating time showed a strong effect on NH4+-N and TN removal, whereas settling time impacted the COD removal.

Bioremediation of intertidal zones polluted by heavy oil spilling using immobilized laccase-bacteria consortium.

Heavy oil pollution in the intertidal zones has become a worldwide environmental problem. In this study, bioremediation on heavy oil pollutants in the intertidal zones using an immobilized laccase-bacteria consortium system was evaluated with the aid of intertidal experimental pools built in the coastal area. It is found that degradation efficiency of the immobilized laccase-bacteria consortium for heavy oil was 66.5% after 100 days remediation, with the reaction rate constant of 0.018 d-1. Gas Chromatograph-Mass Spectrometer analysis shows that degradation efficiency of saturated hydrocarbons and aromatic hydrocarbons were 79.2% and 78.7%, which were 64.9% and 65.1% higher than control. It is further seen that degradation of long-chain n-alkanes of C26-C35 and polycyclic aromatic hydrocarbons with more than three rings were significant. Metagenomic analysis indicates that the immobilized laccase-bacterial consortium has not only increased the biodiversity of heavy oil degrading bacteria, but also accelerated the degradation of heavy oil.

Comprehensive chemical analysis and characterization of heavy oil electric desalting wastewaters in petroleum refineries.

Large quantities of highly polluted point-source wastewaters (EDWs) are generated from electric desalting process of heavy oils (HOs), resulting in severe impacts on the efficiency of wastewater treatment plants in petroleum refineries. In the present study, a comprehensive chemical analysis and characterization of EDWs of two typical Chinese heavy oils, Liaohe heavy oil (LHO) and Karamy heavy oil (KHO), were investigated using Daqing light oil (DLO) as a control. The HO-EDWs (LHO-EDW and KHO-EDW) show high pollutants contents with complicated compositions, more polar dissolved organic pollutants (DOPs), strong emulsion stability and high acute biotoxicity towards Vibrio fischeri, compared to DLO-EDW. LHO-EDW and KHO-EDW have nearly equal pollutants contents but different compositions and distributions, where more types of DOPs exist in KHO-EDW. Large amounts of biologically recalcitrant aromatic compounds, as well as heteroatomic compounds such as CHO, CHOS and CHON species, extensively distribute in HO-EDWs. The organic nitrogen compounds (e.g., anilines and N2-3Ox, N1OxS1) in KHO-EDW most probably contribute to and thus leading to elevated levels of acute biotoxicity. Additionally, highly dispersed colloidal, micron-sized particles and polar compounds promote the emulsification and stabilization of HO-EDWs. These results can guide the development of pretreatment technologies for HO-EDWs, thus improving the treatment and management of heavy oil refineries' wastewater streams.

A novel hybrid fixation versus dual plating for both-bone forearm fractures in older children: A prospective comparative study.

OBJECTIVE: The aim of the present study was to compare the clinical outcomes of hybrid fixation using elastic stable intramedullary nailing (ESIN) for the ulna and plate screw fixation for the radius (Hybrid group) with dual plating fixation for both-bone forearm fractures in children between 10 and 16 years of age. METHODS: Twenty-six patients were treated using a hybrid fixation struct and 30 patients were treated with dual plating fixation. The two groups were compared prospectively according to perioperative data and patient outcome measures. RESULT: The hybrid fixation construct group had 26 patients, with a mean age of 13.27 years (range, 10-16 years) and the dual plate group had 30 patients, with a mean age of 13.33 years (range, 10-16 years). The groups were similar for sex, arm injured, fracture location. Incision length of ulna, duration of surgery and hospital costs were significantly different between the two groups (P < 0.05). There was no significant difference in either time to union or Price scores for function evaluation between the 2 groups (P < 0.05). Complication rates were also similar between the groups. CONCLUSION: Hybrid fixation, using open reduction and internal fixation with a plate-and-screw construct on the radius and closed reduction and elastic intramedullary fixation of the ulna, is an acceptable method for treating both-bone diaphyseal forearm fractures in skeletally immature patients 10-16 years old. The small incision and less cost are the characteristics of this hybrid fixation.

A highly sensitive and selective chemosensor for 2,4,6-trinitrophenol based on L-cysteine-coated cadmium sulfide quantum dots.

2,4,6-Trinitrophenol (TNP) is a common explosive and widely used in military, pharmaceutical, pesticide, printing and dyeing industries. TNP in the wastewater and waste residues will enter into the environment by various ways and lead to serious threat on the environment. It is urgent to develop simple and robust analytical methods for highly sensitive and selective determination of TNP. L-cysteine-coated cadmium sulfide quantum dots (L-Cy-CdS QDs) with strong fluorescence were synthesized at room temperature and characterized by ultraviolet visible absorption spectra, transmission electron microscopy and fourier transform infrared spectrometer. TNP could quench the fluorescence of quantum dots based on the favorable electronic energy transfer, fluorescence resonance energy transfer, and electrostatic interactions. The effects of pH, reaction time and L-Cy-CdS QDs concentration on the fluorescence response were optimized. It was found that the fluorescence quenching of the quantum dots was linear with the concentration of TNP in the range of 0.05-5 µg mL-1, and the limit of detection was as low as 39 ng mL-1. The method can be applied to the quantitative detection of TNP in environmental water samples.

17ß-Estradiol/extrogen receptor ß alleviates apoptosis and enhances matrix biosynthesis of nucleus pulposus cells through regulating oxidative damage under a high glucose condition.

BACKGROUND: Hyperglycemia in the Diabetes mellitus (DM) patients is a potential etiology of disc degeneration. 17ß-estradiol (17ß-E2) supplementation plays an anti-diabetic role in DM patients. OBJECTIVE: This study was aimed to investigate the role and mechanism of 17ß-E2 in regulating nucleus pulposus (NP) cell apoptosis and NP matrix production under a high glucose condition. METHODS: Rat NP cells were cultured in medium with a high glucose concentration (0.2 M). 17ß-E2 was added into the culture medium to investigate its protective effects. The ERß inhibitor PHTPP and ERß activator ERB041 were used to investigate the effects of ERß. NP cell apoptosis was analyzed by flow cytometry and expression of apoptosis-related molecules. NP matrix production was evaluated by expression of matrix macromolecules. Additionally, intracellular reactive oxygen species (ROS) content was also detected. RESULTS: Compared with the control NP cells, 17ß-E2 decreased NP cell apoptosis ratio, down-regulated gene expression of Bax and caspase-3, up-regulated gene expression of Bcl-2, increased protein expression of cleaved PARP and cleaved caspase-3, and increased expression of matrix molecules (aggrecan and collagen II). Moreover, 17ß-E2 decreased ROS content. Further analysis showed that ERß inhibition partly reversed these effects of 17ß-E2 whereas ERß activation further promoted its effects. CONCLUSION: 17ß-E2/ERß interaction attenuates apoptosis and promotes matrix biosynthesis of NP cells through alleviating oxidative damage under a high glucose condition. This study provides new knowledge on strategies for retarding disc degeneration.

Efficiencies and mechanisms of ZSM5 zeolites loaded with cerium, iron, or manganese oxides for catalytic ozonation of nitrobenzene in water.

Discharge of industrial wastewater causes water pollution. It is therefore necessary to treat wastewater prior to discharge. Catalytic ozonation processes (COP) using ZSM5 zeolites loaded with metallic (Ce, Fe, or Mn) oxides to remove nitrobenzene from water were investigated. The total organic carbon (TOC) removal by the COP treatment with NaZSM5-38, HZSM5-38, and NaZSM5-100 were increased by 6.7%, 23.1%, and 19.8%, respectively, in comparison with single ozonation efficiency (39.2%). The loadings of Ce, Fe, or Mn oxides increased the catalytic activity relative to ZSM5 zeolites alone. The Ce loaded material (Ce/NaZSM5-38) had the highest TOC removal (86.3%). The different-metallic-oxides loaded zeolites exhibited different chemical processes during the removal of nitrobenzene from water. During COP treatment, NaZSM5-38 zeolites removed nitrobenzene mainly via OH mediated oxidation. HZSM5-38 and NaZSM5-100 zeolites showed powerful adsorption toward nitrobenzene. Both adsorption and direct ozonation contribute the TOC removal in their early uses. The OH mediated oxidation dominates the TOC removal process as the adsorption became saturated after multiple uses. Surface SiO bonds and/or SiO(H)Al structures are the active sites for ZSM5 zeolites. Efficient surface dispersion of the metallic oxides enhances the catalytic activity. This study shows the high potentials of ZSM5 zeolites as catalysts in COP to efficiently treat refractory wastewaters.

Potential of wheat bran to promote indigenous microbial enhanced oil recovery.

Microbial enhanced oil recovery (MEOR) is an emerging oil extraction technology that utilizes microorganisms to facilitate recovery of crude oil in depleted petroleum reservoirs. In the present study, effects of wheat bran utilization were investigated on stimulation of indigenous MEOR. Biostimulation conditions were optimized with the response surface methodology. The co-application of wheat bran with KNO3 and NH4H2PO4 significantly promoted indigenous MEOR (IMEOR) and exhibited sequential aerobic (O-), facultative (An-) and anaerobic (A0-) metabolic stages. The surface tension of fermented broth decreased by approximately 35%, and the crude oil was highly emulsified. Microbial community structure varied largely among and in different IMEOR metabolic stages. Pseudomonas sp., Citrobacter sp., and uncultured Burkholderia sp. dominated the O-, An- and early A0-stages. Bacillus sp., Achromobacter sp., Rhizobiales sp., Alcaligenes sp. and Clostridium sp. dominated the later A0-stage. This study illustrated occurrences of microbial community succession driven by wheat bran stimulation and its industrial potential.

Potential and optimization of two-phase anaerobic digestion of oil refinery waste activated sludge and microbial community study.

Oil refinery waste activated sludge produced from oil wastewater biological treatment is a major industrial sludge. Two-phase anaerobic digestion of oil refinery waste activated sludge was studied for the first time. Thermal pretreatment under 170 °C is effective on sludge solubilization. At the optimum hydrolytic-acidogenic condition which was pH of 6.5, temperature of 55 °C and HRT of 2 days, 2754 mg/L volatile fatty acids (VFAs) were produced and acetic acid and butyric acid were the key components. Comparative studies of single-phase and two-phase anaerobic digestion in terms of organic removal, biogas production and methane concentration were conducted. The cumulative methane production and soluble COD (SCOD) removal efficiency in the two-phase system were 228 mL/g COD added and 77.8%, respectively, which were 1.6 and 2.1 times higher than those in single-phase anaerobic digestion. Such improved performance is attributed to intensification of dominant microbial population in separated reactors. Caloramator, Ureibacillus, Dechloromonas, Petrobacter, and T78 played important roles in hydrolytic-acidification and oil-organics degradation. Syntrophic bacteria in the family Porphyromonadaceae and the genus Anaerobranca provide acetate for methanogen. The results demonstrated the potential and operating condition of two-phase anaerobic digestion in treatment of oil refinery waste activated sludge.