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关键词： Sulfate reduction   Biogenic sulfide generation   Anaerobic fluidized-bed membrane bioreactor   Moderate temperature   Anaerobic membrane bioreactor   Filtration characteristics  

摘要： The study explored the potential of an up-flow sulfate reducing fluidized-bed membrane bioreactor (SR-FMBR) for biogenic sulfide generation at room temperature together with evaluation of filtration and fouling characteristics developed under various operational conditions. The SR-FMBR was tested at different COD/sulfate (mg/mg) ratios for a total of 127 days, initially at 35 degrees C and then at 23 degrees C. SR-FMBR was able to achieve COD oxidation and sulfate reduction efficiencies up to 98%, and allowed for biogenic sulfide generation up to 600 mg/L (97% of theoretical value) at room temperature. Alkalinity was generated as a result of sulfate reduction and averaged around 1900 mgCaCO(3)/L in the permeate. Hence, starting the bioreactor operation at 35 degrees C and then decreasing it to 23 degrees C did not adversely affect the process performance. High filtration fluxes up to 9.3 L/m(2)/h (LMH) could be maintained at employed hydraulic retention times between 24 h and 6 h. Observing relatively high filtration performance was due to keeping a high fraction of biomass attached to the carrier material, which decreased the cake formation potential on the membrane surface compared to conventional MBR operation. The SR-FMBR performance may further be tested for heavy metal removal under sulfidogenic conditions for acid mine drainage treatment. (C) 2020 Elsevier Ltd. All rights reserved.

摘要： It is shown that a freshly inoculated culture of the model cyanobacterium Synechocystis sp. PCC 6803 consumed almost all phosphate and 50% of nitrate within 6 days from the nutrient-rich BG-11 growth medium, indicating potential of cyanobacteria to purify wastewaters. Synechocystis sp. PCC 6803 control strain also collected nutrients efficiently from a landfill leachate wastewater KA2 (5.9-6.9 mM ammonium and 0.073-0.077 mM phosphate). Wastewaters might induce oxidative stress to microalgae, which prompted us to test growth of sigma factor inactivation strains, as Delta sigBCE and Delta sigCDE strains show superior growth in chemically induced oxidative stress. All cyanobacterial strains, including a stress-sensitive strain Delta sigBCDE, grew well in KA2 for four days, indicating that KA2 did not cause immediate oxidative stress. Completely arrested growth and bleaching of Delta sigBCDE cells after one week in KA2 wastewater point to the importance of group 2 sigma factor-mediated changes in gene expression during wastewater treatment. The growth of Delta sigBCD was arrested early in un-buffered and Hepes buffered (pH 7.5) KA2. In Delta sigBCD, all phosphate transporter genes are upregulated in standard conditions, and Delta sigBCD cells showed growth defects in low-phosphate BG-11 medium. Delta sigBCD cells removed phosphate slower from KA2 than the control strain, but phosphate supplementation of KA2 did not improve growth of Delta sigBCD. The Delta sigBCE strain showed superior growth in a laboratory-scale bioreactor in bright light and removed phosphate even slightly more efficiently than the control strain if KA2 was Hepes buffered although Delta sigBCE grew slowly in un-buffered KA2 and in low-phosphate BG-11 medium. The results indicate that engineering expression of regulatory group 2 sigma factor(s) might be useful for practical applications.

关键词： Membrane fouling   Anaerobic membrane bioreactor   Anaerobic digestion   Extracellular polymeric substances   Soluble microbial products   Immersion depth  

摘要： Membrane fouling is still the main obstacle that hinders the development and implementation of anaerobic membrane bioreactor (AnMBR). In conventional upflow anaerobic reactors, sludge at different height usually presents certain differences in characteristics in terms of particle size, etc. The immersion depth of membrane modules in anaerobic reactors can also influence the fouling of membrane. Thus, it is of great interest to investigate the fouling mechanism with the membrane installed at different heights in reactors. The filtration performance and sludge properties were investigated at different heights of AnMBR. The fouling of membrane in the middle position was severer than that in the top and bottom positions. The total resistance of membrane in the top, middle, and bottom positions was 27.31 x 10(11) m(-1), 34.67 x 10(11) m(-1), and 25.29 x 10(11) m(-1), respectively. By comparing the characteristics and structure of bulk sludge and cake layer at three heights, the bulk sludge in the middle position presented higher content of soluble microbial products (SMP) and finer flocs, and the cake layer was also denser. The results obtained in this study indicated that small size of sludge flocs as well as adhesion of SMP might be the major factors governing membrane fouling at different height in the AnMBR.

关键词： OMBR   Water flux   Membrane process   Modeling   ANFIS   ANN  

摘要： Osmotic Membrane Bioreactor (OMBR) is an emerging technology for wastewater treatment with membrane fouling as a major challenge. This study aims to develop Adaptive Network-based Fuzzy Inference System (ANFIS) and Artificial Neural Network (ANN) models in simulating and predicting water flux in OMBR. Mixed liquor suspended solid (MLSS), electrical conductivity (EC) and dissolved oxygen (DO) were used as model inputs. Good prediction was demonstrated by both ANFIS models with R² of 0.9755 and 0.9861, and ANN models with R² of 0.9404 and 0.9817, for thin film composite (TFC) and cellulose triacetate (CTA) membranes, respectively. The root mean square error for TFC (0.2527) and CTA (0.1230) in ANFIS models was lower than in ANN models at 0.4049 and 0.1449. Sensitivity analysis showed that EC was the most important factor for both TFC and CTA membranes in ANN models, while EC (TFC) and MLSS (CTA) are key parameters in ANFIS models.

关键词： Partial nitritation   Anammox   MBR   Nitrogen removal   Activated sludge  

摘要： A lab-scale membrane bioreactor (MBR) was employed to carry out the partial nitritation/Anammox (PN/A) process from conventional activated sludge. Seed sludge was cultivated under microaerobic conditions for 10 days before seeding into the MBR. The bacterial community was analyzed on the basis of cloning and sequencing of 16S rRNA gene. Relative slow ammonia oxidation rates (3.2-13.0 mgN/L/d) were established in the microaerobic cultivation period. In the continuous MBR operation, the nitritation was achieved in the first 16 days and the reactor produced a balanced ratio between ammonia and nitrite which favored the proliferation of Anammox bacteria. Efficient transition from PN to PN/A was achieved in two months which was supported by appearance of reddish spots on the reactor inner wall and the concurrent consumption of ammonium and nitrite. The PN/A performed a robust and high-rate nitrogen removal capability and achieved a peak nitrogen removal of 1.81 kg N/m(3)/d. 16S rRNA gene-based analysis indicated that "Nitrosomonas sp." and "Candidatus Jettenia sp." accounted for ammonia oxidation and nitrogen depletion, respectively. Denitratisoma facilitated denitrification in the reactor. The present study suggested that a pre-cultivation of seed sludge under microaerobic conditions assists fast realization of PN and further convoyed efficient transition from PN to PN/A. Knowledge gleaned from this study is of significance to initiation, operation, and control of MBR-PN/As. (C) 2020 Elsevier Ltd. All rights reserved.

摘要： The continuous discharge of emerging contaminants (ECs) to the aquatic ecosystem generate concerns due to their unpredictable risks to human and environment. The presence of ECs in source water attributed to the conventional wastewater treatment facilities which are not fundamentally designed to completely eliminate these micropollutants at low concentrations. The aim of this research was to enhance the wastewater treatment to the level of its potential reuse as a source of water. The investigations were conducted at lab and pilot scale in 8 phases and several stages. Initially, the removal of selected ECs was optimized. Subsequently, the by-product formation and their identification were conducted. Then, the study focused on the by-product removal. In subsequent phases, the optimal technological parameters were verified in natural conditions, at the pilot scale in AOP (advance oxidation process) and AO-MEBR (membrane electro-bioreactor) facilities. Such approach permitted to study the removal of sulfamethoxazole (SMX), 17- alpha ethynyl estradiol (EE2), caffeine (CAF) and paracetamol (PCM) from various aqueous solutions (DI water, river water, effluent after wastewater treatment, and wastewater). A developed model investigated the effect of technological parameters on pharmaceuticals' removal efficiency and on by-product abatement. The results showed superior removal efficiency (99%) by both UV/H 2 O 2 AOP and UV/O 3 AOP of SMX, PCM, CAF and EE2 in comparison to sole UVC photolysis (30-40%). UV/O 3 AOP demonstrated an elevated rate and removal by 10-15% higher than ozonation alone. The target ECs such as SMX, PCM were removed by more than 80% in effluent and more than 90% in river water during 60 minutes. The differences in the ECs and their byproducts removal from various aqueous matrices were discussed from the matrix properties perspectives, particularly non-target constituents (EfOM, NOM and sacavengers) present at different amounts in target matrices. The infl

关键词： Microbial protein   Methane oxidizing bacteria   Hydrophobic membranes   Nutrient upcycling  

摘要： Microbial protein is proposed as an alternative protein source with low environmental impact. Methane oxidizing bacteria are already produced at commercial scale from natural gas. However, their productivity is limited because of the creation of explosive atmospheres in the fermenters during production. This work demonstrates the applicability of bioreactors with a membrane-based gas supply via diffusion. Methanotrophic bacteria were successfully cultivated, with growth yields from 0.26 to 0.43 g-VSS g-CH4-1, slightly below those observed in analogous fermenters relying on bubbling. However, ammonia yields ranged from 5.2 to 6.9 g-VSS g-NH3-1, indicating higher nitrogen assimilation than in conventional fermenters. Indeed, protein content increased during the operational period reaching up to 51% of dry weight. The amino acid profile included the majority of the essential amino acids, demonstrating suitability as feed ingredient. Never during the operational period was an explosive atmosphere established in the reactor. Thus, bubble-free membrane bioreactors are a promising technology for microbial protein production relying on explosive gas mixtures.

关键词： Azo dyes   Reactive black-5   Hexavalent chromium   Soil bioaugmentation   Bioreactors   Wastewater treatment  

摘要： In this study, a pre-isolated dye-decolorizing bacterium,Pseudomonas aeruginosaZM130, was tested to explore its potential for the treatment of synthetic and real textile wastewaters in aerobic and anaerobic bench-scale sequencing batch bioreactors (SBRs) as well as in constructed soil columns. The decolorizing ability of strain ZM130 against reactive black-5 (RB5) was optimized following a response surface methodology (RSM)-based approach, and this strain was observed to effectively decolorize RB5 even in presence of a substantial quantity of NaCl salt along multi-metal mixture including Cr6+, Pb2+, Cd2+, and Zn2+. In the SBR containing the immobilized cells of the strain ZM130, more than 80% of the RB5, hexavalent chromium [Cr(VI)], and chemical oxygen demand (COD) were removed from the textile wastewater under partially anaerobic condition using yeast extract as an additional carbon co-substrate. Furthermore, while studying the bioremediating ability of strain ZM130 in constructed soil columns, the maximum color removal (> 90%), Cr(VI) removal (> 95%), and COD removal (> 90%) were achieved in the soil columns bioaugmented with ZM130 together with either sludge or yeast extract. Interestingly, it was further noticed that soil columns augmented withP. aeruginosaZM130 also showed maximum color removal from real textile wastewater in vertical columns filled with sterilized (> 87%) and non-sterilized soil (> 91%). Based on the results of the present research work, it can be concluded thatP. aeruginosaZM130 can serve as an excellent potential candidate for treatment of textile wastewaters in bioreactors as well as in soils.

关键词： Bioplastics   Biorefinery   Gas-liquid mass transfer   Methane conversion   Methanotrophic bacteria   Polyhydroxyalkanoate production  

摘要： Creating additional value out of biogas during waste treatment has become a priority in past years. Biogas bioconversion into valuable bioproducts such as biopolymers has emerged as a promising strategy. This work assessed the operational feasibility of a bubble column bioreactor (BCB) implemented with gas recirculation and inoculated with a polyhydroxybutyrate (PHB)-producing strain using biogas as substrate. The BCB was initially operated at empty bed residence times (EBRTs) ranging from 30 to 120 min and gas recirculation ratios (R) from 0 to 30 to assess the gas-to-liquid mass transfer and bioconversion of CH4. Subsequently, the BCB was continuously operated at a R of 30 and an EBRT of 60 min under excess of nitrogen and nitrogen feast-famine cycles of 24 h:24 h to trigger PHB synthesis. Gas recirculation played a major role in CH4 gas-liquid transfer, providing almost fourfold higher CH4 elimination capacities (similar to 41 g CH4 m(-3) h(-1)) at the highest R and EBRT of 60 min. The long-term operation under N excess conditions entailed nitrite accumulation (induced by O-2 limiting conditions) and concurrent methanotrophic activity inhibition above similar to 60 mg N-NO2-L-1. Adjusting the N-NO3 supply to match microbial N demand successfully prevented nitrite accumulation. Finally, the N feast-famine 24 h:24 h strategy supported a stable CH4 conversion with a removal efficiency of 70% along with a continuous PHB production, which yielded PHB accumulations of 14.5 +/- 2.9% (mg PHB mg(-1) total suspended solids x 100). These outcomes represent the first step towards the integration of biogas biorefineries into conventional anaerobic digestion plants. (C) 2020 Elsevier Ltd. All rights reserved.