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关键词： Bioleaching   WEEE   Acidophilic microorganisms   Printed Circuit Boards  

摘要： Many studies are now focusing on bioleaching methods to recover metals from WEEE. The efficiency of this process is highly dependent on microorganisms but also on the solid-liquid-gas mass transfer, which is controlled by the reactor design. In this study, bioleaching of comminuted spent printed circuit boards (PCBs) was performed in a stirred tank reactor operated in batch mode and in a double-stage continuous bioreactor. The metal dissolution kinetics were compared. The first stage of the continuous bioreactor was a bubble column in which a BRGM-KCC acidophilic consortium comprising Leptospirillum ferriphilum and Sulfobacillus benefaciens was used to oxidise Fe(II) into Fe(III). The resulting liquor was used to leach out metals contained in PCBs in the second stage of the bioreactor with mechanical stirring. The use of two distinct stages allowed the bacteria to adapt gradually to the PCBs and reach high dissolution yields, i.e. 96% Cu, 73% Ni, 85% Zn and 93% Co when 1% (w/v) PCB scraps were added into the bioleaching reactor, with a hydraulic residence time of 48 h. By using the double-stage bioreactor, the concentration of PCB scraps could be increased up to 1.8% (w/v) without reducing bioleaching performance. Biomass concentration in the second stage and adaptation of the microorganisms to the toxicity of the metals were sufficient for only the second stage to be used. Under these conditions, the dissolution kinetics were stable, even when iron was provided only by the comminuted PCBs.

关键词： Recirculating aquaculture system   Woodchip bioreactor   Carbon source   Potato residues   Nitrate   Microbial community  

摘要： Aquaculture needs practical solutions for nutrient removal to achieve sustainable fish production. Passive denitrifying bioreactors may provide an ecological, low-cost and low-maintenance approach for wastewater nitrogen removal. However, innovative organic materials are needed to enhance nitrate removal from the low carbon effluents in intensive recirculating aquaculture systems (RAS). In this study, we tested three additional carbon sources, including biochar, dried Sphagnum sp. moss and industrial potato residues, to enhance the performance of woodchip bioreactors treating the low carbon RAS wastewater. We assessed nitrate (NO3-) removal and microbial community composition during a oneyear in situ column test with real aquaculture wastewater. We found no significant differences in the NO3- removal rates between the woodchip-only bioreactor and bioreactors with a zone of biochar or Sphagnum sp. moss (maximum removal rate 31-33 g NO3-N m(-3) d(-1)), but potato residues increased NO3- removal rate to 38 g NO3--N m(-3) d(-1), with stable annual reduction efficiency of 93%. The readily available carbon released from potato residues increased NO3--N removal capacity of the bioreactor even at higher inflow concentrations (>52 mg L-1). The microbial community and its predicted functional potential in the potato residue bioreactor differed markedly from those of the other bioreactors. Adding potato residues to woodchip material enabled smaller bioreactor size to be used for NO3- removal. This study introduced industrial potato by-product as an alternative carbon source for the woodchip denitrification process, and the encouraging results may pave the way toward growth of blue bioeconomy using the RAS. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： membrane bioreactor   polydimethylsiloxane   pervaporation   nanocomposite   carbon nanotube   graphene oxide  

摘要： BACKGROUND In this work, a pervaporation membrane bioreactor (PVMBR) with the novel ethanol permselective membrane was used to achieve ethanol production with high yield. For this purpose, ethanol produced by Saccharomyces cerevisiae from glucose and pervaporation was performed via dense hydrophobic polydimethylsiloxane (PDMS) having carbon nanotube-graphene oxide (CNT-GO) mixed matrix membrane. Different percentages of CNT-GO (0, 0.25, 0.5, 0.75, and 1) were loaded in polymer matrix. Synthesized membranes were analyzed using FESEM, AFM, FTIR and XRD. RESULTS The bonding of groups in CNT-GO, that was synthesized in this work, and membranes was characterized and confirmed using FTIR test. Considering the existence of 0.75 wt% of CNT-GO in PDMS showed the highest ethanol selectivity of 22.5 in synthetic ethanol-water solution, this incorporation was selected to use in PVMBR. The high ethanol selectivity was proved using XRD patterns. Also, FESEM indicated the optimum dispersion of nanoparticles at 0.75% of loading and AFM proofed the optimum surface roughness at this percentage. CONCLUSIONS The results showed that maximum ethanol production in PVMBR was achieved after 44 h with productivity of 0.5g.l(-1).h(-1) in feed side and 9.89 g.l(-1).h(-1) in permeate side. In fact, PVMBR enhanced the ethanol concentration up to 26 times. (c) 2020 Society of Chemical Industry

摘要： 307

关键词： Osmotic membrane bioreactor   Water permeation intensity   Salt concentration   Nitrification   Bacterial community structure  

摘要： The effects of water permeation intensity on nitrifying bacterial activity, forward osmosis (FO) membrane performance, and bacterial community structure were investigated in an osmotic membrane bioreactor (OMBR). Ammonia was partially oxidized by controlling acidification buffer concentration. Then, the FO module was externally integrated with a nitrifying bioreactor to examine nitrifying bacterial activity in response to the increased salinity. The salinity gradually increased from 2.7 to 45.7 g.L-1 total dissolved solids (TDS). Inhibition of nitrite-oxidizing activity was initiated at a salt concentration of 36.2 g.L-1 TDS. Complete ammonia-oxidizing bacteria inhibition occurred at 45.7 g.L-1 TDS. Illumina high-throughput sequencing revealed that the bacterial community responded to the operational conditions such as the ammonia loading rate and salt concentration. Only two species, Nitrosomonas eutropha and Nitrobacter winogradskyi, were responsible for nitrification in the OMBR. The cellulose triacetate FO membrane showed poor rejection efficiencies for ammonia, nitrite, and nitrate. The FO module was capable to maximally recover 107.8% water in the OMBR. However, the water permeation intensity should be appropriately adjusted to avoid nitrification failure by maintaining the optimal salinity as lower than 35 g.L TDS, which is equivalent to water permeation efficiency of 107.8% in this study.

关键词： Malachite green   Cr(VI)   Bioaugmentation   Membrane bioreactor   Microbiota  

摘要： Textile industry wastewater comprises refractory components, such as highly toxic dyes and hexavalent chromium (Cr(VI)). Aeromonas hydrophila LZ-MG14 was isolated and characterized to develop an effective bioaugmentation strategy for the bioremediation of malachite green (MG) and Cr(VI) from textile wastewater. Strain LZ-MG14 removed 96.8% of MG (200 mg L-1) and 93.71% of Cr(VI) (0.5 mmol L-1) within 12 h with a significant increase in biomass. The mechanism underlying MG mineralization by LZ-MG14 involved N-demethylation and decomposition of conjugated structure, while that underlying Cr(VI) removal was reduction. LZ-MG14 bioaugmentation in a membrane bioreactor (MBR) significantly enhanced the efficiency of MG degradation and Cr(VI) removal in textile wastewater. Additionally, LZ-MG14 successfully colonized the activated sludge and shaped the effective microbiota for MG degradation and Cr(VI) removal. LZ-MG14 bioaugmentation can be potentially used for MG degradation and Cr(VI) removal in the textile wastewater.

摘要： 39

关键词： Microparticle   Recombinant Aspergillus sojae   beta-Mannanase   Al2O3   Talc  

摘要： Beta (beta)-mannanase is an industrial enzyme that has a wide range of uses in industry. Chemically, beta-mannanase mainly influences the beta-1,4-mannose linkages of galactomannans. Many microbes, particularly Aspergillus species, can be utilized to produce mannanases. On the other hand, excessive filamentous clumps of Aspergillus species in bioreactors are difficult to control. Therefore, this study sought to limit the clumps resulted from the excessive fungal growth by adding microparticles into the fermentation medium. Fed-batch fermentations were performed with and without microparticles (control). As a microparticle agent, aluminum oxide (Al2O3) and talc (Mg3Si4O10(OH)(2))) were evaluated as to their effect on fermentation performance. The highest p-mannanase activities were 744.35 and 356.79 U/mL for 5 g/L of Al2O3 and talc, which were 14.16- and 6.80-fold greater, respectively than in the control fermentation. Most of the treatments improved the performance of the fermentation process as the microparticles appeared to disturb the initial phase of spore aggregation. The most effective microparticle type and concentration for production of beta-mannanase in a stirred tank bioreactor with a glucose-based medium were determined to be 5 g/L of Al2O3. These results indicate that the use of microparticles improve p-mannanase fermentation conditions by controlling excessive fungal growth. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

摘要： 305

摘要： 286