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关键词： Biofouling   Biomineralization   Calcium carbonate   MBBR-MBR   Metagenomics   Phosphate  

摘要： Two hybrid moving bed biofilm reactor-membrane bioreactors were used for the treatment of variable-salinity influent wastewater with maximums of 4.5 and 8.5mScm(-1) electric conductivity. Operational conditions of the bioreactors were 6h hydraulic retention time and 2500mgL(-1) total solids. The membrane operated in a cycle of 9min draw-1min backwash and at 23.6Lh(-1)m(-2) flux rate. Membrane biofilm was collected from both systems and cultured in growth media for precipitation of carbonate and phosphate minerals, yielding only Bacillus stratosphericus for the 4.5mScm(-1) scenario and Bacillus stratosphericus, Bacillus toyonensis, Microbacterium esteraromaticum, Comamonas testosteroni, and Janibacter meloni for the 8.5mScm(-1) scenario. Scanning electron microscopy and X-ray analysis showed similarities in morphology and composition for the carbonate crystals from both salinity conditions and differences for the phosphate minerals. Study of the bacterial community of membrane biofilm and mixed liquor showed close similarities between them for the same salinity conditions, with both dominated by genera Rhodanobacter, Chujaibacter, and Thermomonas.

关键词： Denitrification   Cost-assessment   Woodchip bioreactor   Recirculating aquaculture  

摘要： Denitrifying "woodchip" bioreactors are engineered systems, consisting of a carbon filled trench (e.g., with woodchips), designed to remediate nitrogen (N)-enriched water through naturally occurring denitrification, a process where microbes reduce nitrate into inert di-nitrogen gas during their respiration processes. Recent studies have demonstrated the feasibility of woodchip bioreactors for treating aquacultural wastewater, specifically the concentrated effluents generated from recirculating aquaculture (RAS), with the caveat that system lifespan can be reduced from clogging associated with high organic solids loading and bacterial overgrowth. Because this technology is relatively new, particularly for aquaculture applications, lifetime cost-efficiency has not been fully assessed. A cost-estimate of N removal over a one- to five-year anticipated lifespan was obtained by estimating initial capital, recurring, and operational expenditures of a full-scale bioreactor system designed for a RAS production facility, using N removal rates from previous pilot-scale aquaculture wastewater bioreactor research. Assumptions included static N removal rates of 6.06 or 11.75 kg of N removal per year for conservative and maximum sensitivities, respectively 49 and 71% N removal efficiency, and at least one woodchip replacement over the system lifetime across a ten-year planning horizon. Initial capital expenditure totaled $47,838 or roughly $139.88 per m(3) installed with woodchip replacements each $19,469. Ten-year operational expenditure total present value costs included of $3737 for water quality work and $4666 for lifetime maintenance. Cost per kg of N removed per year ranged from $13.35 to $2.83, dependent on woodchip replacement scenarios of one- to five-years, respectively, which demonstrated denitrification bioreactors might offer a low-cost N treatment option for aquacultural farmers.

关键词： Electro-membrane bioreactor   Membrane fouling   Extracellular polymeric substances   Microbial composition   Nutrients removal   Hydraulic retention time  

摘要： Bacterial profile, nutrients removal performance, and membrane fouling behavior were evaluated in an anoxic/oxic electro-membrane bioreactor (A/O e-MBR) treating municipal wastewater at different hydraulic retention times (HRTs) (30, 20, and 15h). The results demonstrated that HRT reduction from 30 to 15h had a negligible effect on chemical oxygen demand (COD), ammonium (NH4+-N), and total phosphorus (TP) removal, showing efficiencies above of 98%, 99%, and 95%, respectively, for any experimental runs. On the other hand, total nitrogen (TN) removal improved significantly from 80.7% to 90.5% as the HRT was reduced from 30 to 15h. Activity batch assays have shown a higher specific nitrate uptake rate (SNUR) at the shorter HRT. Results of DNA sequencing analysis indicated a larger amount of denitrifying bacteria genus and a greater relative abundance of Nitrospira genus at shorter HRTs, supporting the higher SNUR and the greater TN removal. The membrane fouling rate increased by about 16 times during the period with HRT of 15h. Besides, some fouling propensity parameters have shown a worse mixed liquor filterability in this period.

关键词： Anaerobic membrane bioreactor   Ceramic membrane   Chemical cleaning   Domestic wastewater treatment   Membrane fouling  

摘要： In this study, the NaClO-assisted backwash was used to mitigate membrane fouling in anaerobic ceramic membrane bioreactors (AnCMBRs) treating domestic wastewater. Four NaClO concentrations (C-backwash) - 0.05, 0.25, 1 and 10 mg/L were used for backwash. In general, the effectiveness of NaClO-assisted backwash is the balance of two forces - foulants removal from membranes (i.e., the direct effect) and modification of mixed liquor (i.e., the indirect effect). With increased C-backwash, the direct effect of NaClO was enhanced through removal of more proteins. The indirect effect of NaClO was more complicated. The biodegradability of organics in the wastewater and the microbial activities of biomass were improved with low C-backwash. However, high C-backwash deteriorated cell metabolism and led to excessive production of cell lyric products. Optimal C-backwash that was used in this study - the C-backwash that provided the best fouling mitigation and acceptable treatment performances - was 1 mg/L.

关键词： Mixing   Droplet   Magnetic force   Magnetite   Micro-bioreactor  

摘要： Magnetic manipulation of paramagnetic particles had great potential for efficient bioprocessing. In this study, we stirred microliter-volume water droplets formed on a superhydrophobic surface as micro-bioreactors by using paramagnetic magnetite microparticles manipulated by an external magnetic field. We showed that magnetite microparticles in the droplets spontaneously formed rod-like aggregates, which were like commercial stir bars, in an external magnetic field and spun with rotating of magnetic field. Increasing the rotating rate of the magnetic field and increasing the concentration of the microparticles caused the microparticles to fixate at the air/water interface of the droplets and their rotation at the interface with rotating of magnetic field. The active mixing enhanced the enzyme reaction and microorganism proliferation in the droplets. These results demonstrated that manipulating the magnetite microparticles by an external magnetic field efficiently mixed the small droplets as micro-bioreactors. (C) 2018, The Society for Biotechnology, Japan. All rights reserved.

关键词： Photosynthetic bacteria   Wastewater treatment   Light-aerobic condition   Microbial community  

摘要： The combined photosynthetic bacteria (PSB) and membrane bioreactor (MBR) technology has the great advantage of simultaneously realizing wastewater purification and bio-resource recovery and has attracted increasing attention in recent years. Light-oxygen conditions are the most vital factor in wastewater treatment. The special light-aerobic condition was first applied to PSB-MBR wastewater treatment, and it was compared with three typical light-oxygen conditions. The results showed that the highest chemical oxygen demand (COD) removal efficiency (96.28%) and the highest biomass production (1.12 g/L/d) were simultaneously obtained under light-aerobic condition. This phenomenon overcame the limitations whereby optimal pollutant removal and bioresource recovery could not be achieved at the same time. An analysis of the microbial community showed that different light-oxygen conditions caused large variations in the microbial community composition of PSB-MBR. The microbial diversity was lower when light and oxygen co-existed.

关键词： A(2)N-DMBR   community structure   denitrifying phosphorus removal   nutrients removal performance   operation characteristic   removal efficiency  

摘要： An alternate anaerobic/anoxic-aerobic double membrane bioreactors process (A(2)N-DMBR) was proposed to improve denitrifying phosphorus removal efficiency. The system was operated for 70 d under different nitrogen/phosphorus (N/P) ratios with synthetic wastewater to present the performance evaluation of nutrients removal and microbial community structure in the A(2)N-DMBR process. The results showed that when the influent total phosphorus (TP) was 6.4 mg/L, the corresponding N/P ratio of 8.8, the high removal capacity of nitrogen and phosphorus could be achieved with the average effluent TP and total nitrogen (TN) concentration of 0.8 mg/L and 12.0 mg/L, respectively. Periodical test showed that pH and oxidation-reduction potential (ORP) could be used as control parameters for anaerobic phosphate release, and ORP was also closely related with the phosphate uptake in anoxic phase. The high-throughput sequencing analysis revealed that the Proteobacteria and Xanthomonadales-nobank related to biological nitrogen and phosphorus removal was domination bacteria at phylum and genus level in A(2)N-DMBR system, with the proportion of 42.5% and 39.1%, respectively. Furthermore, Dechloromonas, which was further detected as putative denitrifying phosphorus accumulating organisms (DPAOs), was enriched (9.9%) in the system.

关键词： Dairy wastewater   Aluminum   Coagulation   Membrane bioreactor   Membrane fouling  

摘要： Residual aluminum from coagulation process potentially results in operation problems for the subsequent treatment processes in the dairy wastewater treatment train such as membrane bioreactor (MBR). The objective of this study was to investigate the effect of residual aluminum (Al) on the performance and stability of MBR. A Hybrid Coagulation-MBR pilot was operated for 70 d using a hollow fiber membrane including four phases of operation. The finding of this study illustrated the MBR feasibility to control the Al concentration in the effluent to be below 0.5 mg/L, with > 90% Al removal. The residual Al was predominantly accumulated in the sludge and removed from the reactor by controlled wasting. Moreover, the residual Al resulted in increasing the transmembrane pressure with dTMP/dt equals 22.2, 31.6, and 35.3 m bar/d in the 1st, 2nd, and 3rd cleaning phase, respectively, resulting in irreversible membrane fouling. Overall, the combination of coagulation-MBR processes yielded up to 95% COD removal, subsequently, providing potential water reuse for the diary process.

关键词： Bioreactor design   Bioethanol   Cellulase   Enzymatic hydrolysis   Yields of glucose  

摘要： Cellulases are costly, a principal challenge of enzymatic hydrolysis of cellulosic materials for bioethanol production. For an efficient cellulase production, fungi are preferred over bacteria due to their permeation capability and versatile substrate consumption. Some limitations in the enzymatic hydrolysis step prevent the process to be economically feasible. Different strategies have been investigated to overcome these limitations, including genetic engineering, enzyme recycling, high solid loadings, pretreatment technologies, supplementation of cellulases with additives and application of nanomaterials for improving the thermal and pH stability of cellulases. Several studies have been performed in various bioreactors with the target to procure higher yields of glucose in the enzymatic hydrolysis step. The key factors for designing a bioreactor include efficient mixing, sufficient mass transfer, low shear stress, low foaming problems and low consumption of water and energy. In this scenario, different bioreactor configurations, including stirred tank bioreactor, horizontal rotating tubular bioreactor, airlift bioreactor, membrane bioreactor, reciprocating plate bioreactor, solid-state fermentation bioreactors have been reviewed for cellulase production with the aim to investigate main factors for designing a bioreactor. [GRAPHICS] .

关键词： Aeration   Bioreactor   Computational fluid dynamics   OpenFOAM  

摘要： Hydrodynamics, oxygen transfer, and oxygen uptake in bubble-column and airlift bioreactors were studied using multiphase Euler-Euler computational fluid dynamics (CFD) simulations. Interphase mass transfer of oxygen was modeled with a liquid mass-transfer coefficient and sustained driving force provided by a phenomenological model for microbial oxygen uptake rate (OUR). Laboratory-scale reactor simulations of a bubble-column (0.15 m diameter and 0.75 m initial liquid height) showed reasonable agreement with gas holdup and mass transfer experiments reported in the literature. Commercial-scale bubble-column and airlift reactor simulations (5 m diameter and 25 m initial liquid height) were simulated using this validated model. Similar trends for the variation of overall gas holdup and oxygen concentrations with superficial velocity were observed for both of the commercial-scale reactors. However, the simulation results indicate differences in hydrodynamics, such as better recirculation in the airlift reactors that enables favorable distribution of oxygen in the reactor. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.