Display omitted
•The pros, cons and progress in full-scale MBR application are summarized.•Statistics on capital and operating costs of MBR are provided and compared with CAS.•Efficiencies in ...treatment of ordinary and emerging pollutants are reviewed.•Long-term operation stability is discussed in relation to membrane fouling.•Future challenges of MBR application are outlined from multiple perspectives.
Membrane bioreactor (MBR) technology for wastewater treatment has been developed for over three decades. Our latest survey shows that MBR applications for wastewater treatment are still in rapid growth today. This review summarizes the pros, cons and progress in full-scale MBR applications. Critical statistics on the capital cost, operating cost, footprint, energy consumption and chemical consumption of full-scale MBRs are provided, and are compared to those of conventional activated sludge (CAS) processes with/without tertiary treatment. The efficiencies in full-scale treatment of ordinary pollutants (C, N and P), pathogens (bacteria and viruses) and emerging pollutants (e.g., trace organic pollutants) are reviewed. The long-term operation stability of full-scale MBRs is also discussed with several examples provided, with special attention placed on the seasonal variation of membrane fouling. Finally, the future challenges of MBR application are outlined from the perspectives of fouling control, pollutant removal, cost-effectiveness and competitiveness in specific fields of application.
The need for energy efficient Domestic Wastewater (DWW) treatment is increasing annually with population growth and expanding global energy demand. Anaerobic treatment of low strength DWW produces ...methane which can be used to as an energy product. Temperature sensitivity, low removal efficiencies (Chemical Oxygen Demand (COD), Suspended Solids (SS), and Nutrients), alkalinity demand, and potential greenhouse gas (GHG) emissions have limited its application to warmer climates. Although well designed anaerobic Membrane Bioreactors (AnMBRs) are able to effectively treat DWW at psychrophilic temperatures (10–30 °C), lower temperatures increase methane solubility leading to increased energy losses in the form of dissolved methane in the effluent. Estimates of dissolved methane losses are typically based on concentrations calculated using Henry's Law but advection limitations can lead to supersaturation of methane between 1.34 and 6.9 times equilibrium concentrations and 11–100% of generated methane being lost in the effluent. In well mixed systems such as AnMBRs which use biogas sparging to control membrane fouling, actual concentrations approach equilibrium values. Non-porous membranes have been used to recover up to 92.6% of dissolved methane and well suited for degassing effluents of Upflow Anaerobic Sludge Blanket (UASB) reactors which have considerable solids and organic contents and can cause pore wetting and clogging in microporous membrane modules. Microporous membranes can recover up to 98.9% of dissolved methane in AnMBR effluents which have low COD and SS concentrations. Sequential Down-flow Hanging Sponge (DHS) reactors have been used to recover between 57 and 88% of dissolved methane from Upflow Anaerobic Sludge Blanket (UASB) reactor effluent at concentrations of greater than 30% and oxidize the rest for a 99% removal of total dissolved methane. They can also remove 90% of suspended solids and COD in UASB effluents and produce a high quality effluent. In situ degassing can increase process stability, COD removal, biomass retention, and headspace methane concentrations. A model for estimating energy consumption associated with membrane-based dissolved methane recovery predicts that recovered dissolved and headspace methane may provide all the energy required for operation of an anaerobic system treating DWW at psychrophilic temperatures.
Primary fuel to unit operation energy conversion process. Display omitted
•Anaerobic systems can lose between 11 and 100% of generated methane in the effluent.•Membrane systems can recover up to 98.9% dissolved methane.•Microporous membranes may ares suitable for AnMBR effluent degassing.•Down Hanging Sponge reactors can efficiently recover dissolved methane and produce a high quality effluent.•Net-zero wastewater treatment may be achieved with dissolved methane recovery.
Synthetic biology based on bacteria has been displayed in antitumor therapy and shown good performance. In this study, an engineered bacterium Escherichia coli MG1655 is designed with NDH-2 enzyme ...(respiratory chain enzyme II) overexpression (Ec-pE), which can colonize in tumor regions and increase localized H
O
generation. Following from this, magnetic Fe
O
nanoparticles are covalently linked to bacteria to act as a catalyst for a Fenton-like reaction, which converts H
O
to toxic hydroxyl radicals (•OH) for tumor therapy. In this constructed bioreactor, the Fenton-like reaction occurs with sustainably synthesized H
O
produced by engineered bacteria, and severe tumor apoptosis is induced via the produced toxic •OH. These results show that this bioreactor can achieve effective tumor colonization, and realize a self-supplied therapeutic Fenton-like reaction without additional H
O
provision.
•Performance of a single AFMBR was compared with that of a staged AFMBR system.•The scouring effect of the GAC for fouling control was effective in both systems.•A 2–4h HRT gave effluent COD removal ...of 93–96%.•Behaviors of SS, EPS and SMP were similar in both systems.•The single AFMBR is an effective alternative to the staged AFMBR system.
Performance of a single anaerobic fluidized membrane bioreactor (AFMBR) was compared with that of a staged anaerobic fluidized membrane bioreactor system (SAF-MBR) that consisted of an anaerobic fluidized bed bioreactor (AFBR) followed by an AFMBR. Both systems were fed with an equal COD mixture (200mg/L) of acetate and propionate at 25°C. COD removals of 93–96% were obtained by both systems, independent of the hydraulic retention times (HRT) of 2–4h. Over more than 200d of continuous operation, trans-membrane pressure (TMP) in both systems was less than 0.2bar without significant membrane fouling as a result of the scouring of membrane surfaces by the moving granular activated carbon particles. Results of bulk liquid suspended solids, extracellular polymeric substances (EPS), and soluble microbial products (SMP) analyses also revealed no significant differences between the two systems, indicating the single AFMBR is an effective alternative to the SAF-MBR system.
Crude oil pollution is one of the most serious environmental issues today, and the clean-up procedure is perhaps the most difficult. Within one to three weeks, the vast majority of oil bacteria may ...degrade approximately 60% of the crude oil, leaving approximately 40% intact. The by-product metabolites produced during the breakdown of oil are essentially organic molecules in nature. These metabolites inhibit its enzymes, preventing the oil bacteria from further degrading the oil. By combining a variety of different oils with heterotrophic bacteria in a bioreactor, the rate of crude oil biodegradation was accelerated. In this study, two strains of oil-resistant, heterotrophic bacteria (OG1 and OG2-Erythrobacter citreus) and a bacterium that uses hydrocarbons (AR3-Pseudomonas pseudoalcaligenes) were used. Gas chromatography-mass spectroscopy was used to investigate the effectiveness of this consortium of symbiotic bacteria in the biodegradation of crude oil. According to gravimetric and gas chromatography analyses, the consortium bacteria digested 69.6% of the crude oil in the bioreactor, while the AR3 single strain was only able to destroy 61.9% of it. Under the same experimental conditions, consortium bacteria degraded approximately 84550.851 ppb (96.3%) of 16 aliphatic hydrocarbons and 9333.178 ppb (70.5%) of 16 aromatic hydrocarbons in the bioreactor. It may be inferred that the novel consortium of symbiotic bacteria accelerated the biodegradation process and had great potential for use in increasing the bioremediation of hydrocarbon-contaminated locations.
Effect of consortium bacteria on oil biodegradation. Display omitted
•Crude oil contamination is a major environmental challenge.•Bacteria can breakdown around 60% of crude oil.•Metabolites hinder bacteria from degrading oil.•A bacteria concoction enhanced crude oil biodegradation.•A symbiotic bacterial consortium degraded up to 69.6% of crude oil.
Induced pluripotent stem cells (iPSCs) have emerged as a consistent cell source for ‘off-the-shelf’ therapeutic T cells, with particular interest in CD8 T cells for CAR-T cell applications. ...Traditionally, Notch signaling, crucial for T-lineage differentiation, has been delivered through DLL4-expressing feeder cells or DLL4 protein-coated vessels in static culture, but these methods have proven inefficient for generating CD8 T cells from iPSCs at therapeutic scale. We have previously shown a method involving our proprietary DLL4/VCAM-1-conjugated magnetic beads (‘Engineered Thymic Niche’; ETN) for precisely modulating Notch signaling in a scalable suspension bioreactor-based culture. In this study, we have used ETN technology for the generation of functional CD8+ T cells in a stirred tank bioreactor, starting with a clonal iPSC cell line with a CD19-CAR inserted in at the TRAC locus. The CD8 T cells were functionally capable of multiple rounds of in vitro tumor cell lysis and sustained tumor growth inhibition in vivo.
iPSCs expressing CD19-CAR were differentiated to CD34+ cells in 250 mL stirred-tank reactors (STR), yielding an average of 300 million cells per batch, at 87% CD34+ purity and an efficiency of 3.5 lympho-competent progenitors per input expanded iPSC. iPSC-derived CD34+ cells were further differentiated in a 250mL STR in the presence of ETN, yielding over 5 x 106 mature CD4-CD8+ T cells mL-1 expressing engineered CAR with high efficiency. This ETN-based cell differentiation process has shown to be readily scalable with Proof-of-Concept (PoC) of up to 1.6L STR showing similar outputs to 250mL.
CD19-CAR expressing iPSC-CD8+ T cells derived using the scalable STR platform were capable of multiple rounds of in vitro cytotoxic activity to a range of effector cells (E:T ratio) proliferation, and cytokine secretion comparable to primary T cells. Furthermore, tumor growth inhibition potential of STR-derived iPSC-CD8+ T cells in an in vivo PoC study, using a mouse model with CD19+ tumor, was comparable to primary T cells. This is a significant advancement in generation of ‘off-the-shelf’, highly functional CD8+ T cells using a clonal iPSC line in a small footprint automated bioreactor which have greater capacity for linear scale-up and process control than traditional T cell manufacturing systems. This PoC study is a step toward the development of robust, cost-effective, safe, and efficacious allogeneic immunotherapies.
Synthetic biology based on bacteria has been displayed in antitumor therapy and shown good performance. In this study, an engineered bacterium Escherichia coli MG1655 is designed with NDH‐2 enzyme ...(respiratory chain enzyme II) overexpression (Ec‐pE), which can colonize in tumor regions and increase localized H2O2 generation. Following from this, magnetic Fe3O4 nanoparticles are covalently linked to bacteria to act as a catalyst for a Fenton‐like reaction, which converts H2O2 to toxic hydroxyl radicals (•OH) for tumor therapy. In this constructed bioreactor, the Fenton‐like reaction occurs with sustainably synthesized H2O2 produced by engineered bacteria, and severe tumor apoptosis is induced via the produced toxic •OH. These results show that this bioreactor can achieve effective tumor colonization, and realize a self‐supplied therapeutic Fenton‐like reaction without additional H2O2 provision.
A Fenton‐like bioreactor based on bacteria is reported for tumor therapy without exogenous H2O2 provision. It is found that this bioreactor can achieve effective tumor colonization, and realize a self‐supplied therapeutic Fenton‐like reaction without additional H2O2 provision.
Display omitted
•The roughness of biofilm is a convenient index to evaluate the maturity of biofilm.•Tightly-bound protein and polysaccharide determines the stability of biofilm.•The development of ...biofilm could be divided into three stages.•Gammaproteobacteria are the most dominant microbial species in class level at the last stage.
This work aims at revealing the adhesion characteristics and microbial community of the biofilm in an integrated moving bed biofilm reactor–membrane bioreactor, and further evaluating their variations over time. With multiple methods, the adhesion characteristics and microbial community of the biofilm on the carriers were comprehensively illuminated, which showed their dynamic variation along with the operational time. Results indicated that: (1) the roughness of biofilm on the carriers increased very quickly to a maximum value at the start-up stage, then, decreased to become a flat curve, which indicated a layer of smooth biofilm formed on the surface; (2) the tightly-bound protein and polysaccharide was the most important factor influencing the stability of biofilm; (3) the development of biofilm could be divided into three stages, and Gammaproteobacteria were the most dominant microbial species in class level at the last stage, which occupied the largest ratio (51.48%) among all microbes.
•Low viscous DES-water blends can be used in continuous processes for biocatalysis.•The pH control increases the conversion, using DES in a fed-batch reactor.•Fed-batch reactor reached the highest ...concentration of product 33 g/L.•The semicontinuous and continuous bioreactors reached similar productivities.•Biocatalyst stability was high in a packed-bed reactor, without loss for 10 days.
This work explores for the first time the use of Deep Eutectic Solvents (DES) with phosphate buffer 100 mM pH 7 as cosolvent (10% v/v) in biocatalytic reactions in fed-batch and packed-bed bioreactors. The lipase-catalyzed esterification of glycerol and benzoic acid is studied, as it involves two substrates with different polarities (for which DES are needed). In the fed-batch bioreactor, the highest conversion (90%) was obtained at a substrate flow rate of 0.01 mL/min. The fed-batch operation increased the conversion by 59% compared to the batch mode. Regarding productivity, semi-continuous and continuous bioreactors showed analogous results. Upon recirculation of the reaction media in the continuous bioreactor, a conversion of 67% was achieved in 7 cycles of operation. The stability of the biocatalyst in the packed-bed bioreactor decreased only 2% in 10 days, demonstrating the attractiveness that low viscous DES-water mixtures with continuous processes may have.
While cleaning wastewater, biological wastewater treatment processes such as membrane bioreactors (MBR) produce a significant amount of sludge that requires costly management. In the ...oxic-settling-anoxic (OSA) process, sludge is retained for a temporary period in side-stream reactors with low oxygen and substrate, and then it is recirculated to the main reactor. In this way, excess sludge production is reduced. We studied the influence of the rate of sludge exchange between MBR and side-stream anoxic reactors on sludge yield reduction within MBR. Two MBRs, namely, MBROSA and MBRcontrol, each coupled with separate external anoxic side-stream reactors, were run in parallel for 350 days. Unlike MBRcontrol, MBROSA had sludge exchange with the external reactors connected to it. During the investigation over a sludge interchange rate (SIR) range of 0–22%, an SIR of 11% achieved the highest sludge reduction (58%). Greater volatile solids destruction i.e., bacterial cell lysis and extracellular polymeric substance (EPS) destruction occurred at the SIR of 11%, which helped to achieve the highest sludge reduction. The enhanced volatile solids destruction was evident by the release of nutrients in the external anoxic reactors. It was confirmed that the sludge yield reduction was achieved without compromising the wastewater treatment quality, sludge settleability and hydraulic performance of the membrane in MBR.
Display omitted
•MBR was integrated with anoxic side-stream reactors for sludge yield reduction.•58, 45 and 34% sludge reduction were achieved at 11, 16.5 and 22% SIR, respectively.•Sludge reduction coincided with increased nitrification/denitrification in MBROSA.•Overall effluent quality and sludge settleability in MBROSA was unaffected.•Membrane fouling in MBROSA was not adversely impacted.
