Comparison of NF membrane fouling and cleaning by two pretreatment strategies for the advanced treatment of antibiotic production wastewater.

The nanofiltration (NF) membrane fouling characteristics and cleaning strategies were investigated and compared for treating membrane bioreactor (MBR) effluent and MBR-granular activated carbon (GAC) effluent of an antibiotic production wastewater by DK membrane. Results showed that the fouling of treating MBR effluent was more severe than that of treating MBR-GAC effluent. After filtering for 216 h, the difference of membrane flux decline was obvious between MBR effluent and MBR-GAC effluent, with 14.9% and 10.3% flux decline, respectively. Further study showed that organic fouling is the main NF membrane fouling in the advanced treatment of antibiotic production wastewater for both of the two different effluents. Soluble microbial by-product like and tyrosine-like substances were the dominant components in the foulants, whereas humic-like substances existing in the effluents had little contribution to the NF membrane fouling. A satisfactory efficiency of NF chemical cleaning could be obtained using combination of acid (HCl, pH 2.0-2.5) and alkali (NaOH + 0.3 wt% NaDS, pH 10.0-10.5). The favorable cleaning strategy is acid-alkali for treating the MBR-GAC effluent, while it is alkali-acid for treating the MBR effluent.

Influence of cellulose viscosity on the physical, mechanical, and barrier properties of the chitosan-based films.

This research paper presents a comprehensive investigation into developing biodegradable films for food packaging applications using chitosan (CN) in conjunction with three distinct types of cellulose (CE), each characterized by varying viscosities. The primary objective was to assess the influence of cellulose viscosity on the physical, mechanical, and barrier properties of the resulting films. The medium-viscosity cellulose imparted numerous advantageous qualities to the biodegradable films. These films exhibited optimal thickness (31 µm), ensuring versatility in food packaging while maintaining favorable mechanical properties, blending strength, and flexibility. Also, medium-viscosity cellulose significantly improved the films' barrier performance, particularly regarding oxygen permeability [1.80 × 10-6 (g.mm.m-2. s-1)]. Furthermore, the medium-viscosity cellulose contributed to superior moisture-related properties, including reduced water vapor permeability [14.80 × 10-9 (g.mm.m-2. s-1. Pa-1)], moisture content (13.22 %), and water solubility (22.87 %), while maintaining an appropriate degree of swelling (41.88 %). Moreover, the study employed advanced analytical techniques, including FTIR, XRD, and TGA, to provide critical insights into the films' chemical, structural, and thermal aspects. This research underscored the importance of the viscosity of film formulation materials as a crucial element in designing and efficiently producing films for food packaging.

Development and properties of bacterial cellulose, curcumin, and chitosan composite biodegradable films for active packaging materials.

To deal with serious environmental damage resulting from plastic packaging materials, biodegradable films using natural products have gained considerable attention. Here, we provide a simple, fast, and environmentally-friendly route to construct a biodegradable film using chitosan (CS), bacterial cellulose (BC), and curcumin (Cur). Composite films (CSn-BC-Cur) using CS with different molecular weights were investigated, and their water moisture content (MC), water solubility (WS), contact angle (CA), mechanical properties, barrier properties, and antioxidant properties were compared. The obtained films were characterized by SEM, XRD, and TGA. The results showed that chitosan with a higher molecular weight presented higher contact angles and mechanical properties, along with a lower moisture content, water vapor transmission rate, and oxygen transmission rate. Furthermore, when the composite film was placed in 95 % ethanol, it released active substances. The results suggest that these composite films can be used as promising materials for food packaging.

Does the biological treatment or membrane separation reduce the antibiotic resistance genes from swine wastewater through a sequencing-batch membrane bioreactor treatment process.

Swine wastes are the reservoir of antibiotic resistance genes (ARGs), which can potentially spread from swine farms to the environment. This study establishes a sequencing-batch membrane bioreactor (SMBR) for ARG removal from swine wastewater, and analyzes the effect of biological treatment and membrane separation on the ARG removal at different solid retention times (SRTs). The SMBR removed 2.91 logs (copy number) of ARGs at a short SRT (12 days). Raising the SRT reduced the removal rates of the detected genes by the biological treatment. Under the relative long SRT (30 days), ARGs and mobile genetic elements (MGEs) were maximized within the reactor and were well removed by membrane separation, with the average genes removal rate of 2.95 (copy number) and 1.18 logs (abundance). At the relatively low SRT, the biological treatment showed the dominant ARG removal effect, while the membrane separation took the advantages of ARG removal especially at the relatively long SRT. The ARG profile was related to the shift of the microbial community structure. The ARGs coexisted with the functional bacteria (ammonia oxidizing bacteria, nitrite oxidizing bacteria and denitrifiers), suggesting they are hosted by the functional bacteria.

Numerical optimization of membrane module design and operation for a full-scale submerged MBR by computational fluid dynamics.

The hydrodynamics in the membrane module of a full-scale sMBR at 500 m3/d was simulated by computational fluid dynamics (CFD) in this study. Several key indexes, including membrane distance (d), aeration design, height of gas-liquid dispersion hm, and freeboard height hf and operational conditions, including SADp and liquid viscosity, were optimized through investigating their impacts on water velocity distribution and membrane shear stress. The CFD model was validated by comparing the simulated trace element RTD curves with experimental results. The optimal design and operational parameters for the full scale sMBR are as following: membrane distance d = 35 mm, air diffusers parallel located 75-100 mm under the bottom of the membrane module, the free board height hf adjusted to 400 mm, and the SADp recommended as 20 in the full-scale MBR studied.

Fouling characteristics and cleaning strategies of NF membranes for the advanced treatment of antibiotic production wastewater.

The nanofiltration (NF) membrane fouling characteristics and cleaning strategies were investigated through a laboratory-scale NF fouling test treating membrane bioreactor (MBR) effluent and MBR-granular activated carbon (GAC) effluent of an antibiotic production wastewater by DK and NF90 membranes, respectively. Results showed that organic fouling is the main NF membrane fouling for treating both the MBR effluent and MBR-GAC effluent. Soluble microbial by-product (SMP)-like and aromatic protein-like substances were the dominant components in the foulants, whereas humic-like substances had little contribution to the NF fouling. The fouling of DK was more severe than that of NF90. However, foulants respond by UV254 were more easily to foul NF90 membrane. It could get satisfactory effect using combined cleaning of acid (HCl, pH 2.0∼2.5) and alkali (NaOH + 0.3 wt% NaDS, pH 10.0∼10.5). The favorable cleaning strategy is "acid + alkali" for treating MBR-GAC effluent, while it is "alkali + acid" for treating MBR effluent.

Fouling analysis of membrane bioreactor treating antibiotic production wastewater at different hydraulic retention times.

Membrane fouling, including foulants and factors, was investigated during hydraulic retention time (HRT) optimization of a membrane bioreactor (MBR) that treated wastewater from the production of antibiotics. The results showed that HRT played an important role in membrane fouling. Trans-membrane pressure (TMP), membrane flux, and resistance were stable at -6 kPa, 76 L m-2 h-1 bar-1, and 4.5 × 1012 m-1 when HRT was at 60, 48, and 36 h, respectively. Using Fourier transform infrared spectroscopy, foulants were identified as carbohydrates and proteins, which correlated with effluent organic matter and effluent chemical oxygen demand (COD) compounds. Therefore, membrane fouling trends would benefit from low supernatant COD (378 mg L-1) and a low membrane removal rate (26 %) at a HRT of 36 h. Serious membrane fouling at 72 and 24 h was related to soluble microbial products and extracellular polymeric substances in mixed liquor, respectively. Based on the TMP decrease and flux recovery after physical and chemical cleaning, irremovable fouling aggravation was related to extracellular polymeric substances' increase and soluble microbial products' decrease. According to changes in the specific oxygen uptake rate (SOUR) and mixed liquor suspended solids (MLSSs) during HRT optimization in this study, antibiotic production wastewater largely inhibited MLSS growth, which only increased from 4.5 to 5.0 g L-1 when HRT was decreased from 72 to 24 h, but did not limit sludge activity. The results of a principal component analysis highlighted both proteins and carbohydrates in extracellular polymeric substances as the primary foulants. Membrane fouling associated with the first principal component was positively related to extracellular polymeric substances and negatively related to soluble microbial products. Principal component 2 was primarily related to proteins in the influent. Additional membrane fouling factors included biomass characteristics, operational conditions, and feed characteristics.

Optimization of MBR hydrodynamics for cake layer fouling control through CFD simulation and RSM design.

Membrane fouling is an important issue for membrane bioreactor (MBR) operation. This paper aims at the investigation and the controlling of reversible membrane fouling due to cake layer formation and foulants deposition by optimizing MBR hydrodynamics through the combination of computational fluid dynamics (CFD) and design of experiment (DOE). The model was validated by comparing simulations with measurements of liquid velocity and dissolved oxygen (DO) concentration in a lab-scale submerged MBR. The results demonstrated that the sludge concentration is the most influencing for responses including shear stress, particle deposition propensity (PDP), sludge viscosity and strain rate. A medium sludge concentration of 8820mgL-1 is optimal for the reduction of reversible fouling in this submerged MBR. The bubble diameter is more decisive than air flowrate for membrane shear stress due to its role in sludge viscosity. The optimal bubble diameter was at around 4.8mm for both of shear stress and PDP.

Numerical simulation of scaling-up for AEC-MBRs regarding membrane module configurations and cyclic aeration modes.

The airlift external circulation membrane bioreactors (AEC-MBRs) have been attracting attentions due to their capabilities of nutrient removal with lower energy demand and smaller footprint. The gap between laboratory study and full-scale AEC-MBRs regarding hydrodynamics needs to be addressed. In this study, impacts of seven design variables and cyclic aeration modes on hydrodynamics were studied for the scale-up of AEC-MBRs with computational fluid dynamics modelling. The results demonstrated that shear stress on membranes was 14.7% higher in full-scale MBR with only 15% of SADm of lab-scale MBR while it showed an overall higher sensitivity to the design variables in lab-scale MBRs. Cyclic aeration modes created a sinusoidal pattern of shear stress and generated more fluctuations and were expected to reduce more irreversible fouling. When a shifting frequency of 5s/5s was applied in AEC-MBR, 50% of aeration energy was reduced and yield water with good quality was harvested.

CFD simulation and optimization of membrane scouring and nitrogen removal for an airlift external circulation membrane bioreactor.

Cost-effective membrane fouling control and nitrogen removal performance are of great concern in airlift external circulation membrane bioreactors (AEC-MBRs). Computational fluid dynamics (CFD) model incorporating sub-models of bio-kinetics, oxygen transfer and sludge rheology was developed for the cost-effective optimization of a lab-scale AEC-MBR. The model was calibrated and validated by extensive measurements of water velocities and water quality parameters in the AEC-MBR. The validated results demonstrated that the optimized height of gas-liquid dispersion was at around 300mm. The shear stress on membrane surface was equalized and had an average value of 1.2Pa under an air flowrate of 1.0m(3)h(-1). The model further revealed that the high nitrogen removal efficiency (>90%) was achieved due to the high recirculation ratio driven by airlift force without destroying the oxygen deprivation and enrichment in the anoxic and oxic zone, respectively.

[Energy Consumption Comparison and Energy Saving Approaches for Different Wastewater Treatment Processes in a Large-scale Reclaimed Water Plant].

Energy consumption is the main performance indicator of reclaimed water plant (RWP) operation. Methods of specific energy consumption analysis, unit energy consumption analysis and redundancy analysis were applied to investigate the composition and spatio-temporal distribution of energy consumption in Qinghe RWP with inverted A2/O, A2/O and A2/O-MBR processes. And the A2/ O-MBR process was mainly analyzed to identify the main nodes and causes for high energy consumption, approaches for energy saving were explored, and the energy consumption before and after upgrading for energy saving was compared. The results showed that aeration was the key factor affecting energy consumption in both conventional and A2/O-MBR processes, accounting for 42.97% and 50.65% of total energy consumption, respectively. A pulsating aeration allowed an increasing membrane flux and remarkably reduced the energy consumption of the A2/O-MBR process while still meeting the effluent standard, e.g., the membrane flux was increased by 20%, and the energy consumptions per kiloton wastewater and kilogram COD(removed) were decreased by 42.39% to 0.53 kW-h-kg-3 and by 54.74% to 1.29 kW x h x kg(-1), respectively. The decrease of backflow ratio in the A2/O-MBR process within a certain range would not deteriorate the effluent quality due to its insignificant correlation with the effluent quality, and therefore may be considered as one of the ways for further energy saving.

[Anaerobic membrane bioreactors for treating agricultural and food processing wastewater at high strength].

As the second largest amounts of COD discharged in 41 kinds of industrial wastewater, it is of great urgency for the agricultural and food processing industry to control water pollution and reduce pollutants. Generally the agricultural and food processing industrial wastewater with high strength COD of 8 000-30 000 mg x L(-1), is mainly treated with anaerobic and aerobic processes in series, but which exists some issues of long process, difficult maintenance and high operational costs. Through coupling anaerobic digestion and membrane separation together, anaerobic membrane bioreactor (AnMBR) has typical advantages of high COD removal efficiency (92%-99%), high COD organic loading rate [2.3-19.8 kg x (m3 x d)(-1)], little sludge discharged (SRT > 40 d) and low cost (HRT of 8-12 h). According to COD composition of high strength industrial wastewater, rate-limiting step of methanation could be either hydrolysis and acidification or methanogenesis. Compared with aerobic membrane bioreactor (MBR), membrane fouling of AnMBR is more complicated in characterization and more difficult in control. Measures for membrane fouling control of AnMBR are almost the same as those of MBR, including cross flow, air sparging and membrane relaxation. For meeting discharging standard of food processing wastewater with high strength, AnMBR is a promising technology with very short process, by enhancing COD removal efficiency, controlling membrane fouling and improving energy recovery.

Expression of intracellular interferon-alpha confers antiviral properties in transfected bovine fetal fibroblasts and does not affect the full development of SCNT embryos.

Foot-and-mouth disease, one of the most significant diseases of dairy herds, has substantial effects on farm economics, and currently, disease control measures are limited. In this study, we constructed a vector with a human interferon-α (hIFN-α) (without secretory signal sequence) gene cassette containing the immediate early promoter of human cytomegalovirus. Stably transfected bovine fetal fibroblasts were obtained by G418 selection, and hIFN-α transgenic embryos were produced by somatic cell nuclear transfer (SCNT). Forty-six transgenic embryos were transplanted into surrogate cows, and five cows (10.9%) became pregnant. Two male cloned calves were born. Expression of hIFN-α was detected in transfected bovine fetal fibroblasts, transgenic SCNT embryos, and different tissues from a transgenic SCNT calf at two days old. In transfected bovine fetal fibroblasts, expression of intracellular IFN-α induced resistance to vesicular stomatitis virus infection, increased apoptosis, and induced the expression of double-stranded RNA-activated protein kinase gene (PKR) and the 2'-5'-oligoadenylate synthetase gene (2'-5' OAS), which are IFN-inducible genes with antiviral activity. Analysis by qRT-PCR showed that the mRNA expression levels of PKR, 2'-5' OAS, and P53 were significantly increased in wild-type bovine fetal fibroblasts stimulated with extracellular recombinant human IFN-α-2b, showing that intracellular IFN-α induces biological functions similar to extracellular IFN-α. In conclusion, expression of intracellular hIFN-α conferred antiviral properties in transfected bovine fetal fibroblasts and did not significantly affect the full development of SCNT embryos. Thus, IFN-α transgenic technology may provide a revolutionary way to achieve elite breeding of livestock.