共查询到20条相似文献,搜索用时 171 毫秒
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A limiting factor for the reuse and recycling of treated tannery wastewater for irrigation and other uses is the high salt content, which persists even after conventional treatment. Reverse osmosis (RO) membrane treatment has been shown to significantly reduce the salt contents of tannery effluents. However, the high organic content of tannery effluent leads to rapid scaling and biofouling of RO membranes with a consequent reduction in flux rates and performance. Membrane bioreactors (MBR) have been shown to be highly effective in the removal of organic pollutants and suspended solids from tannery effluent. This research investigated the use of a combined MBR and RO treatment process to treat tannery effluents to an acceptable level for irrigation purposes. The MBR was operated at 17-20 h retention time, at a F/M ratio of 0.52 kg COD x kg SS(-1) x day(-1) and a volumetric loading rate of 3.28 kg COD x m(-3) x day(-1). This treatment reduced the COD, BOD, and ammonia concentrations of the effluent by 90-100%. The MBR was shown to be an excellent pretreatment prior to RO technology, due to the high removal efficiency of organic compounds and suspended solids, with average concentrations of 344 mg x L(-1) COD and 20 mg x L(-1) BOD achieved in the permeate. RO treatment reduced the salt content of the MBR permeate by up to 97.1%. The results of the research demonstrated that the MBR system developed was appropriate for the treatment of tannery effluents and, in combination with the RO treatment, reduced the salt content to acceptable levels for irrigation. The MBR pretreatment reduced bio-fouling and scaling of subsequent RO treatment and improved the overall performance of the RO unit. It is believed that this is the first investigation of a combined MBR and RO treatment for tannery effluents. This research provided data for an outline design of a full-scale MBR and RO plant with a treatment capacity of 5000 m3 per day for mixed tannery effluents. 相似文献
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为了探究超滤(UF)+纳滤(NF)组合工艺回收甘薯淀粉加工废水中多糖的技术可行性,通过UF+NF双膜法中试实验,研究了操作压力、进水流量、运行时间对NF膜分离效果的影响,采用正交实验优化了NF膜清洗参数。结果表明:当操作压力为0.2 MPa、进水流量为550 L/h时,UF(60 ku)对蛋白截留率为94.1%。NF最佳运行条件为操作压力0.3 MPa、进水流量450 L/h,运行时间3 h,透过液多糖浓度低于4.8 mg/L,多糖、化学需氧量(COD)截留率分别为98%、85.2%。清洗剂种类、清洗剂浓度、清洗时间对NF膜清洗效果影响显著(p<0.01),而清洗温度对NF膜清洗效果影响不显著(p>0.05),影响程度大小顺序为清洗时间>清洗剂种类>清洗剂浓度>清洗温度;最优清洗参数时(温度30℃、清洗时间15 min、碱性蛋白酶浓度0.06%),NF膜通量恢复率为92.1%。 相似文献
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Decolorization of vegetable oils by membrane processing 总被引:2,自引:0,他引:2
K. Kondal Reddy Rangaswamy Subramanian Takahiro Kawakatsu Mitsutoshi Nakajima 《European Food Research and Technology》2001,213(3):212-218
Membrane decolorization studies of chlorophyll added sunflower oil and crude soybean oil were conducted in a batch membrane cell using two polymeric composite membranes (NTGS-2100 and NTGS-1100), and one polyethylene microfiltration membrane (PE-30). NTGS-2100 membrane could remove up to 96% and 72% chlorophyll from the undiluted and oil-hexane (50 wt%) solutions, respectively. Permeate oil flux was very low when undiluted oil was used as feed, but improved many fold by diluting with hexane. NTGS-1100 membrane gave higher permeate flux compared to NTGS-2100, but showed reduced rejection. Absorbance spectra of crude soybean oil and the permeate in the 350-550 nm range showed a greater degree of decolorization by polymeric composite membranes. PE-30 membrane showed insignificant rejection of color compounds. The permeate of conventionally bleached soybean oil showed a reduction in extinction coefficients at 232 and 270 nm, indicating possible rejection of dienes and trienes by the composite polymeric membranes. The membrane process was effective in reducing the color compounds in crude vegetable oils besides offering many advantages over the conventional process. 相似文献
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S. Mukhopadhyay P.M. Tomasula D. Van Hekken J.B. Luchansky J.E. Call A. Porto-Fett 《Journal of food science》2009,74(6):M319-M327
ABSTRACT: Thermal preservation is used by the egg industry to ensure the microbiological safety of liquid egg white (LEW); however, it does not eliminate all microorganisms and impairs some of the delicate functional properties of LEW. In this study, a pilot-scale cross-flow microfiltration (MF) process was designed to remove the natural microflora present in commercial LEW, obtained from a local egg-breaking plant, while maintaining the nutritional and functional properties of the LEW. LEW, containing approximately 106 ± 1.7 colony forming units (CFU) per milliliter of total aerobic bacteria, was microfiltered using a ceramic membrane with a nominal pore size of 1.4 μm, at a cross-flow velocity of 6 m/s. To facilitate MF, LEW was screened, homogenized, and then diluted (1 : 2, w/w) with distilled water containing 0.5% sodium chloride. Homogenized LEW was found to have a threefold lower viscosity than unhomogenized LEW. Influence of MF temperature (25 and 40 °C) and pH (6 and 9) on permeate flux, transmission of egg white nutrients across the membrane, and microbial removal efficiency were evaluated. The pH had a significantly greater influence on permeate flux than temperature. Permeate flux increased by almost 148% when pH of LEW was adjusted from pH 9 to pH 6 at 40 °C. Influence of temperature on permeate flux, at a constant pH, however, was found to be inconclusive. Microbial removal efficiency was at least 5 log10 CFU/mL. Total protein and SDS-PAGE analysis indicated that this MF process did not alter the protein composition of the permeate, compared to that of the feed LEW, and that the foaming properties of LEW were retained in the postfiltered samples. 相似文献
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Silica/titania nanotubes composite membranes were successfully prepared from silica/titania sols using porous alumina support membranes. XRD patterns of the composite membranes confirmed that the embedding of amorphous silica into nanophase titania matrix helped to increase the thermal stability of titania which suppressed the phase transformation from anatase to rutile and decreased the size of titania particles. Ninety-five percent of the pore volume of composite membrane was located in mesopores with diameters ranging from 1.4 to 10 nm. The surface of these composite membranes exhibited extremely high affinity for water under UV irradiation with water contact angle decreased from 62 degrees to nearly 5 degrees within 80 min. By coupling membrane separation with photocatalysis technique, the removal efficiency of Direct Black 168 was improved remarkably; being 85% within 100 min, while the values were 66% and 73% with photocatalysis alone or membrane separation alone during the same time, respectively. Good photocatalytic activity and wettability of composite membrane under UV irradiation helped to obtain high permeate flux across the composite membrane. The silica/titania nanotubes composite membrane had the multifunctions of separation, degradation, and improvement of membrane flux in photooxidation of organic contaminants in wastewater. 相似文献
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聚醚砜超滤膜分离菜籽油/乙醇混合物的研究 总被引:1,自引:1,他引:0
用聚醚砜超滤膜分离菜籽油/乙醇混合物,研究了混合物中菜籽油质量分数(20%~60%)、操作压力(0.15~0.3 MPa)和时间(10~60 min)等参数对分离效果的影响,并探讨了该膜渗透通量的数学模型.结果表明:膜的渗透通量随着操作压力的升高而升高,随时间的延长和混合物中菜籽油质量分数的提高而降低;膜对油脂的截留率随着操作压力的升高、混合物中菜籽油质量分数的提高而降低.当操作压力为0.15 MPa、菜籽油/乙醇混合物质量分数为20%时,得到最高的油脂截留率为95.03%. 相似文献
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Kim J Kim K Ye H Lee E Shin C McCarty PL Bae J 《Environmental science & technology》2011,45(2):576-581
Anaerobic membrane bioreactors have potential for energy-efficient treatment of domestic and other wastewaters, membrane fouling being a major hurdle to application. It was found that fouling can be controlled if membranes are placed directly in contact with the granular activated carbon (GAC) in an anaerobic fluidized bed bioreactor (AFMBR) used here for post-treatment of effluent from another anaerobic reactor treating dilute wastewater. A 120-d continuous-feed evaluation was conducted using this two-stage anaerobic treatment system operated at 35 °C and fed a synthetic wastewater with chemical oxygen demand (COD) averaging 513 mg/L. The first-stage was a similar fluidized-bed bioreactor without membranes (AFBR), operated at 2.0-2.8 h hydraulic retention time (HRT), and was followed by the above AFMBR, operating at 2.2 h HRT. Successful membrane cleaning was practiced twice. After the second cleaning and membrane flux set at 10 L/m(2)/h, transmembrane pressure increased linearly from 0.075 to only 0.1 bar during the final 40 d of operation. COD removals were 88% and 87% in the respective reactors and 99% overall, with permeate COD of 7 ± 4 mg/L. Total energy required for fluidization for both reactors combined was 0.058 kWh/m(3), which could be satisfied by using only 30% of the gaseous methane energy produced. That of the AFMBR alone was 0.028 kWh/m(3), which is significantly less than reported for other submerged membrane bioreactors with gas sparging for fouling control. 相似文献
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Raw milk (2,710 kg) was separated at 4°C, the skim milk was pasteurized (72°C, 16 s), split into 3 batches, and microfiltered using pilot-scale ceramic uniform transmembrane pressure (UTP; Membralox model EP1940GL0.1μA, 0.1 μm alumina, Pall Corp., East Hills, NY), ceramic graded permeability (GP; Membralox model EP1940GL0.1μAGP1020, 0.1 μm alumina, Pall Corp.), and polymeric spiral-wound (SW; model FG7838-OS0x-S, 0.3 μm polyvinylidene fluoride, Parker-Hannifin, Process Advanced Filtration Division, Tell City, IN) membranes. There were differences in flux among ceramic UTP, ceramic GP, and polymeric SW microfiltration membranes (54.08, 71.79, and 16.21 kg/m2 per hour, respectively) when processing skim milk at 50°C in a continuous bleed-and-feed 3× process. These differences in flux among the membranes would influence the amount of membrane surface area required to process a given volume of milk in a given time. Further work is needed to determine if these differences in flux are maintained over longer processing times. The true protein contents of the microfiltration permeates from UTP and GP membranes were higher than from SW membranes (0.57, 0.56, and 0.38%, respectively). Sodium-dodecyl-sulfate-PAGE gels for permeates revealed a higher casein proportion in GP and SW permeate than in UTP permeate, with the highest passage of casein through the GP membrane under the operational conditions used in this study. The slight cloudiness of the permeates produced using the GP and SW systems may have been due to the presence of a small amount of casein, which may present an obstacle in their use in applications when clarity is an important functional characteristic. More β-lactoglobulin passed through the ceramic membranes than through the polymeric membrane. The efficiency of removal of serum proteins in a continuous bleed-and-feed 3× process at 50°C was 64.40% for UTP, 61.04% for GP, and 38.62% for SW microfiltration membranes. The SW polymeric membranes had a much higher rejection of serum proteins than did the ceramic membranes, consistent with the sodium-dodecyl-sulfate PAGE data. Multiple stages and diafiltration would be required to produce a 60 to 65% serum protein reduced micellar casein concentrate with SW membranes, whereas only one stage would be needed for the ceramic membranes used in this study. 相似文献
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Zita Šereš Julianna Gyura Matild Eszterle Mirjana Djurić 《European Food Research and Technology》2006,223(6):829-835
Non-sucrose compounds having intensive colour tend to build into the sucrose crystals during the crystallization. Their removal, or decrease of their concentration in sugar syrup, is a very important operation. The subject of this laboratory investigation was a separation process performed by ceramic tubular membrane in two modes of operation: with static mixer (SM) and without static mixer (NSM). In order to compare two alternatives as well as to determine optimal operating conditions, in both modes, solution flow rate, temperature, transmembrane pressure and process duration were varied independently and their influence on the permeate flux as well as on the efficiency of decolourization and purification were examined. The cross-flow filtration was carried out on ceramic tubular membrane with pore diameter of 20 nm. The obtained results have shown that permeate flux increased approximately 30%, at 80 °C, and 65%, at 70 °C, when static mixer was used. Significant part of coloured compounds—45% in average, determined by the absorbance measurement of permeate/feed, was separated from the raw sugar syrup. Decolourization in SM-mode is greater than the decolourization in NSM-mode (30% after 0.5 h and 55% after 2 h). Purity was eliminated with an efficiency of 80% in average compared to the feed, with the similar success when NSM-mode and SM-mode of operation were applied, particularly at the end of ultrafiltration. 相似文献