沉淀-超滤工艺膜反洗水的回收处理

在处理以地表水为水源的沉淀池出水时,超滤技术存在产水率较低的问题,反洗水的回收可以有效地提高系统的产水率和降低运行成本。试验设计了两套小试微滤膜系统,将膜反洗水经过预处理后按1∶9比例与滦河水混合作为一套小试膜系统进水,另外一套小试膜系统处理滦河水。试验考察了两种预处理方式对于混配水膜系统的出水水质及膜污染的影响。结果表明,在膜反洗水中投加混凝剂和粉末活性炭（PAC）后,相对仅投加混凝剂的预处理方式,混配水系统的出水水质得到改善,UV₂₅₄和COD_Mn的去除率分别提高了9%和6.3%,预处理方式对于混配水系统出水浊度没有影响,比通量衰减速率降低了16.6%。在反洗水经混凝和PAC吸附后,混配水和滦河水系统出水水质与膜污染状况未见显著差异。     

Application of hybrid coagulation–microfiltration process for treatment of membrane backwash water from waterworks

A coagulation–microfiltration (MF) system was studied to treat the discharged membrane backwash water (MBW) to meet the drinking water quality requirements. The values of dissolved organic carbon (DOC) and trihalomethanes formation potential (THMFP) in MBW were higher than those in Luan River water (LRW, the raw water for a pilot-scale membrane plant, which produced MBW used in this study), and organic matter enriched in MBW distributed mainly in molecular weight (MW) > 10k Da. When 15 mg FeCl₃/L and 15 mg/L powdered activated carbon (PAC) were added into the system, the average concentration of DOC was reduced from 5.731 mg/L in MBW to 3.377 mg/L in the treated water, and the average UV₂₅₄ was reduced from 0.047 to 0.030 cm⁻¹. The removal of organic matter was main in the range of MW > 30k Da. Efficient organic removal by the hybrid coagulation–MF system resulted in significant reduction of THMFP in the treated water. Concentrations of trihalomethanes, turbidity, bacteria and coliforms in the treated water were below the limit value of the drinking water standards. The results show that the treated water from MBW is with satisfactory organic and microbiological quality.     

Contribution of Main Pollutants in Oilfield Polymer-Flooding Wastewater to the Total Membrane Fouling Resistance

Polymer flooding technology has been used in the oilfield, but huge amounts of polymer-flooding wastewater are produced with oil extraction. Therefore, the treatment and recycle of this wastewater become very significant. In this study, the membrane technology was used to treat synthetic oilfield polymer-flooding wastewater in laboratory-scale dead-end/cross-flow test unit with flat polyvinylidene fluoride (PVDF) membrane (MW 100 kDa). We systematically inspected the membrane fouling mechanism, the variety of total fouling resistance, the dominant resistance, and the filtration proceeds in the filtration process. The orthogonal method and multivariate linear regression method were applied to analyze the influencing degree of main pollutants concentration which contains partially hydrolyzed polyacrylamide (HPAM), oil and suspended solid on the total membrane fouling resistance. According to a comparison of the average rates of change of total membrane fouling resistance for the HPAM concentration, oil concentration, and suspended solid (SS) concentration in single solute solution, double solute solution, synthetic oilfield polymer-flooding wastewater, and the value of pH, HPAM can decrease the average rate of change of total membrane fouling resistance for other two solutes and has the crucial effect on the total membrane fouling resistance. The sequence of influence degree on the total membrane fouling resistance is the HPAM concentration > oil concentration > suspended solid concentration. Moreover, the membrane cleaning effect was studied by using SEM images and the pure water flux.     

Mathematical Modeling of Flux in Ultrafiltration Membrane for Water Treatment

Abstract

Calculation of water flux in a spiral ultrafiltration element was conducted by the novel proposed method, in which all necessary parameters were determined solely from membrane sheet test. By comparing water flux of the commercial element with the data from membrane sheet measurement, this study found that the tendency of water flux variation with time in the membrane element was similar to that which occurred in the membrane sheet, including the consideration of scale‐up effect due to hydrodynamics influence. Therefore, it is possible to express the variation of water flux in the membrane element based on the results from membrane sheet measurement using a practical water source. Surface water and sea water were separately employed to carry out a pilot test with an 8‐inch spiral membrane element, made of polyvinylidene fluoride(PVDF) with a molecular weight cut‐off of 150 kDa, and water fluxes under various transmembrane pressures. Calculations were approximate agreement with that of the pilot test, which enables us believe that the proposal method is reliable for designing a practical ultrafiltration system.     

典型水处理工艺处理黄浦江原水有机物变化规律初探

该文从分子量转化的角度对水体中有机物在水处理工艺过程中的转化进行了研究.针对特定的水质特征(小分子有机物居多),比较了3种不同的氧化剂(臭氧、氯和高锰酸钾)对有机物分子量(molecular weight,MW)的转化情况.试验证实臭氧氧化可明显减少MW＞30 kDa的有机物含量,进一步通过絮凝沉淀和过滤工艺可使MW＞...     

Tubular Membrane Filtration with A Side Stream and its Intermittent Backwash Operation

The tubular membrane filtration system is widely applied to solid-liquid separation processes. Any improvements to the filtration module would increase separation efficiency, thus reducing operating costs. In this experiment, PMMA powder with an average particle diameter of 0.8 µm was filtered by a ceramic tubular membrane with an average pore size of 0.2 µm, and the impacts of the operating variables, such as suspension concentration, the filtration pressure, and the crossflow velocity on the permeate flux were discussed. In order to understand the increased permeate flux, the proposed module is comparable to the tubular membrane filtration module, but with an additional side stream under the same filtration mass flow rate. In addition, variations of shear force on the membrane surface are analyzed by CFD simulation, and the influence of backwash operations on the permeate flux is discussed. The results show that the side stream membrane filtration increased the shear force on the membrane surface, reduced fouling on the membrane surface, and increased the permeate flux. Furthermore, a backwash operation with a side stream flow channel could effectively clean the particles deposited in the module, thus, increasing the permeate flux.     

常规处理与深度处理工艺对南京长江原水中有机物去除效能比较

以长江南京段原水为研究对象,通过常规处理及深度处理工艺(强化过滤工艺和生物活性炭工艺)对长江南京段水源水中有机物的去除效能进行对比研究。结果表明常规工艺对CODMn、UV254、DOC及BDOC的去除率分别为30%、41%、27%及25%。强化常规工艺和生物活性炭工艺各指标的去除率分别为34%和52%、48%和50%、37%和40%及74%和82%。强化过滤工艺及生物活性炭工艺对1,2,4-三氯苯的去除效果明显,能显著提高出水水质。常规工艺对MW大于5 kDa的有机物去除效果明显,强化过滤工艺对MW小于1 kDa的有机物去除率大于25%,生物活性炭工艺对各个分子量区间的去除效果都比较好,特别是对原水中占多数的MW小于1 kDa的有机物去除率大于30%。     

Filtering surface water with a polyurethane-based hollow fiber membrane: effects of operating pressure on membrane fouling

Membrane fouling seriously restricts applications of membrane technology. A novel strategy was ap-plied in this study to retard membrane fouling by changing operating pressure with the pressure responsibility membrane. A polyurethane-based hollow fiber membrane was used to treat surface water for evaluating the effect of operating pressure on membrane fouling. Some bench-scale tests in dead-end mode were carried out. In the experi-ments without backwashing, as operating pressure increased, severe membrane fouling occurred on membrane sur-face, while the permeate quality was improved obviously, which is considered to be due to shrinkage deformation. The total resistance, irreversible resistance and reversible resistance under different backwash pressures were de-termined in filtration/backwashing test. With the increase of backwash pressure, the total resistance decreased, and more importantly, the irreversible resistance also decreased, which implies that small particles deposited inside membrane pores and cake layers on membrane surface are effectively removed. Similar results could be obtained in mass balance tests. The results of the present study indicate that the application of pressure responsibility membrane in surface water treatment may be an effective strategy for reducing membrane fouling.     

Ultrafiltration of Wastewater from Isolated Soy Protein Production: Fouling Tendencies and Mechanisms

Membrane separation processes appear to be a good alternative in wastewater treatment systems. One of the biggest limitations is the decrease in permeate flux, which is caused mostly by concentration polarization and fouling phenomena. The extent of these phenomena are dependent on the interactions between the different solution compounds, membrane-solution interactions, and the operating conditions. The fouling tendencies of three different commercial tubular ceramic membranes (5, 20, and 50 kDa) during the ultrafiltration of an isolated soy protein (ISP) wastewater were evaluated through determination of the water permeate flux before and after the wastewater ultrafiltration and using Hermia's Model. The wastewater from ISP production is a complex solution characterized by a very high organic load: reaches COD values greater than 18,000 mg · L^?1. The wastewater proteins are small molecules (8 to 50 kDa) that could not be removed during the industrial processing. The recovery of these small proteins and their return to the ISP production process would result in both economical and environmental benefits by increasing the final product yield and reducing significantly the wastewater organic load. All the membranes tested presented a large fouling tendency: 65% (5 kDa membrane), 69% (20 kDa membrane) and 76% (50 kDa membrane). The best fit to Hermia's Model for all of the UF membranes was obtained by the complete blocking model.     

A Silicon Microseparator based Pervaporation Process for Separation of Ethanol/Water Mixtures using a Polymer Membrane

Abstract

The selective removal of water from ethanol through pervaporation was demonstrated in a microchannel device using a commercial membrane. Photolithography and dry etching techniques were employed for fabrication of the microseparator with hydraulic diameters of 30 µm to 80 µm. Experiments conducted at 90°C and 2–3 Torr, with Reynolds Numbers ranging from 8 to 91, resulted in an average water and ethanol permeance of 1.2×10^?3 and 8×10^?5 cm³/cm² · s · cmHg respectively. A mass transfer analysis involving Sherwood correlations was used to calculate the theoretical boundary layer resistance. The comparison of overall mass transfer coefficient with the boundary layer coefficients suggests that the membrane was the dominant resistance for this system.     

上海市供水在线水质仪表的应用及管理

本文介绍了上海市供水黄浦江及长江原水水质 ,水厂出厂水水质及净水厂加矾加氯自动化系统的水质监测仪表的配置应用及管理情况     

高纯水预处理系统中水的回收及利用

结合生产实际,对高纯水预处理系统中砂滤器的反洗水及超滤机组浓排水、反洗水进行回收利用,通过对高纯水系统流程的技术改造,增设了一个Ф8000 mm×6000 mm,容积300 m3的沉淀池;2台 SGB65-50A管道泵及两组型号为 UF1A200;处理量为35 m3/h 超滤系统,可以实现节水30 m3/h,提高公司经济效益,全年实现经济效益近20余万元.     

Water Purification by Membrane Distillation Process

Abstract

The demineralization of water by membrane distillation (MD) has been investigated. In the first stage of investigations the tap water or boiled tap water was employed as a feed, and the water recovery coefficient exceeding 75% was achieved. The obtained concentrate was supplied to the second stage of MD installation. The quality of distillate was stable and practically independent of the feed concentration. The produced distillate has the electrical conductivity in the range of 1.4–2.5 µS/cm. The precipitation of salt deposit on the membrane surface was observed during the water demineralisation, especially in the first stage of MD. The membrane morphology and the composition of precipitate layer were studied using scanning electron microscopy coupled with energy dispersion spectrometry. The formed deposit caused clogging of the membrane surface (pores), and resulted in a gradual decline of the module efficiency. Moreover, the formation of the deposit on the membrane surface was the major reason of the partial membrane wettability.     

Treatment of Oily Waste Water Using Low-Cost Ceramic Membrane: Flux Decline Mechanism and Economic Feasibility

Abstract

This work addresses the applicability of different membrane pore blocking models for the prediction of flux decline mechanisms during dead end microfiltration (MF) of stable oil-in-water (o/w) emulsions using relatively low-cost ceramic membranes. Circular disk type membranes (52.5 mm diameter and 4.5 mm thickness) were prepared by the paste method using locally available low-cost inorganic precursors such as kaolin, quartz, calcium carbonate, sodium carbonate, boric acid, and sodium metasilicate. Characterization of the prepared membrane was done by SEM analysis, porosity determination, and pure water permeation through the membrane. Hydraulic pore diameter, hydraulic permeability, and hydraulic resistance of the membrane was evaluated as 0.7 µm, 1.94 × 10^?6 m³/m²·s·kPa and 5.78 × 10¹¹ m²/m³, respectively. The prepared membrane was used for the treatment of synthetic stable o/w emulsions of 40 and 50 mg/L crude oil concentration in batch mode with varying trans-membrane pressure differentials ranging from 41.37 to 165.47 kPa. The membrane exhibited 96.97% oil rejection efficiency and 21.07 × 10^?6 m³/m²·s permeate flux after 30 min of experimental run at 165.47 kPa trans-membrane pressure for 50 mg/L oil concentration. Different pore blocking, models such as complete pore blocking, standard pore blocking, intermediate pore blocking and cake filtration were used to gain insights into the nature of membrane fouling during permeation. The observed trends for flux decline data convey that the decrease in permeate flux was initially due to intermediate pore blocking (during 1 to 10 minutes of experimental run) followed with cake filtration (during 10 to 30 minutes of experimental run). Based on retail prices of the inorganic precursors, the membrane cost was estimated to be 130 $/m². Finally, preliminary process economic studies for a single stage membrane plant were performed for the application of the prepared membrane in industrial scale treatment of o/w emulsions. A process economics study inferred that the annualized cost of the membrane plant would be 0.098 $/m³ feed for treating 100 m³/day feed with oil concentration of 50 mg/L.     

饮用水安全保障关键技术集成及工程示范

以北江水为原水,通过中试试验分别考察了以强化混凝、两相催化氧化助凝、活性炭吸附、膜分离和紫外消毒为核心的多种饮用水安全保障关键技术。结果表明以强化混凝为核心的工艺在重金属去除方面有优异的表现,两相催化氧化助凝技术在节能减排方面表现突出,超滤膜技术在浊度去除方面有优势,臭氧一生物活性炭工艺对有机物的去除效果较好,紫外消毒技术能有效减少消毒过程中有毒有害副产物的生成。     

膜生物反应器中膜的清洗研究

对膜生物反应器处理柠檬酸酸洗废水中膜的清洗进行了研究，通过不同的清洗方法对膜通量的恢复程度进行评价。确定了反冲洗时间及反冲洗周期，经过试验研究与分析，在反冲洗的同时结合正洗的清洗方法，效果好于单纯的反冲洗方法；确定了化学清洗剂种类、清洗剂的用量以及化学清洗周期。采用物理清洗与化学清洗相结合的方法，清洗效果很好。保证了MBR的稳定运行。     

Water Gas Shift Reaction in a Membrane Reactor Using a High Hydrogen Permselective Silica Membrane

A membrane reactor (MR) for the water gas shift (WGS) reaction was developed by integrating a highly hydrogen permselective silica membrane. The membrane was prepared using an extended counter-diffusion chemical vapor deposition (CVD) method. A tetramethylorthosilicate (TMOS) silica source was fed from one side of the membrane support and oxygen gas fed from the other. The dense silica film was deposited on a porous support by pressurizing the side that TMOS is supplied. A high hydrogen permselective silica membrane was obtained by this method. A commercial Pt catalyst was used in the WGS reaction. Efficacy of the silica membrane toward the WGS reaction was investigated as a function of temperature (523-623 K), steam/carbon monoxide (S/C) ratio (1-3), differential pressure (0-100 kPa), and gas hourly space velocity (GHSV; 1800-5400 h^?1). The CO conversion in the MR was higher than that for a fixed bed reactor (FBR) under all experimental conditions, and was also higher than the thermodynamic equilibrium conversion under almost all experimental conditions. This was due to the selective abstraction of hydrogen from the product stream by the silica membrane. At an S/C of 1.0, the CO conversion in the MR was superior to that in a FBR by 16.8%.     

The Role of Synthetic Membrane Pre-Treatment in Influencing Filtration Performance over Multiple Operational Cycles

Manufacturers of polymeric membrane filters used for treating food streams routinely recommend that they are chemically cleaned prior to first use. In this paper, two pre-treatment methods are compared for the filtration of a spent sulphite liquor [SSL] (17.8 wt.% dry solids) using a 20 kg mol^?1 molar mass cut off (MMCO) fluoropolymer membrane. In an extension of previous work that considered the effect of the application of a pre-treatment protocol over a single operational cycle, this paper reports the effect of pre-treatment protocols over four complete fouling and cleaning cycles. The pre-treatment methods evaluated were the conditioning with water at 60°C only [Protocol 1], and the conditioning with water at 60°C followed by cleaning with 0.5 wt.% NaOH [Protocol 2]. Results are presented that demonstrate that for the system examined, the positive effect of the NaOH pre-treatment protocol diminished after three complete operational cycles, and disappeared after four cycles.     

Influence of Water Compositions and Conditioning on Flux Enhancement in an Immersed Membrane System

Abstract

The objective was to quantify the importance of operational conditions, aeration, and physico‐chemical conditioning on membrane fouling intensity. The suspension filterability was also analysed by using frontal filtration and a cake filtration model. Results pointed out the moderated role of aeration to reduce compound accumulation on the membrane surface. It did not appear as a determining criterion to prevent membrane fouling. In contrast, the physico‐chemical conditioning appeared as a determining criterion to increase critical flux. According to the experimental conditions 200 l/m²/h/bar membrane permeability could be maintained transmembrane pressure (TMP) when filtering stored rainwater. This permeability value was 2–3 times higher than the values obtained without conditioning. Moreover, according to the low turbidity of such stored rainwater and because of the high selectivity of the membrane, the coagulation step, a very low amount of 10 mg/l FeCl₃, was sufficient to intensify the filtration step. This conditioning interest appeared less significant when filtering salted water in immersed membrane systems, but a 20 mg/l FeCl₃ addition appeared sufficient to double the value of critical flux. Nevertheless filtration in frontal mode pointed out the significant impact of physico‐chemical conditioning in reducing the cake deposit hydraulic resistance.     

Comparative Studies on Coagulation and Adsorption as a Pretreatment Method for the Performance Improvement of Submerged MF Membrane for Secondary Domestic Wastewater Treatment

Abstract

Membrane fouling is the main limitation of water and wastewater treatment. Coagulation and adsorption can remove organic materials which play an important role in fouling phenomena. Thus, this study focused on the comparison of the hybrid process of coagulation and adsorption coupled with microfiltration (MF) membrane for the secondary domestic wastewater from an apartment complex in Gwangju city, South Korea. Coagulation and adsorption were adopted as a pretreatment method prior to MF treatment. Three different powdered activated carbon (PAC) and ferric chloride were used as an adsorbent and as a coagulant. MF was operated in a submerged mode using hollow fiber polyethylene membrane with pore size of 0.4 µm for the separation of suspended organic solids resulted from coagulation or PAC particles, which are used for adsorbing organics dissolved in wastewater. Prior to study on the hybrid system, the performance of coagulation and adsorption processes were optimized individually for the removal of organics. Then, the overall performance for the hybrid system of coagulation/MF and PAC/MF was evaluated based on TOC removal, turbidity removal, and flux decline. It was found that the combined coagulation/MF and PAC/MF showed similar performance for TOC removal while coagulation/MF resulted in a significant decrease of the flux decline.