COD Removal from Concentrated Wastewater Using Membranes

Membranes can be used for wastewater treatment. The selection of the appropriate membrane depends on a number of factors, such as waste characteristics, nature of materials present in the wastewater, concentration, temperature, pH, etc. If the wastewater contains low molecular weight organics, reverse osmosis (RO) is the best treatment process. RO membranes allow solvent (water) to pass and prevent the transport of organics, either completely or partially. In this study, raw wastewater from an alcohol manufacturing plant was treated using a RO process. The chemical oxygen demand (COD) of the wastewater was between 35000-40000 mg/l due to the presence of organic components. Eight polymeric membranes (e.g. FT30, PVD, DSII, DS, BW30, 37100, 3750 and NF45) were used in total. None of the membranes were able to reduce COD to a desirable level (i.e. less than 200 mg/l) in one step. However a two-step process could be designed for wastewater treatment. Based on data obtained for flux and rejection, the NF45 nanofiltration membrane exhibited the best performance. A high volume of fluid can pass through the NF45 membrane because of its high porosity. The flux of this membrane (i.e. 15 kg/m².h) was higher than the reverse osmosis membranes tested. The NF45 membrane decreased COD to a greater extent than the other membranes tested (52%). While the PVD membrane showed better efficiency compared to the other reverse osmosis membranes, probably because of its material of construction and configuration.     

Purification and Concentration of Caustic Mercerization Wastewater by Membrane Processes and Evaporation for Reuse

A membrane-based treatment strategy was developed for purifying the highly alkaline textile mercerization wastewater. 0.2-μm MF and 100 kDa UF membranes were evaluated as pretreatment alternatives before 10 kDa UF and 200 Da NF membranes. Turbidity was almost totally removed by both pretreatment options, while UF (100 kDa) showed higher COD retention than MF. In total recycle mode of filtration, fouling of both UF and MF membranes were 80% reversible by physical and almost totally reversible (≥ 97%) by chemical cleaning. In the second stage filtrations applied to the pretreated wastewater samples, NF could yield high (97-98%) COD retentions and low permeate COD concentrations (≤ 22 mg/L), while 10 kDa UF could only reduce the COD concentration to 150 mg/L. While no NaOH was lost in the MF+UF process, the use of NF as second stage resulted in 12-17% NaOH retention. The permeate flux in all second stage processes were stable, implying that the majority of the feed components that would cause fouling had been removed in the pretreatment stages. Permeate of the MF+NF sequence was concentrated by evaporation with no foaming problems, showing that the hybrid process can be applied to recycle a purified and concentrated caustic stream to the mercerization process.     

纳滤膜在治理农药废水污染中的应用研究

选用DK型、NF90型纳滤膜治理农药废水污染,并对其适用性与应用效果进行了研究.考察了两种膜对不同料液浓度废水的治理效果与处理效率,得到纳滤膜对COD、TP、NH<,3>-N、电导率的去除规律及其适用范围.试验结果表明,将DK型与NF90型纳滤膜组合可发挥不同膜的应用优势、提高处理效率,适用于治理高浓度、高盐分的吡虫啉农药废水污染.     

Impact of Solute Properties and Water Matrix on Nanofiltration of Pesticides

The application of different nanofiltration membranes for the separation of pesticides, i.e., atrazine and dimethoate, from aqueous solutions is described. The nanoflitration membranes DK, NF270, NF200, and NF90 were tested for the pesticide retention performance in a stirred dead‐end filtration system. NF90 demonstrated the best pesticide retention with over 95 % for atrazine and approximately 80 % for dimethoate. All membranes consistently showed better retention of atrazine than of dimethoate. Dissolving the pesticides in river or tap water amplified the overall pesticide retention performance, indicating that filtration in water treatment plants could render superior pesticide retention. However, a lower flux was obtained for the filtration of tap and river water.     

Effectiveness in the Removal of Organic Compounds from Municipal Landfill Leachate in Integrated Membrane Systems: Coagulation – NF/RO

The article presents the results of studies concerning the hydraulic permeability of integrated membrane systems during the treatment of municipal landfill leachate. The laboratory-scale experiments were conducted to determine the effectiveness of coagulation as a pretreatment option for treating stabilized landfill leachate and effectiveness of nanofiltration (NF) and reverse osmosis (RO) processes. The municipal landfill leachates were analyzed for the concentration of the following: polycyclic aromatic hydrocarbons (PAHs), nitrate nitrogen, ammonium nitrogen, chemical oxygen demand (COD), total organic carbon (TOC), total carbon (TC), suspended soils (SS), turbidity, pH. The commercially available coagulant – aluminum sulfate Al₂(SO₄)₃·18H₂O (alum) was used as a coagulant. The NF process was carried out at the transmembrane pressure of 1.5 MPa. The membrane separation process was based on a thin film membrane (DK). The transmembrane pressure of the RO stood at 2 MPa and for this process one polyamide membrane (AG) was used. The level of leachate treatment was defined for raw and cleaned wastewater indicators. Both NF and RO membranes allowed obtaining the high level of pollutants removal. In the coagulation–NF system, the removal efficiency was equal to 77% for PAHs, 88% for COD, 72% for ammonium nitrogen, 80% for nitrate nitrogen, 67% for TOC, 80% for TC, 96% for SS and during the RO – 86% for PAHs, 98% for COD, 93% for ammonium nitrogen, 87% for nitrate nitrogen, 89% for TOC, 100% for TC, 98% for SS. The calculations based on the assumptions of the mathematical filtration model (relaxation) made it possible to predict the efficiency of commercial filtration membranes used for leachate treatment.     

Nanofiltration of single and mixed salt solutions: Analysis of results using principal component analysis (PCA)

The retention of single (NaCl) and mixed (Na₂SO₄ + NaCl) salt solutions by nanofiltration membranes was analysed using principal component analysis (PCA). Seven variables—five different membranes (Desal-5DK, NF 270, NF Filmtec, NF 20 and ESNA-1-LF), flux and salt concentration—were taken into account in the analysis. The dependences of NaCl retention on these variables for single and mixed solutions were evaluated by PCA.Differences and similarities between the obtained results and those from a previous study based on a univariate method were observed. The PCA results from single and mixed salt solution experiments indicated that the NF 20 membrane differs from the others; a finding that is in accordance with earlier observations. The difference could be explained by the fact that the NF 20 membrane was not charged at the filtration pH (6) and by its bigger pore size.For single salt solutions, the results for the NF Filmtec and NF 270 membranes (manufactured by Filmtec) resembled each other when using the PCA method; a finding which could not be shown using a univariate method. These membranes did not resemble each other when filtering mixed salt solutions.Analysis of the results when using the PCA method for the single and mixed salt solutions indicated that the retention of the ESNA-1-LF membrane behaved differently from all the other tested membranes. While a negative retention for NaCl in a mixed solution was observed with the other membranes, the ESNA membrane showed a positive retention which was close to the retention of a reverse osmosis membrane (above 80%).The results showed that both salt concentration and permeate flux had major effects on the salt retentions of the NF 20, NF Filmtec, NF 270 and Desal-5DK membranes.     

纳滤/反渗透膜处理重金属废水的性能

The performance of different nanofiltration （NF） and reverse osmosis （RO） membranes was studied in treating the toxic metal effluent from metallurgical industry. The characteristics and filtration behavior of the processes including the wastewater flux, salt rejection and ion rejection versus operating pressure were evaluated. Then the wastewater flux of RO membrane was compared with theoretical calculation using mass transfer models, and good consistency was observed. It was found that a high rejection rate more than 95% of metal ions and a low Chemical Oxygen Demand （COD） value of 10 mg·L^-1 in permeate could be achieved using the RO composite membrane, while the NF rejection of the salt could be up to 78.9% and the COD value in the permeate was 35 mg·L^-1. The results showed that the product water by both NF and RO desalination satisfied the State Reutilization Qualification, but NF would be more suitable for large-scale industrial practice, which offered significantly higher permeate flux at low operating pressure.     

An advanced treatment of high-strength opium alkaloid processing industry wastewaters with membrane technology: pretreatment, fouling and retention characteristics of membranes

This paper presents the results of the laboratory and pilot-scale membrane experiments of opium alkaloid processing industry effluents. Different types of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes were evaluated for membrane fouling, permeate flux and their suitability in separating COD, color and conductivity. Experiments demonstrated that membrane treatment is a very promising advanced treatment option for pollution control for opium alkaloid processing industry effluents. Almost complete color removal was achieved with NF and RO membranes. COD and conductivity removals were also greater than 95% and met the current local standards. Nevertheless, pretreatment was an important factor for the NF and RO membrane applications. Membrane fouling occurred with direct NF membrane applications without UF pretreatment. The total estimated cost of the UF and NF treatment system was calculated as $0.96/m³, excluding the concentrate disposal cost.     

Influence of filtration conditions on the performance of nanofiltration and reverse osmosis membranes in dairy wastewater treatment

Filtration performance and fouling of nanofiltration (NF) and reverse osmosis (RO) membranes in the treatment of dairy industry wastewater were investigated. Two series of experiments were performed. The first one involved a NF membrane (TFC-S) for treating the chemical-biological treatment plant effluents. The second one used a RO membrane (TFC-HR) for treating the original effluents from the dairy industry. The permeate flux was higher at higher transmembrane pressures and higher feed flowrates. The curves of permeate flux exhibited a slower increase while the feed flowrate decreased and the pressure increased. Membrane fouling resulted in permeate flux decline with increasing the feed COD concentration. Furthermore, the flux decline due to the COD increase was found higher at higher pressures for both NF and RO membranes.     

The influence of degreasing agents used at car washes on the performance of ultrafiltration membranes

The influence of washing chemicals used at car washes on the flux and retention of three ultrafiltration (UF) membranes has been studied. Eleven commercial degreasing agents, two shampoo agents and a wax were included in the investigation. The membrane performance when treating waste water collected at a car wash at different times of the year was also studied. The retention of the different chemicals varied greatly, but there was no significant difference in COD retention among the three UF membranes. The highest flux was observed when treating the alkaline degreasing agents and the shampoo solutions. The flux and COD retention when treating the waste water from the car wash were 30–50 l/m ² h and 60%, respectively. One of the low-retention degreasing agents was treated by nanofiltration (NF). The retention was significantly higher when using NF, but the COD concentration in the permeate was still too high to allow the permeate to be discharged without further treatment.     

Treatments of stainless steel wastewater containing a high concentration of nitrate using reverse osmosis and nanomembranes

A nanomembrane (NTR 729HF) and three different types of reverse osmosis (RO) membranes (CPA2, LFC1, and ESPA1) were tested for the treatment of high concentration of nitrate wastewater from stainless steel industry. All the tested RO membranes showed higher rejection rates (90–99% at 1000–60 mg/L of NO₃⁻ -N) than the NF membrane. The rejection rate and flux of RO membranes were not highly affected by pH variation and Ca²⁺ as co-existing ion. However, the rejection rate of NF, which was 67% at 60 mg/L of feed concentration, was decreased as pH decreased and Ca²⁺ concentration increased indicating that charge repulsion is one of the major rejection mechanisms. As nitrate concentration increased from 20 to 1000 mg/L in feed water, the removal rate decreased from 67 to 20% in NF membrane. The flux of RO was relatively high and ESPA1 (a low-pressure RO type) showed more than two times higher flux compared to the NF. ESPA1 was successfully tested for a longterm experiment with real stainless steel wastewater for 30 days of experimental period. Current study implicates that RO membranes could be an alternative for the treatment of stainless steel wastewater.     

Stainless steel membrane UF coupled with NF process for the recovery of sodium hydroxide from alkaline wastewater in chitin processing

The recovery of sodium hydroxide from alkali wastewater in chitin processing was investigated using stainless steel ultrafiltration membrane (SSM) and HDS-04 nanofiltration (NF) membranes with membrane area of 0.35 m² and 1.4 m², respectively. Flux behaviors were observed with respect to filtration time, volumetric concentration ratio (VCR), operating pressure, temperature, and cleaning. As the VCR increased, the permeate flux declined while almost the same concentration of NaOH was permeable. The SSM and NF operations end with a concentrated protein solution that needed a small amount of waste acid for neutralization and easy spray drying and the permeate of the NaOH solution can be reused. Concentrations of NaOH that govern reusability of permeate were measured to be independent on VCR. The most suitable VCRs for SSM and NF in terms of maintaining relatively good membrane productivity and high rejection of protein and chemical oxygen demand (COD) were approximately 50. At a VCR of 50, the total rejections of protein, COD and suspended solid (SS) were 82.5%, 94% and 100%, respectively, while total NaOH recovery was 96% with SSM average flux 270 LMH and NF average flux 25 LMH. SSM filtration was essential for the pretreatment of the alkali wastewater before it was fed into the NF system.     

纳滤工艺深度处理焦化废水的中试研究

以焦化废水为研究对象,考察了取消超滤预处理系统后,纳滤处理系统对该类废水污染物的处理效果。结果表明:纳滤工艺可直接应用于焦化废水的深度处理,COD去除率稳定在70%以上,出水COD维持在45mg/L以下;对氨氮的去除率可达50%以上;对总硬度的脱除率达96%以上,出水硬度维持在3.5 mg/L左右,各项水质均优于循环冷却水要求。虽然单独纳滤工艺稳定运行周期相对双膜工艺较短,但两种工艺的污染差异可通过化学清洗加以消除。     

纳滤—电渗析处理纤维染色废水反渗透浓水研究

针对反渗透处理纤维染色废水过程中产生的高COD、高色度和高盐含量浓水,研究采用纳滤-电渗析集成技术对其进行脱色、一二价盐分离和盐浓缩中试。结果表明,纳滤膜NF5和NF4分别用于废水脱色和分盐,经过2级纳滤处理后废水色度降低至原水的1/1200,COD从原水的200 mg/L降低至小于100 mg/L,Cl^-和SO4^2-离子的质量浓度比从原水的3:2提高到21:1。电渗析可将纳滤膜NF4透过液中的总溶解盐浓缩至质量分数10%以上。盐浓缩液可重新用于染色,染色效果良好。表明该集成技术在纤维染色废水的深度处理上具备良好的工业化应用前景。     

兼氧水解-加压接触氧化塔处理含盐吡虫啉废水

对兼氧水解-加压接触生物氧化塔处理高含盐吡虫啉废水进行了试验研究。主要考察了兼氧水力停留时间、氧化塔压力、氧化塔容积负荷、农药废水含盐质量分数对系统运行效果的影响。结果表明:吡虫啉废水经水解预处理后,其COD从5 000 mg/L降至3 500 mg/L左右,可生化性明显提高,BOD5/COD由0.20升高到0.351;加压接触氧化塔在压力p为0.2—0.3 MPa,体积负荷Nv<18.2 kg/(m3.d)时,其COD去除率可达70%以上,其极限含盐质量分数可达2.8%;该组合工艺具有处理效果好、处理时间短、占地少、适用性强、耐盐性能好的特点,适用于处理高盐工业废水。     

Preparation and characterization of nanofiltration membranes fabricated from poly(amidesulfonamide), and their application in water–oil separation

Nanofiltration membranes prepared from selected types of poly(amidesulfonamide) (PASA) targeted to retain either sucrose, raffinose, or β‐cyclodextrin were fabricated in conditions deduced from a chemometric method. Membrane performance was characterized by the permeation of solutions containing 1000 ppm carbohydrates and metal ions. To demonstrate the dependence of the membrane properties on the polymer structure, the separation characteristics of a series of four PASA homopolymers and four PASA copolymers were established. The results allowed us to screen out several promising PASA materials for the NF separation process. In addition, the superiority of the PASA materials, characterized by excellent retention and high flux rate, was evident from the results of a study comparing it with polysulfonamide, poly(ether amide), and commercially available regenerated cellulose. As a means of pollution control, the PASA NF membranes have been proven to be effective in removing oil from oily wastewater. Under an operating pressure of 2–3 psi, a constant flux of 5 L m^?2 h^?1 and 99.6% retention of a solution of 5000 ppm olive oil could be achieved with the PASA membranes over a period of 430 h. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1803–1810, 2003     

UF,NF处理酵母废水可行性研究

采用ＵＦ或ＮＦ技术可以处理酵母生产中不同阶段高浓度有机物的废水，废水经ＵＦ膜处理可１００％回收酵母蛋白等成份，对色度浊度具有〉９０％的去除率，从浓缩液中回收的酵母蛋白等成份，经进一步浓缩干燥可作动物饲料添加剂，干燥物蛋白质含量〉３０％，膜透过液含有发酵过程所需的营养成分，可重新用于发酵生产用水。废水用ＮＦ膜处理对ＣＯＤ去除率〉９０％并接近或达到排放标准，对于直接从发酵液中经高速离心分离的酵母废水（     

Electrodialysis in an Integrated NF/ED Process for Water Recovery in the Leather Industry

Electrodialysis (ED) was assessed for integration in a nanofiltration NF/ED sequence for water reuse in the leather industry. Two ED feeds composed of different model solutions were used: Model Solution FED1, which is a surrogate of a nanofiltration permeate generated by the NF processing of a biologically treated leather effluent, and Model Solution FED2, which has the same salt concentration as FED1 but with an organic matter content that is approximately ten times higher. The electrodialysis experiments were carried out in a five-compartment bench cell using cationic and anionic membranes HDX 100 and HDX 200. The final product water, with a conductivity ranging from 3.28 to 3.67 mS cm^?1, can be reused as process water for beamhouse operations. With respect to chloride and COD parameters, the ED product water meets the requirements of process water, even for dyeing operations. An alkaline membrane cleaning process for fouling removal was also tested for the membranes using Model Solution FED2. The cleaned membranes were evaluated in terms of visual aspect, polarization curves, TGA, and SEM/EDS analysis. The results obtained with the cleaned membranes were very similar to those obtained with the new ones in ED experiments with Model Solution FED2.     

纳滤膜过滤多组分离子电解质溶液的模型与计算——Ⅱ模拟计算

以扩展的Nernst-Planck方程在膜微孔内浓度梯度微分方程和解膜微孔内浓度梯度微分方程的有关参数和方程为基础,研究了聚酰胺纳滤膜DK2540过滤多组分电解质溶液的分离特性。结果显示,在多组分电解质溶液中,Donnan电位和溶剂化能决定了纳滤模型中的传递方程和分离系数;多离子组分(至少9种离子)的矿山酸性废水的纳滤过程描述有许多不足之处,还应进一步改进。     

Removal of heavy metals from wastewater by membrane processes: a comparative study

Wastewater containing copper and cadmium can be produced by several industries. The application of both reverse osmosis (RO) and nanofiltration (NF) technologies for the treatment of wastewater containing copper and cadmium ions to reduce fresh water consumption and environmental degradation was investigated. Synthetic wastewater samples containing Cu²⁺ and Cd²⁺ ions at various concentrations were prepared and subjected to treatment by RO and NF in the laboratory. The results showed that high removal efficiency of the heavy metals could be achieved by RO process (98% and 99% for copper and cadmium, respectively). NF, however, was capable of removing more than 90% of the copper ions existing in the feed water. The effectiveness of RO and NF membranes in treating wastewater containing more than one heavy metal was also investigated. The results showed that the RO membrane was capable of treating wastewater with an initial concentration of 500 ppm and reducing the ion concentration to about 3 ppm (99.4% removal), while the average removal efficiency of NF was 97%. The low level of the heavy metals concentration in the permeate implies that water with good quality could be reclaimed for further reuse.