Study on backwash wastewater from rapid sand-filter by monolith ceramic membrane

To verify the feasibility of membrane micro-filtration process to treat the sand-filter backwash wastewater and the sediment sludge withdrawn from the coagulation-flocculation-settling tank, a multi-lumen monolith ceramic membrane module was applied in a test pilot plant. The ceramic membrane filtration was operated very stably at the filtration flux of 4 m/day when the sand-filter backwash wastewater was fed. The membrane filtration was also operated very stably at the flux of 2 m/day when the mixture of the sand-filter backwash wastewater and the sediment sludge was fed. The level of these substances in the membrane filtrate was very low and met drinking water standards.     

Adsorption of Organic Solutes on Membrane Filters during Aqueous Phase Filtration. I. Basic Rate and Equilibrium Studies Using Toluidine Blue

Abstract

Membrane filters are made from a wide variety of polymeric materials, in a wide range of pore sizes, and are used in large numbers (several hundred million per year) to filter particulates from many types of solutions. However, during filtration, organic solutes are adsorbed by these membranes, often quite extensively. Thus, the composition of the filtrate can be very different from that of the original solution. A systematic study has been initiated to quantify and explain the adsorption of organic solutes during membrane filtration as affected by membrane type (material, pore size, presence/absence of wetting agents), solute type, pH, ionic strength, and filtration flow rate. Our first studies have employed a dye (toluidine blue) as the dissolved organic solute, and 11 membrane filters made of mixed cellulose esters, polyvinylidene difluoride, polytetrafluoroethylene, and polycarbonate. The results of these studies, which are both equilibrium and kinetic in nature, are presented. These results indicate how adsorption effects may be minimized.     

Critical risk points of nanofiltration and reverse osmosis processes in water recycling applications

NF/RO membrane filtration processes have been recognized as an important technology to facilitate water recycling. Those processes are well-proven technologies, which can be used to remove a wide range of contaminants including trace contaminants that are of particular concern in water recycling. However, risk implications in association with brine or concentrate and membrane cleaning wastewater disposal have to date not been adequately understood. This study examines the adsorption and release process of several endocrine-disrupting chemicals (EDCs) during NF/RO filtration processes. Results reported here indicate that the membrane can serve as a large reservoir for EDCs and their release may be possible during membrane cleaning or erratic pH variation during operation. Treatment of membrane cleaning solution should be carefully considered when EDCs are amongst the target contaminants in NF/RO membrane filtration.     

Preparation and filtration testing of diatomite filtering layer by acid leaching

Ceramic membrane filter consisting of the filtration layer obtained from natural diatomite particles (finer than 50 μm) by coating onto a large porosity support made of quartz-based materials was fabricated. The coating was achieved by pressure filtration at 5 bar and later sintering applied at 600 °C. The sintered product was leached by the hot acid solution (5 M HCl; 75 °C) for 1 h. The characteristic skeletal structure of diatomite (fine microscopic pores) could be obtained without deforming the structural integrity of coating. Filtration response of the filter was tested in dead-end and periodic pressure filtration modes. The filtered particles were of calcite (finer than 1.5 μm) obtained from a marble factory wastewater stream. The diatomite leaching increased the filtration capacity of the filter media more than two times. The filtrate has high clarity (0.1 NTU turbidity). The coating maintained structural stability during a filtration process performed at 5 bar and backflushing of 4 bar.     

Development of a biofilm-MBR for shipboard wastewater treatment: The effect of process configuration

The direct discharge of wastewater from ships is prohibited by the International Maritime Organization, especially discharge of oily bilge water. This study aims to develop a compact onboard integrated wastewater treatment system for all the wastewater streams on ships, including grey water, black water and bilge water, using biofilm-MBR technology. Both dead-end side-stream and recycle side-stream configurations of a biofilm-MBR concept have been investigated. Flat sheet ceramic membranes from KeraNor AS were applied in the membrane filtration unit. A good membrane permeate quality was achieved in each process configuration, with oil concentrations < 5 mg/L. However, the membrane was seriously fouled when the dead-end side-stream configuration was operated with a high filtration unit recovery (93%). A significantly improved membrane performance, and better permeate quality, was achieved by recycling the concentrate solution back to the biofilm reactor due to better bio-flocculation and biodegradation of oil compounds in the process. The effect of process configuration was investigated by comparing oil concentration, SMP, TSS, FCOD, TCOD, PSD of the concentrate solutions around the membrane in filtration unit. The membrane fouling rate was found to be directly related to oil concentration and oily biomass characteristics in the membrane filtration unit.     

Preparation and performance of three‐layered structure composite membrane for heavy metal ions and hazardous dyes rejection

A three‐layered structure composite membrane was successfully fabricated by electrospinning cellulose acetate (CA)/poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) fibrous layers and coating the chitosan (CS) solution on the CA/PHBV substrate as a barrier layer. For obtaining the proper mechanical property and high filtration performance, different content of glycerol was investigated to mix in CS coating solution. The ovalbumin tests showed that this triple‐structure type of filtration media exhibited a high flux rate (up to 730 L/m² h at the feed pressure of 0.15 MPa) and an excellent rejection rate (98%). The permeation flux of the membrane was significantly higher than other reported electrospun fiber membranes with similar rejection ratios. The CA/PHBV‐CS composite membrane was also used to remove disperse dye and metal ion for water purification. These prepared membranes exhibited efficient adsorption separation performance toward disperse yellow dye with the maximum adsorption capacity reaching up to 188.52 mg/g. The equilibrium absorption capacities of the three tested ions (Cu(II), Pb(II), and Cr(III)) were 46.26, 88.31, and 190.14 mg/g, respectively. Consequently, these membranes can be promising materials in wastewater treatment. © 2018 Society of Plastics Engineers POLYM. ENG. SCI., 59:E322–E329, 2019. © 2018 Society of Plastics Engineers     

Investigation of two ultrafiltration membranes for treatment of olive oil mill wastewater

In this study, a promising treatment method is given for the olive oil mill wastewater (OMWW). Although the same steps of this method have been used in different studies before, flow scheme is novel. The membrane filtration of pretreated OMWW was investigated by using two ultrafiltration membranes in this study. Pretreatment steps were pH adjustment (pH = 2) and cartridge filter filtration, and pH adjustment (pH = 6) and cartridge filter filtration. Each step of cartridge filter filtration was batch process and effluent from the filter was recycled back to OMWW tank. Pretreated OMWW was sent to feed vessel of experimental set-up. Recovery of olive oil in the OMWW was realized collecting it from the top of pretreated OMWW. Ultrafiltration membranes used were JW and MW membranes supplied by Osmonics. The effects of main operating parameters (transmembrane pressure, feed flow rate, pH and membrane type) on the permeate flux and membrane fouling were examined. The effectiveness of the different membranes and operating conditions was evaluated using retention coefficients calculated from COD and TOC of experimental studies. The highest permeate flux (25.9 l/m² h) was obtained using MW membrane under operational conditions of Qf = 200 l/h flow rate and TMP = 4 bar, while the highest removals were obtained at Qf = 100 l/h flow rate and TMP = 1 bar. COD, TOC, SS, oil and grease concentrations of MW membrane effluent were 6400 mg/l, 2592 mg/l, 320 mg/l, and 270 mg/l, respectively.     

Evaluation of coagulation and PAC adsorption pretreatments on membrane filtration for a surface water in Korea: A pilot study

Application of membrane filtration has been significantly expanded throughout the world in two decades. A project was launched to facilitate the application of membrane filtration in drinking water plants in Korea in 2004. Five pilot plants each with a capacity of 500 m³/d were installed in a Gueui Drinking Water Plant. The Han River water was a main raw water source for the plants. Key parameters of the raw water were examined. The raw water characteristics are tremendously varied with seasons and rain fall, especially in terms of turbidity and algae numbers. The operation of pretreatment was of substantial importance due to the variation of the raw water. Coagulation and powdered activated carbon adsorption were performed as pretreatment options of microfiltration. The coagulant doses were optimized with increasing turbidity compared to the conventionally used operational manual. PAC adsorption was applied to overcome fouling by high algae numbers. The addition of PAC relieved the aggravation of fouling. However, the PAC addition could not stop the undergoing fouling. A set of laboratory experiments showed that the removal of floc aggregates after coagulation and PAC was critical to maintain high water flux in the membrane system.     

全氟或多氟烷基物质水处理技术研究进展

自然界废水和饮用水中发现了大量的全氟烷基和多氟烷基物质（PFASs）,因此全氟或多氟烷基物质已成为有机污染物类的全球问题。常规的水处理技术包括混凝、絮凝、过滤、沉淀与生物处理过程都不能完全地去除PFASs。而特定的先进处理技术包括吸附、膜处理与光催化可以有效地去除PFASs,故需要了解深度处理过程中各种PFASs的去除机制,各种PFASs的不同物理化学特性使研究化合物在水溶液中迁移较为困难。在现有研究中关于水质条件对去除PFASs的影响的信息很少,本文全面总结了在不同水质条件下（如pH、温度、溶液中离子、天然有机物和溶质浓度）对去除PFASs的影响,以及先进水处理技术如吸附、膜处理和光催化技术的最新知识。     

A core-shell amidoxime electrospun nanofiber affinity membrane for rapid recovery Au (III) from water

An affinity membrane was prepared by coaxial electrospinning and amidoxime (AONFA), and it was applied to selectively recovery Au (III) from an aqueous solution. The static adsorption results showed that, when pH at 5, the maximum adsorption capacity of AONFA membrane for Au (III) was 509.3 mg·g^-1. AONFA membrane exhibit much higher affinity and selectivity towards Au (III) than other metal cations. The membrane could be regenerated effectively by mixture solution of thiourea and HCl, and the desorption ratio reached almost 100% after 4 hours desorption. The dead-end filtration results showed that, the membrane utilization efficiency and adsorption capacity can be improved by increasing the flow rate, while increasing the concentration shorted the breakthrough process and had little impact to adsorption capacity. We can flexibly adjust the flow rate and concentration according to the situation to obtain the maximum utilization efficiency of the membrane in filtration process. The dynamic adsorption capacity is higher than the static adsorption capacity. The adsorption mechanism for Au (III) is electrostatic adsorption and reduction. Thus, AONFA membrane filtration was demonstrated to be a promising method for continuous recover Au (III) from wastewater.     

Characteristics and potential applications of a novel forward osmosis hollow fiber membrane

There has been a resurgence of interest in forward osmosis (FO) as a potential means of desalination, dewatering and in pressure retarded osmosis, which Sidney Loeb was advocating over 3 decades ago. This paper describes the characteristics and potential applications of a newly developed FO hollow fiber membrane, which was fabricated by interfacial polymerization on the inner surface of a polyethersulfone (PES) hollow fiber. This FO membrane presents excellent intrinsic separation properties, with a water flux of 42.6 L/m² h using 0.5 M NaCl as the draw solution and DI water as the feed with the active layer facing the draw solution orientation at 23 °C. The corresponding ratio of salt flux to water flux was only 0.094 g/L, which is superior to all other FO membranes reported in the open literature. To evaluate different application scenarios, various NaCl solutions (500 ppm (8.6 mM), 1 wt.% (0.17 M) and 3.5 wt.% (0.59 M)) were used as the feed water to test the performance of the FO membrane. The membrane can achieve a water flux of 12.4 L/m² h with 3.5 wt.% NaCl solution as the feed and 2 M NaCl as the draw solution, suggesting it has good potential for seawater desalination.     

高效空气过滤用PTFE膜材料的结构和性能

聚四氟乙烯(PTFE)膜高效空气过滤材料以其过滤效率高、初始阻力小和无硼释放等优点,在电子工业洁净室中得到了广泛的应用,然而目前尚缺乏PTFE膜与传统滤材结构及性能的系统对比研究。本文选取了两种商业应用的PTFE膜高效滤材,采用扫描电子显微镜、孔径分析仪、自动滤材测试仪等多种表征手段对材料的微观结构和过滤性能与超细玻璃纤维(简称玻纤)滤材进行了较为全面的对比研究,结果表明,PTFE膜本质上也是一种纤维类滤材,其纤维平均直径为60～85nm,远低于玻纤滤材的668.8nm;高效PTFE膜的过滤效率与玻纤滤材相当,且其初始阻力不及玻纤滤材的50%,但PTFE膜滤材的容尘性能不及玻纤滤材,更适合应用于有再生或预过滤装置的场所。     

Continuous and efficient removal of THMs from river water using MF membrane combined with high dose of PAC

A combination of microfiltration (MF) membrane with a high concentration (40 g/L of the reactor) of powdered activated carbon (PAC) efficiently and continuously removed trihalomethanes (THMs) and total organic carbon (TOC) from river water for a period of two months. Without PAC, the membrane reactor was able to remove less than 18% of THMs and less than 5% of TOC; with PAC, 65 to 95% of THMs and TOC were removed. Even though the THMs concentration in the influent was steadily increasing (reaching 50 μg/L), THMs concentration in the effluents from the reactors with PAC were consistently below 15 μg/L. While the MF membranes alone could not remove organics, PAC and microbial activity in the biofilm deposited on the PAC particles assured long term and continuous removal of THMs. No additional PAC was added into or removed from the reactors during the filtration period. Operational parameters such as the backwashing of the membrane, interval of the filtration cycle and biological pretreatment of the river water had a small effect on the extent of THMs removal, but they increased the filtration time prior to membrane cleaning and improved the overall performance of the reactors.     

Short-term fouling propensity and flux behavior in an osmotic membrane bioreactor for wastewater treatment

The short-term fouling behavior of forward osmosis (FO) membrane in an osmotic membrane bioreactor (OMBR) was investigated, using NaCl or MgCl₂ as the draw solutions. The effect of membrane orientation, mixed liquor suspended solids (MLSS) concentration and draw solution (DS) osmotic pressure on water flux and membrane fouling behaviors was examined, along with the effects of simulated elevated salinity on sludge properties and on membrane fouling. Water flux and membrane fouling were not significantly affected by both MLSS concentration (4.91–12.60 g/L) and osmotic pressure (3.0–15.0 MPa), but were severely affected by elevated salinity, due to changes in activated sludge properties, in particular the increase in extracellular polymeric substances (EPS) and sludge hydrophobicity. MgCl₂ as the DS showed more significant influence on activated sludge properties and membrane fouling than NaCl but gave rise to lower salt accumulation. Analyses of the membrane foulants showed that small sludge floc/particles and EPS (in particular, proteins) were enriched in the fouling layer. UPLC–MS/MS analyses of the proteins showed that hydrophobic proteins were the main cause of membrane fouling.     

Removal of virus from water by filtration using microporous membranes made of poly(N-benzyl-4-vinylpyridinium chloride)

Two types of microporous filter materials were developed for removing virus from water by using poly(N-benzyl-4-vinylpyridinium chloride) that captures virus in water. Conventional ultrafiltration using one to three sheets of 145-μm-thick cellulose nitrate membrane with a pore size of 0.45 μm and coated with 1.7 mg/g of poly(N-benzyl-4-vinylpyridinium chloride-co-styrene) showed 99.4–99.998% removal (2.2–4.7 log₁₀-unit reduction in concentration) of bacteriophage T4, whereas the control experiments using noncoated membrane showed 91–96% removal (1.0–1.4 log₁₀-unit reduction in concentration) of the virus. A composite 360-μm-thick microporous membrane with a pore size of 20 ¨︁m was prepared that consisted of connected minute beads of 1.7 ¨︁m in diameter made of crosslinked poly(N-benzyl-4-vinylpyridinium chloride) and reinforced by a nonwoven cloth. Simple filtration using one sheet of the composite membrane at 34.2cm/h showed 99.96–99.9995% removal (3.4–5.3 log₁₀-unit reduction in concentration). The virus was not detected in the filtrate when two sheets of the composite membrane were used. © 1996 John Wiley & Sons, Inc.     

γ‐Radiation‐treated starch/poly(vinyl alcohol) composites for cotton fabric sizing

Films of different composites based essentially on maize starch (MS)/poly(vinyl alcohol) (PVA) blends were prepared by the solution‐casting technique and subjected to various doses (20–100 kGy) of γ‐radiation. The MS/PVA blends were modified by the addition of glycerol (GY) and a graft copolymer (GP) of MS with acrylamide separately or together with the polymer blend solutions before casting. The γ‐treated composites were evaluated in terms of the apparent viscosity and their suitability as sizing materials for cotton fabrics. The sizeability of these composites for cotton fabrics was assessed in terms of the size removal percentage at different temperatures and the effect on the tensile properties and water absorption. The change in the apparent viscosity with the shear rate showed that γ‐irradiation improved the behavior of MS/PVA blends and their composites with GY or GP as a sizing material for cotton fabrics. Moreover, the improvement in the tensile mechanical properties of the sized cotton fabrics with these composites gave further support to this finding. The results for the size removal percentage and water adsorption indicated that these composites could be removed by washing at 70°C for 10 min. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3818–3826, 2004     

用活性炭吸附强化超滤过程脱除废水中染料的研究(英文)

In this study, orange G dye was efficiently removed from aqueous solution by ultrafiltration (UF) mem-brane separation enhanced with activated carbon adsorption. The powdered activated carbon (PAC) was deposited onto the UF membrane surface, forming an intact filter cake. The enhanced UF process simultaneously exploited the high water permeation flux of porous membrane and the high adsorption ability of PAC toward dye molecules. The influencing factors on the dye removal were investigated. The results indicated that with sufficient PAC incor-poration, the formation of intact PAC filtration cake led to nearly complete rejection for dye solution under opti-mized dye concentration and operation pressure, without large sacrificing the permeation flux of the filtration process. Typically, the dye rejection ratio increased from 43.6% for single UF without adsorption to nearly 100% for the en-hanced UF process, achieving long time continuous treatment with water permeation flux of 47 L·m 2·h 1. The pre-sent study demonstrated that adsorption enhanced UF may be a feasible method for the dye wastewater treatment.     

Hydrogen storage on chemically activated carbons and carbon nanomaterials at high pressures

Hydrogen adsorption measurements have been carried out at different temperatures (298 K and 77 K) and high pressure on a series of chemically activated carbons with a wide range of porosities and also on other types of carbon materials, such as activated carbon fibers, carbon nanotubes and carbon nanofibers. This paper provides a useful interpretation of hydrogen adsorption data according to the porosity of the materials and to the adsorption conditions, using the fundamentals of adsorption. At 298 K, the hydrogen adsorption capacity depends on both the micropore volume and the micropore size distribution. Values of hydrogen adsorption capacities at 298 K of 1.2 wt.% and 2.7 wt.% have been obtained at 20 MPa and 50 MPa, respectively, for a chemically activated carbon. At 77 K, hydrogen adsorption depends on the surface area and the total micropore volume of the activated carbon. Hydrogen adsorption capacity of 5.6 wt.% at 4 MPa and 77 K have been reached by a chemically activated carbon. The total hydrogen storage on the best activated carbon at 298 K is 16.7 g H₂/l and 37.2 g H₂/l at 20 MPa and 50 MPa, respectively (which correspond to 3.2 wt.% and 6.8 wt.%, excluding the tank weight) and 38.8 g H₂/l at 77 K and 4 MPa (8 wt.% excluding the tank weight).     

Controlling floc sizes in a pipe between pump and membrane inlet

Cake resistance is influenced by floc size deposited on membrane surface. Enlarging floc size can reduce cake resistance. The small particles are enlarged by coagulation and flocculation processes in conventional mixing tank at membrane filtration system. Fully-grown flocs for reducing the cake resistance, however, are ruptured while passing through a pump. In light of this fact, this study aims to experimentally look at the reaggregation phenomenon through control of G-values in pipe from pump to inlet of membrane. In addition, reaggregation phenomenon of the mixing system is compared with first-aggregation in-line injection system in which coagulant is injected just before a pump. These results suggest that first-aggregation of in-line injection system is better than reaggregation of mixing system for G-value above 3100 s^− 1. G-values in pipe of real world membrane filtration system are usually much larger than 3100 s^− 1. Due to reason, in-line injection system is expected to perform better than mixing tank as proved in this study.