Process intensification in the textile industry: the role of membrane technology

Process intensification is a concept that was recently introduced in the chemical industry for the purpose of reducing environmental emissions, energy consumption and materials consumption. The principle of process intensification can be used in related industries as well; textile finishing is an exemplary activity where it may have a significant long-term added value. Membrane technology can be a key factor in the recycling and reuse of energy, water and chemicals. In this paper, an integral approach for treatment of aqueous process streams in the textile finishing industry is proposed. The proposed process includes microfiltration pretreatment of used finishing baths, followed by a dual nanofiltration (NF) unit. These can be operated at elevated temperatures so that no further energy is needed for preheating of recycle streams. In the proposed treatment scheme, the first of the NF units uses a loose nanofiltration membrane that retains most of the organic fraction but not the dissolved salts. The second unit uses a tight nanofiltration membrane, which produces a permeate fraction that can be directly reused, and a concentrated brine that is fed to a membrane crystallizer. In this unit, salts are recovered and recycled for use in new dye baths. The concentrate stream from the first NF unit is fed to a membrane distillation unit, where the high temperature is advantageously used for further concentration. The remaining fraction is not reusable, given the fact that most dyes are hydrolyzed after exhaustion of the bath, but has a significant energetic value, which can be utilized for compensation of energy losses and preheating of suppletion water, by using an incineration process with energy recovery. The concept was not tested experimentally, but a simulation for a 500 m3/d production unit shows that it is feasible, although modifications may be necessary depending on the nature of the finishing baths. Furthermore, the membrane choice in the first NF unit is a critical aspect.     

Application of membrane bioreactor technology for wastewater treatment and reuse in the Mediterranean region: Focusing on removal efficiency of non-conventional pollutants

The Mediterranean Region is a semi-arid area whose land is facing serious erosion, causing adverse impacts on agriculture. To improve the water availability, researchers have proposed the reclamation and reuse of treated wastewater. In this paper, we report the main findings of 10 years of research on the efficiencies of a conventional activated sludge process and a submerged membrane bioreactor, with particular emphasis on the removal of non-conventional pollutants. The studies showed that the membrane bioreactor produced a virtually solids-free, high-quality permeate: most nutrients, heavy metals, and persistent organic pollutants were removed, and in particular, dioxins, furans, and polychlorinated biphenyls were typically present at concentrations below the detection limit. Moreover, the total coliforms count decreased by 4–5 log and Escherichia coli was absent from the membrane bioreactor permeate. These results, combined with the continuing reduction of the capital and operating costs for this approach, suggest that membrane bioreactors are an increasingly cost-effective technology to produce treated effluents that are suitable for reuse.     

纳滤膜去除内分泌干扰物/医药化合物研究进展

如何有效去除水中内分泌干扰物、医药活性化合物等有机微污染物的研究逐渐增加,其中,纳滤膜由于其较高的去除率得到了广泛关注。但由于纳滤膜去除这些物质的分离机理较为复杂,有时并不明确,给实验带来较大困难。文章总结了纳滤膜去除水中内分泌干扰物/医药活性化合物的典型应用及其三种分离机理——筛分作用、电荷作用、吸附作用,并对去除过程中所产生的问题和解决方案加以总结。为今后纳滤膜去除内分泌干扰物/医药活性化合物的研究提供参考依据。     

厌氧-准好氧型填埋的渗滤液实验研究

通过室内模拟试验，在渗滤液回灌的厌氧填埋柱基本进入稳定状态后，改用准好氧运行方式。同时监测了渗滤液中有机物浓度以压温度、pH值的变化。改变模拟垃圾柱的运行方式两个月以后。氨氯浓度由2000mg／L迅速下降至101．48mg／L，试验结果显示，准好氧运行方式可以解决生物反应器填埋场进入稳定阶段后存在的氨氮浓度高的问题，加速填埋场的稳定。     

不同操作条件对纳滤膜去除水中五价砷的研究

采用纳滤膜（NF90）过滤自配含砷水,研究在不同操作条件下纳滤膜对水中砷去除效果的影响。本实验探讨膜进水浓度、水的pH值、膜进水温度、操作压力、水中天然有机物浓度等对膜除砷效率的影响。结果表明：纳滤膜对水中五价砷（As（Ⅴ））的去除率很高,最高去除率能达到99%,在实验的前2.5个小时内,砷的去除率均在90%以上。但是,纳滤膜除砷效率随着时间变化,去除率会降低。不同的操作条件对纳滤膜除砷的影响很大,研究不同条件的影响对应用很有意义。     

Effects of feeding time and organic loading in an anaerobic sequencing batch biofilm reactor (ASBBR) treating diluted whey

An investigation was carried out on the performance of an anaerobic sequencing batch biofilm reactor (ASBBR) treating diluted cheese whey when submitted to different feed strategies and volumetric organic loads (VOL). Polyurethane foam cubes were used as support for biomass immobilization and stirring was provided by helix impellers. The reactor with a working volume of 3 L treated 2 L of wastewater in 8-h cycles at 500 rpm and 30 degrees C. The organic loads applied were 2, 4, 8 and 12 g COD L(-1) d(-1), obtained by increasing the feed concentration. Alkalinity was supplemented at a ratio of 50% NaHCO(3)/COD. For each organic load applied three feed strategies were tested: (a) batch operation with 8-h cycle; (b) 2-h fed-batch operation followed by 6-h batch; and (c) 4-h fed-batch followed by 4-h batch. The 2-h fed-batch operation followed by 6-h batch presented the best results for the organic loads of 2 and 4 g COD L(-1) d(-1), whereas the 4-h fed-batch operation followed by 4-h batch presented results slightly inferior for the same organic loads and the best results at organic loads of 8 and 12 g COD L(-1) d(-1). The concentration of total volatile acids varied with fill time. For the higher fill times maximum concentrations were obtained at the end of the cycle. Moreover, no significant difference was detected in the maximum concentration of total volatile acids for any of the investigated conditions. However, the maximum values of propionic acid tended to decrease with increasing fill time considering the same organic load. Microbiological analyses revealed the presence of Methanosaeta-like structures and methanogenic hydrogenotrophic-like fluorescent bacilli. No Methanosarcina-like structures were observed in the samples.     

Optimization of membrane-based CO2-removal from natural gas using simple models considering both pressure and temperature effects

Simple models for permeability and selectivity variations of the CO₂/CH₄ system in 6FDA-2,6-DAT membrane have been derived that include both temperature and pressure effects simultaneously in a single equation. The proposed models were used in MATLAB, for a membrane-based CO₂-removal process design for natural gas sweetening. The effects of the following factors on design parameters were examined: feed temperature, feed pressure and permeate pressure. The effect of permeate pressure was found to be very significant in the optimization process. In order to reduce hydrocarbon losses to below 2%, a two-stage membrane process was modeled and simulated in MATLAB, and the extent of desired hydrocarbon recovery was shown to be crucial in the optimization process. It has also been shown that there exist minima for the total required area of the two-stage membrane-based process, and as the CO₂ load increases in the feed, the position of these minima shift to higher values of methane loss.     

Treatment of Landfill Leachate Wastewater by Nanofiltration Membrane

Abstract

Nanofiltration (NF) membrane is an alternative lower energy membrane type compared to reverse osmosis membrane. NF is suitable for rejection of ions and molecules with molecular weight greater than 200 Da. In this study leachate wastewater from a sanitary landfill site in Malaysia was filtered through a NF membrane in order to determine the rejection capability of the membrane towards pollutants such as chemical oxygen demand (COD), conductivity, nitrate, ammonia-nitrogen, and heavy metals such as Pb, Cd, Cu, Zn, Fe. The NF membrane used was HL membrane, which under the atomic force microscope (AFM) imaging, showed visible discrete pores. The overall rejections of the pollutants were more than 85% except for nitrate and ammonia nitrogen. NF can be considered an alternative for advanced filtration especially within a hybrid treatment system combining biological–physical treatment and membrane filtration.     

带锈涂料的研究

主要研究了以改性环氧树脂和聚乙烯醇缩丁醛为基料的钢铁带锈涂料,通过对成膜物质、转化剂、渗透剂、颜料等的研究,我们得到了集稳定、转化、渗透为一体的多功能涂料。经过实验测试,该涂料的各项性能指标都达到了设计要求,并且本工艺方案简单易行、省时高效,具有较高的实用价值。     

Groundwater purification by membrane technology

Hyperfiltration and nanofiltration membranes were tested with different water matrices for the removal of excess fluoride from underground water. Initially, the experiments were done with synthetic samples prepared by adding known amounts of sodium fluoride and calcium chloride in distilled water. The effect of feed water composition, pH, temperature of feed water, operating pressure, and feed water flow rate on separation efficiency of both types of membrane was studied by varying one parameter at a time and keeping all other parameters constant. Thus, the optimum operating conditions for the process were determined and after that ground water samples collected from three villages of district Gurgaon, Haryana, India (Farukhnagar, Wazirpur, and Mevka) were treated under optimum operational conditions. The mass transfer coefficient and membrane parameters were estimated for each data point using two-parameter model (Film theory and Solution-diffusion model) to study the concentration polarization on membrane surface. The nanofiltration membrane showed high percentage rejection of bivalent ions when compared to monovalent ions in a binary system. But in multicomponent system, when fluoride and calcium coexisted, the removal of fluoride was comparable to calcium removal because of the low solubility product of calcium fluoride. The results with RO membrane revealed that it removes practically all the ions present in water at high pressure, which need to be passed through a lime column to remineralize the water, to make it suitable for drinking purposes, whereas by running the system at low pressure which will further reduce the cost of operation, rejection percentage goes down to get permeate of required quality.     

Membrane filtration coupled with chemical precipitation to treat recirculating aquaculture system effluents

Effluents from recirculating aquaculture systems (RAS) contain high concentrations of nitrogen and phosphorous wastes and thus often require proper treatment to prevent potential detrimental impacts on receiving water bodies. The purpose of this study was to evaluate the feasibility of membrane filtration coupled with chemical precipitation as a pretreatment step with emphasis on phosphorus removal from RAS effluents. Chemical precipitation tests were conducted by adding magnesium chloride and alum at different chemical concentrations and pH values, respectively. Crossflow, flat-sheet membrane filtration modules were used to examine the effects of transmembrane pressure and crossflow velocity in terms of solid/liquid separation efficiency and permeate flux decline. The results showed that membrane filtration can effectively separate the phosphorus precipitates after chemical precipitation. The total phosphorus in the treated effluent was reduced to less than 0.05 mg L(-1) with a removal efficiency of more than 90%. However, much lower removal efficiencies were obtained for total organic carbon (TOC), total nitrogen, and turbidity. It was concluded that membrane filtration coupled with chemical precipitation can become an effective, compact treatment technology to meet the stringent regulatory requirements for RAS effluent discharge.     

渗透蒸发技术去除水中的挥发性有机污染物

渗透蒸发技术是一种新型膜分离技术,主要用于有机溶剂脱水、水中脱除有机物与有 机物之间的分离。本文主要介绍渗透蒸发技术在脱除水中挥发性有机污染物方面的应用。     

有机溶剂回收技术的研究

本文对有机溶剂的回收方法，如吸附法、吸收法、冷凝法和膜分离法等的研究进展与应用进行了综述。其中，吸附法在工业上的应用最为广泛，本文着重介绍了吸附法的工艺以及吸附剂的研究。而膜分离法作为最有发展前景的一种回收方法，主要问题为提高膜的通量和选择性。     

The effects of leachate recirculation with supplemental water addition on methane production and waste decomposition in a simulated tropical landfill

In order to increase methane production efficiency, leachate recirculation is applied in landfills to increase moisture content and circulate organic matter back into the landfill cell. In the case of tropical landfills, where high temperature and evaporation occurs, leachate recirculation may not be enough to maintain the moisture content, therefore supplemental water addition into the cell is an option that could help stabilize moisture levels as well as stimulate biological activity. The objectives of this study were to determine the effects of leachate recirculation and supplemental water addition on municipal solid waste decomposition and methane production in three anaerobic digestion reactors. Anaerobic digestion with leachate recirculation and supplemental water addition showed the highest performance in terms of cumulative methane production and the stabilization period time required. It produced an accumulated methane production of 54.87 l/kg dry weight of MSW at an average rate of 0.58 l/kg dry weight/d and reached the stabilization phase on day 180. The leachate recirculation reactor provided 17.04 l/kg dry weight at a rate of 0.14l/kg dry weight/d and reached the stabilization phase on day 290. The control reactor provided 9.02 l/kg dry weight at a rate of 0.10 l/kg dry weight/d, and reached the stabilization phase on day 270. Increasing the organic loading rate (OLR) after the waste had reached the stabilization phase made it possible to increase the methane content of the gas, the methane production rate, and the COD removal. Comparison of the reactors' efficiencies at maximum OLR (5 kgCOD/m(3)/d) in terms of the methane production rate showed that the reactor using leachate recirculation with supplemental water addition still gave the highest performance (1.56 l/kg dry weight/d), whereas the leachate recirculation reactor and the control reactor provided 0.69 l/kg dry weight/d and 0.43 l/kg dry weight/d, respectively. However, when considering methane composition (average 63.09%) and COD removal (average 90.60%), slight differences were found among these three reactors.     

Bioleaching of heavy metals from sewage sludge: A review

During the treatment of sewage, a huge volume of sludge is generated, which is disposed of on land as soil fertilizer/conditioner due to the presence of nitrogen, phosphorus, potassium and other nutrients. However, the presence of toxic heavy metals and other toxic compounds in the sludge restricts its use as a fertilizer. Over the years, bioleaching has been developed as an environmentally friendly and cost-effective technology for the removal of heavy metals from the sludge. The present paper gives an overview of the various bioleaching studies carried out in different modes of operation. The various important aspects such as pathogen destruction, odor reduction and metal recovery from acidic leachate also have been discussed. Further, a detailed discussion was made on the various technical problems associated with the bioleaching process, which need to be addressed while developing the process on a larger scale.     

Effect of reservoir flushing on downstream river water quality

The effect of short-term reservoir flushing on downstream water quality in the Geum River, Korea was studied using field experiments and computer simulations. The reservoir release was increased from 30 to 200 m(3)/s within 6 h for the purpose of this experiment. The flushing discharge decreased the concentrations of soluble nitrogen and phosphorus species considerably, but the experimental results revealed a negative impact on organic forms of nutrients and biochemical oxygen demand (BOD). A dynamic river water quality model was applied to simulate the river hydraulics and water quality variations during the event. The model showed very good performance in predicting the travel time of flushing flow and the variations of dissolved forms of nitrogen and phosphorus constituents. However, it revealed a limited capability in simulating organic forms of nutrients and BOD because it does not consider the re-suspension mechanism of these constituents from sediment during the wave front passage.     

Anaerobic whey treatment by a stirred sequencing batch reactor (ASBR): effects of organic loading and supplemented alkalinity

An assessment was made of cheese whey treatment in a mechanically stirred anaerobic sequencing batch reactor (ASBR) containing granular biomass. The effect of increasing organic load and decreasing influent alkalinity supplementation (as sodium bicarbonate) was analyzed. The reactor operated on 8-h cycles with influent COD concentrations of 500, 1000, 2000 and 4000 mg/L, corresponding to volumetric organic loads of 0.6 to 4.8 mgCOD/L.d. Organic COD removal efficiencies were always above 90% for filtered samples. These results were obtained with an optimized alkalinity supplementation of 50% (ratio between mass of NaHCO3 added and mass of influent mgNaHCO3/mgCOD) in the assays with 500 and 1000 mgCOD/L and of 25% in the assays with 2000 and 4000 mgCOD/L. Initial alkalinity supplementation was equal to the mass of influent COD (100%). The system showed formation of viscous polymer-like substances. These were probably of microbiological origin occurring mainly at influent CODs of 2000 and 4000 mg/L and caused some biomass flotation. This could, however be controlled to enable efficient and stable reactor operation.     

Coliquefaction of coal and polystyrene in supercritical water

The coliquefaction of coal and polystyrene (PS) in supercritical water (SCW) was carried out in a 50-mL batch stainless steel autoclave reactor, and the effects of the polymer ratio by weight (10–40%), reaction temperature (633.5–703.5 K), and reaction time (30–120 min) were investigated. The main products were analyzed qualitatively by Fourier transform infrared spectroscopy and high-performance liquid chromatography. The results show that polystyrene stimulates coal liquefaction as a hydrogen donor, and the synergistic effects during coliquefaction in SCW were confirmed. The conversion reached a maximum of 62.26% after 60 min at 673.5 K. The phase behavior during coliquefaction was observed in a fused silica capillary reactor using a combined microscope and video recorder system.     

化学实验室"三废"的处理方法

本文论述了含汞等9类化学实验室常见废弃物的处理方法，还介绍了4种有机溶剂的回收与提纯，指出实验室必须加强其废弃物的处理，做到防患于未然，杜绝污染事故的发生。     

Wastewater management in a cane molasses distillery involving bioresource recovery

Waste management involving bioresource recovery in a cane molasses-based distillery engaged in the manufacture of rectified spirit (alcohol) is described. The spentwash generated from the distillation of fermenter wash is highly acidic (pH 4.0-4.3) with high rates of biochemical and chemical oxygen demand (BOD: 52-58, COD: 92-100 kg/m3) and suspended solids (2.0-2.5 kg/m3). Biogas is recovered from high strength raw spentwash through the full-scale application of a biomethanation system as pretreatment option, comprising anaerobic fixed film reactors. This, combined with subsequent concentration through multiple effect evaporators (MEE), and utilization of concentrated effluent for biocomposting of pressmud (another by-product of the industry) for production of biomanure contributes to the elimination of effluent discharges.