Removal of Nitrate from Ground Water by a Hybrid Process Combining Electrodialysis and Ion Exchange Processes

Abstract

In regions where agricultural activities are highly intensive, nitrate concentrations in ground water are usually above the permissible level for nitrate in drinking water. There are several physicochemical and biological treatment processes typically used to remove nitrate contamination from ground water. In this study, an electrodialysis‐ion exchange hybrid process was used for the removal of nitrate from ground water obtained from an agricultural area in the Western Anatolia religion in Turkey. Nitrate was effectively removed from the ground water. The effect of other ionic species such as chloride and sulfates on nitrate removal by electrodialysis has also been studied using deionized water that was dosed with selected anionic and cationic species.     

Prozeßvergleich von Umkehrosmose und Elektrodialyse am Beispiel der Nitrat-Entfernung aus Grundwässern

Comparison of reverse osmosis and electrodialysis for removal of nitrate from groundwater . Reverse osmosis and electrodialysis are membrane processes suitable for desalination of aqueous solutions. Both processes were tested on a pilot scale in a waterworks for removal of nitrate from groundwater. A combination of the processes was also considered with a view to very high concentration of the residual water. The article shows how information gathered from long-term reverse osmosis trials and the experiments with the electrodialysis plant with industrial membrane dimensions can provide a basis for safe design of large plants. Treatment costs for large capacities are shown for the example of the above feed water. The advantages and disadvantages of reverse osmosis and electrodialysis are compared. This comparison demonstrates fitting applications of the two processes in other areas (chemical industry, sewage treatment).     

饮用水中硝酸盐的去除

作为重要的饮用水源,地下水中硝酸盐的污染日趋严重,硝酸盐对人体健康有严重的危害。物化方法(离子交换、电渗析、反渗透等)、生物反硝化、化学反硝化等工艺都可不同程度地去除作为饮用水的地下水中的硝酸盐,这些方法各有优缺点。本文综述了地下水中硝酸盐去除方法的应用和研究现状,并对其发展趋势做了简单的讨论。     

Parametric studies on the performance of anion exchange for nitrate removal

Ion exchange performance to remove nitrate in surface and underground water was studied experimentally in batch and continuous operation systems under various conditions. Data were collected by using commercially available strong-base anion-exchange resins of C1 and OH types. Equilibrium curves, obtained through the batch system and plotted as the concentration ratio versus run time, were used to evaluate the effects of temperature, resin type, and initial feed concentration on the equilibrium characteristics of nitrate. The selectivity coefficients of the resins were correlated as a function of temperature by using the Kraus-Raridon equation. Breakthrough curves, obtained through the continuous column system and plotted as the ratio of effluent to influent concentration versus solution volume passed through the experimental column, gave detailed results about the effects of the system parameters, such as temperature, resin type, feed concentration, volumetric flow rate, column diameter and height on the performance of the anion exchange to remove nitrate. The results of this study could be scaled up and used as a design tool for a water-purification system of real ground water and surface water treatment processes.     

Water denitrification by a hybrid process combining a new bioreactor and conventional electrodialysis

A feasibility study of an innovated denitrification process is achieved in this present work. It consists of a combination of the electrodialysis (ED) and the Column of Immobilized Biomass on Granular Activated Carbon – CIBGAC. In order to perform the electrodialysis process, the influence of various parameters such as current intensity, chloride, and sulphate concentrations were estimated. Therefore, an optimum efficiency of the denitrification for an applied current intensity value of 50 mA was obtained. The competition between the chloride and nitrate ions was encountered using the electrodialysis process inducing a slow electromigration of the nitrates. In contrary, the presence of sulphate ions had no influence on the electrodialysis during the denitrification. On the other hand, the biological denitrification of brines by electrodialysis was carried out. A clear decrease of pH was observed from 7.5 to 6.2 and the monitoring of the nitrate and nitrite ions through the bio-compartment affirmed the efficiency of this process. The successful establishment of the hybrid denitrification process was realized. Indeed, the treated water in dilute compartment was in conformity in terms of nitrates concentration and even more the concentrations of different ions are below the amounts recommended by the World Health Organization (WHO). TOHOH he brine solution after biological treatment agrees with WHO standards in terms of nitrate and nitrite ions.     

The water problem in egypt

Egypt faces the prospect of rapid growth of populatlon which is a vital problem since agricultural land is not available at the same rate. More land should be reclaimed through development of water resources.The Nile river constitutes an immense water supply but one third of its water is lost through pumping low salinity drainage water to the Mediterranean Sea utilizing costly electric power. Therefore, feasibility studies on recycling this water must be carried out.Along the banks of the Nile, drinking water could be obtained supplied through either small water purification plants or electrodialysis desalination plants, and the economics of the two methods should be compared before deciding on either method.Another source is underground water with a salinity varying between 2000 and 11,000 ppm. For such brackish water, either the electrodialysis or reverse osmosis process can be used.Then there is the Egyptian sea shore which extends over 3000 km. and where the salinity of the sea varies between 33,000 and 45,000 ppm. Here flash distillation processes are suitable.The present paper briefly describes available water resources in Egypt and discusses possible solutions to supplying the fresh water required in different areas.The present investigation concentrates on the feasibility and economics of utilizing the electric supply from the grid at periods other than the peak loads for operating electrodialysis plants. It is estimated that a series of electrodialysis plantsrunning for lOh/day would provide 2.6 million m³/day at an operating cost of 10¢/m³ in addition to capital costs.     

棉花模板Zn/Ti/Fe-LDO吸附水中硝酸盐机制

通过共沉淀-焙烧法制备以棉花为模板的Zn/Ti/Fe焙烧态类水滑石（YLDO）和无棉花模板的Zn/Ti/Fe焙烧态类水滑石（NLDO）,运用SEM、N₂吸附法、FTIR和XRD对其进行表征,考察YLDO和NLDO对水中硝酸盐的吸附机制及其紫外光催化再生的机理。结果表明,YLDO在形态中引入棉花的遗迹,比表面积增大为74.8 m²·g^-1,大孔数量增加;在化学成分上引入了C元素,提高了吸附性能;形成磁性物质,可通过磁性分离回收。pH为7、298 K时,YLDO对水中硝酸盐的最大吸附量为66.57 mg·g^-1,比NLDO增加了22.6%。YLDO和NLDO吸附硝酸盐的吸附等温线符合Langmuir方程,吸附动力学可用准二级动力学方程来描述,吸附热力学研究表明吸附过程为自发吸热过程。吸附饱和的YLDO和NLDO可在紫外光照射下再生,5次再生循环后仍保持较高的吸附性能。YLDO可通过吸附-磁分离-紫外光催化再生工艺有效去除水中硝酸盐,不产生二次污染,在硝酸盐废水处理中具有潜在的应用前景。     

Adsorptive Removal of Nitrate and Phosphate from Water by a Purolite Ion Exchange Resin and Hydrous Ferric Oxide Columns in Series

Elevated concentrations of nitrate and phosphate in surface and ground waters can lead to eutrophication, and nitrate can also cause health hazards to humans. The adsorption process is generally considered to be an efficient technique in removing these ions provided that the adsorbent is highly selective for these ions. Removal of nitrate and phosphate from a synthetic water (50 mg N/L as nitrate, 15 mg P/L as phosphate) and a wastewater (12.9 mg N/L as nitrate, 5.9 mg P/L as phosphate) using a Purolite A500P anion exchange resin and a hydrous ferric oxide (HFO) columns (60 cm height, 2 cm diameter, flow rate 1 m/h) in series containing 1–10% (w/w) of these adsorbents and the remainder anthracite (90–99%) were studied. Data from batch adsorption experiment at various concentrations of adsorbents satisfactorily fitted to Langmuir adsorption isotherm for nitrate and phosphate on Purolite with adsorption maxima of 64 mg N/g and 7 mg P/g and only for phosphate on HFO with adsorption maxima of 14 mg P/g. Both batch and column experiments showed that Purolite selectively removed nitrate and HFO selectively removed phosphate. The Purolite column BTC time was greater for nitrate than for phosphate. At the highest percentage by weight of Purolite almost all nitrate was removed in batch study and up to 1000 min in column study, but it was not able to remove a comparatively high percentage of phosphate. However, when the effluent from the Purolite column was passed through the HFO column almost all phosphate was removed. The two columns when set up in series also removed almost all nitrate and phosphate from the wastewater.     

Lactic acid production by electrodialysis Part II: Modelling

One interesting alternative to the usual end-of-pipe processes for treating waste water produced during cheese-making involves its fermentation to sodium lactate. Then, electrodialysis can be used to recover free lactic acid from the fermentation broth. The design and optimization of such a process is aided by a suitable mathematical model. This work presents a model of the performance of an electrodialysis stack to be used in such a process. Its reliability has been assessed by comparison with experimental data for free lactic acid recovery from sodium lactate solutions. A suitable procedure for estimating some process-dependent parameters is also discussed.     

Desalting in Australia : The development of a new process for brackish water

The present status of desalination in Australia, the world's driest continent, is reviewed. The well-established techniques of distillation, electrodialysis and reverse osmosis have been utilized to obtain potable water from underground sources or the sea. In remote areas where mining and tourism are major industries, about 30 plants with capacities of up to 900 m³/day have been installed.The future application of large scale desalting is likely to be for municipal purposes in more highly populated regions. The emphasis has been on the treatment of water of moderate salinity which may be of surface, underground, sewage or industrial origin.A new ion exchange desalination process is described which has been developed in Australia to upgrade mildly brackish water to potable or industrial standards. Developed jointly by CSIRO and ICI Australia, the process uses “Sirotherm” resins which are regenerated by hot water, in contrast to the conventional regeneration by chemicals. This uses low grade or waste heat, reduces operating costs compared with existing processes and saves adding extra regenerant chemicals to the environment.Operation of a 600 m³/day plant to remove 80% of the salinity in a 600 ppm municipal supply has recently commenced at a factory site in Adelaide, Australia. A 20 m³/day pilot plant has successfully demonstrated the removal of salt from reclaimed sewage in Tokyo, Japan, where water reuse is fast becoming mandatory. The resin is now available commercially throughout the world.     

硝酸铵废水深度处理技术

针对目前用电渗析法处理硝酸铵废水的现象,提出以电去离子处理作为硝酸铵废水深度处理,弥补现有电渗析处理的不足,达到硝酸铵废水处理系统"零排放",做到废水资源化利用,硝酸铵和水全部回收。这种改良型电渗析处理方法,除可使浓水中氨氮的质量分数达10%以上外,系统出水氨氮的质量浓度小于或等于5 mg/L。     

硝酸铵废水深度处理技术

针对目前用电渗析法处理硝酸铵废水的现象,提出以电去离子处理作为硝酸铵废水深度处理,弥补现有电渗析处理的不足,达到硝酸铵废水处理系统＂零排放＂,做到废水资源化利用,硝酸铵和水全部回收。这种改良型电渗析处理方法,除可使浓水中氨氮的质量分数达10%以上外,系统出水氨氮的质量浓度小于或等于5 mg/L。     

Nitrate reduction of well water by reverse osmosis and electrodialysis - studies on plant performance and costs

Reverse osmosis as well as electrodialysis are capable of reducing the nitrate content of well water to permissible limits. The specific treatment costs of both processes are almost identical, provided the concentrates can be discharged without costs and water losses are unimportant. An advantage of RO is its simplicity which is of special importance for small scale applications. The reliability of reverse osmosis has been proved by experiments with a pilot plant installed at a municipal waterwork. The pilot plant has been operated continuously for more than 27.000 hours without any noticeably decrease of selectivity.Electrodialysis is advantageous compared to reverse osmosis in cases, where a high water recovery is essential, for example in case of a subsequent evaporation of the concentrate. With polarity reversal and in combination with a crystallizer, water recovery rates of 99% are possible.In any case however “zero discharge” processes are expensive. In addition to the specific treatment costs of the membrane stage of about 0.35 DM/t product, 0.5–0.7 DM/t product have to be expected for the evaporation of the concentrate, even if the water recovery rate of the membrane stage is 99%.     

Development of an electrodeionization process for removal of nitrate from drinking water Part 1: Single-species testing

A bench-scale study was performed to develop and evaluate the use of electrodeionization as a technology for the removal of nitrate from drinking water. Electrodeionization is an emerging technology that combines electrodialysis and ion exchange. Treatment of distilled water that was dosed with sodium nitrate was studied. The impact of design and operating conditions on nitrate flux and energy consumption for nitrate removal was evaluated. Increasing the voltage applied to the unit resulted in an increased nitrate flux out of the water stream but resulted in an increased energy consumption per equivalent of nitrate removed. Increasing the membrane spacing resulted in decreased fluxes and increased energy consumption. The type of resin employed in the process clearly had an impact on the fluxes, and the presence of any anion-exchange resin resulted in an improved performance compared to operation in the electrodialysis mode. Increasing the number of membrane pairs in the unit resulted in a decreased nitrate flux but appeared to have little impact on the energy consumed. Nitrate fluxes increased with nitrate concentration but appeared to approach a maximum flux at very high concentrations. At lower nitrate concentrations there was an increased energy consumption that likely resulted from the electrolysis of water at the lower ionic strength. Increasing the process flow rate appeared to have little impact on nitrate flux but resulted in higher energy consumption. Operation in recycle mode produced similar results to the once-through mode when conditions of similar outlet water composition were compared.     

Nitric acid and sodium hydroxide generation by electrodialysis using bipolar membranes

An electrodialysis process with bipolar membranes was used to generate HNO3 and NaOH from NaNO3 which can be found in industrial waste waters. The current efficiency of this process is limited by proton leakage through the anion exchange membrane (AEM), co-ion leakage through bipolar membranes (BPM) and water transport through the ion exchange membranes. Three cell configurations using three or two compartment cells with different anion or cation exchange membranes (CEM) in stack series were used and compared. Electrodialysis with three compartments gives the best current efficiencies for nitric acid and sodium hydroxide production from sodium nitrate.     

Optimization of fluoride removal from brackish water by electrodialysis

The study showed that desired potable water can be easily obtained by electrodialysis from fluoride-rich brackish water. Studies have been performed to defluoridate brackish water containing 3000 ppm of total dissolved solids (TDS) and 3 ppm of fluoride using electrodialysis. The behaviour of water parameters (ion contents, TDS, pH, total hardness) with electrodialysis parameters (duration, flow rate, temperature, voltages) is followed. Optimal operational conditions for obtaining desired potable water have been proposed.     

Effect of Process Parameters on Separation Performance of Nitrate by Electrodialysis

Abstract

The electrodialytic separation of nitrate from water was investigated as a function of feed characteristics such as applied voltage, feed flow rate, and nitrate concentration in the solution. The separation performance was evaluated in terms of percent removal of nitrate, process time, and energy consumptions. TS‐1‐10 electrodialysis equipment (Tokuyama) was used in experimental studies. During the unsteady state run of the ED system, both inlet and outlet concentrations of nitrate and conductivities of streams were measured at certain time intervals until the current drops to 0.01 A. It was obtained that the percent removal of nitrate from the solution increased when the concentration of nitrate in the feed solution increased. The operation time became shorter when a high potential was applied.     

Use of electrodialysis to remove silver ions frommodel solutions and wastewater

The feasibility of the removal of Ag⁺ ions in a model solution and a sample of rinse water provided from an industrial plating plantwas investigated in a batch electrodialysis system. The experiments were carried out using two different types of ion-exchange membranes. The effects of applied potential, pH value and initial silver concentration on the duration of electrodialysis and energy consumption were examined. Full removal of Ag+ ions was achieved from model solutions and the sample of rinse water. The most convenient applied voltage and energy consumption values to remove silver ions are reported. These results will be useful for designing and operating different capacities of electrodialysis plants for recovering Ag⁺ ions.     

Electrodialysis, a mature technology with a multitude of new applications

Electrodialysis is a mature process which is applied since more than 50 years on a large industrial scale for the production of potable water from brackish water sources. But more recently electrodialysis in combination with bipolar membranes or with ion-exchange resins has found a large number of new interesting applications in the chemical process industry, in the food and drug industry as well as in waste water treatment and the production of high quality industrial water.In this paper the principle of electrodialysis is described and its advantages and limitations in various applications are pointed out. More recent developments in electrodialysis as well as in related processes such as electrodialytic water dissociation or continuous electrodeionization are discussed and their present and potential future applications are indicated. Research needs for a sustainable growth of electrodialysis and related processes are pointed out.     

椰壳活性炭对加替沙星的吸附及缓释性能研究

研究了水溶液中椰壳活性炭对喹诺酮药物加替沙星（GTFX）的吸附性能,测定了不同温度下的吸附等温线并分析了其吸附热力学参数。结果表明：活性炭对加替沙星的吸附符合Freundlich方程,ΔH=-1.7374kJ/mol,说明活性炭对GTFX的吸附过程为放热过程,且ΔH<20kJ/mol,表明吸附过程主要为物理吸附。同时,测得吉布斯自由能ΔG<0,表明吸附质从溶液到吸附剂表面的吸附过程是自发过程,其吸附主要是熵驱动。对椰壳活性炭进行了硝酸及氨水改性,研究了3种不同活性炭对GTFX的缓释性能,结果显示,与椰壳活性炭相比,经硝酸氧化改性后的活性炭缓释性能有较大的提升,而经氨水改性的活性炭缓释性能有所下降,3种不同活性炭对GTFX的缓释均符合Higuchi方程释药模式。