Cations refer to positively charged ions dissolved in the water. Drinking water treatment for nitrate acknowledgments this document is largely based on the report titled an assessment of the state of nitrate treatment alternatives 2011 prepared for the american water works association awwa through collaboration with chad seidel, ph. For example, in softening processes, calcium and magnesium ions hardness are. In the field of water treatment, the most common uses of. Our systems are also efficient in reducing toxic metals, radium reduction, unwanted color, perchlorates and dbp precursor. Ion exchange resins are used in wastewater treatment pro. Ion exchange for dummies water treatment and purification. In the ion exchange process, sodium ions are used to coat an exchange medium in the softener. If the water is softened further as in the ion exchange process then the hard water must be mixed. In each of the treatment processes, the goal is the same. In the context of water purification, ionexchange is a rapid and reversible process in which impurity ions present in the water are replaced by ions released by. Continuous ion exchange processes are usually of the downflow and packedbed column type. Ion exchange resins and processes for industrial water treatment. Ion exchange is used in water treatment for the following two applications.
Theory and application focuses on the applications, complexities, and theoretical aspects of ion exchange. Sodium ions are supplied from dissolved sodium chloride salt, also called brine. Pdf wastewater treatment by ion exchange researchgate. Jun 05, 2017 ion exchange ix systems are used across a variety of industries for water softening, purification, and separation purposes. More precisely, the term encompasses a large variety of processes where ions are exchanged between two electrolytes. Industrial applications for ion exchange processes are numerous. Fundamentals of radium and uranium removal from drinking. In water treatment, it is primarily used for softening where calcium and magnesium ions are removed from water. A small community in british columbia, canada, needed a water treatment process that required minimal maintenance but could handle the communitys unique challenges. Rohm and haas ion exchange ion exchange introduction 1 fd sep 2008 ion exchange for dummies an introduction water water is a liquid. Addressing nitrate in alifornias drinking water with a focus on tulare lake basin and salinas valley. All natural waters contain some foreign substances, usually in small amounts.
As hard water passes through a softener, the calcium and magnesium trade places with sodium ions figure 1. Awwa b11619 electrodialysis and ionexchange membrane systems. Claudia cobzaru, vassilis inglezakis, in progress in filtration and separation, 2015. Article views are the countercompliant sum of full text article downloads since november 2008 both pdf and html across all institutions and individuals. Ion exchange water treatment budapest university of. Ion exchange cation exchange resins process water water. These functionalized polymers adsorb particular anions or cations from the liquid and discharge others. Ion exchange membranes used for ed process depending on the type of ionic groups attached to the membrane matrix, ion exchange membranes are classified into anion exchange membranes and cation exchange membranes. A cation resin is one that exchanges positive ions.
The wastewater that is produced by ion exchange machines is also used for water treatment. It removes impurities that are likely to affect the pr performance of downstream units based on ion exchange andor membrane and thermal processes. Ion exchange softening, also known as sodium zeolite softening is a typical example of how the ion exchange process works to purify the water by removing the hardness level caused by presence of calcium and magnesium. In the field of water treatment, the most common uses of ion exchange are. With this in mind, lets take a closer look at the technology and operation of ion exchange resins and processes used today in industrial water treatment systems. Reverse osmosis ro and electrodialysis, both membrane processes, remove dissolved solids from water using membranes. Ion exchange in water and waste treatment symposium. Ion exchangers exchange one ion for another, hold it temporarily, and then release it to a regenerant solution. Our range of products includes water, waste water treatment and recycling plants using various physicochemical processes for settling, clarification, filtration, disinfection, membranes and ion exchange technology, ion exchange resins. Ion exchange in water and waste treatment symposium introduction. Ion exchange water treatment systems university of rhode island.
Cation softening resin will remove most positively charged ions in water. Aside from its use to purify drinking water, the technique is widely applied for purification and separation of a variety of industrially and medicinally. Wastewater treatment by ion exchange method trade science inc. Ion exchange is an effective, versatile means of conditioning boiler feedwater. This book discusses the kinetics of fixedbed ion exchange. Measurements of hardness are given in terms of the. The process of ion exchange is one of the most utilized techniques in water and wastewater treatment as well as in separation processes as chemical synthesis, medical research, food processing, mining, agriculture, etc. Our systems are also efficient in reducing toxic metals, radium reduction, unwanted color.
Cation exchange involves the replacement of the hardness ions with a nonhardness ion. There are two general types of ion exchange resins. Household water softeners are ion exchange devices. The chemical reactions of ion exchange softening is shown in. Ion exchange involves removing the hardness ions calcium and magnesium and replacing them with nonhardness ions, typically sodium supplied by dissolved sodium chloride salt, or brine. The exchange medium can be natural zeolites or synthetic resin beads that resemble wet sand. A highperformance liquid chromatographic method using a borateformate buffer system and an aminex a27 ionexchange resin has been developed for the separation of heptose nucleotides from. Ion exchange usually describes a processes of purification of aqueous solutions using solid polymeric ion exchange resin.
Advantages and disadvantages of iron exchange biotech. Water treatment is the bestknown and biggest field of application for ion exchange resins. Ion exchange is widely used in the food and beverage industry, hydrometallurgy, metals finishing, chemical, petrochemical, pharmaceutical technology, sugar and sweetener production, ground and potable water treatment, nuclear, softening, industrial water treatment, semiconductor, power, and many other industries. For example, in a sodium zeolite softener, scaleforming calcium and magnesium ions are replaced with sodium ions. Ion exchange water treatment systems pure aqua, inc.
Hard water is usually defined as water which contains a high concentration of calcium and magnesium ions. Ion exchange resins are polymers that are capable of exchanging particular ions within the polymer with ions in a solution that is passed through them. Water containinghardness ions calcium and magnesium is passedthrough a cation exchange resin in the sodium form. Ion exchange and membrane processes are becoming used extensively in water and wastewater treatment.
The resin used for softening is called the sodium exchanger. Awwa b11619 electrodialysis and ionexchange membrane. Cation exchange involves the replacement of the hardness ions. Children who drink water with levels of fluoride ion exchange is one of the most utilized techniques in water and wastewater treatment as well as in separation processes as chemical synthesis, medical research, food processing, mining, agriculture, etc. Ion exchange in water softening water softening is not a wastewater process. Some water treatment devices that remove chemicals, such as reverse osmosis, ion exchange, or distillation systems, might also remove fluoride. While the chemistry of individual ion exchange reactions varies from one application to the next, ix is a treatment process where dissolved ions are replaced by other, more desirable, ions of a similar electrical charge. Ion exchange ix processes are reversible chemical reactions for removing dissolved ions from solution and replacing them with other similarly charged ions. Ion exchange sswm find tools for sustainable sanitation. Negatively charged groups, such as so3, coo, po32, po3h, c6h4o, etc.
Filters that remove chemicals often do not effectively remove germs, and vice versa. Also, inclusion of ion exchange as wastewater treatment and purification stage allows for removal and eventual recovery of ionic components in an effluent prior. This service may include inspection, repair, system upgrades, resin cleaning, resin replacement, disposal of spent resins or complete regeneration services. What is an ion exchange system and how does it work. Introduction to ion exchange techniques for water desalination course no. For this reason, natural water does not exist as a chemically pure substance. The softener contains a microporous exchange resin. Pdf treatment of secondary sewage effluent by anion exchange has been investigated.
This is normally used in steam boilers and industrial water treatment applications. Ion exchange is used extensively in both water and wastewater treatment. Wastewater treatment by ion exchange article pdf available in water research 66. A typical water treatment plant consists of the following sections. In the first section of the present chapter the kinetics and thermodynamics of. In dilute solution, the hardness ions are selectively held. Ion exchange equilibria water softening is a very efrcient process. Children who drink water with levels of fluoride ion exchange resins are used to remove dissolved particles from liquids. It is a very effective and efficient method of water softening. Standard water softeners are cation exchange devices. Biological ion exchange provides doc removal in small. Jan 27, 2016 ion exchange is a water treatment process commonly used for water softening or demineralization, but it also is used to remove other substances from the water in processes such as dealkalization, deionization, and disinfection. Therefore, functional groups are bonded to the polymer beads.
The application of ion exchange to water treatment and purification these are three ways in which ion exchange technology can be used in water treatment and purification. Most water treatment ix processes operate in a continuous mode. Ion exchange is a water treatment method where one or more undesirable ionic contaminants are removed from water by exchange with another nonobjectionable, or less objectionable ionic substance. This standard sets minimum requirements for ion exchange membrane iem systems such as electrodialysis ed, electrodialysis reversal edr, electrodialysis metathesis edm, and electrodeionization edi used for water and reclaimed water treatment systems. Introduction to ion exchange techniques for water desalination. When the resin capacity is exhausted, it is regenerated. Metals like lead, radium, barium, alumi num and copper are effectively removed with. Back to awwa b11619 electrodialysis and ion exchange membrane systems this standard sets minimum requirements for ion exchange membrane iem systems such as electrodialysis ed, electrodialysis reversal edr, electrodialysis metathesis edm, and electrodeionization edi used for water and reclaimed water treatment systems. Ion exchange is primarily used for the removal of hardness ions, such as magnesium and calcium, and for water demineralization. Softened water should have a hardness of about 80 to 90 mgl as calcium carbonate. Both the contaminant and the exchanged substance must be dissolved and have the same type of electrical charge positive or negative.