Using ion exchange to remove metals from a mixed waste effluent from research facilities.

Water Treatment Plant Design, Fifth Edition By American Society of Civil Engineers

AWT: The Analyst

Silica is poorly ionized at neutral pH and has limited solubility. Membrane and precipitation processes can be quite effective at elevated pH but are either ineffective or less than wonderful at neutral pH. Demineralizers, with hydroxide-form anion resin, remain one of the best methods for removing silica, especially when TDS removal is also required.

The chemistry of silica in water and the methods of its removal.

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AWT: The Analyst

AWT: The Analyst

AWT: The Analyst

AWT: The Analyst

Hardness minerals, calcium and magnesium, as well as some other dissolved ions, will leave spots on rinsed surfaces if the water is allowed to dry. Here’s how to prevent it from happening.

Water Treatment Plant Design, Fourth Edition By American Society of Civil Engineers

Frank Desilva talks about the new ResinTech manufacturing facility in New Jersey, how he makes ion exchange a more interesting topic for conversations and sales presentations, and one of the positives he sees coming out of the pandemic.

How to remove arsenic from water using brine regenerable anion resin.

The rinse bath for plating gets contaminated through the finishing operation, but that doesn’t mean it has to go down the drain. Frank Desilva talks about closing the loop.

Cities throughout the Southwest have found that next-generation ion-exchange technologies provide a reliable, economical, ready-made way to leverage local groundwater resources without the expense of a hard-piped treatment facility or the problems of dealing with waste management.

Procedures and standards to incorporate in the operation of a portable exchange DI regeneration plant.

A guide to understanding the basic principles of ion exchange for the metal finishing industry.

The history of PFAS, measurement techniques and removal methods.

Chelating resins are gaining acceptance as the best available technology for the removal of transition and heavy metal cations from ground water and from plating rinse waters. These specialty ion exchange resins are capable of removing metals selectively in the presence of other ions such as calcium, magnesium and sodium. This paper describes the various types of chelating resins that are commercially available, discusses the conditions under which they will and will not work, and explores the input require-ments necessary to optimize a system design.

Countercurrent regeneration is a method that has tried unsuccessfully to get into the mainstream of the water softening industry. Despite various application strategies, it’s often dismissed as too complex and with little value in brine savings. Time will tell if other issues such as salt and the environment make the technique practical.

Recently, a handful of portable exchange deionization (PEDI) operators in California were cited for excessive discharges of copper. How and why could this happen when the general use of the portable exchange tanks was treatment of potable water, not copper-containing wastewaters? Here’s an explanation and some suggestions.

The concept of water softening has been in use longer than many of us may have been led to believe. Here, the author gives a brief historical lesson as well as a look into the future on where he sees the industry headed.

Silica has always confounded water treatment dealers in how to handle it and greatly reduce the contaminant. As we discover more information about silica due to further studies, though, some technologies have come to the fore. A good place to begin is to examine the chemistry of silica and how it pertains to various approaches available to dealers.

Scientists use deionized water in a variety of areas from glassware washing to DNA synthesis. To provide the proper deionization system, it’s important to understand the specific needs and requirements of laboratory grade water. Laboratory water systems come in standard configurations with a variety of available options.

As a general class, the arsenic adsorbents are all based on similar adsorbent chemistry. An insoluble metal oxide/hydroxide is the adsorbent, which is contained in some type of granular substrate that is porous enough to expose the adsorption sites to the water, yet robust enough to maintain its shape under the conditions of use. Arsenic in the form of arsenate, an anion, is adsorbed by co-precipitation onto the metal oxide, while arsenate (trivalent arsenic) is attracted by chelating forces. Precipitated arsenate, in most cases, is tightly bound to the oxide and does not come back off under any normal conditions found in potable water. All of the arsenic adsorbents promise extremely long throughputs by targeting the arsenic species, while ignoring common ions, such as sulfate, chloride, sodium, calcium, etc.

How to balance a partial water analysis to make up for missing parameters.

Factors affecting the efficiency and performance of brine regenerated water softeners

What compounds can leach from softener resins when exposed to chlorine or other oxidants?

The ResinTech story.

A little of this and a little of that may work in spicing a pot of stew, but when it comes to ion exchange float, you’d better know all the considerations in choosing new resin to add. More often than not, it’s a like-to-like equation. Here, such issues are discussed in detail for the dealer, who may also do commercial/light industrial work.

Methods of producing ultrapure POU water for laboratory use.

There are many uses a water conditioner can be put to beyond simply softening water. Some require more care and expertise because of potential health risks if not handled properly. Following is an overview on this concept.

Discussion of various methods of fluoride removal from water sources.

New rules released late last year from the Food and Drug Administration (FDA) on water purification for kidney dialysis patients will have a big impact on portable exchange deionization (PEDI) tank services. The quality control focus requires much documentation.

The removal of insoluble ferric iron by water softeners can be problematic. Softening resins filter to approximately two microns in size but ferric iron particles are often smaller than one micron.Depending on particle size, flowrate and resin size and uniformity, removal can be as little as 10 percent or as much as 90 percent with 25- to 75-percent removal more typical. Fine-mesh resins do better than larger resins.

Water softening is an inherently efficient process. This is true for the service cycle, where sodium ions on the resin are exchanged for hardness ions in the water. And, unlike most chemical reactions, it’s true during the reverse exchange, or regeneration, where sodium ions in the brine are swapped for hardness ions on the resin. Few chemical processes are efficient in both directions. The reason for water softening efficiency is a phenomenon called selectivity reversal that’s caused by changes in the solution concentration when the ion exchange reaction involves ions of unequal valence. The principal of selectivity reversal underlies all ion exchange theory and is the science behind the art of softening water.

In Part 1, we discussed aspects of ion selectivity as they relate to water softening, including selectivity coefficients, apparent selectivity and selectivity reversal. In Part 2, we take up the mathematical relationships of concentration, valence and capacity, which underlie the theory of water softening.

A recent spate of regulations in a number of states has served notice to resin suppliers that current processes will need to be modified. A couple areas of concern are salt discharge and brine efficiency. The following article describes the role of regeneration and how proven techniques may make new regulations a moot point.

Though its popularity as a water treatment alternative is increasing, activated carbon can have a substantial effect on pH. These “spikes” in pH become even more pronounced in various high-purity applications. Pre-wetted carbons, however, answer many of those concerns in a sufficient manner. The advantages of pre-wetted pH adjusted acid-washed carbons are discussed.

Silica is poorly ionized at neutral pH and has limited solubility. Membrane and precipitation processes can be quite effective at elevated pH but are either ineffective or less than wonderful at neutral pH. Demineralizers, with hydroxide-form anion resin, remain one of the best methods for removing silica, especially when TDS removal is also required.

Silica has always confounded water treatment dealers in how to handle it and greatly reduce the contaminant. As we discover more information about silica due to further studies, though, some technologies have come to the fore. A good place to begin is to examine the chemistry of silica and how it pertains to various approaches available to dealers.

Water Treatment Plant Design, Fourth Edition By American Society of Civil Engineers

Water Treatment Plant Design, Fifth Edition By American Society of Civil Engineers

Countercurrent regeneration is a method that has tried unsuccessfully to get into the mainstream of the water softening industry. Despite various application strategies, it’s often dismissed as too complex and with little value in brine savings. Time will tell if other issues such as salt and the environment make the technique practical.

New rules released late last year from the Food and Drug Administration (FDA) on water purification for kidney dialysis patients will have a big impact on portable exchange deionization (PEDI) tank services. The quality control focus requires much documentation.