Evaluation of a New Ion Exchange Drinking Water System

By H. Martin Jessen

Introduction

This article explores the effectiveness of a new ion exchange technology (see Figure 1) that employs electricity to perform ion exchange, extracting dissolved solids, and producing high quality drinking water. It investigates product claims, reveals how this technology works, shows independent lab results of product effectiveness, and compares the product to the current state-of-the-art POU technology, conventional RO systems. The technology reduces TDS and uses activated carbon to improve water quality by removing taste and odor.

Product claims

This unit claims several features not previously offered in a POU drinking water system:

• Reduction in water waste compared to RO
• Operates using programmable software and display indicator lights that provide consumers with detailed system status
• Customized taste control that allows consumers to control the taste of their drinking water for more or less mineral content by ’dialing up’ power to the system
• Reduces many difficult-to-remove health contaminants such as nitrate/nitrite, perchlorate, arsenic III and V and hexavalent chromium

New method for TDS reduction

At the heart of the system are specialty TDS reduction cartridges. Specially formulated cation and anion resin is processed into a thin sheet (Figure 2) with the anion on one side and the cation on the other. This material is then rolled into logs, cut to length and capped (Figure 3). The resulting cartridges are inserted into cell housings that include a cathode and anode. When consumers draw water, the electrical current is activated, extracting dissolved solids from the feed water (Figure 4). After producing a pre-set volume of water, the system automatically reverses electrode polarity to release dissolved solids from the cation and anion media, thus regenerating itself (Figure 5). The regeneration process takes approximately 32 minutes for both cartridges (16 minutes each). Because this system operates in a batch process, all water going to the system during service mode goes to the storage tank or faucet. Water goes to the drain only in regeneration mode. The overall result is faster water production with less water waste. A pre-filter removes suspended solids and a granular activated carbon post-filter polishes the water just before it is delivered to the faucet. The system is capable of producing 0.5 gpm (1.89 L/m), thus filling a storage tank in minutes.

Programmable taste control

Programmable to match feed water quality, the system is set in two steps, similar to a 10-speed bike. Analogous to the front sprocket, the first setting has two speeds – high or low. If TDS is 400 or less, the installer sets the system for low TDS; if TDS is above 400 ppm, the system is set for high TDS. Setup is accomplished by removing the front panel from the enclosure and pushing a button on the control panel. Once the system is installed and set, consumers have five settings to choose from. This control is similar to the five speeds on the back sprocket of the bike. If consumers want to leave more minerals in their water, they dial down the power, thus using less electricity, which causes the unit to extract fewer minerals. If TDS is above 600 ppm, a flow restrictor is used to increase contact time in the cell tower, resulting in better TDS reduction. Although TDS reduction varies based on feed water quality, even with taste control settings, typical TDS reduction for this system is 70 percent on the minimum setting and 95 percent on maximum. Drinking water quality is a function of residual chlorine and other contaminants that affect taste and odor as well as TDS levels. Some argue that too low a TDS level makes water taste ‘flat’ whereas too high a level is also objectionable –in the end, it’s a matter of personal taste. The technology allows the consumer to adjust product water TDS by increasing or decreasing the electrical power applied during the deionization stage. The higher the electrical power the lower the TDS level in the product level. An activated carbon filter reduces residual chlorine and other non-ionic contaminants.

Less water waste

With a typical RO system, a home using one gallon (3.78 liters) of drinking water a day could waste from 3,000 to 10,000 gallons (11,356.23 to 37,854.11 liters) of water over the course of a year. Under the same conditions, this ion exchange water treatment system will waste 110 gallons (416.39 liters) on low TDS feed water and 164 gallons (620.8 liters) on high TDS feed water. Some newer ROs (such as water-on-water systems) claim much lower waste rates and in actual operation, use three gallons (11.3 liters) of water for each gallon of product water for a 25-percent recovery rate, as compared to the 55 percent or 70 percent recovery of the electrical ion exchange technology, depending on feed water quality and manner in which the technology is deployed. Comparatively, this system will waste 110 gallons (416.39 liters) on low TDS feed water and 164 gallons (620.8 liters) on high TDS feed water, compared to 1,095 gallons for the RO with the latest technology.

In the water treatment industry, rated RO recovery is determined under lab conditions that never exist in the home. While the lab recovery rating may be 33 percent, actual recovery is more likely less than 10 percent. Further, if feed water temperature drops, recovery will drop even further. Up to 96.5 percent feed water is wasted with traditional POU ROs*.

Recovery with this system is not affected by water temperature, feed water pressure or back pressure from the tank. Under the conditions cited above, it uses 1.2 gallons (4.54 liters) of water in the regeneration process. At the low TDS setting, regeneration occurs after the system treats 3 gallons (11.35 liters) of drinking water – a 70-percent recovery. At the high setting, regeneration occurs after 1.5 gallons (5.67 liters) of drinking water are produced for a 55-percent recovery. Feed water pressure can be from 20-100 psi and temperature can be from 33-100°F (0.55-37.7°C).

Cartridge life

The system’s sediment and carbon filters should be replaced after producing 650 gallons (2,460.51 liters) of drinking water. The cartridges will produce 1,300 gallons (4,921.03 liters) if the feed water hardness is 20 grains per gallon or less. Excessive hardness, which causes scale accumulation in the cartridges, is the most significant limiting factor in system performance. With soft feed water, cartridges will last much longer. Typical life performance in hard (18 grain) and soft water are shown in Figures 6 and 7.

Contaminant reduction performance

As measured by independent laboratories, the ion exchange drinking water system effectively removes a wide range of contaminants. Table 1, which summarizes an independent laboratory’s recent tests, shows all (except arsenic V and selenium) contaminants were removed to non-detect levels by the water treatment method. Further, it shows all results easily meet NSF/ANSI 53 requirements. To obtain a measure of the selectivity of the electric ion exchange water treatment cartridge for each contaminant, compare the contaminant reduction to the TDS reduction result in Table 1.

• Flowrate: 0.45 gpm, three-gallon service cycle, 70-percent recovery
• All tests were performed according to NSF/ANSI Standard 53, low pH (6.5) except for fluoride (pH=7.3)
• Two electric ion exchange water treatment systems tested. Poorest results from the two sets of data are reported.

When tested according to NSF/ANSI Standard 53 at another independent laboratory, an earlier model of this system reduced perchlorate by 96 percent, nitrate and nitrite by 93 percent, monochloroacetic acid by 80 percent and chloramine by 40 percent. Results obtained using a later model of the ion exchange water treatment system for customer contaminant reduction for a variety of cations and anions, including arsenic III and arsenic V, are presented in Table 2. While arsenic III concentration in the feed water is very low and the detection limit of 2 ppb only allows one to conclude this ion was removed >55 percent, combined arsenic results suggest a substantially greater reduction. The cartridges are effective for removing weak acids because the anion exchange resin is in the strong base (hydroxide) form after regeneration. It is also effective for weak bases such as ammonia and to a lesser extent chloramine, because the cation resin layer is in the acid form after regeneration. Alkalinity and several other contaminants were also effectively reduced with an earlier model of the system, as shown in Table 3.

Power usage

Electricity is used to deionize the water as it flows through the TDS reduction cartridge – no chemicals are used at any time. When the system calls for water, the power supply / computer delivers the programmed wattage to the cartridge(s), the greater the power setting, the higher the TDS reduction. A key characteristic of the system is current density. The technology operates at ~1 mA/cm2 of membrane cross-section area. Maximum current in a cell is ~1.65 A. The system calls for power during the three stages of operation:

1. Idle (includes three sub-stages)
   1. Fully idle
   2. Fan running to cool the system
   3. System checking for water demand
   4. 5W used when fully idle, 6W when the fan is on and 26W when checking for water demand
2. Deionization
   1. Power varies at the 10 settings (high or low TDS and five dial settings)
   2. Range of output power is at 65V to 300V and 17 to 282W
3. Regeneration
   1. Regeneration involves reversing polarity and operating at maximum power, then reduced power
   2. Waste water is discharged to the drain in spurts

Total power used results in a cost of 1-2 cents per gallon of water produced depending on the dial setting, power costs and actual water usage. At 3.5 gallons (13.24 liters) produced per day, the cost is slightly less than one cent per gallon.

Bacteriostasis and disinfection results

Independent laboratories measured at least two-log (100-fold) reduction of bacteria and MS-2 virus with this system. In the presence of sufficient chloride ions, bacteria reduction was six log and virus reduction was four log – the threshold limits to meet US EPA Purifier Guide Standard requirements.

Here are five characteristics of the system’s ability to deactivate microorganisms:

1. Generation of H⁺ (acid) at one electrode and within the TDS reduction cartridge
2. Generation of OH^– (base) at other electrode as well as in membranes
3. Formation of Cl₂ (chlorine) and other free radicals
4. Quaternary ammonium groups in the anion membrane layer promote cell membrane destruction
5. Electric field effects (electroporation)

A report by V. Evtodienko of a study conducted by Diagnostic Technologies at the University of Carleton, Ottawa, Canada during April – July 2006 itemized the following results:

1. Experiments on E. coli reduction during the deionization cycle of a unit confirmed free chlorine (generated by the unit) is the main mechanism of bacteria inactivation
2. The main killing of microorganisms happened in the upstream space between the outer electrode and ion-exchange cartridge.
3. An un-powered unit doesn’t retain microorganisms at all.

In a series of experiments, carried out between September 29 and October 6, 2005, Biovir Laboratories tested bacteria and virus deactivation at various deionization currents and various flow rates to explore the bacteria and virus deactivation capabilities of an earlier unit model and reported the following:

“The chlorine created in the system is thought to be one of the principal microbe deactivation mechanisms. Increasing the influent chloride concentration did not necessarily increase the amount of chlorine in the product water (Table 6), but did tend to increase the level of bacteria and virus deactivation (Table 7). Lower flow rates also increased deactivation. A summary of chloride concentration and flow rate, versus log bacteria and virus reduction is given in the last section of this report.”

Comparison of systems

When comparing the ion exchange water treatment system to an RO system, several key characteristics stand out as significant. Most notably, the ion exchange treatment system reduces the amount of water waste, produces superior flowrates, prevents microbial growth in the membranes and is unaffected by water temperature, feed pressure or back pressure from a tank. A comprehensive list of comparisons is presented in Table 5.

Conclusion

A new technology employing electricity to perform ion exchange, effectively reduces a wide range of dissolved solids to produce high quality drinking water provides high flowrates directly to a faucet or to refill a tank, is relatively unaffected by water temperature and water pressure and provides feedback to the consumer indicating system status. Most importantly, compared to conventional RO systems and bottled water, this new drinking water system wastes much less water and provides consumers the ability to adjust the taste of their water with the turn of a dial.

Reference

1. Ted Kuepper, Ted; Lovo, Robert Lovo and Silbernagel, Mark. An Open-Loop Recirculation Flow Pattern: Eliminating Water Waste in Membrane-Based POU Applications, Part 2 of 2, Water Conditioning & Purification, August 2001.

About the Author

H. Martin Jessen, Vice President of Pionetics Corporation, has over 35 years experience in for profit, non-profit and governmental agency management. He has managed operating divisions and directed the marketing efforts for major water industry corporations. Jessen also serves as Vice President of Rayne Water Corporation and previously held senior management positions with US Filter Corporation. Active in public affairs, Jensen currently serves on the WQA Board of Directors, and is Chairman of the WQA Government Relations Committee and Vice President of PWQA. He is also a Board Member of the Arizona Water Quality Association (AWQA), Phoenix Parks & Conservation Foundation, a founding member and officer of Great Lakes Protection Fund and past Member of USGS Committee on Water Data. Jessen can be reached at [email protected].

About the System

The LINX^® water treatment system is currently available in two applications: under-the-sink and a water cooler module. LINX technology employs electricity to perform ion exchange, extracting dissolved solids, and producing high quality drinking water.

About Pionetics Corporation:

Pionetics Corporation of San Carlos, CA, is an innovative water technology company that develops smart water treatment products. The privately owned firm, financially backed by Kline Hawkes & Co, NGEN Partners and Unilever Technology Ventures Fund, has been issued over 50 patents worldwide. For more information, visit www.LINXWater.com.