At Water Innovations, Inc. we engineer solutions for wastewater treatment, closed loop water recycling and purification. We utilize ion exchange to produce the highest quality water with the lowest waste volume. Our Best-In-Class ion exchange systems utilize Smart Regeneration Control (SRC) delivering precise regeneration chemistry feeds, controlled regeneration rinse volume and grain set-point automatic adjustment. Click on the video to learn more…
Water Innovations can be reached at firstname.lastname@example.org or by telephone at 760.466.7583
Tyler Roudenbush – Water Innovations’ Employee of the Quarter!
Hired in January 2013, Tyler is one of Water Innovations longest-tenured employees. In the past nearly 4 years, Tyler has become a critical employee in many areas. One day he can be writing new PLC programing code, the next building a control panel, and then and then be taking care of the company’s IT requirements. He provides excellent customer support either in the office or the field, which is a hallmark of our company. Tyler always demonstrates a positive attitude toward work responsibilities, co-workers, and customers, and serves as a role model for others. His on-going commitment to quality in carrying out job responsibilities, and his critical skills is an asset to Water Innovations. At times, Tyler has been pushed on assignments and responsibilities beyond his comfort zone and has succeeded and grown professionally from the frequent challenges. He is highly deserving of this recognition!
To learn more about Water Innovations Inc., Products or services give us a call at 760-294-1888 or email us at email@example.com
World-Class Equipment and Process Expertise
Ion Exchange Rinsewater Recycling | Proprietary Precipitation Chemistries | Reverse Osmosis | Water Purification | Rinsewater Recycling | Batch & Continuous Waste Treatment | Hydrus Water Softening & Filtration | Evaporation for Zero-Liquid Discharge | Anodizing Waste Water Treatment
Theory of Technology
Ion exchange refers to a process where different ions in solution are exchanged, or replaced, by other ions. An ion exchange media, or resin, is used to accomplish this.
Ion exchange resin is an insoluble, porous, polymer bead. The beads have a very high molecular weight and carry a functional group with either positive (+) or negative (-) charge, known as exchange sites. Negatively charged resin is called cation resin and attracts positive ions, or cations. Positively charged resin is called anion resin and attracts negative ions, or anions. They can be further classified as weak and strong acid cation resins and weak and strong base anion resins. The porosity of the bead allows water to flow through the bead, increasing the amount of contact with the exchange sites.
The strength and characteristics of the exchange sites, along with the characteristics of the ions, determine a resin’s affinity for certain ions. For example, ions with multiple charges, (e.g. Ca++) have a stronger attraction to the resin than ions with single charges. Ions of equal charge are selected by the resin based on molecular weight. Heavier ions are selected first. A resin’s selectivity is also based on an equilibrium principle. Basic water softening theory originated from this principle. In general, calcium has a +2 charge, while sodium has a +1 charge. A cation exchange resin has a higher affinity for calcium over sodium in a weak solution, such as tap water. However, in a concentrated sodium chloride brine solution, the selectivity reverses. Thus, cation exchange resin in a water softener is rinsed with a brine solution to remove the calcium from the resin bed. This is known as regeneration.
The ion exchange process is used to soften water, deionize water, scavenge metals, and recycle waste water (another form of deionization). All of these processes are accomplished utilizing the above methods.
When designing an ion exchange system, the characteristics of the influent stream need to be examined. Based on this data, a determination is made as to the most beneficial type of ion exchange treatment. The following explains these parameters.
The total dissolved solids (TDS) of the inlet water provides the total quantity of contaminants in the water and is reported as parts per million (ppm) or mg/l. The higher level of TDS, the more often the system will regenerate. Levels above 750 mg/l TDS should not be treated with ion exchange. Often times the TDS of the water is equated with the conductivity. Due to different conductive characteristics of different ions, that is not always accurate. For example, a stream with no contaminants other than silica will be very low in conductivity, yet may have very high TDS. While there are charts and equations that correlate TDS with conductance, it is best to initially analyze specifically for TDS and individual ions.
The total suspended solids (TSS) is the quantity of solids in the water that can be removed by filtration. These solids are not dissolved in the water and will not be removed by ion exchange resin. High concentrations of TSS require additional filtration. Levels should not be above 5 mg/l entering the ion exchanger, or the chance for suspended solids fouling greatly increases.
The level of suspended oils and greases coming into an ion exchange bed should not be above 0.1 mg/l. Higher levels will cause a fouling of the ion exchange resin, which would prevent it from operating properly. The inlet temperature of the water should not exceed 100oF. If the temperature does exceed this level, special design considerations are required. A temperature of 140oF can be deionized with special resins; however, expected resin life at this temperature is not more than two years. The level of organics can greatly affect the structure and ability of ion exchange resins. This is also true for free chlorine. When levels of chlorine or organics exceed 1 mg/l, additional treatment through carbon or other absorbent material is recommended. Both the maximum and average values for each of these parameters should be taken into account. While the maximum averages may be well within specifications, peak levels may drastically affect the deionization process.
Prefiltration of the water is almost always a must. Solids, which are in the water, if not removed, will plug any ion exchange column. This is especially true in the packed-bed designs of high purity systems. Adequate filtration for deionization applications is less than 5 micron filtration, usually through replaceable bags or cartridges. Particles smaller than this size are usually passed through the resin bed, causing it no harm.
This first step of the actual deionization process uses cation resins to remove positively charged ions from the water. Using the “opposites attract” rule, the negatively charged cation resin binds and removes positively charged molecules from the water. These constituents include sodium, calcium, magnesium, iron, and other metals. As these positively charged molecules are removed, hydrogen ions are released from the resin. This is the element which is exchanged off the cation resin in the deionization process.
Following the cation exchange process, the negatively charged molecules in the water are removed by the anion exchange process. Typical anion molecules present in water include chlorides, sulfates, nitrates, carbon dioxide, and silica. As the resin removes these molecules, an hydroxide ion (OH) is released. It is important that the cation exchanger be functioning properly and located before the anion. Should multivalent cations come into contact with the anion resin, they will usually precipitate within the resin bed and foul it. This is the most common type of fouling which can occur, and especially common with calcium. The H+ ions from the cation exchanger and the OH– ions from the anion exchanger immediately recombine to form water.
A polishing unit, either a cation or a mixed bed (a combination of both cation and anion resin) can be used following the cation/anion process. Without any polishing, the minimum quality of water that can be produced is between 50,000 ohm/cm (50 K) and 1,000,000 ohm/cm (1 meg). With the polishing unit, the quality can be raised all the way to 18,300,000 ohm/cm. This quality is achieved by the use of a mixed bed polisher. A cation polisher will raise the quality to above 5,000,000 ohm/cm (5 meg). When any of the resins used in the deionization process become exhausted, or have exchanged off all of their respective ions, the resins must be regenerated.
Cation resins use acids to regenerate (25-50% strength). Hydrochloric is the preferred and easiest acid to use. While other acids may be used, special regeneration techniques are required. Anion resins use sodium hydroxide (caustic) for their regeneration. The regeneration process can either be co-current flow or countercurrent. This means in the same direction as the process flow, or in the opposite direction. A countercurrent system will maximize the chemical’s ability to regenerate the resin and minimize the volume of waste.
The solution produced from this regeneration sequence will contain the same constituents as the incoming water, however, they will be concentrated and in a strong acid or caustic background. By combining the regeneration from the cations and anions, a partial neutralization can be made. However, the pH range can vary greatly in this type of mixture. It is usually necessary to send this solution to a neutralization system prior to its being discharged.
Water Innovations can be reached at firstname.lastname@example.org or by telephone at 760.466.7583
Ion Exchange Systems
This calculation is “fully-burdened” including ongoing operating costs and routine & long-term service requirements. While calculated for a 10 gpm CIX10S, it can be generally applied to all CIX systems. Based upon known CIX operating parameters and typical water & chemical costs, with 24-hour operation 26 days per month at 10 gpm flow with feed water @ 200-ppm TDS.
Labor: Assumed $12 per hour wage and a routine daily operating requirement of 1.5 hour – $468 per month
Electricity: Assumed 460V 3Ph power @ $0.10 per KWH to operate feed & DI Water pumps – $35 per month
Bag Filters: Assumed 2X per week change out of 20-inch 5 micron filters @ $5 each – $40 per month.
Resin Replacement: Conservatively-assumed every 4 years of 5-ft3 cation @ $100/ft3 & anion @ $250/ft3, 1 man-day labor at $150, waste disposal of 2.5 drums @ $150 each; for $2,350 total or $49 per month.
Carbon Replacement: Once per year including 3-ft3 @ $250 & ½ man-day at $75 for $255 total or $27 per month.
Regeneration chemistry: Assumed 2 cation regens per day using 9.8-gal 32% HCl @ $2/gal or $19.60/Day & 3 anion regens per day using 5.1 gal 50% NaOH @ $3/gal or $15.30/day for $39.20/day or $1,019 per month
Wastewater: Assumed 1 carbon backwash/week producing 80-gallons or a total of 320-gallons per month, 3 cation regenerations per day producing 255-gallons or a total of 6,630-gallons per month, and 3 anion regenerations per day producing 285-gallons or a total of 7,410-gallons per month with a combined water/sewer cost of $6/1,000-gallons and treatment costs of $9/1,000-gallons, for a combined cost of $215 per month.
Total Operating Cost: Total estimated operating cost as detailed per above is $1,853 per month.
DI Water Cost: At 10-gpm service 24 hours-per-day/26 days-per-month, 374,400 gallons of rinsewaters would be processed each month with 14,360 gallons lost to backwash & regeneration for a total volume of DI water produced of 359,640. $1,853/359,640=$0.00515 or $5.15 per 1,000 gallons of DI water produced.
Comparison with Alternatives: While every facility is different, the assumed combined cost for wastewater treatment and water/sewer is $15 per 1,000 gallons or nearly 3X rinsewater recycling by ion exchange so for 374,400 gallons per day, the expense for conventional treatment is $5,616 per month. The expense for DI Water from Service DI is typically $50 or more per 1,000-gallons or 10X or more than on-site regenerable ion exchange for a relative monthly expense for SDI of $18,700. Another alternative is Reverse Osmosis (RO) followed by Service DI with an operating cost somewhat less than recycling by ion exchange although “back-end” RO is problematic because of the potential for membrane fouling which greatly increases its need for membrane replacement and overall operating cost.
This calculation was performed by Steven A. Ward, Vice President of Sales for Water Innovations which engineers and markets ion exchange water recycling systems. Steven earned an MPH degree, completed his thesis examining the economics of wastewater treatment in the printed circuit board industry. For more information please contact Sales@waterinnovations.net or by telephone at 760.294.1888 to discuss how this estimate may differ from other applications.