Ion 302 Surveying a Water Softener
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This document discusses surveying and troubleshooting water softeners. It covers monitoring softener performance, conducting a survey of softener operations, performing an elution study to evaluate regeneration efficiency, troubleshooting issues like short service runs or high hardness, analyzing resin samples, and identifies resources for additional information. The goal is to collect data, gain knowledge, and use available resources to properly maintain high-performing water softeners.
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Ion 302 Surveying a Water Softener
- 1. ION-302 Surveying a Water Softener Presented by Crown Solutions University James McDonald, PE, CWT October 31, 2011
- 2. Agenda 1. Water Softeners 2. Monitoring 3. Surveying 4. Elution Study 5. Troubleshooting 6. Resin Analysis 7. Resources 8. Summary 2
- 3. 1 Water Softeners 3
- 4. Water Softeners 4
- 5. Ion Exchange Reactions Na Ca Na Na Na Na+ Ca2+ Na Na Na Na Na+ Na+ Mg2+ Na Na Na Mg Na+ Na HCO3- HCO3- Ca++ Ca++ R-(Na+)4 + Cl- R- + (Na+)4 Cl- Mg++ Mg++ SO4-- SO4--
- 6. Keeps Going and Going… 6
- 7. 2 Monitoring 7
- 8. Softener Monitoring Total Hardness Testing • Beginning • Before regeneration • During Incoming Water Hardness • More • Less • Same 8
- 9. Softener Capacity (Ec) * (ft3) *17.1 Softened Gallons = TH Typical Strong Acid Cation Resin Where: Softening Exchange Capacities • Ec = Exchange Capacity (grains/ft3) Salt Capacity (lb/ft3) (gr/ft3) • ft3 = Cubic feet of resin 6 21,000 • TH = Total hardness (ppm or mg/L as CaCO3) 8 24,000 10 27,000 12 29,000 Capacity Percentage? 15 30,000 • 90% common 9
- 10. Softener Calculations & Survey Workbook Association of Water Technologies (AWT) • Pretreatment Subcommittee Worksheets • Capacity, Survey Form, Elution Study, Interpretive Curves, Troubleshooting, NaCl Properties, Resin Analysis, Regenerant Water, References 10
- 11. 3 Surveying 11
- 12. Surveying Operations Manual Conduct a Survey 12
- 13. Regeneration Steps Service Flow Backwash Brine Cycle Slow Rinse Fast Rinse 13
- 14. Surveying Resin Bed Depth • “Stick the resin” Unit Freeboard • Minimum 50% bed expansion during backwash Service Flow Rate • 2-14 gpm/ft2 possible • 6 gpm/ft2 typical 14
- 15. Surveying Backwash Water Temperature • Cooler water more dense & viscous • Avoid resin loss Backwash Flow Rate • 6 gpm/ft2 typical • Based upon water temperature Backwash Time • 10 minutes • Longer for dirtier resin beds 15
- 16. Surveying Concentrated Brine Solution Strength • Salometer Quantity of Salt Used • Measure brine usage & saturation • “NaCl Properties” worksheet Expected Leakage • Total Hardness of 50 ppm as CaCO3 Leakage approximately 0.1 ppm as CaCO3 • 500 ppm ≈ 1 ppm • 1,000 ppm ≈ 2 ppm 16
- 17. Surveying Slow Rinse Flow Rate • Same as brine flow rate Fast Rinse Flow Rate • Often 1.5 x Slow Rinse Flow Rate Total Rinse Required • 60 gal/ft3 resin is typical 17
- 18. 4 Elution Study 18
- 19. Elution Study Very useful tool Test regeneration efficiency 50 Salometer Degrees (% Saturation) 45 40 35 30 25 20 15 10 5 0 0 10 20 30 40 50 60 70 Time (minutes) 19
- 20. Elution Study During Brine Cycle Measure brine saturation every 3-5 minutes • Salometer & 250 mL graduated cylinder Graph results “30 degrees for 30 minutes” Salometer Degrees (% Saturation) 50 45 40 35 30 25 20 15 10 5 0 0 10 20 30 40 50 60 70 Time (minutes) 20
- 21. 5 Troubleshooting 21
- 22. Troubleshooting Short Service Runs High Hardness in the Product Water High Pressure Drops 22
- 23. Troubleshooting Interpreting Elution Curves 80 60 Salometer Degrees (% Salometer Degrees (% 70 50 60 Saturation) Saturation) 50 40 40 30 30 20 20 10 10 0 0 -10 10 30 50 70 -10 10 30 50 70 Time (minutes) Time (minutes) 60 50 Salometer Degrees (% 50 Salometer Degrees (% 40 Saturation) 40 Saturation) 30 30 20 20 10 10 0 0 -10 10 30 50 70 Time (minutes) 0 20 40 60 80 Time (minutes) 23
- 24. 6 Resin Analysis 24
- 25. Resin Analysis Core sample • Representative of entire bed Grain thief or hollow pipe Backwash & drain first 3+ oz sample typically required “Softener Calculations & Survey Workbook” • Resin Analysis Worksheet 25
- 26. Resin Analysis Labs ResinTech www.resintech.com Purolite www.purolite.com 26
- 27. 7 Resources 27
- 28. Resources Softener Calculations & Survey Workbook • References Worksheet ResinTech www.resintech.com Purolite www.purolite.com 28
- 29. Regenerant Wastewater Characteristics Influent Water Characteristics Average Regeneration Water Characteristics Regeneration Water Volume 29
- 30. 8 Summary 30
- 31. Summary Data, information, knowledge More to know Use resources 31
Editor's Notes
- During this presentation, we will cover.
- Sodium zeolite water softeners come in all shapes, sizes, and colors, but regardless, their main goal is to soften water. That is, to remove hardness or, technically, calcium and magnesium.
- Now, it would be great if this process kept going and going and going, and water softeners do keep going and going if they are maintained properly. These machines aren’t flashy with red lights and whirling gears and are easy to forget until they run out of salt or something else goes wrong and suddenly hard water is causing problems down stream.
- It is vitally important to monitor the performance and capabilities of a water softener.Test the total hardness of the softened water at the beginning of a service run, at the end near regeneration, and throughout the service run.Test the hardness of the incoming water. Has it changed? Is it more or less hard?Calculate the capacity of the water softener.
- There are a few ways to calculate the softening capacity of a water softener. The equation shown is one way.The strong acid cation resin’s exchange capacity (Ec) is multiplied by the cubic feet of resin, then 17.1, and then divided by Total Hardness in ppm or mg/L as CaCO3. The table to the right lists typical strong acid cation resin softening exchange capacities, but you should always refer to the manufacturer’s specifications for the specific resin when possible.Theoretically, the results yield 100% capacity, but in practice, you will get hardness leakage before 100% is reached. A typical rule of thumb is shoot for 90% capacity, so multiply your results by 90%.
- This brings me to the “Softener Calculations & Survey Workbook.” This Microsoft-Excel-based tool was developed for the Association of Water Technologies (AWT) by the Pretreatment Subcommittee, which I chair. This workbook tool includes worksheets on capacity calculations, a survey form, an elution study data table and graph, interpretive curves, troubleshooting advice, NaCl properties, resin analysis guidance, regenerant water estimates, and references. We will cover each worksheet as appropriate throughout the presentation.(Move to Workbook) Taking a look at the workbook itself, we start with the Instructions. (Review the instructions)Now, taking a look at the “Capacity” worksheet, we see another way to calculate softener capacity. This worksheet allows you to enter total hardness as ppm CaCO3, iron as ppm Fe, cubic feet of resin, exchange capacity in grains/ft3, and has a 90% assumption in green for expected % capacity. It then calculates the softening capacity in gallons.For example, if we have 250 ppm of total hardness, 0.1 ppm iron, and 20 cubic feet of resin, we can enter those values into our worksheet (enter values). What is our exchange capacity? Let’s use the help comment in cell A7 for guidance. If you hover your mouse of cell A7, the help comment pops up. At 10 lb/ft3 salt dosage is typical, so we’ll stick with the 27,000 grains/ft3 already entered. We’ll also stick with 90% capacity. This example softener should be able to soften 55,404 gallons of hard water before a regeneration is required.
- As a responsible water manager, you should really get to know your water softener. This is to ensure both long-term, efficient operation of the softener and to help with troubleshooting should a problem arise.First, if there is an operations manual, you should thoroughly review it. Second, you should conduct a survey of the unit. The “Softener Calculations & Survey Workbook” has a Survey Form worksheet just for this purpose. (Move to Survey Form worksheet) Taking a look at this worksheet, we see there are columns for Parameters, Manufacturer Specifications, Resin Specifications, and Actual Data. Not all the fields will be filled out, but this should be pretty easy to figure out. We will cover some of these items in more detail soon, but let’s look down the list of items to survey. (Review the Survey From workbook line by line)
- As a review of terminology, let’s briefly discuss the steps required for a softener regeneration.Service Flow: This is the flowrate and direction of flow during normal water softener operation.Backwash: When a regeneration is initiated, the first step is a backwash to fluff up the resin bed and wash out any debris or resin fines. The flow is in the opposite direction of the Service Flow.BrineCycle: This is the heart of the regeneration cycle, as high levels of brine (NaCl) refresh the resin by “eluting” the calcium and magnesium off the resin beads so it can be sent down the drain.SlowRinse: This is a continuation of the Brine Cycle to allow sufficient reaction time between the brine and resin.FastRinse: This final step flushes out any remaining brine and settles the resin bed back down for the next Service Cycle.
- Going into more detail for some of the Survey Worksheet items we just covered, let’s start with Resin Bed Depth.Resin Bed Depth: You’ll need to “stick the resin” with a small diameter pipe until it hits the support media to get a measure of resin bed depth. Some like to mark the resin depth with the date on the side of the softener.Unit Freeboard: There needs to be room for the resin bed to expand by at least 50% during backwash.Service Flow Rate: A range of 2-14 gpm/ft2 is possible, with 6 gpm/ft2 typical.
- Backwash Water Temp: This can be very important, because as the water temperature drops, the density and viscosity of water increases, which could lead to resin loss with backwashes during the colder months when none was experienced during the warmer months. The chart on the right is for DOWEX HGR-W2 resin at 77 F. In this example, for a 50% bed expansion, one would need 9 gpm/ft2.BackwashFlowRate: 6 gpm/ft2 is typical, but depends upon the water temperature as we just saw.BackwashTime: 10 minutes is common, with longer times used for dirtier resin beds.
- Concentrated Brine Solution Strength: Using a Salometer or hydrometer, this should be near 100% in the brine tank right before regeneration. If not, steps to mix or agitate the brine solution may be necessary. The picture on the right is a salometer.QuantityofSaltUsed: You can determine this by measuring how much brine was used during regeneration, measuring saturation with a Salometer, and using the “NaCl Properties” worksheet to calculate the weight of salt consumed. (Go to “NaCl Properties” worksheet and discuss briefly.)ExpectedLeakage: The amount of hardness “leakage” is dependent upon the concentration of sodium, calcium and magnesium in the influent. When total influent hardness is 50 ppm as CaCO3, leakage is about 0.1 ppm. Influent of 500 ppm yields 1.0 ppm leakage and 1,000 ppm yields 2 ppm. Refer to the resin technical specifications for more accurate leakage numbers.
- Slow Rinse Flow Rate: This flow rate is usually the same as the brine flow rate, since it is considered part of the brining step to allow more time for the brine to regenerate the resin beads.FastRinseFlowRate: This flowrate is used to rinse out the remaining brine and settle the resin bed back into place. It can often be 1.5 times the Slow Rinse Flow Rate.TotalRinseRequired: The total amount of water required to accomplish a regeneration is typically around 60 gal/ft3 resin.
- One of the most useful tools to troubleshoot and monitor the efficiency of a water softener is an elution study. Elution studies are performed on softeners to determine whether or not they are being regenerated efficiently. During the Brine Cycle of a regeneration, the concentration of the brine exiting the water softener is measured by using a salometer or hydrometer. (Switch to camera to show salometer.)
- When the brine cycles begins, collect samples of the regeneration water leaving the softener and use the salometer to measure how saturated the water is with brine (NaCl). You should take a measurement every 2-5 minutes for the duration of the brine cycle and into the slow rinse cycle until the brine levels drop. The more frequently you take a sample, the smoother your elution curve will be.Graph your results because the shape of the curve can tell you a lot about how efficient the brine cycle was and what problems the softener may have. The “Softener Calculations & Survey” workbook has a worksheet to help you conduct your elution study. (Go to “Elution Study” worksheet and review.)
- Water softeners can be reliable units that produce soft water day in and day out if maintained properly. There are troubles that can pop up though. Examples include: short service runs, high hardness in the product water, and high pressure drops. The “Softener Calculations & Survey” workbook has a “Troubleshooting” worksheet that can help point you in the right direction. (Go to” Troubleshooting Worksheet” and review.)
- Now, we’ve talked about how to do an elution study. We also just talked about how doing an elution curve can help you troubleshoot, but how do you interpret the elution curves. Once again, the “Softener Calculations & Survey” workbook has an “Interpretive Curves” worksheet to help you do just this. (Go to “Interpretive Curves” worksheet and review.)
- One should do as much troubleshooting as possible in the field because results can happen much faster than sending resin in for analysis and waiting several weeks for the results. When a resin analysis is necessary, be sure to get a core sample…something representative of the entire resin bed. A grain thief or hollow pipe will work. For example, a ¾” piece of PVC piping. Sample all the way down to the support media after the unit has been backwashed and drained. At least a 3-ounce sample is typically required for softener resin. The “Softener Calculations & Survey Workbook” has more information on its Resin Analysis worksheet. (Go to Resin Analysis worksheet and review contents.)
- There are several labs than can do resin analysis. Here are a couple of providers: ResinTech and Purolite.
- You have plenty of resources available. Several are listed in the Reference worksheet in the “Softener Calculations & Survey Workbook.” (Go to References Worksheet & review list of references.)ResinTech and Purolite have great websites with technical bulletins and white papers available.Don’t forget your local resin manufacturer representative either.
- One last worksheet I want to show you is the “Regenerant Wastewater Characteristics” worksheet. (Go to “Regenerant Wastewater Characteristics” worksheet.) This worksheet allows you to enter influent water characteristics and softener assumptions. It then calculates an estimate of what the total wastewater would look like for calcium, magnesium, chlorides, and sodium plus an estimate of total regeneration water volume.
- In summary, what seems like a simple water softener on the surface requires a lot of data, information, and knowledge to ensure efficient operation. We’ve covered a lot of information in this webinar, but there is so much more that could be covered. I recommend you refer to your softener’s Operations Manual, the references listed in the “Softener Calculations & Survey” Workbook, the online resources listed, books, articles, etc.