Question of the Day: Softener Elution Study

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Question of the Day: Softener Elution Study
Why and how is an elution study preformed on a water softener?

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3 Answers

  1. Poor regeneration practices are often the cause of problems in zeolite softener systems. 

     

    An elution study is used to identify and correct softener problems. The study plots the concentration (specific gravity) of brine from a zeolite softener during regeneration along with recording cycle times.

  2. An elution study is performed on a water softener during regeneration to determine how well each step has been set up, and to look at results of each step:

    (1) during back-wash is there any loss of resin?  What is the flow rate, and does the vessel/system shudder or slam at the beginning of the back-wash?

    (2) during brine draw what is the salt concentration profile over time?  This means sampling repeatedly during this step, and plotting results.  What are the calcium, magnesium, etc. concentration profiles over time during this step?  Are you stopping brine flow too soon, or are you wasting brine after there is no further elution of calcium and magnesium?

    (3) during slow rinse step, is the flow rate correct, and what is the conductivity profile over time?

    (4) during fast rinse, are you allowing sufficient rinse in to settle the resin bed well?  Is the flow rate correct, and is there still a highly elevated conductivity profile, or not?  How much residual hardness is detected during this step?

  3. Softener elations are performed to document the hydraulic characteristics of the operation - including Service, Backwash, Brine Introduction, Displacement Rinse, and Service or Fast Rinse.  Elation studies are often performed as a troubleshooting exercise when the softener is either operating with less than expected soft water volume between regenerations or with poor quality water during operation.  Each regeneration step is documented:  Backwash Flow and Duration; Brine introduction Flow and Brine Concentration exiting the softener versus time - goal being at least 10% Brine exit the softener for 30 minutes; Displacement Rinse Flow and exit brine concentration versus time; and finally Service Rinse Flow and exit brine concentration versus time.  A plot is created with time on the x-axis and brine concentration on the y-axis.  This plot is then analyzed and compared to design specifications.  Conclusions and recommendations are developed based upon the analysis of the elation study.