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Model Overview

Model Overview. Two independent models Recurrence analysis model Defines setpoint conditions for pH and temperature Provides input to reach model Mass balance reach model Defines downstream trajectory of ammonia standard Defines downstream trajectory of ammonia concentration

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Model Overview

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  1. Model Overview • Two independent models • Recurrence analysis model • Defines setpoint conditions for pH and temperature • Provides input to reach model • Mass balance reach model • Defines downstream trajectory of ammonia standard • Defines downstream trajectory of ammonia concentration • Provides mechanism for setting permit limits such that the instream concentration will not exceed the standard at any point downstream

  2. Recurrence Model Organization • Tasks are segregated onto 10 separate pages • Some pages do not require attention • In simplest case, entries are needed on 3 pages • “Controls” • “Raw Data” • “Chronic” • sometimes also “Select pHT” • Output is on one page open “Test Recur Model.xls” now

  3. Controls

  4. Constants (you are unlikely to change) Region VII web page is useful source of info and calculation sheets

  5. Select pHT Same pattern for temperature, but only one set of default amplitudes

  6. Raw Data

  7. Data Screening • Review data carefully before loading in model (graphs are good) • Blanks are not acceptable • Judgment is required (check max and min); nothing is eliminated automatically • pH receives more attention than temperature • Outliers • Missing values • Big gaps in time are not desirable

  8. Initiate Screening • Return to Controls page • Under “Model Initiation Controls”, select button 1. “Raw Data Preparation” • Will see 10 data errors (list in Appendix A) • Make changes and compare with max/min table • There will be three probable outliers (blue)

  9. Conclude Screening • After entries have been completed or revised, return to Controls page • Under “Model Initiation Controls”, select button 2. “Accept Data Set” • Continue by pressing button 3. “Acute/Chronic Calculations” • Wait until macro ends and cursor is on cell Q2 of the “Chronic” page

  10. Set Chronic Threshold • Adjust threshold value until exceedances per year (cell Q4) is <0.33 • Approach to threshold is steep; can’t get very close without going over • Click on “Accept Threshold” button to conclude this step • Move to “Setpoint” page to view results • Setpoints must be transferred manually to the reach model

  11. Setpoint

  12. Reach Model Organization • One page controls model operation • Three pages hold input data • Separate pages carry out the mass balance calculations for acute and chronic conditions • User input may be required on every page (look for cells with yellow background)

  13. Control

  14. Control (continued)

  15. Setpoint • Abbreviated to facilitate viewing • Must copy setpoints from recur model (loaded in test model) • Chronic setpoint temperature is applied to acute conditions solely for purpose of tracking ambient K3

  16. Chem • Similar blocks for pH and total ammonia • Dimensioned for up to 30 source entries • Already loaded in test model

  17. Flow • Same layout as Chem page; up to 30 sources possible; Source names linked to Chem page • Acute columns not shown • Graphs at bottom • Data already loaded on test model

  18. ChronicMod • AcuteMod page has same layout, but 3 columns hidden (linked to chronic for Reach length, Source and Setpoint offsets • You must enter offsets

  19. Defining Offsets • In this example, only sources are two WWTPs; define offsets on ChronicMod • Enter “1” in cell D28 (WWTP A) • Enter “2” in cell D159 (WWTP B) • Setpoint offset must be entered in every reach (row) to which it applies; only one • Enter 1 in Cells D28:D209 • Guides rebound at all points downstream of WWTP A • Use more offsets if more setpoints defined

  20. Return to Control Page • Enter source offsets for WWTPs • Enter trial values for chronic ammonia (e.g., 20 mg/L in all months • Define scenario month in cell B5; start with January • Adjust until standard met; usually good to set both WWTPs equal initially • Proceed to next month...then Acute

  21. Output on Control page

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