Model Overview

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 lt0.33
• Approach to threshold is steep cant 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 D28D209
• Guides rebound at all points downstream of WWTP A
• Use more offsets if more setpoints defined

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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

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Output on Control page