Modelling chlorination

Step-by-step Guide

InfoWorks WS Pro can model water quality in a network, tracking dissolved substances as they travel through it.

Water quality runs—especially those dealing with chlorination—tend to happen over an extended time to create a more stable simulation.

This example sets a baseline chlorination for all nodes in the network to represent the residue chlorine within the network. Then, it simulates regular doses of chlorine to the reservoir to maintain a concentration level throughout the network.

To set the baseline chlorination:

1. From the Model Group window, Session 02, drag-and-drop BridgeNet into the workspace to open the GeoPlan.
2. In the Scenarios toolbar, select Create scenario.
3. Name the new scenario “Water Quality”.
4. Enable Create matching scenario in the Control.
5. Click OK.

6. In the Scenarios toolbar, in the Select scenario drop-down, ensure that Water Quality is selected.
7. Zoom into the reservoir on the left side of GeoPlan.
8. Double-click node 544421 to view its properties.

9. In the Properties panel, expand Water Quality.
10. In the Water Quality Concentration cell, click More (…).

11. In the profile graph window, in the Date Time column, expand the drop-down and select May 2, 2022.

12. Leave the time of day set to 00:00:00.
13. In the Conc. (mg/l) column, enter “1”.
14. In the second row, set the date to May 2, 2022.
15. Set the time to 08:00:00.
16. Set the concentration to “100”.
17. In the third row, set the date to May 2, 2022.
18. Set the time to 14:00:00.
19. Set the concentration to “1”.
20. Click OK.
21. In the Properties panel, Water Quality section, enable Repeat Profile.

To set the same dates, times, and concentrations for the other reservoir node:

22. Repeat Step 10 to re-open the profile graph window for the first node.
23. In the table, select all the values.

24. Copy the values.
25. Click OK.
26. Repeat Steps 8-10 to open the profile graph window for the second node, 530491.
27. Click in the top-left cell of the table.
28. Paste the values.
29. Click OK.

30. Commit the changes to the database.

To create a new solute data object to test in the system, by assigning the properties of a substance to it:

31. In the Model Group window, right-click Session 02 and select New > Solute Data Group.
32. In the New Name – Solute Data Group dialog box, click OK.
33. Right-click Solute Data Group and select New > Solute Data.

34. In the New Name – Solute Data dialog box, enter the name “Chlorine”.
35. Click OK.
36. In the Model Group window, under Solute Data Group, double-click Chlorine.
37. In the Solute Data – Chlorine window, Basic Water Quality tab, select Conservative Substance.
38. Set the Initial Concentration or Unset Nodes (mg/l) to “5”.
39. Set the Concentration Limit (mg/l) to “500”.
40. Click Save.

41. Close the window.

To simulate regular doses of chlorine to the reservoir:

42. Create a new Run using the BridgeNet and BridgeCon network and control.
43. In the Create New Scenario dialog box, enter the name “Water Quality-Chlorine”.
44. Enable Experimental.
45. In the Scenarios tab, disable the Base scenario.
46. Enable the Water Quality scenario.
47. Under Run Parameters, set the End field to May 9, 2022, to run the model for an extended time.

Notice the Start field is already set to May 2, 2022, a week before the end of the run. It is not necessary to set exact times for either of these fields.

48. In the Run Type group box, expand the drop-down and pick Water Quality.
49. From the Model Group window, drag the Chlorine solute data into the Water Quality Options dialog box and drop it in the Solute Data group box.

50. Click OK.

Note: To easily reopen the Water Quality Options dialog box, click Options in the Run Type group box.

51. Click Save.
52. Click Run.

In the Model Group window, under Run Group, the simulation results now appear under Water Quality Chlorine.

53. Drag-and-drop Water Quality into the GeoPlan.
54. In the Tools toolbar, click Graph.
55. In the GeoPlan, double-click a node.

56. In the Select what to graph for dialog box, select Concentration 01 (mg/l).
57. Click OK.

It is possible to include more than one substance at a time in a simulation, to compare how the concentrations of each dissipate over time. In this case, Concentration 01 represents the chlorine data object. Adding multiple solute data objects adds them to this list.

A graph opens, showing chlorine concentration at the selected node over time. In this example, because the selected node is immediately downstream from the reservoir, the initial concentration is low (around 5 mg/l), and then increases suddenly as chlorine arrives.

For comparison, graph concentrations at other nodes in the network.