Generic Treatment Node

Transfer Functions

For each pollutant (TSS, TN, TP and gross pollutants), performance of the Generic Treatment can be described using one of three options as shown below:

1. A concentration-based capture efficiency (defined by a table) - define the outlet concentration as a function of the inlet concentration;
2. A flow-based capture efficiency (defined by a table) - Entered in a table, this allows you to define a percentage of capture of each pollutant as a function of the flow. A 100% capture represents a total reduction of the pollutants, whereas 0% capture means that the node has no effect on the pollutant. Note that if your table does not cover the entire hydrograph then music extrapolates linearly using the last two values of the table; or
3. A combination of the above options  - When the option Both is selected, the concentration-based transfer function is applied on the captured percentage of the flow. This provides greater flexibility and more options in your model. For example, you can model reduced efficiency with higher inflows into the GPT. The concentration-based reduction can now be altered by the flow-based efficiency, thus providing higher accuracy. For example:
   1. When inflow is 0.931m3/s and input concentration for TSS is 304mg/L, the flow-based capture efficiency will be 100%. Then, the concentration-based transfer function will apply to 100% of the incoming flow, i.e.304 mg/L*0.1 = 30.4 mg/L. So the output concentration for TSS will be 304mg/L.
   2. In the case, when inflow is 2.35m3/s and input concentration for TSS is 410mg/L, the flow-based capture efficiency will be 60%. Then, the concentration-based transfer function will apply to the captured flow (i.e. 60% here). 60% of the flow with 410 mg/L reduced to 410*0.1 = 41 mg/L and 40% of the flow not captured, at 410 mg/L gives the final value of TSS concentration as 0.6*41+0.4*410 = 188.6mg/L.

         The Properties dialog shown above is used in the example described next.

To use the function editor:

• Select the required pollutant using the radio-buttons adjacent to each pollutant. For each pollutant, you can choose how to display the transfer functions: as a concentration based transfer function only, as a flow-based capture efficiency only, or both. This is done using the appropriate radio buttons above the Transfer Function Tables.

• You can add new points in the table manually. You can also import the file.

If you wanted to simulate a Generic Treatment which removed 90% of all gross pollutants, you would create a straight line with a slope (ie. output/input) of 0.1, as expressed by the form:

• Gross Pollutant Output = 0.1 • Gross Pollutant Input.

Using the above example, this would be created by entering an output value of 100 for an input value of 1000.

• inflow rate and water quality

• outflow rate and water quality

• low and high flow bypass rate and water quality

• total outflow rate (sum of outflow and bypasses) and water quality.