MUSIC allows you to simulate the performance of any other treatment measure, that is not included in the default range of treatment measures provided. For example, you may wish to compare the performance of a stormwater strategy which used only non-structural methods (community education, etc) with the installation of a gross pollutant trap (GPT). In MUSIC X Version, Generic Treatment Device is used as GPT as well for treating Gross Pollutants.
MUSIC provides a Generic Treatment Node, for which the user describes the performance using a series of transfer functions.
Generic Treatment Node Properties Dialogue Box
Inlet Properties
Low Flow Bypass
All of the stormwater that approaches the generic node below the user-defined Low Flow Bypass amount will bypass the node. Any flow above the Low Flow Bypass (subject to the presence of a High Flow Bypass) will enter and be treated by the node.
High Flow Bypass
When the stormwater inflow rate exceeds the user-defined High Flow Bypass amount, only a flow rate equal to the High Flow Bypass (less that specified in any Low Flow Bypass) will enter and be treated by the node. All of the stormwater flow in excess of the High Flow Bypass amount will bypass the node and will not be treated.
Tip Box
The Low and High Flow Bypasses are assumed to occur simultaneously. So for a Low Flow Bypass of 2m3/s, a High Flow Bypass of 8m3/s, and inflow of 10m3/s:
Transfer Functions
For flow, performance of the Generic Treatment can be described using flow based capture efficiency as shown below:
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:
- A concentration-based capture efficiency (defined by a table) - define the outlet concentration as a function of the inlet concentration;
- 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
- 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.
The Properties dialog shown above is used in the example described next.
This table shown below has been extracted from the recorded file. Notice the following:
- At 19:54, the inflow is 0.237 m3/s, so the flow based capture efficiency will be 100%. Then, the concentration based transfer function will apply to 100% of the incoming flow, i.e. 234 mg/L • 0.4 = 93.5 mg/L.
- At 20:00, the inflow is 1.63 m3/s, so the capture percentage is 50% (as defined in the table of the previous figure). Then, the concentration based transfer function will apply to the captured flow (i.e. 50% here).
- 50% of the flow with 50.2 mg/L reduced to 50.2•0.4 = 20 mg/L and 50% of the flow not captured, at 50.2 mg/L gives the final value of 0.5•20+0.5•50.2 = 35.1mg/L.
Time | Inflow (m3/s) | Totaloutflow (m3/s) | TSSinflow(mg/l) | TSSoutflow(mg/l) | TSStotaloutflow(mg/l) |
|---|---|---|---|---|---|
25/04/1970 19:54 | 0.237 | 0.237 | 234 | 93.5 | 93.5 |
25/04/1970 20:00 | 1.63 | 1.63 | 50.2 | 35.1 | 35.1 |
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.
It is possible to view or save various flows and water quality as below for the Generic Treatment Node:
- 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.
You need to select them to record before you run.