Modeling treatment for pollutants at nodes or ponds in SewerGEMS and CivilStorm

  Applies To 
  Product(s): CivilStorm, SewerGEMS
  Version:  CONNECT Edition, V8i
  Area: Layout and Data Input


What is the workflow to model treatment for pollutants in nodes and ponds using the Explicit (SWMM) solver in SewerGEMS and CivilStorm?


For this type of analysis, you would need to use EPA-SWMM features, so the solver needs to be set to Explicit (SWMM) in the calculation options.(Analysis>Calculation Options)

In the properties of the pond or node, find the section SWMM Extended Data. Find the property field Apply Treatment and set this to True. Then click in the Treatment Collection to open a new dialog. The Treatment Collection will include the pollutant and a treatment expression. For more information on the treatment expression and how this is formatted, see the Help documentation related to treatment. The EPA-SWMM user manual will have additional information as well.

A note on pond TSS removal

It's essentially impossible to have an accurate model of TSS (Total Suspended Solids) removal at a pond based on simple parameters such as detention time.

Consider the kinds of solids that are in pond influent; they can range from colloidal clay which will not be removed much at all to sandy erosion from a construction site that will tend to settle much better.

As for the treatment expression to model this, consider an equation such as the one mentioned here (SWMM Water Quality manual) or here, possibly adjusting it if you have data from ponds in the area with similar solids. High precision is not to be expected.

Reference: (forum discussion) TSS removal in a permanent retention (wet) pond

See Also

SWMM User Manual

SWMM water quality User Manual

Prediction of quality characteristics of sewers

Modeling septicity / hydrogen sulfide (H2S)

(Forum) TSS removal in a permanent retention (wet) pond

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