Software for P-Removal Structure Design

top pict 3









What is Phrog Software?

Phrog (Phosphorus Removal Online Guidance) is software for designing a site specific P removal structure to meet desired P removal goals.  Phrog allows the user to design a custom P removal structure based on user specified information:

  • Site hydrology (total annual flow volume, peak flow rates, hydraulic head)
  • Typical dissolved P concentrations at site
  • Desired P removal performance of structure (% P removed)
  • Desired lifetime of structure
  • Characteristics of the specific P sorption materials (PSMs) that are locally available to the user
  • Desired peak flow rates through the P removal structure
  • Desired contact time (not necessary for all PSMs)
  • Maximum area or length that can be utilized for the P removal structure
  • Preferred pipe diameter to be used for the P removal structure

The software is flexible enough to allow the user to design a P removal structure with any effective PSM that is available to them for any scenario that allows for P rich water to be channeled through a bed of PSMs.  This includes both urban and rural environments.  For example, a P removal structure can be incorporated into bio-retention cells (rain gardens), surface inlets, wastewater treatment, ditch filters, storm water inlets, runoff filters, etc., anywhere that flowing water with high concentrations of dissolved P can be channeled into a single point.

In addition, Phrog software also allows the user to predict the performance and lifetime of an existing P removal structure.  It is important to keep in mind that Phrog works on a load (i.e. mass of pollutant) basis; this is critical because not only are current point and non-point source water discharge regulations based on loading, but it is the P load that directly impacts a water body.  An example of the simple and user-friendly interface for Phrog input is shown below:

Online Phrog input


The Phrog output specifies the mass of the PSM (identified by the user) that is necessary to meet the P removal goals.  Phrog output provides the orientation in which the PSMs must be placed at that site, and also the number of drainage pipe, in order to meet the desired maximum flow rate specified by the user.  In addition, Phrog output provides a table that shows how much cumulative dissolved P is removed on an annual basis throughout the entire lifetime of the PSMs i.e. until the PSMs are “spent” and no longer effective at removing dissolved P.  An example of Phrog output for design of a bed style P removal structure is shown below:

Online Phrog output

The flexibility of the input interface allows the user to examine several different scenarios for a single site to explore the possibilities.  For example, one can easily vary the size or slope of the drainage pipe, P removal goal or lifetime, and even experiment with different PSMs that have pre-set characteristics.

Last, while the software and concept of P removal structures are targeted to capturing dissolved P, Phrog will allow the user to additionally estimate how much particulate P and total P are also trapped by a designed structure.  In other words, Phrog works by determining a design by meeting the specified P removal goals for dissolved P, but it will also let the user know how much particulate and total P will additionally be removed by that structure, at that site, if the user provides some additional optional inputs.

If you are interested in using the Phrog software or would like to design a P removal structure, please contact Chad Penn at or Stuart Wilson at  If you would like to see a demonstration of the software, please click on the “Tutorial” link located near the top of the page.  A book dedicated to designing P removal structures and also serve as a software guide for Phrog is currently being written and will be published by Springer.




PhROG logo (official tm)