Water Quality Analysis

Application Overview:

• See Water Quality Setup for details on user input options for this application.  

• For general details on running an application, selecting and displaying output variables, see Running DEW Applications.  

• The Available Output Variables for the application are described in the last section of this topic.

The Water Quality Application utilizes initializing (or preceding) quality conditions and results from the Fluid Flow application to calculate various constituent concentrations, source propagations, and water age throughout the network for the applicable time period.  The results include the effects of transport, mixing, and chemical reactions occurring in the bulk fluid and at pipe wall.  

• Changes in constituent concentrations in a pipe are modeled using conventional one-dimensional advective-reactive transport, which assumes negligible longitudinal dispersion and a fully-mixed bulk fluid.  

• At pipe junctions, concentrations are mixed by performing a (flow-weighted average) mass balance on constituents entering and leaving the junction, assuming junction turbulence creates complete and instantaneous mixing of all incoming flows.

• The standard DEW model treats tanks and reservoirs as completely mixed points of known initial/boundary conditions for constituents, which can be synchronized with available data from SCADA system.

• The application models first order decay for bulk chlorine.

• Source trace analysis is used to determine the percentage of water from a defined source that occurs at a particular location.  

• Water "age" is referenced in global terms, i.e. respective to the elapsed time since the water left the user-specified source, and in local terms, which is the elapsed time that the water has been in the current component/location.  

Application Run / Results:

See Running DEW Applications for general details on running the application, selecting and displaying output variables.

The Water Quality application can be run directly or from within the Fluid System Analysis application.  In both cases, the Fluid Flow application must be run to determine the applicable hydraulic solution for the network at simulation time.  

1. When running Water Quality as a standalone application:

1.  Fluid Flow Analysis must be selected for execution before Water Quality, as shown (highlighted) in the figure below.  
   

2. Verify that Fluid Flow setup parameters are configured as desired for simulation.  (See Fluid Flow Setup for details)

3. Upon execution, The Water Quality Application Setup dialog is launched for user input, as applicable.

2. The Fluid System Analysis application automatically runs the Fluid Flow Analysis and Water Quality Analysis, sequentially calling each application for the duration of the specified time steps.  While the application prompts for the Fluid, Mixing, and Reaction time steps, the user must assure that each analysis has been otherwise configured with the desired setup parameters, e.g. Convergence Criteria, Friction Calculation Method, etc.  See Fluid System Analysis application for more details.

The results can be color-coded into the drawing using variable range display to indicate:

• Purging of "Old" fluid (i.e. with unknown age) from system

• Relative propagation of a specific source through the network

• Targeted constituent concentrations (e.g. Chlorine, Contaminant, etc) throughout system

• Stagnant regions, i.e. areas of network with excessive water aging

Available Output Variables:

For general details on running an application, selecting and displaying output variables, see Running DEW Applications.  The output variables available for display from the Fluid Flow application are described in the following table.