# EPANET: [REACTIONS]

[REACTIONS]

Purpose:

Defines parameters related to chemical reactions occurring in the network.

Formats:

ORDER BULK / WALL / TANK value

GLOBAL BULK / WALL value

BULK / WALL pipeID value

TANK tankID value

LIMITING POTENTIAL value

ROUGHNESS CORRELATION value

Definitions:

ORDER is used to set the order of reactions occurring in the bulk fluid, at the pipe wall, or in tanks, respectively. Values for wall reactions must be either 0 or 1. If not supplied the default reaction order is 1.0.

GLOBAL is used to set a global value for all bulk reaction coefficients (pipes and tanks) or for all pipe wall coefficients. The default value is zero.

BULK, WALL, and TANK are used to override the global reaction coefficients for specific pipes and tanks.

LIMITING POTENTIAL specifies that reaction rates are proportional to the difference between the current concentration and some limiting potential value.

ROUGHNESS CORRELATION will make all default pipe wall reaction coefficients be related to pipe roughness in the following manner:

Head Loss Equation | Roughness Correlation
--- | ---
Hazen-Williams | F / C
Darcy-Weisbach | F / log(e/D)
Chezy-Manning | F * n

where F = roughness correlation, C = Hazen-Williams C-factor, e = Darcy-Weisbach roughness, D = pipe diameter, and n = Chezy-Manning roughness coefficient. The default value computed this way can be overridden for any pipe by using the WALL format to supply a specific value for the pipe.

Remarks:

1. Remember to use positive numbers for growth reaction coefficients and negative numbers for decay coefficients.
2. The time units for all reaction coefficients are 1/days.
3. All entries in this section are optional. Items offset by slashes (/) indicate allowable choices.

Example:

[REACTIONS]
ORDER WALL 0 ;Wall reactions are zero-order
GLOBAL BULK -0.5 ;Global bulk decay coeff.
GLOBAL WALL -1.0 ;Global wall decay coeff.
WALL P220 -0.5 ;Pipe-specific wall coeffs.
WALL P244 -0.7