example.msx

[TITLE]
Arsenic Oxidation/Adsorption Example

[OPTIONS]
  AREA_UNITS M2             ;Surface concentration is mass/m2
  RATE_UNITS HR             ;Reaction rates are concentration/hour
  SOLVER     RK5            ;5-th order Runge-Kutta integrator
  TIMESTEP   360            ;360 sec (5 min) solution time step
  RTOL       0.001          ;Relative concentration tolerance
  ATOL       0.0001         ;Absolute concentration tolerance

[SPECIES]
  BULK AS3   UG             ;Dissolved arsenite
  BULK AS5   UG             ;Dissolved arsenate
  BULK AStot UG             ;Total dissolved arsenic
  WALL AS5s  UG             ;Adsorbed arsenate
  BULK NH2CL MG             ;Monochloramine

[COEFFICIENTS]
  CONSTANT Ka   10.0        ;Arsenite oxidation rate coefficient
  CONSTANT Kb   0.1         ;Monochloramine decay rate coefficient
  CONSTANT K1   5.0         ;Arsenate adsorption coefficient
  CONSTANT K2   1.0         ;Arsenate desorption coefficient
  CONSTANT Smax 50          ;Arsenate adsorption saturation limit

[TERMS]
  Ks       K1/K2            ;Equil. adsorption coeff.

[PIPES]
  ;Arsenite oxidation
  RATE    AS3    -Ka*AS3*NH2CL
  ;Arsenate production
  RATE    AS5    Ka*AS3*NH2CL - Av*(K1*(Smax-AS5s)*AS5 - K2*AS5s)
  ;Monochloramine decay
  RATE    NH2CL  -Kb*NH2CL
  ;Arsenate adsorption
  EQUIL   AS5s   Ks*Smax*AS5/(1+Ks*AS5) - AS5s
  ;Total bulk arsenic
  FORMULA AStot  AS3 + AS5

[TANKS]
  RATE    AS3    -Ka*AS3*NH2CL
  RATE    AS5    Ka*AS3*NH2CL
  RATE    NH2CL  -Kb*NH2CL
  FORMULA AStot  AS3 + AS5

[QUALITY]
  ;Initial conditions (= 0 if not specified here)
  NODE    Source AS3   10.0
  NODE    Source NH2CL 2.5

[REPORT]
  NODES   C   D                ;Report results for nodes C and D
  LINKS   5                    ;Report results for pipe 5
  SPECIES  AStot YES            ;Report results for each specie
  SPECIES  AS5   YES
  SPECIES  AS5s  YES
  SPECIES  NH2CL YES