Activated Sludge

Currently, we assume that we have an ideal sensor (without noise).

The general characteristics of the bioreactor are:

• Number of compartments (bioreactor) = 5
  • Non-aerated compartments = compartment number 1-2. Volume = 1500 m^3
  • Aerated compartments = compartment number 3-5. Volume = 3000 m^3

Combine flow block

1. RAS: flow returned from Settler
2. primary: flow from primary clarifier
3. storage: flow from storage tank
4. thickener: flow from thickener
5. Qintr: internal returned flow from bioreactor 5

Hyd_delay block

This block is placed to deal with algebraic loop. Timeconstance = 0.0001.

Carboncombiner block

Each bioreactor carbon input

Biorector 1 to 5

Inputs

1. Output flow from Carboncombiner block
   1. Q
   2. T
   3. Soluble: Si, Ss, So, Sno, Snh, Snd, Salk
   4. Particulate: Xi, Xs, Xbh, Xba, Xp, Xnd, TSS
2. KLa (oxygen transfer coefficient, per day)
   1. KLa1 (biorector 1) = 0
   2. KLa2 = 0
   3. KLa3 = output from SO4 control block (ideal sensor)
   4. KLa4 = output from SO4 control block (ideal sensor)
   5. KLa5 = 0.5* output from SO4 control block (ideal sensor)

Parameters

1. Initial state of each variable to solve ODE (each bioreactor has different initial state value).
2. PAR1:
   1. mu_H = 4
   2. K_S = 10
   3. K_OH = 0.2
   4. K_NO = 0.5
   5. b_H = 0.3
   6. mu_A = 0.5
   7. K_NH = 1
   8. K_OA = 0.4
   9. b_A =0.05
   10. ny_g = 0.8
   11. k_a = 0.05
   12. k_h = 3
   13. K_X = 0.1
   14. ny_h = 0.8
   15. Y_H = 0.67
   16. Y_A = 0.24
   17. f_P = 0.08
   18. i_XB = 0.08
   19. i_XP = 0.06
   20. Particulate2TSS = 0.75

ODE

Reactor mass balance.

Temperature compensation

Temperature dependency for oxygen saturation concentration (So) and oxygen transfer coefficient (KLa).

1. Solve the ODE to get the current bioreactor temperature.
2. Calculated the new parameter according to the current temperature in the reactor.
3. Calculate So_sat_temp and KLa_temp.

Soluble

1. So:
   1. if KLa < 0.0, So = abs(KLa)
   2. dSo/dt = Q/vol((So_in - So)) + reac8 + KLa_temp(So_sat_temp - So)
2. Other: dSoluble{i}/dt = Q/vol*(Soluble_in{i} - Soluble{i}) + reac{i}

Particulate

1. No ODE for TSS. TSS is depended on Xi, Xs, Xbh, Xba, and Xp.
2. Other: dParticulate{i}/dt = Q/vol*(Particulate_in{i} - Particulate{i}) + reac{i}

Reaction rate

Outputs

1. Q = same as input
2. T = output from ODE
3. Soluble = output from ODE
4. Particulate = output from ODE except TSS
   1. TSS = 0.75*(Xi + Xs + Xbh + Xba + Xp)

S04 control block

The primary control objective for the default strategies is to maintain the dissolved oxygen concentration in the fifth compartment at a predetermined set point value (2 g(-COD)/m^3)

Inputs

1. So from bioreactor 4
2. So set point point = SO_ref = 2 g(-COD)/m^3

Outputs

1. KLa (oxygen transfer coefficient, per day)