Activated Sludge Process

QSDsan: Quantitative Sustainable Design for sanitation and resource recovery systems

This module is developed by:

This module is under the University of Illinois/NCSA Open Source License. Please refer to for license details.

class qsdsan.sanunits._activated_sludge_process.ActivatedSludgeProcess(ID='', ins: Sequence[AbstractStream] | None = None, outs: Sequence[AbstractStream] | None = (), thermo=None, init_with='WasteStream', F_BM_default=1, include_construction=False, N_train=2, T=308.15, X_i0=None, X_v=1210, X_e=15, X_w=10000, SLR=20, SF=4, aeration_power=1, q_hat=12, K=20, Y=0.5, b=0.396, f_d=0.8, COD_factor=1.42, q_UAP=1.8, q_BAP=0.1, k1=0.12, k2=0.09, K_UAP=100, K_BAP=85, F_BM={'Pump building': 1.1800826, 'Pumps': 1.1800826}, lifetime={'Pump pipe stainless steel': 15, 'Pump stainless steel': 15, 'Pumps': 15}, **kwargs)

A steady-state activated sludge process containing rectangular continuously stirred tank reactors and clarifiers for settling based on [1] (largely followed Example 6.2) and code scripts for [2] .

Single tank and clarifier are assumed to have the same width; pump/blower buildings are assumed to have the same width as the total tanks/clarifiers.

  • ins (Iterable) – Influent, air for aeration.

  • outs (Iterable) – Effluent, waste activated sludge sludge, gas emission.

  • N_train (int) – Number of treatment train, should be at least two in case one failing.

  • T (float) – Temperature in the aeration tank/anaerobic digester, [K].

  • X_i0 (float) – Inert biomass concentration in the influent, [mg VSS/L], will calculated based on inert_biomass of the current CompiledComponents if not provided.

  • X_v (float) – Reactor volatile suspended solids (biomass concentration in the aeration tank), referred to as mixed volatile liquor suspended solids (MLVSS, assumed to be the same as MLSS in [2]), [mg/L]. X_v = X_i + X_a (inert + active)

  • X_e (float) – Biomass concentration in the effluent, [mg VSS/L].

  • X_w (float) – Biomass concentration in the waste activated sludge, [mg VSS/L].

  • SLR (float) – Solids loading rate for the clarifier, [lb/ft2/d].

  • SF (float) – Safety factor to scale up the minimum solids retention time (SRT), should be larger than 1.

  • aeration_power (float) – Unit power usage for aeration, [kWh/kg O2].

  • q_hat (float) –

    Maximum specific rate of substrate utilization, [mg BOD/mg VSS/d], other important definitions are:

    • q_hat = mu_hat * Y (mu_hat is maximum specific growth rate, [1/time])

    • r_ut = -q_hat*(S/(K+S))*X_a (r_ut is rate of substrate utilization, [substrate mass/volume/time])

  • K (float) – Substrate concentration giving one-half the maximum rate, [mg COD/L].

  • Y (float) – Biomass yield, [mg VSS/mg BOD].

  • b (float) – Endogenous decay coefficient, [1/d].

  • f_d (float) – Fraction of the active biomass that is biodegradable.

  • COD_factor (float) – Biomass-to-COD conversion factor, [mg COD/mg VSS].

  • q_UAP (float) –

    Maximum specific rate of utilization-associated products degradation, [mg COD/mg VSS/d].

    SMP = UAP + BAP

    • SMP: soluble microbial products

    • UAP: utilization-associated products, produced directly from substrate metabolism

    • BAP: biomass-associated products, produced by basic metabolism

  • q_BAP (float) – Maximum specific rate of biomass-associated products degradation, [mg COD/mg VSS/d].

  • k1 (float) – UAP-formation coefficient, [mg COD/mg BOD].

  • k2 (float) – BAP-formation coefficient, [mg COD/mg VSS/d].

  • K_UAP (float) – Half-maximum rate concentrations for UAP, [mg COD/L].

  • K_BAP (float) – Half-maximum rate concentrations for BAP, [mg COD/L].

  • kwargs (dict) – Other attributes to be set.


See also

MATLAB codes used in ref 1, especially the system layout diagrams.

property A_clarifier

[float] Area of the clarifier, [ft2].

property D_WW

[float] Depth of the wet well for mixed liquor storage, [ft].

property D_tank

[float] Depth of the aeration tank, [ft].

property HRT

[float] Hydraulic retention time, [d].

property L_BB

[float] Length of the blower building, [ft].

property L_WW

[float] Length of the wet well for mixed liquor storage, [ft].

property L_tank

[float] Length of the aeration tank, [ft].

property N_train

[int] Number of treatment train, should be at least two in case one failing.

property Q

[float] Influent flow rate, [m3/d].

property Q_ras

[float] Return activated sludge flow rate, [m3/d].

property Q_was

[float] Waste activated sludge flow rate, [m3/d].

property R

[float] Sludge recycle ratio.

property V_tank

[float] Volume of the aeration tank, [ft3].

property W_BB

[float] Width of the blower building, [ft].

property W_PB

[float] Width of the pump building, [ft].

property W_WW

[float] Width of the wet well for mixed liquor storage, [ft].

property W_dist

[float] Width of the distribution channel, [ft].

property W_eff

[float] Width of the effluent channel, [ft].

property W_tank

[float] Width of the aeration tank, [ft].

auxiliary_unit_names: tuple[str, ...] = ('heat_exchanger',)

class-attribute Name of attributes that are auxiliary units. These units will be accounted for in the purchase and installed equipment costs without having to add these costs in the baseline_purchase_costs dictionary. Heat and power utilities are also automatically accounted for.

property constr_access

[float] Extra room for construction access, [ft].

property excav_slope

[float] Slope for excavation (horizontal/vertical).

property freeboard

[float] Freeboard added to the depth of the reactor tank, [ft].

line: str = 'Activated sludge process'

class-attribute Name denoting the type of Unit class. Defaults to the class name of the first child class

property t_slab

[float] Concrete slab thickness, [ft], default to be 2 in thicker than the wall thickness.

property t_wall

[float] Thickness of the wall concrete, [ft]. default to be minimum of 1 ft with 1 in added for every ft of depth over 12 ft.