Toilet

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 https://github.com/QSD-Group/QSDsan/blob/main/LICENSE.txt for license details.

class qsdsan.sanunits._toilet.MURT(ID='', ins: Sequence[AbstractStream] | None = None, outs: Sequence[AbstractStream] | None = (), thermo=None, init_with='WasteStream', degraded_components=('OtherSS',), N_user=1, N_tot_user=1, N_toilet=None, if_toilet_paper=True, if_flushing=True, if_cleansing=False, if_desiccant=True, if_air_emission=True, if_ideal_emptying=True, CAPEX=0, OPEX_over_CAPEX=0, lifetime=10, N_squatting_pan_per_toilet=1, N_urinal_per_toilet=1, if_include_front_end=True, **kwargs)

Multi-unit reinvented toilet.

The following components should be included in system thermo object for simulation: Tissue, WoodAsh, H2O, NH3, NonNH3, P, K, Mg, CH4, N2O.

The following impact items should be pre-constructed for life cycle assessment: Ceramic, Fan.

Parameters:

  • ins (Iterable(stream)) – waste_in: mixed excreta.

  • Outs (Iterable(stream)) – waste_out: degraded mixed excreta. CH4: fugitive CH4. N2O: fugitive N2O.

  • N_squatting_pan_per_toilet (int) – The number of squatting pan per toilet.

  • N_urinal_per_toilet (int) – The number of urinals per toilet.

  • if_include_front_end (bool) – If False, will not consider the capital and operating costs of this unit.

See also

qsdsan.sanunits.Toilet

property collection_period

[float] Time interval between storage tank collection, [d].

line: str = 'MURT'

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

property tau

[float] Retention time of the unit, same as collection_period.

class qsdsan.sanunits._toilet.PitLatrine(ID='', ins: Sequence[AbstractStream] | None = None, outs: Sequence[AbstractStream] | None = (), thermo=None, init_with='WasteStream', degraded_components=('OtherSS',), N_user=1, N_toilet=1, N_tot_user=None, if_toilet_paper=True, if_flushing=True, if_cleansing=False, if_desiccant=False, if_air_emission=True, if_ideal_emptying=True, CAPEX=449, OPEX_over_CAPEX=0.05, lifetime=8, if_leaching=True, if_shared=True, if_pit_above_water_table=True, **kwargs)

Single pit latrine based on Trimmer et al., a subclass of qsdsan.sanunits.Toilet.

The following components should be included in system thermo object for simulation: Tissue, WoodAsh, H2O, NH3, NonNH3, P, K, CH4, N2O.

The following impact items should be pre-constructed for life cycle assessment: Cement, Sand, Gravel, Brick, Plastic, Steel, Wood, Excavation.

Parameters:

  • ins (stream obj) – Excreta.

  • outs (Iterable(stream obj)) – Recyclable mixed excreta, stream leached to soil, fugitive CH4, and fugitive N2O.

  • lifetime (int) – Lifetime of this pit latrine, [yr].

  • if_leaching (bool) – If infiltration to soil occurs (i.e., if the pit walls and floors are permeable).

  • if_shared (bool) – If the toilet is shared.

  • if_pit_above_water_table (bool) – If the pit is above local water table.

Examples

bwaise systems

References

[1] Trimmer et al., Navigating Multidimensional Social–Ecological System Trade-Offs across Sanitation Alternatives in an Urban Informal Settlement. Environ. Sci. Technol. 2020, 54 (19), 12641–12653. https://doi.org/10.1021/acs.est.0c03296.

See also

qsdsan.sanunits.Toilet

property K_leaching

[float] Fraction of input K that leaches to the soil (if if_leaching is True).

property MCF_decay

[float] Methane correction factor for COD degraded during storage.

property N2O_EF_decay

[float] Fraction of N emitted as N2O during storage.

property N_leaching

[float] Fraction of input N that leaches to the soil (if if_leaching is True).

property P_leaching

[float] Fraction of input P that leaches to the soil (if if_leaching is True).

property emptying_period

[float] Time interval between pit emptying, [yr].

line: str = 'Pit latrine'

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

property liq_leaching

[float] Fraction of input water that leaches to the soil (if if_leaching is True). If not set, then return the maximum of fraction of N, P, K leaching

property pit_V

[float] Volume of the pit, [m3].

property pit_area

[float] Area of the pit, [m2].

property pit_depth

[float] Depth of the pit, [m].

property sludge_accum_rate

[float] Sludge accumulation rate, [L/cap/yr].

property tau

[float] Retention time of the unit, same as emptying_period but in day.

class qsdsan.sanunits._toilet.Toilet(ID='', ins: Sequence[AbstractStream] | None = None, outs: Sequence[AbstractStream] | None = (), thermo=None, init_with='WasteStream', degraded_components=('OtherSS',), N_user=1, N_toilet=1, N_tot_user=None, if_toilet_paper=True, if_flushing=True, if_cleansing=False, if_desiccant=False, if_air_emission=True, if_ideal_emptying=True, CAPEX=None, OPEX_over_CAPEX=None, price_ratio=1.0)

Abstract class containing common parameters and design algorithms for toilets based on Trimmer et al.

Parameters:

  • degraded_components (tuple) – IDs of components that will degrade (simulated by first-order decay).

  • N_user (int, float) – Number of people per toilet. Note that this number can be a float when calculated from N_tot_user and N_toilet.

  • N_toilet (int) – Number of parallel toilets. In calculation, N_toilet will be calculated as ceil(N_tot_user/N_user).

  • N_tot_user (int) –

    Total number of users.

    Note

    If N_tot_user is provided (i.e., not “None”), then updating N_user will recalculate N_toilet, and vice versa.

  • if_toilet_paper (bool) – If toilet paper is used.

  • if_flushing (bool) – If water is used for flushing.

  • if_cleansing (bool) – If water is used for cleansing.

  • if_desiccant (bool) – If desiccant is used for moisture and odor control.

  • if_air_emission (bool) – If emission to air occurs (i.e., if the pit is completely sealed off from the atmosphere).

  • if_ideal_emptying (bool) – If the toilet appropriately emptied to avoid contamination to the environmental.

  • CAPEX (float) – Capital cost of a single toilet.

  • OPEX_over_CAPEX (float) – Fraction of annual operating cost over total capital cost.

  • price_ratio (float) – Calculated capital cost will be multiplied by this number to consider the effect in cost difference from different locations.

References

[1] Trimmer et al., Navigating Multidimensional Social–Ecological System Trade-Offs across Sanitation Alternatives in an Urban Informal Settlement. Environ. Sci. Technol. 2020, 54 (19), 12641–12653. https://doi.org/10.1021/acs.est.0c03296.

See also

qsdsan.processes.Decay

property MCF_aq

[float] Methane correction factor for COD lost due to inappropriate emptying.

property N2O_EF_aq

[float] Fraction of N emitted as N2O due to inappropriate emptying.

property N_toilet

[int] Number of parallel toilets.

property N_tot_user

[int] Number of total users.

property N_user

[int, float] Number of people per toilet.

property N_volatilization

[float] Fraction of input N that volatilizes to the air (if if_air_emission is True).

property cleansing_water

[float] Amount of water used for cleansing (if if_cleansing_water is True), [kg/cap/hr].

property desiccant

[float] Amount of desiccant used (if if_desiccant is True), [kg/cap/hr].

Note

Value set by desiccant_V and desiccant_rho.

property empty_ratio

[float] Fraction of excreta that is appropriately emptied.

Note

Will be 1 (i.e., 100%) if if_ideal_emptying is True.

property flushing_water

[float] Amount of water used for flushing (if if_flushing_water is True), [kg/cap/hr].

static get_emptying_emission(waste, CH4, N2O, empty_ratio, CH4_factor, N2O_factor)

Calculate emissions due to non-ideal emptying based on Trimmer et al.,

Parameters:

  • stream (WasteStream) – Excreta stream that is not appropriately emptied (before emptying).

  • CH4 (WasteStream) – Fugitive CH4 gas (before emptying).

  • N2O (WasteStream) – Fugitive N2O gas (before emptying).

  • empty_ratio (float) – Fraction of excreta that is appropriately emptied..

  • CH4_factor (float) – Factor to convert COD removal to CH4 emission.

  • N2O_factor (float) – Factor to convert COD removal to N2O emission.

Returns:

  • stream (WasteStream) – Excreta stream that is not appropriately emptied (after emptying).

  • CH4 (WasteStream) – Fugitive CH4 gas (after emptying).

  • N2O (WasteStream) – Fugitive N2O gas (after emptying).

property if_N2O_emission

[bool] Whether to consider N degradation and fugitive N2O emission.

line: str = 'Toilet'

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

property toilet_paper

[float] Amount of toilet paper used (if if_toilet_paper is True), [kg/cap/hr].

class qsdsan.sanunits._toilet.UDDT(ID='', ins: Sequence[AbstractStream] | None = None, outs: Sequence[AbstractStream] | None = (), thermo=None, init_with='WasteStream', degraded_components=('OtherSS',), N_user=1, N_toilet=1, N_tot_user=None, if_toilet_paper=True, if_flushing=False, if_cleansing=False, if_desiccant=True, if_air_emission=True, if_ideal_emptying=True, CAPEX=553, OPEX_over_CAPEX=0.1, lifetime=8, T=298.15, safety_factor=1, if_prep_loss=True, if_treatment=False, **kwargs)

Urine-diverting dry toilet with liquid storage tank and dehydration vault for urine and feces storage, respectively, based on Trimmer et al., a subclass of qsdsan.sanunits.Toilet.

The following components should be included in system thermo object for simulation: Tissue, WoodAsh, H2O, NH3, NonNH3, P, K, Mg, CH4, N2O.

The following impact items should be pre-constructed for life cycle assessment: Cement, Sand, Gravel, Brick, Plastic, Steel, StainlessSteelSheet, Wood.

Parameters:

  • ins (stream obj) – Excreta stream.

  • outs (Iterable(stream obj)) – Recyclable liquid urine, recyclable solid feces, struvite scaling (irrecoverable), hydroxyapatite scaling (irrecoverable), fugitive CH4, and fugitive N2O.

  • lifetime (int) – Lifetime of this UDDT, [yr].

  • T (float) – Temperature, [K].

  • safety_factor (float) – Safety factor for pathogen removal during onsite treatment, must be larger than 1.

  • if_treatment (bool) – If has onsite treatment.

Examples

bwaise systems

References

[1] Trimmer et al., Navigating Multidimensional Social–Ecological System Trade-Offs across Sanitation Alternatives in an Urban Informal Settlement. Environ. Sci. Technol. 2020, 54 (19), 12641–12653. https://doi.org/10.1021/acs.est.0c03296.

See also

qsdsan.sanunits.Toilet

property collection_period

[float] Time interval between storage tank collection, [d].

property fec_moi_min

[float] Minimum moisture content of feces.

property fec_moi_red_rate

[float] Exponential reduction rate of feces moisture.

line: str = 'UDDT'

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

property log_removal

Desired level of pathogen inactivation.

property prep_sludge

[float] Fraction of total precipitate appearing as sludge that can settle and be removed.

property struvite_pKsp

[float] Precipitation constant of struvite.

property tank_V

[float] Volume of the urine storage tank, [m3].

property tau

[float] Retention time of the unit, same as collection_period.

property treatment_V

[float] Volume needed to achieve treatment target (if treating), [d].

property treatment_tau

[float] Time for onsite treatment (if treating), [d].

property ur_pH

Urine pH.

property vault_V

[float] Volume of the feces dehydration vault, [m3].