diff --git a/ProcessLib/ComponentTransport/Tests.cmake b/ProcessLib/ComponentTransport/Tests.cmake
index b1e59587d21004d65973a056503be1075c72233e..89070f85d7119bed5fb146d0ec8646c7934390bd 100644
--- a/ProcessLib/ComponentTransport/Tests.cmake
+++ b/ProcessLib/ComponentTransport/Tests.cmake
@@ -295,6 +295,69 @@ AddTest(
elder_pcs_0_ts_80_t_21038400.000000_reference.vtu elder_pcs_0_ts_80_t_21038400.000000.vtu conc conc 1e-1 1e-5
)
+AddTest(
+ NAME LARGE_2D_ComponentTransport_ElderPython
+ PATH Parabolic/ComponentTransport/elder
+ EXECUTABLE ogs
+ EXECUTABLE_ARGS elder-python.prj
+ WRAPPER time
+ TESTER vtkdiff
+ REQUIREMENTS OGS_USE_PYTHON AND NOT OGS_USE_MPI
+ DIFF_DATA
+ elder_pcs_0_ts_0_t_0.000000_reference.vtu elder_python_pcs_0_ts_0_t_0.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_100_t_26298000.000000_reference.vtu elder_python_pcs_0_ts_100_t_26298000.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_120_t_31557600.000000_reference.vtu elder_python_pcs_0_ts_120_t_31557600.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_140_t_36817200.000000_reference.vtu elder_python_pcs_0_ts_140_t_36817200.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_160_t_42076800.000000_reference.vtu elder_python_pcs_0_ts_160_t_42076800.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_180_t_47336400.000000_reference.vtu elder_python_pcs_0_ts_180_t_47336400.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_200_t_52596000.000000_reference.vtu elder_python_pcs_0_ts_200_t_52596000.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_20_t_5259600.000000_reference.vtu elder_python_pcs_0_ts_20_t_5259600.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_220_t_57855600.000000_reference.vtu elder_python_pcs_0_ts_220_t_57855600.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_240_t_63115200.000000_reference.vtu elder_python_pcs_0_ts_240_t_63115200.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_260_t_68374800.000000_reference.vtu elder_python_pcs_0_ts_260_t_68374800.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_280_t_73634400.000000_reference.vtu elder_python_pcs_0_ts_280_t_73634400.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_300_t_78894000.000000_reference.vtu elder_python_pcs_0_ts_300_t_78894000.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_320_t_84153600.000000_reference.vtu elder_python_pcs_0_ts_320_t_84153600.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_340_t_89413200.000000_reference.vtu elder_python_pcs_0_ts_340_t_89413200.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_360_t_94672800.000000_reference.vtu elder_python_pcs_0_ts_360_t_94672800.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_380_t_99932400.000000_reference.vtu elder_python_pcs_0_ts_380_t_99932400.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_400_t_105192000.000000_reference.vtu elder_python_pcs_0_ts_400_t_105192000.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_40_t_10519200.000000_reference.vtu elder_python_pcs_0_ts_40_t_10519200.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_420_t_110451600.000000_reference.vtu elder_python_pcs_0_ts_420_t_110451600.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_440_t_115711200.000000_reference.vtu elder_python_pcs_0_ts_440_t_115711200.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_460_t_120970800.000000_reference.vtu elder_python_pcs_0_ts_460_t_120970800.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_480_t_126230400.000000_reference.vtu elder_python_pcs_0_ts_480_t_126230400.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_500_t_131490000.000000_reference.vtu elder_python_pcs_0_ts_500_t_131490000.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_60_t_15778800.000000_reference.vtu elder_python_pcs_0_ts_60_t_15778800.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_80_t_21038400.000000_reference.vtu elder_python_pcs_0_ts_80_t_21038400.000000.vtu pressure pressure 1e-1 1e-5
+ elder_pcs_0_ts_0_t_0.000000_reference.vtu elder_python_pcs_0_ts_0_t_0.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_100_t_26298000.000000_reference.vtu elder_python_pcs_0_ts_100_t_26298000.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_120_t_31557600.000000_reference.vtu elder_python_pcs_0_ts_120_t_31557600.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_140_t_36817200.000000_reference.vtu elder_python_pcs_0_ts_140_t_36817200.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_160_t_42076800.000000_reference.vtu elder_python_pcs_0_ts_160_t_42076800.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_180_t_47336400.000000_reference.vtu elder_python_pcs_0_ts_180_t_47336400.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_200_t_52596000.000000_reference.vtu elder_python_pcs_0_ts_200_t_52596000.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_20_t_5259600.000000_reference.vtu elder_python_pcs_0_ts_20_t_5259600.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_220_t_57855600.000000_reference.vtu elder_python_pcs_0_ts_220_t_57855600.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_240_t_63115200.000000_reference.vtu elder_python_pcs_0_ts_240_t_63115200.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_260_t_68374800.000000_reference.vtu elder_python_pcs_0_ts_260_t_68374800.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_280_t_73634400.000000_reference.vtu elder_python_pcs_0_ts_280_t_73634400.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_300_t_78894000.000000_reference.vtu elder_python_pcs_0_ts_300_t_78894000.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_320_t_84153600.000000_reference.vtu elder_python_pcs_0_ts_320_t_84153600.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_340_t_89413200.000000_reference.vtu elder_python_pcs_0_ts_340_t_89413200.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_360_t_94672800.000000_reference.vtu elder_python_pcs_0_ts_360_t_94672800.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_380_t_99932400.000000_reference.vtu elder_python_pcs_0_ts_380_t_99932400.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_400_t_105192000.000000_reference.vtu elder_python_pcs_0_ts_400_t_105192000.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_40_t_10519200.000000_reference.vtu elder_python_pcs_0_ts_40_t_10519200.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_420_t_110451600.000000_reference.vtu elder_python_pcs_0_ts_420_t_110451600.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_440_t_115711200.000000_reference.vtu elder_python_pcs_0_ts_440_t_115711200.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_460_t_120970800.000000_reference.vtu elder_python_pcs_0_ts_460_t_120970800.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_480_t_126230400.000000_reference.vtu elder_python_pcs_0_ts_480_t_126230400.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_500_t_131490000.000000_reference.vtu elder_python_pcs_0_ts_500_t_131490000.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_60_t_15778800.000000_reference.vtu elder_python_pcs_0_ts_60_t_15778800.000000.vtu conc conc 1e-1 1e-5
+ elder_pcs_0_ts_80_t_21038400.000000_reference.vtu elder_python_pcs_0_ts_80_t_21038400.000000.vtu conc conc 1e-1 1e-5
+)
+
AddTest(
NAME 2D_ComponentTransport_HeterogeneousPermeability
PATH Elliptic/square_100x100_ComponentTransport
diff --git a/Tests/Data/Parabolic/ComponentTransport/elder/elder-python-bcs.py b/Tests/Data/Parabolic/ComponentTransport/elder/elder-python-bcs.py
new file mode 100644
index 0000000000000000000000000000000000000000..3d815d21b7bc5486b97ffaf7c6e9bb7c147cf67d
--- /dev/null
+++ b/Tests/Data/Parabolic/ComponentTransport/elder/elder-python-bcs.py
@@ -0,0 +1,34 @@
+import OpenGeoSys
+
+
+class BCPressure(OpenGeoSys.BoundaryCondition):
+ def getDirichletBCValue(self, t, coords, node_id, primary_vars):
+ x, y, z = coords
+
+ if x == -150 and z == 75:
+ # prescribe pressure of 0
+ return (True, 0.0)
+
+ # no Dirichlet BC
+ return (False, 0.0)
+
+
+class BCConcentration(OpenGeoSys.BoundaryCondition):
+ def getDirichletBCValue(self, t, coords, node_id, primary_vars):
+ x, y, z = coords
+
+ if z == -75:
+ # prescribe concentration of 0
+ return (True, 0.0)
+
+ if z == 75 and x >= 0:
+ # prescribe concentration of 1
+ return (True, 1.0)
+
+ # no Dirichlet BC
+ return (False, 0.0)
+
+
+# instantiate the BC objects used by OpenGeoSys
+bc_p = BCPressure()
+bc_c = BCConcentration()
diff --git a/Tests/Data/Parabolic/ComponentTransport/elder/elder-python.gml b/Tests/Data/Parabolic/ComponentTransport/elder/elder-python.gml
new file mode 100644
index 0000000000000000000000000000000000000000..d22068fc2b35f4f29064dcf89bd42163dcc610b2
--- /dev/null
+++ b/Tests/Data/Parabolic/ComponentTransport/elder/elder-python.gml
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:b4fb7c7bc4ddbc37a38f1fdbaabc23eb415fe842ae2dbd4a5c9791fa7f93dc83
+size 1282
diff --git a/Tests/Data/Parabolic/ComponentTransport/elder/elder-python.prj b/Tests/Data/Parabolic/ComponentTransport/elder/elder-python.prj
new file mode 100644
index 0000000000000000000000000000000000000000..2132e3beecfa76ea1d095e962cca295ae1b376a2
--- /dev/null
+++ b/Tests/Data/Parabolic/ComponentTransport/elder/elder-python.prj
@@ -0,0 +1,201 @@
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!-- vim: ft=xml sw=2
+-->
+<OpenGeoSysProject>
+ <mesh>elder.vtu</mesh>
+ <geometry>elder-python.gml</geometry>
+ <python_script>elder-python-bcs.py</python_script>
+ <processes>
+ <process>
+ <name>HC</name>
+ <type>ComponentTransport</type>
+ <integration_order>2</integration_order>
+ <process_variables>
+ <concentration>conc</concentration>
+ <pressure>pressure</pressure>
+ </process_variables>
+ <fluid>
+ <density>
+ <type>ConcentrationDependent</type>
+ <reference_density>1000</reference_density>
+ <reference_concentration>0</reference_concentration>
+ <fluid_density_difference_ratio>0.2</fluid_density_difference_ratio>
+ </density>
+ <viscosity>
+ <type>Constant</type>
+ <value>1.0e-3</value>
+ </viscosity>
+ </fluid>
+ <porous_medium>
+ <porous_medium id="0">
+ <permeability>
+ <permeability_tensor_entries>kappa1</permeability_tensor_entries>
+ <type>Constant</type>
+ </permeability>
+ <porosity>
+ <type>Constant</type>
+ <porosity_parameter>constant_porosity_parameter</porosity_parameter>
+ </porosity>
+ <storage>
+ <type>Constant</type>
+ <value>0.0</value>
+ </storage>
+ </porous_medium>
+ </porous_medium>
+ <decay_rate>decay_rate</decay_rate>
+ <fluid_reference_density>rho_fluid</fluid_reference_density>
+ <retardation_factor>retardation_factor</retardation_factor>
+ <solute_dispersivity_longitudinal>alpha_l</solute_dispersivity_longitudinal>
+ <solute_dispersivity_transverse>alpha_t</solute_dispersivity_transverse>
+ <molecular_diffusion_coefficient>Dm</molecular_diffusion_coefficient>
+ <specific_body_force>0 0 -9.81</specific_body_force>
+ <secondary_variables>
+ <secondary_variable type="static" internal_name="darcy_velocity" output_name="darcy_velocity"/>
+ </secondary_variables>
+ </process>
+ </processes>
+ <time_loop>
+ <processes>
+ <process ref="HC">
+ <nonlinear_solver>basic_picard</nonlinear_solver>
+ <convergence_criterion>
+ <type>PerComponentDeltaX</type>
+ <norm_type>NORM2</norm_type>
+ <reltols>1e-3 1e-3</reltols>
+ </convergence_criterion>
+ <time_discretization>
+ <type>BackwardEuler</type>
+ </time_discretization>
+ <time_stepping>
+ <type>FixedTimeStepping</type>
+ <t_initial> 0.0 </t_initial>
+ <t_end>1.3149e8</t_end>
+ <timesteps>
+ <pair>
+ <repeat>10</repeat>
+ <delta_t>262980</delta_t>
+ </pair>
+ </timesteps>
+ </time_stepping>
+ <output>
+ <variables>
+ <variable>conc</variable>
+ <variable>pressure</variable>
+ <variable>darcy_velocity</variable>
+ </variables>
+ </output>
+ </process>
+ </processes>
+ <output>
+ <type>VTK</type>
+ <prefix>elder_python</prefix>
+ <timesteps>
+ <pair>
+ <repeat>1</repeat>
+ <each_steps>20</each_steps>
+ </pair>
+ </timesteps>
+ </output>
+ </time_loop>
+ <parameters>
+ <parameter>
+ <name>rho_fluid</name>
+ <type>Constant</type>
+ <value>1000.0</value>
+ </parameter>
+ <parameter>
+ <name>alpha_l</name>
+ <type>Constant</type>
+ <value>0</value>
+ </parameter>
+ <parameter>
+ <name>alpha_t</name>
+ <type>Constant</type>
+ <value>0</value>
+ </parameter>
+ <parameter>
+ <name>Dm</name>
+ <type>Constant</type>
+ <value>3.57e-6</value>
+ </parameter>
+ <parameter>
+ <name>decay_rate</name>
+ <type>Constant</type>
+ <value>0.0</value>
+ </parameter>
+ <parameter>
+ <name>retardation_factor</name>
+ <type>Constant</type>
+ <value>1</value>
+ </parameter>
+ <parameter>
+ <name>p_ini</name>
+ <type>MeshNode</type>
+ <field_name>p_ini</field_name>
+ </parameter>
+ <parameter>
+ <name>c_ini</name>
+ <type>MeshNode</type>
+ <field_name>c_ini</field_name>
+ </parameter>
+ <parameter>
+ <name>constant_porosity_parameter</name>
+ <type>Constant</type>
+ <value>0.1</value>
+ </parameter>
+ <parameter>
+ <name>kappa1</name>
+ <type>Constant</type>
+ <values>4.84404e-13 0 0 0 4.84404e-13 0 0 0 4.84404e-13</values>
+ </parameter>
+ </parameters>
+ <process_variables>
+ <process_variable>
+ <name>conc</name>
+ <components>1</components>
+ <order>1</order>
+ <initial_condition>c_ini</initial_condition>
+ <boundary_conditions>
+ <boundary_condition>
+ <geometrical_set>elder</geometrical_set>
+ <geometry>whole_domain_boundary</geometry>
+ <type>Python</type>
+ <bc_object>bc_c</bc_object>
+ </boundary_condition>
+ </boundary_conditions>
+ </process_variable>
+ <process_variable>
+ <name>pressure</name>
+ <components>1</components>
+ <order>1</order>
+ <initial_condition>p_ini</initial_condition>
+ <boundary_conditions>
+ <boundary_condition>
+ <geometrical_set>elder</geometrical_set>
+ <geometry>whole_domain_boundary</geometry>
+ <type>Python</type>
+ <bc_object>bc_p</bc_object>
+ </boundary_condition>
+ </boundary_conditions>
+ </process_variable>
+ </process_variables>
+ <nonlinear_solvers>
+ <nonlinear_solver>
+ <name>basic_picard</name>
+ <type>Picard</type>
+ <max_iter>300</max_iter>
+ <linear_solver>general_linear_solver</linear_solver>
+ </nonlinear_solver>
+ </nonlinear_solvers>
+ <linear_solvers>
+ <linear_solver>
+ <name>general_linear_solver</name>
+ <eigen>
+ <precon_type>ILUT</precon_type>
+ <solver_type>BiCGSTAB</solver_type>
+ <max_iteration_step>5000</max_iteration_step>
+ <error_tolerance>1e-12</error_tolerance>
+ </eigen>
+ </linear_solver>
+ </linear_solvers>
+</OpenGeoSysProject>
diff --git a/web/content/docs/benchmarks/python-bc/elder-benchmark/elder.md b/web/content/docs/benchmarks/python-bc/elder-benchmark/elder.md
new file mode 100644
index 0000000000000000000000000000000000000000..04b5ba1dde5c0fe7fb7f3219e34caba7d9303309
--- /dev/null
+++ b/web/content/docs/benchmarks/python-bc/elder-benchmark/elder.md
@@ -0,0 +1,27 @@
++++
+project = "Parabolic/ComponentTransport/elder/elder-python.prj"
+author = "Christoph Lehmann"
+date = "2018-08-16T09:18:00+02:00"
+title = "Saturated Variable-Density Flow and Mass Transport (Elder) with Python BC"
+weight = 3
+
+[menu]
+ [menu.benchmarks]
+ parent = "python-bc"
+
++++
+
+{{< data-link >}}
+
+## Motivation of this test case
+
+The aim of this test is:
+
+* to show that it is possible to prescribe BCs only on parts of a given geometry
+* to assert that Python BCs work with processes involving more than one physical
+ field.
+
+## Details
+
+This test is a copy of [this test case]({{< ref "../../hydro-component/elder.md" >}}).
+Please check the original test case for any details.