diff --git a/exercises/exercise-biomineralization/chemistry/simplebiominreactions.hh b/exercises/exercise-biomineralization/chemistry/simplebiominreactions.hh
index f7a0f62ab5f0c8ca8baa2e368c9671cacb8560cc..99cce503b46d018e2b541ef636033c72c8c2f5ac 100644
--- a/exercises/exercise-biomineralization/chemistry/simplebiominreactions.hh
+++ b/exercises/exercise-biomineralization/chemistry/simplebiominreactions.hh
@@ -24,6 +24,9 @@
 #ifndef DUMUX_BIOMIN_REACTIONS_HH
 #define DUMUX_BIOMIN_REACTIONS_HH
 
+#include <dumux/common/parameters.hh>
+// #include <dumux-course/exercises/exercise-biomineralization/components/urea.hh>
+
 namespace Dumux {
 
 /*!
@@ -98,6 +101,7 @@ public:
 
         // TODO: dumux-course-task
         // compute rate of ureolysis by implementing Z_urease,biofilm and r_urea
+        Scalar rurea = 0.0;
 
         // compute/set dissolution and precipitation rate of calcite
         Scalar rprec = 0.0;
diff --git a/exercises/exercise-biomineralization/components/biofilm.hh b/exercises/exercise-biomineralization/components/biofilm.hh
index c3348a092628269aeb7d4c9b48d9d6bcd09f51eb..500c33eeff82da2530dac5307117691fd21f9eba 100644
--- a/exercises/exercise-biomineralization/components/biofilm.hh
+++ b/exercises/exercise-biomineralization/components/biofilm.hh
@@ -26,9 +26,9 @@
 
 #include <dumux/material/components/base.hh>
 #include <dumux/material/components/solid.hh>
+#include <dumux/common/parameters.hh>
 
-namespace Dumux {
-namespace Components {
+namespace Dumux::Components {
 
 /*!
  * \ingroup Components
@@ -71,7 +71,6 @@ public:
     }
 };
 
-} // end namespace Components
-} // end namespace Dumux
+} // end namespace Dumux::Components
 
 #endif
diff --git a/exercises/solution/exercise-biomineralization/chemistry/simplebiominreactions.hh b/exercises/solution/exercise-biomineralization/chemistry/simplebiominreactions.hh
index 250333faedcafa721dbf9cbcf879e6b7c71a7083..e5c6083570cfcda61a59473f019ff8cd25d54db0 100644
--- a/exercises/solution/exercise-biomineralization/chemistry/simplebiominreactions.hh
+++ b/exercises/solution/exercise-biomineralization/chemistry/simplebiominreactions.hh
@@ -24,6 +24,8 @@
 #ifndef DUMUX_BIOMIN_REACTIONS_HH
 #define DUMUX_BIOMIN_REACTIONS_HH
 
+#include <dumux/common/parameters.hh>
+
 namespace Dumux {
 
 /*!
diff --git a/exercises/solution/exercise-biomineralization/components/biofilm.hh b/exercises/solution/exercise-biomineralization/components/biofilm.hh
index c3348a092628269aeb7d4c9b48d9d6bcd09f51eb..89784cf14d2d755827d9e03a1460242318cd1bb4 100644
--- a/exercises/solution/exercise-biomineralization/components/biofilm.hh
+++ b/exercises/solution/exercise-biomineralization/components/biofilm.hh
@@ -24,11 +24,12 @@
 #ifndef DUMUX_BIOFILM_HH
 #define DUMUX_BIOFILM_HH
 
+#include <dumux/common/parameters.hh>
+
 #include <dumux/material/components/base.hh>
 #include <dumux/material/components/solid.hh>
 
-namespace Dumux {
-namespace Components {
+namespace Dumux::Components {
 
 /*!
  * \ingroup Components
@@ -71,7 +72,6 @@ public:
     }
 };
 
-} // end namespace Components
-} // end namespace Dumux
+} // end namespace Dumux::Components
 
 #endif
diff --git a/exercises/solution/exercise-biomineralization/components/urea.hh b/exercises/solution/exercise-biomineralization/components/urea.hh
index 1dc533034e6aa916663ce26efc8b45b6c8536d84..6d94c979c67bf0b39982f10f484395be4edf4d8c 100644
--- a/exercises/solution/exercise-biomineralization/components/urea.hh
+++ b/exercises/solution/exercise-biomineralization/components/urea.hh
@@ -26,8 +26,7 @@
 
 #include <dumux/material/components/base.hh>
 
-namespace Dumux {
-namespace Components {
+namespace Dumux::Components {
 
 /*!
  * \ingroup Components
@@ -52,7 +51,5 @@ public:
 
 };
 
-} // end namespace Components
-} // end namespace Dumux
-
+} // end namespace Dumux::Components
 #endif
diff --git a/exercises/solution/exercise-biomineralization/solidsystems/biominsolidphase.hh b/exercises/solution/exercise-biomineralization/solidsystems/biominsolidphase.hh
index b74567665f787c46d733426296c43ddfb2481435..be3a1f656c75d5cb320c5bdee2759b6b2fc3b976 100644
--- a/exercises/solution/exercise-biomineralization/solidsystems/biominsolidphase.hh
+++ b/exercises/solution/exercise-biomineralization/solidsystems/biominsolidphase.hh
@@ -27,12 +27,12 @@
 #include <string>
 #include <dune/common/exceptions.hh>
 
-#include "../components/biofilm.hh"
+#include <dumux/common/parameters.hh>
 #include <dumux/material/components/calcite.hh>
 #include <dumux/material/components/granite.hh>
+#include "../components/biofilm.hh"
 
-namespace Dumux {
-namespace SolidSystems {
+namespace Dumux::SolidSystems {
 
 /*!
  * \ingroup SolidSystems
@@ -195,7 +195,6 @@ public:
 
 };
 
-} // end namespace SolidSystems
-} // end namespace Dumux
+} // end namespace Dumux::SolidSystems
 
 #endif