The next day, 100 mL water samples were
collected from each tank for laboratory analysis of total nitrogen
(TN) and total phosphorous (TP) in unfiltered samples by Chemisch
Biologisch Laboratorium Bodem, accredited according to NEN-ENISO/
IEC 17025 standard (registration number RvA L342). Prior to
sampling, the biofilm attached to the walls and deposits on the
bottom of the tank were brought into suspension. Additionally, two
groundwater samples were collected and analyzed for TN and TP
concentrations..