2.6. Total solids and Wortmannin sampling
Suspended biomass samples were taken from R1 and R2 on a weekly basis in triplicates. From day 240, wall-biofilms were also sampled weekly.
In R3, proper quantification of the total solids was allowed because of regular reintroduction of the effluent biomass, a lower sampling frequency, reduced biofilm formation on the walls possibly due to the lower temperatures, and sampling right after re-suspension of wall-biofilms by brushing. No microbiological characterization was performed for R3.
2.7. Analytical methods
NH4+ was analyzed using a flow injection analyzer (Foss FIA star 5000, Rellingen, Germany). NO2− and NO3− were analyzed by ion chromatography (Compact IC 761, Metrohm, Herisau, Switzerland). COD was measured photometrically with test kits (Hach Lange, Düsseldorf, Germany). Prior to analysis, the samples were filtered using 0.45 μm filters. TSS was determined according to standard methods (American Public Health Association, 2005).