With the biomass from the SBRs, batch nitrification tests were performed. Erlenmeyers flasks of 1 L (n = 3) were filled with 0.5 L microbial suspension from either the glycerol SBR or the acetate SBR. These were spiked from a (NH4)2SO4 solution to obtain a total ammonia nitrogen (TAN) concentration of ca. 14 mg L1, and placed on a shaker at 150 rpm and 25 C. Initial volatile suspended solids (VSS), TAN, nitrite nitrogen (NO2 –N) and nitrate nitrogen (NO3 –N) concentrations were determined. Every half hour during a total of 3 h, samples for TAN, NO2 –N and NO3 –N analysis were taken. Sampling was performed by settling the flasks for 2 min before the actual sample time and filtering 10 mL of the supernatant over a 0.45 lm filter (ChromafilAO-45/25, Machery-nagel, Germany). The samples were stored at 4 C until further analysis.