The nominal pore sizes of the applied Tubular ceramic ISOFLUX® membrane elements (TAMI Germany, Hermsdorf, Germany) were 1.4 μm (batches A and C) and 0.8 μm (batches B and D). The membrane elements were 1178 mm long and had 8 tubular channels with a hydraulic diameter of 6 mm. The membrane surface of each element was 0.2 m2. Prior to each filtration run the filtration apparatus including the membrane element was sanitised with a 400 ppm chlorine solution and rinsed with cold tap water. The cross flow velocity was 4.0 m s−1, trans membrane pressure (TMP) was 0.7 bar; the temperature was maintained at 30 ± 2 °C. The observed permeate flux was 75 L m−2 h−1 in batches A and C and 12.7 and 14.9 L m−2 h−1 in batches B and D, respectively.
Filtration was stopped when 5.0 kg of permeate were obtained. Samples were taken from permeate and retentate and stored at −30 °C prior to analysis.