Combining submerged membrane technology with anaerobic and ...

Chapter 55.3. Material and methods5.3.1. Experimental set-up and operating strategyA 176 L bioreactor (figure 5.1) was operated at ambient temperature (17-23 ºC). A120 L volume UASB system was used for the first methanogenic stage. The effluent of theUASB reactor was led to an aerobic biofilm chamber (36 L), with biomass growing ontoplastic support and in suspension. 18.5 L (50% of the effective volume) of Kaldnes K3support were added in this chamber. Finally, the membrane filtration was carried out in a20 L aerobic chamber, where a membrane module Zenon ZW10 with a surface area of 0.9m 2 was employed. This module consisted of PVDF hollow-fibre membrane, with a poresize of 0.04 µm. The membrane was operated in cycles of 7.5 min with a permeationperiod of 7 min and a backwashing period of 0.5 min. The filtration chamber was aerated inorder to minimize membrane fouling. The specific air demand (SAD m) applied to themembrane was 0.7 Nm 3·m -2·h -1 . An internal recirculation between filtration and aerobicstages was implemented in the MBR (R=1). The operation of the system was controlled bya PLC (Siemens S7-200) connected to a computer. Trans-membrane Pressure (TMP) datawas measured with an analogue pressure sensor (Efector500 PN-2009) and collected inthe PC via an analogue PLC module Siemens EM 235.Table 5.1. Main operational conditions of the bioreactor during the different periods.Period days Feeding Recirculation 1 Ratio Support 2I 0-175 Synthetic yes 0.15 yesII 176-260 Synthetic no - yesIII 261-540 Synthetic yes 0.15-0.075 yesIV 541-569 Synthetic no - yesV 570-635 Synthetic no - noVI 636-680 Synthetic yes 0.075 yesVII 700-875Synthetic +aerobic sludge 3no (fed) - yes1 Sludge recirculation between aerobic biofilm chamber and UASB reactor2 Plastic carriers Kaldnes K3 in the aerobic biofilm chamber3 Aerobic sludge was fed between days 769 and 841132