Combining submerged membrane technology with anaerobic and ...

Chapter 1into the UASB with a ratio of 50-800%. Nitrogen removal was promoted by recirculating theN-NO X, produced by nitrification in the MBR, to the UASB. On the other hand, Buntner etal. (2010) operated at ambient temperatures and the MBR sludge was recirculated to theUASB with a ratio of 7.5-15% from a first chamber of the MBR, with biomass growing ontoplastic support and in suspension. Nitrogen was not removed using this configuration inthe case of Buntner et al. (2010). The results obtained in both of systems were similar withapplied fluxes between 12 and 15 L·m -2 ∙h -1 , and a stable COD removal efficiency of above98.0%.Phattaranawik and Leiknes (2010) proposed a hybrid vertical anaerobic sludge–aerated biofilm reactor (HyVAB) coupled with external submerged membrane filtration formunicipal wastewater treatment. The HyVAB featured an upper chamber of aerobicbiofilm, a lower chamber of anaerobic activated sludge, and a roof-shaped separatorlocated between the chambers, to prevent diffusion of dissolved oxygen to the anaerobicchamber. The lower chamber was used for anaerobic digestion of aerobic sludge waste.Lower COD removal (above 80%) than those obtained by An et al. (2008) and Buntner etal. (2010) were reported. Nevertheless, the applied fluxes were considerably higher (up to23 L·m -2 ∙h -1 ). Although very low nitrogen removal was observed, denitrification processmight be enhanced by recirculating part of the effluent (from the aerobic biofilm chamber orfrom the membrane chamber) to the anaerobic chamber.Finally, Zhang et al. (2005) proposed a staged anaerobic and aerobic membranebioreactor with the anaerobic zone in the bottom part and the membrane modulesubmerged in the aerobic zone, in the upper part of the reactor. Some porcelain carrierswere installed in order to prevent the blockade of the orifice between the two parts of thereactor. COD removal efficiencies above 97 % and fluxes in the range of 5-14 L·m -2 ∙h -1were achieved. The anaerobic digestion of COD produced a great amount of methane,which passed to the aerobic zone of the reactor with the wastewater anaerobicallydigested. The denitrification using methane as carbon source could be integrated withanaerobic methanogensis through the special structure of the reactor used in this work. Allammonium was nitrified and more than 84% of N-NO X was then denitrified.Denitrification using methane as carbon source was also stimulated in the systemproposed by Buntner et al. (2010) with some modifications such as the implementation ofan anoxic chamber by the elimination of aeration in the first chamber of the MBR and theelimination of the recirculation between the MBR and the UASB. This configurationfavoured denitrification process using the dissolved methane present in the effluent of the52