Mathematical model analysis on the enhancement of aeration efficiency using ladder-type flat membrane module forms in the Submerged Membrane Bio-reactor (SMBR)

Abstract

The cross-flow shearing action produced from the inferior aeration in the Submerged Membrane Bio-reactor (SMBR) is an effective way to further improve anti-fouling effects of membrane modules.Based on the widely-applied vertical structure of flat membrane modules, improvements are made that ladder-type flat membrane structure is designed with a certain inclined angle θ so that the cross-flow velocity of bubble near the membrane surface can be held, and the intensity and times of elastic collision between bubbles and membrane surface can be increased. This can improve scouring action of membrane surface on aeration and reduce energy consumption of strong aeration in SMBR. By deducing and improving the mathematics model of collision between bubble and vertical flat put forward by Vries, the relatively suitable incline angle θ under certain aeration place and in certain size rang of bubble can be obtained with the computer iterative calculation technology. Finally, for many groups of ladder-type flat membrane in parallel placement in the practical application of SMBR, some suggestions are offered: the interval distance of membrane modules is 8-15 mm, and aeration should be operated at 5-7 mm among membrane modules, and the optimal design angle of trapeziform membrane is 1.7°-2.5°. membrane bioreactor, flat membrane, membrane module form, aeration, mathematical modelIn the Submerged Membrane Bio-reactors (SMBR), the bubble produced during the aerating can not only provide the necessary oxygen for the microorganisms, but also results in a gas-liquid cross-flow on the membrane surface and an increased shearing force. In this way, the enhanced aerating intensity can increase the disorderly cross-flow and the shearing force on the membrane surface, commix the laminar flow boundary layer, inhibit the growth and condensation of cake architecture, and thus delay the effect of concentration polarization, which is an effective way to control the membrane fouling [1] .However, too high aerating intensity will do harm to the activated sludge flocs, decrease inter-effect of the microorganisms, inorganic granule and extra-cellular polymeric substances and thus aggregate Zoogloeadis with more extra-cellular polymeric substances released, which might shorten sludge floc dimension, and even worsen the membrane filtration process [2] . Moreover, the energy-consumption of the aerating accounts for more than 80% [3] , thus the high cost of operation has been the main obstacle of the SMBR in the industrial application.

Recent advances in membrane crystallization

“…The helical membrane module refers to the constant helical rotation of the flat membrane, where the mass transfer can be improved dramatically through bubble collision, turbulence, and vortex mixing. 104,105 Besides, concentration polarizations are obviously decreased under the helical configuration. 106 Jie et al 107 designed a novel helical membrane by twisting the flat membrane (Fig.…”