ANAEROBIC-DIGESTION BY A CERAMIC MEMBRANE ENCLOSED REACTOR

A reactor with an external pressure type ceramic membrane module was designed to complete a compact system which brings about a reduction of permeability power requirements. The applicability of the reactor to methane fermentation was examined using heat-treated liquor obtained from sewage sludge. The experiments were carried out at 3 steps of CODcr-loading (Run 1; 4.53, Run 2; 7.98, Run 3; 15.4 kg CODcr/m3. d). The permeation flux stabilized at 0.06 in Run 1 and 0.11 m3/m2.d in Run 2, where the membrane surface was backwashed with N2 gas. In Run 3, the membrane surface was additionally washed by circulating the gas yielded by the fermentation to increase the permeation flux, which stabilized at 0.2 m3/m2.d. The CODcr removal was 79.3 in Run 1, 83.2 in Run 2, and 80.2% in Run 3, respectively. In all cases, the BOD removal exceeded 95%, and there was no significant difference in the gas yield, which was 0.41 to 0.43 (l/g CODcr supplied) and 0.50 to 0.54 (l/g CODcr decomposed). Since the BOD could be greatly reduced even at 0.6 d of HRT and the microbiol cell concentration could be easily controlled, it seems possible to that the efficiency of this reactor can be further improved.