Small-scale sewage plant experiment by pretreatment and methanization of suspended solids

Anaerobic Membrane Reactors

“…Until recently there was very little information available about any temperatures other than mesophilic. Murata et al (1994) treating sewage using an external membrane unit coupled with a CSTR obtained a VSS reduction rate at 55 • C of 67-78%, but the difference between 35 • C and 55 • C was not large in relation to the heating energy. At 35 • C, VSS reductions were 51-79% at a VSS volumetric load of 0.93-1.94 kg·m -3 ·d -1 , an HRT of 4.2-8.4 d and a SRT of 42-335 d; this compares with conventional AD at an HRT of 15-30 d. Decreasing the temperature from 30 • C to 25 • C did not greatly reduce the VSS reduction rate; a rate from 67% to 70% was maintained with a VSS volumetric load of about 1 kg·m -3 ·d -1 .…”

“…This appears to be the lowest recorded HRT using AnMBRs, and demonstrates that good removals are possible at low HRTs. SRTs in AnMBRs can be as low as 25 d and as high as 335 d (Liao et al 2006;Murata et al 1994), and this can be controlled fairly easily with sludge wastage rates. Clearly at long SRTs the sludge will be minimal and very non-biodegradable, however, one factor which may reduce the attractiveness of long SRTs is the fact that biomass-associated products (BAPs), which form part of SMPs in the digester, tend to increase with SRTs, and this tends to increase effluent COD .…”