ANAEROBIC-DIGESTION OF A SYNTHETIC WASTE-WATER CONTAINING STARCH BY A MEMBRANE REACTOR

The anaerobic degradation of a synthetic wastewater containing starch as the sole carbon source was studied in an anaerobic membrane bio-reactor. The influence of HRT at a constant organic loading rate of 2 g COD.l-1.d-1 was firstly examined. The range of HRT studied was between 135 and 6 hours. The performance of the reactor remained good until a hydraulic retention time of 11 hours was reached. The HRT of 6 hours showed a sharp decrease of the performance. Nevertheless, a COD removal yield of 80% was obtained at this HRT. Secondly, the influence of the organic loading rate was investigated at a constant solid retention time of 52 days. The organic loading rate was increased from 7 to 24 g CODi.l-1.d-1. Volatile solids and volatile suspended solids were proportional to the organic loading rate. Furthermore, a decrease in the COD removal yield was observed. At the organic loading rate of 24 g COD i.l-1.d-1, COD removal yield and specific removal rate were respectively of 87% and 0.57 g COD(r.g) VSS-1.d-1. Membrane flux was not limiting when the volatile solids concentration was below 40 g.l-1 and was between 20 and 10 l.h-1.m-2. Membrane flux was near its upper limit for a volatile solids concentration of 74 g.l-1 and was equivalent to 4 l.h-1.m-2 for a linear velocity of 2.5 m.s-1.