Anaerobic digestion of a synthetic wastewater 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 CODi.1‐1 .d‐1, COD removal yield and specific removal rate were respectively of 87% and 0.57 g CODr.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 101.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.