MEMBRANE-COUPLED ANAEROBIC DIGESTION OF SEWAGE SLUDGE: A PILOT STUDY

Anaerobic digestion of solids is a common process used in sludge management. It may be applied in treatment of process waste solids and primary and secondary sludge from industrial and municipal waste treatment plants. Use of membranes eliminates the need for coagulant addition reducing operating cost and inhibitory effects. A 550-L completely mixed anaerobic digester was operated under mesophilic conditions (35°C). Vibrating and cross-flow ultrafiltration (UF) membrane systems were evaluated for their potential in membrane-coupled anaerobic digestion. The vibrating membrane flux ranged from1.6 m3/m2-d to 2.0 m3/m2-d and the cross-flow membrane operated at flux of 3.4 m3/m2-d – 3.6 m3/m2-d. Application of membranes did not adversely affect the biological performance of the digester: a volatile solids reduction of 59% was observed at an average mixed liquor suspended solids concentration of 1.8%.