Practical Application of the ADUF Process to the Full-Scale Treatment of a Maize-Processing Effluent

Abstract

ADUFR (anaerobic digestion ultrafiltration) is a membrane-assisted process for positive separation of biomass from the treated effluent. Pilot and full-scale ADUFR studies were carried out on a maize-processing effluent (15 kgCOD/m3) at the Meyerton mill of Messrs. African Products, South Africa. The results after 15 months of full-scale operation have illustrated the merits of the process for the production of a colloid-free effluent at a mean COD removal efficiency of 97%. The permeate flux varied in the range 37 to 8 l.m−2.h−1 at 35°C, inlet pressure of 450 kPa, linear tube velocity of 1.6 m/s and digester suspended solids concentration of 21 kg/m3. Periodic chemical cleaning of the unsupported tubular polyethersulphone membranes with EDTA was only commenced after 13 months operation. A mean plant space load rate of 3 kgCOD.m−3.d−1 guaranteed reliability to withstand high COD shock loadings due to variations in the feed load. Bio-membrane separation technology of this nature holds important economic advantages for the treatment of a wide spectrum of organic industrial effluents.