Cheese whey anaerobic digestion - Effect of chemical flocculant addition

Abstract

Two stirred tank digesters were operated with biomass retention by internal settling during effluent removal. In one digester a flocculating agent was used to enhance microbial aggregation and settling. The unflocculated digester achieved a maximum stable loading rate of 8-8.5kg COD/m 3. day and biomass density of 19.3g VSS/l compared to the flocculated digester which achieved a (non-maximal) stable loading rate of 12.3kg COD/m 3. day and biomass density of 43.3g VSS/l. Both digesters had a COD conversion efficiency greater than 97%. Operation of a stirred tank digester in a mix/settle mode allows a significant increase in biomass levels over conventional continuously stirred digesters. The addition of a chemical flocculant significantly enhances this improvement. © 1983 Science and Technology Letters.