DEFINITION OF OPTIMAL CONDITIONS FOR THE HYDROLYSIS AND ACIDOGENESIS OF A PHARMACEUTICAL MICROBIAL BIOMASS

The effect of operational parameters such as hydraulic retention time (HRT), influent substrate concentration (So), pH, temperature and recy cling on the acidogenic digestion of a pharmaceutical biomass was inve stigated. The total COD content of the pharmaceutical effluent used wa s 50 g/litre, only 13.6% occurred in soluble form and consisted mostly of protein (22 g/litre). Substrate degradation was quantified in term s of COD, protein and carbohydrate degradation. Variations in COD solu bilization were mainly due to protein solubilization. The best results , in terms of COD solubilization and concentrations of produced VFA, w ere obtained at pH = 8.5, T = 35 degrees C and OLR = 5.4 gCOD/litre/da y. Under these conditions 50.6% of the initial COD content was solubil ized and 17.1 g/litre of volatile fatty acids (VFA) were produced. Rec ycling of biomass resulted in greater COD solubilization but in lower acidogenic activity. Moreover, the effluent of the acidogenic reactor showed poor settling properties. (C) 1997 Elsevier Science Ltd.