Aerobic digestion of cheese whey

Abstract

The main objetive of this work was to evaluate the anaerobic digestion of cheese whey (68.000mg COD/l), without whey pH adjustment, incomplete mixture semi-continuous laboratory reactors with temperature maintained at 35° ± 1°C. Cattle manure with 8% total solids was used for seeding the reactors. The experiment was carried out for a period of 100 days. The first 20 days were characterized for the aclimatization of seed manure and four 20 days periods as hydraulic retention times (¸). A loading of 3,0g COD/l digester/day was fed to each digestor. In the 1rst ¸ the loading was divided in three portions and fed to the reactors at intervals of 8 hours. In the 2nd t h e loading was divided in two portions and fed to the reactors at intervals of 12h; in the 3th ¸ a 6h interval of feeding was used, and the loading divided in four portions; the 4th ¸ was characterized by feeding the total loading to the reactor at once. The experiment was controled by the following analysis: volatile acidity, alkalinity, pH, volume of biogas produced and chemical oxigen demand (COD). The results obtained show an effect of the feeding system on the process of anaerobic digestion of whey. The increase in volatile organic acid production at the retention times studied caused a change in the equilibrium of the microbial population and consequently lowered the efficiency of the process. Under these condition biogas production expressed as 1.gas/g of COD used was 0.35 l/g.