STARTING-UP AN ANAEROBIC HYBRID FILTER FOR THE FERMENTATION OF WASTE-WATER FROM FOOD-INDUSTRY

The wastewater from a food processing factory, characterised by fluctu ations of flow rate, organic strength, and pH, were originally treated by a traditional suspended-biomass digester working at about 25 degre es C. In order to improve the digester efficiency, either in terms of degradation ability or biogas production yield, a set of tests has bee n carried out on laboratory scale, whose results indicated the way to correctly transform it into an anaerobic hybrid filter. The unacceptab le conversion yield of organic substances into biogas observed in the original system has been improved by the presence of the filling mediu m, due to a marked increase in biomass retention time. The start-up of anaerobic digestion has been studied in this reactor at two different temperatures (25 and 30 degrees C), in order to evaluate the possible advantage of heating the system, simulating continuous variations in feed strength, pH, and composition.