Abstract
Digestions of a strong liquid waste (50–150 g chemical oxygen demand (COD)/litre) initiated with granular sludge were stable at a loading rate of 18 g COD/1itre. day, using a high recycle rate. Specific rates of removal of lactic acid and ethanol were measured. Granules consisted of regions with different dominant populations of microorganisms. Granular sludge did not develop from municipal digester sludge, but stable digestion was maintained (6.5–9.C g COD/1itre. day) by recycling treated liquid to dilute the incoming feed stream. Addition of nitrogen was not necessary but phosphorus addition (110 mg P/litre) was required.