Anaerobic digestion of slaughterhouse wastewater using a combination sludge blanket and filter arrangement in a single reactor

A laboratory-scale anaerobic reactor, in which the bottom two-thirds were occupied by a sludge blanket and the upper one-third by submerged small cubes of polyurethane foam, was evaluated for the anaerobic treatment of slaughterhouse wastewater. The reactor was operated at 35°C during the two experimental studies. In the first study, the chemical oxygen demand (COD) concentration of the wastewater was increased from 3·74 to 10·41 g l?1 whilst maintaining a constant hydraulic retention time (HRT) of 1·5 days. In the second, the HRT was decreased from 1·35 to 0·50 days, whilst maintaining a constant influent COD concentration of 10·41 g l?1. The results showed that this type of reactor was suitable for the anaerobic treatment of this wastewater and demonstrated a high COD removal of between 90·2 and 93·4% at organic loading rates between 2·49 and 20·82 g COD l?1 day?1. At an HRT of 0·5 days, the reactor achieved a methane yield of 0·345 l CH4 STP per gram of COD removed. This yield is higher than the values reported in previous studies.