The anaerobic treatment of slaughterhouse wastewater in fixed-bed reactors

Abstract

The experiments showed that fixed-bed reactors are suitable for the anaerobic treatment of unsettled wastewater rich in solid substances, such as slaughterhouse wastewater. Two fixed-bed reactors with loading rates of 2–18·5 g/l day and hydraulic retention times of 5 to 0·5 day were run in parallel, the biological efficiency achieved was, on average, η COD = 85−30% (bamboo as carrier) and η COD = 80−27% (bones as carrier). Even with higher loading rates methanization was stable in both reactors. The recirculation of part of the outflow can have a positive or negative influence on the reactor performance depending on the substrate concentration in the inflow. In all the comparative investigations the COD elimination rates obtained for the unsettled wastewater were below those obtained for the settled wastewater. Measurements of the fluid volume showed that a biomass enrichment in both fixed-bed reactors was completed within the first half year and that a balance had been achieved between the fixed and suspended biomass. During the entire course of the experiments both reactors were operationally reliable.