Settling of food-processing anaerobic sludge

This paper presents preliminary results of settling tests on anaerobic sludge from food-processing wastewater treatment, using 2, 4, and 8 L cylinders. A sedimentation model from the literature was applied to the sedimentation data. The specific settling velocities for the 2 and 4 L cylinders did not differ ( t -test; P = 0.896), therefore the data were pooled. The specific settling velocity mean was nearly three times higher ( P = 0.027) for the 8 L cylinder (21.03 × 10 −4 ± 6.27 × 10 −4 m/s) than the pooled smaller cylinder size (7.29 × 10 −4 ± 2.32 × 10 −4 m/s). Measurement challenges were encountered while working with the 8 L cylinder. Given that tests using a 1 L cylinder resulted in sludge compression, the results indicate that use of both 2 and 4 L cylinders is feasible for lab-scale measurement of sludge settling.