Aerobic biodegradation of wheat stillage (distillery wastewater) at an elevated temperature—Effect of solids separation

The aim of the study was to determine how the separation of solids affects the course and efficiency of the batch process of wheat stillage (distillery wastewater) biodegradation using meso- and thermophilic bacteria of the genus Bacillus. The processes with and without solids separation were conducted for 144h in a 5-L bioreactor, with aeration at 1.6vvm, stirrer revolutions of 550/min, at a constant pH (pH=6.5) and the temperature of 45°C. The results have shown that the separation of solids is superfluous, because it had only a minor effect on the reduction in the chemical oxygen demand determined in the substrate upon solids separation (SCOD). The extent of SCOD reduction amounted to 88.25% for non-filtered and 92.85% for filtered stillage. Moreover, during biodegradation of the non-filtered stillage the bacterial consortium was able per se to remove more than 50% of the suspended solids present in the stillage in the amount of approx. 50g/L (the biomass produced being neglected).