Aerobic treatment of maize-processing wastewater in a 50-liter rotating biological reactor

Corn (maize)—processing effluents, known as nejayote, were aerobically treated in a 50-liter laboratory-scale rotating biological reactor. Removal of organic compounds, evaluated as chemical and biochemical oxygen demand (COD and BOD), as well as reducing sugars, was monitored. Operating conditions were: feed COD, 6·4 g/liter; rotational disc speed, 16 rpm; hydraulic retention time, 2·5 days. A comparison with previous experiments, carried out in a 150liter reactor, to consider scaling-up effects (1:3) was performed. Final COD removal was 84·6%. The application of an exponential model to reducing-sugars degradation was highly satisfactory, and the value of the constant was −0·352. Generated biomass was bromatologically evaluated, and average results in per cent of total dry biomass were: protein content, 41·5; fat, 3·4; fiber, 14·8; ash, 15·1.