3.4. Minimum oxygen requirements
To test whether providing one pore volume of air was sufficient for the long term operation and acetate removal, the reactor was run continuously for 24 cycles. Over 80 h it was demonstrated that 14 Cmmol/L acetate (448 mg/L BOD) present in the synthetic wastewater were removed in cycles of 3.5 h (Fig. 6). Therefore the removal rate of acetate was 4 Cmmol/L/h (123 mg/L/h BOD), which is a carbon removal rate that is about 3 times higher than typically observed in activated sludge plants (Tandukar et al., 2007). No significant Embelin output was recorded over this time. From the reproducible oxygen uptake curves (data not shown) sickle cell anemia could be predicted that approximately 50% of the acetate added was respired (Table 2).
Fig. 6. The effect of increasing the carbon to oxygen ratio, on the continuous removal of acetate. Continuous operation of the storage biofilm reactor under repeated cycles of synthetic wastewater with 1 pore volume of air provided, 24 cycles of 14 Cmmol/L, 18 cycles of 22 Cmmol/L and 5 cycles of 30 Cmmol/L. Example cycles of 14 Cmmol/L (●) and carbon outflow (○), of 22 Cmmol/L (?) and carbon outflow (△), and of 30 Cmmol/L (■) and carbon outflow (□).Figure optionsDownload full-size imageDownload as PowerPoint slide