Laboratory studies of in-reactor granular-sludge yield (Ygran) were carried out to investigate the effect of substrates rich in proteins. Both lab-scale upflow anaerobic sludge blanket (UASB) and shake-flask systems were used to monitor the behaviour of the sludge. Influent based on molasses with a COD to N ratio of 100:2.5-3.0 gave good Ygran; increasing substitution of the carbohydrate COD by protein COD resulted in a deterioration of the sludge characteristics. The negative effects appear to be related to the protein rather than to the NH4+ formed. Of the various environmental parameters examined, the surface tension of the mixed liquor was the main deviating factor. At a proper range of oxygenation i.e., by means of monitoring of both the input COD to oxygen ratio (gCOD gO2−1) and the daily oxygen loading rate (mgO2 gVSS−1.d−1), the UASB reactors treating the nitrogen-rich wastewater showed enhanced Ygran with only a minor reduction in methanogenesis. A range of working conditions in which this principle can be applied to decrease fluffy growth to the advantage of granular increase is proposed.
Organic and ammonium nitrogen and oxygen in relation to granular sludge growth in lab-scale UASB reactors
J. Thaveesri, K. Gernaey, B. Kaonga, G. Boucneau, W. Verstraete; Organic and ammonium nitrogen and oxygen in relation to granular sludge growth in lab-scale UASB reactors. Water Sci Technol 1 December 1994; 30 (12): 43–53. doi: https://doi.org/10.2166/wst.1994.0579
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