Mathematical modeling and intensive chemical analysis are used to quantify the relationships among the heterotrophic bacteria, autotrophic bacteria, and key inorganic (NH4+-N and NO3−-N) and organic (COD) compounds of municipal wastewater treated in a pilot-scale membrane bioreactor (MBR) operated with aerobic-anoxic cycles. Key features of the model for MBR are no biomass in the effluent, partial removal of biomass-associated products by the membrane, and D.O. cycling with 9 mg/L during aeration period and 0.5 mg/L for the anoxic period. The model explains the key trends in the cyclic data: NH4+-N is consumed only during aerobic periods and rises steadily during anoxic period; NO3−-N is produced only during aerobic periods, but declines in anoxic periods; The soluble COD in treated water mainly consists of BAP and is relatively constant through the cycle. Advantages of introducing an anoxic cycle to the continuous-flow MBR process are reduction of total effluent nitrogen, oxygen consumption, and sludge production as a consequence of denitrification. On the other hand, the anoxic period causes an increase in the average effluent NH4+-N.
Advanced analysis of membrane-bioreactor performance with aerobic-anoxic cycling
D. G. V. de Silva, V. Urbain, D. H. Abeysinghe, B. E. Rittmann; Advanced analysis of membrane-bioreactor performance with aerobic-anoxic cycling. Water Sci Technol 1 August 1998; 38 (4-5): 505–512. doi: https://doi.org/10.2166/wst.1998.0707
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