Modeling of Sewage Circulating Reactor: An Approach to Recirculating Wastewater in Sewers

Uttam K. Manandhar
Hans Schroder

DOI: 10.2190/RK6Y-L3GB-847W-U1JW


One way to exploit the self-purifying capacity of flowing wastewater is to recirculate it so that a portion of the conveyance conduit works as a circulating biological reactor (referred to as a Sewage Circulating Reactor, SCR). This study deals with the formulation of a mathematical model for this system based on suspended-growth and biofilm kinetics. The model simulated the performance of the system satisfactorily and showed that all three biological reactions, carbon oxidation, nitrification, and denitrification, occurred simultaneously in the system. The model simulation also indicated that both suspended and film biomasses were significant at low loadings in terms of organic carbon removal. At higher loadings, suspended biomass was more significant than biofilm biomass for COD removal. The maximum substrate utilization rates (Km values) for carbon oxidation, nitrification, and denitrification were obtained by fitting simulated profiles with the experimental ones. The km values for carbon oxidation and nitrification were higher for experimental runs with higher DO levels or lower loadings. However, the Km value for denitrification was higher for the case of higher loadings.

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