10.2190/RK6Y-L3GB-847W-U1JW RK6YL3GB847WU1JW 2 Modeling of Sewage Circulating Reactor: An Approach to Recirculating Wastewater in Sewers 241 262 20020509 20020509 20020509 20020509 RK6YL3GB847WU1JW.pdf http://baywood.metapress.com/link.asp?target=contribution&id=RK6YL3GB847WU1JW 3 Uttam K. Manandhar Hans Schroder SERD, Asian Institute of Technology, Thailand 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 (K_m values) for carbon oxidation, nitrification, and denitrification were obtained by fitting simulated profiles with the experimental ones. The k_m values for carbon oxidation and nitrification were higher for experimental runs with higher DO levels or lower loadings. However, the K_m value for denitrification was higher for the case of higher loadings. M. Green, G. Shelef, and A. Messing, Using the Main Sewerage System Main Conduits for Biological Treatment: Greater Tel Aviv as a Conceptual Model, <i>Water Research, 19</i>:8, pp. 1023-1028, 1985. R. L. Stoyer, <i>The Pressure Pipe Wastewater Treatment System</i>, presented to the 2nd Annual Sanitary Engineering Research Laboratory Workshop on Wastewater Reclamation and Reuse, Tahoe City, California, 1970. C. M. Koch and J. Zandi, Use of Pipelines as Aerobic Biological Reactors, <i>Journal of Water Pollution Control Federation, 45</i>, pp. 2537-2548, 1973. U. K. Manandhar and H. Schroder, Sewage Circulating Reactor—An Approach to Recirculating Wastewater in Sewers, <i>Environment Technology Letters, 16</i>, pp. 201-212, 1995. G. H. Chen, H. Ozaki, and Y. Terashima, Modelling of the Simultaneous Removal of Organic Substances and Nitrogen in a Biofilm, <i>Water Science and Technology, 21</i>, pp. 791-804, 1989. V. G. Levich, <i>Physicochemical Hydrodynamics</i>, Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1962. P. Harremoes, Biofilm Kinetics, in <i>Water Pollution Microbiology</i>, Vol. 2, R. Mitchell (ed.), Wiley, New York, 1978. U. K. Manandhar, Sewage Circulating Reactor: An Approach to Recirculating Wastewater in Sewers, <i>Doctoral Dissertation EV-93-2</i>, AIT, Bangkok, Thailand, 1993. P. B. Saez and B. E. Rittmann, Improved Pseudoanalytical Solution for Steady-State Biofilm Kinetics, <i>Biotechnology and Bioengineering, 32</i>, pp. 379-385, 1988. K. J. Williamson and P. L. McCarty, Verification Studies of the Biofilm Model for Bacterial Substrate Utilization, <i>Journal of Water Pollution Control Federation, 48</i>:2, pp. 281-296, 1976. K. M. Brown, Computer Oriented Algorithm for Systems of Simultaneous Nonlinear Algebraic Equations, in <i>Numerical Solution of Systems of Nonlinear Algebraic Equations</i>, G. D. Byrne and C. A. Hall (eds.), Academic Press, Orlando, Florida, 1973. P. L. McCarty, Stoichiometry of Biological Reactions, <i>Progress in Water Technology, 7</i>:1, pp. 157-172, 1975. E. Gonenc and P. Harremoes, Nitrification in Rotating Disc Systems: I Criteria for Transition from Oxygen to Ammonia Rate Limitation, <i>Water Research, 19</i>:9, pp. 1119-1127, 1985. Metcalf and Eddy, Inc., <i>Wastewater Engineering: Treatment, Disposal, Reuse</i>, McGraw Hill Book Co., New York, 1991. E. Arvin and P. Harremoes, Concepts and Models for Biofilm Reactor Performance, <i>Water Science and Technology, 22</i>:1/2, pp. 171-192, 1990. S. Jayamohan, S. Ohjaki, and K. Hanaki, Effect of DO on Kinetics of Nitrification, <i>Water Supply, 6</i>, Brussels, pp. 141-150, 1988. J. E. Alleman, Elevated Nitrite Occurrence in Biological Wastewater Treatment Systems, <i>Water Science and Technology, 17</i>, pp. 409-419, 1984.