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TECHNICAL REPORTS

Behavior of an Aerated Submerged Fixed-Film Reactor (ASFFR) under Simultaneous Organic and Ammonium Loading

Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, P.O. Box 14155-6446, Tehran, Iran

^* Corresponding author (rnabizadeh{at}sina.tums.ac.ir)

Received for publication May 10, 2005. The performance of an aerated submerged fixed-film reactor (ASFFR) under simultaneous organic and ammonium loading and its effect on nitrification was studied. Organic loadings varied in the range of 1.93 to 5.29 g chemical oxygen demand (COD) m^–2 d^–1 and NH₄–N loadings were in the range of 116 to 318 mg NH₄–N m^–2 d^–1. Increments of loading rates were obtained both by increasing the flow rate and increasing the influent substrate in individual pilot runs. Results showed that with organic loading rates up to 3.97 g COD m^–2 d^–1, complete nitrification was achievable. Although high organic loading such as 5.29 g COD m^–2 d^–1 could cause nitrification to stop, shifting to lower organic loadings made nitrification start and set rapidly to its previous steady-state concentrations. Comparison of results showed that in the ASFFR, nitrification would be severely affected by an organic loading rate of 5.29 g COD m^–2 d^–1 by increasing either the flow or the influent substrate. It should be noted that the average value of dissolved oxygen was 3.4 mg L^–1 with an air supply of 15 L min^–1, and there was no indication of oxygen limitation. The results of this study show the flexibility of ASFFRs under changing organic loads. Furthermore, for achieving complete nitrification and optimum application of these reactors for protecting receiving water from the environmental hazards of ammonium, the maximum organic loading that would present complete nitrification should be considered.

Abbreviations: ASFFR, aerated submerged fixed-film reactor • BOD, biological oxygen demand • COD, chemical oxygen demand • HRT, hydraulic retention time