Abstract
The effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater was investigated. Experiments were conducted in a modified Ludzack–Ettinger pilot-plant configuration for 365 days. Total nitrification of an influent concentration of 1200 mg NH 4 +–N l −1 was obtained in this period. Influent COD/N ratios between 0.71 and 3.4 g COD g N −1 were tested by varying the nitrogen loading rate (NLR) supplied to the pilot plant. An exponential decrease of nitrification rate was observed when the influent COD/N ratio increased. The experimental COD/N ratio for denitrification was 7.1±0.8 g COD g N −1 while the stoichiometric ratio was 4.2 g COD g N −1. This difference is attributable to the oxidation of organic matter in the anoxic reactor with the oxygen of the internal recycle. The influence of influent COD/N ratio on the treatment of high-strength ammonium industrial wastewater can be quantified with these results. The influence of COD/N ratio should be one of the main parameters in the design of biological nitrogen removal processes in industrial wastewater treatment.
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