This study investigated the effects of dissolved oxygen (DO) concentration and flow conditions on the conversation rates and pathways of nitrogenous compounds in an pilot open channel. Ammonium sulfate and glucose were added externally as the substrates in the substrate in the investigation. The experimental results showed that under conditions of constant flow velocity and DO concentration above 1 mg/l, the removal rates of total nitrogen (including nitrite, nitrate and ammonium nitrogens) varied linearly withthe removal rates of ammonium nitrogen. Comparison of the removal ratefor each individual nitrogenous component reveals the following order of removal rates: ammonium nitrogen>total nitrogen>nitrate nitrogen>nitrite nitrogen. Moreover, the nitrite concentration was less than 1 mg/l, all nitrogenous compounds was observed: total nitrogen>nitrate nitrogen>nitrite nitrogen>ammonium nitrogen. The results indicated that the conversation pathwats of nitrogenous compounds can be divided into four different types depending on the DO concentration level. The rest results also revealed that an increase in the flow velocity significantly influenced the conversion rates of nitrogenous compounds. While a V-shaped relation of the removal rates of total nitrogen vs the Reynolds nunbers was odserved for low DO below 1.5 mg/l. an inverted V-shaped relation occured at high DO above 5 mg/l.
