EFFECTS OF ORGANIC-MATTER ON THE CONVERSION RATES OF NITROGENOUS COMPOUNDS IN A CHANNEL REACTOR UNDER VARIOUS FLOW CONDITIONS

This study investigated the effects of organic matter on the conservat ion rates of nitrogenous compounds in a deep mixed films channel react or under high dissolved organic (DO) and various flow conditions. A se ries of batch tests was performed to examine the effects of organic ma tter, with and without the addition of glucose, on variations of the n itrogenous compounds. Experimental results indicated that increasing t he organic matter concentration under all flow conditions decreased th e concentrations of nitrate and total nitrogens; however, an enormous build-up of nitrite occurred in the water column. Also, the conversion pathways of nitrogenous compounds changed from ammonification and nit rification to assimilation, ammonium oxidation and denitrification. Mo reover, changing the flow velocity significantly influenced the conver sion rates of nitrification and denitrification. When adding organic m atter, the rate of nitrite to gaseous products became greatly enhanced if the flow velocity increased within the turbulent regime; increasin g velocity seemed only to inhibit the rate of conversion from nitrate to nitrite. In contrast, when organic matter was not added, the rates of ammonium oxidation exceeded those of nitrite oxidation within all f low regimes. Experimental results further demonstrated that nitrite ox idation was the rate-limiting process of nitrification under the low o rganic matter conditions. On the other hand, when sufficient amounts o f organic matter were present, the processes of nitrite to gaseous pro ducts and nitrate to nitrite dominated the rate of denitrification und er the laminar and turbulent regimes, respectively. (C) 1998 Elsevier Science Ltd. All rights reserved.