| The presence of nitrogenous or nitrogen-containing wastes in the final effluents from sludge digesters or several industries can adversely impact or pollute aquatic life, cause dissolved oxygen depletion, eutrophication and methemoglobinemia in receiving water. For this reason, greater efforts have been exerted on improving and discovering techniques and strategies to reduce the amount of nitrogen in wastewater. Nowadays, the most common way to remove nitrogen from wastewater is the combination of two sequential biological processes (nitration, denitrification) which is also called conventional biological removal of nitrogen.Recently, anaerobic ammonium oxidation (Anammox) as a new and promising biological alternative to conventional nitrogen removal from wastewater has received special attention since its discovery. Later on, a new biological removal of nitrogen process named as deammonification has been made based on this new discovery. However, the application of deammonification can be limited by its inhibition by certain compounds, such as dissolved oxygen (DO), substrate nitrite and the low growth rate of Anammox bacteria. These inhibitory effects make the start-up of nitrogen removal process difficult and complex, so a model-based approach would be very useful. Especially, using modelling in the development of Anammox process is more crucial. Even if a model is not fully correct, the trends provided by model simulations greatly help the development of processes based on slow growing bacteria.In our study, the granulation of deammonification was investigated in a single, oxygen-limited, sequencing batch reactor (SBR). The reactor was started anaerobically and fed using the Van de Graaf medium to cultivate Anammox biomass after inoculation with methanogenic granular sludge. Subsequently, mixture gas (air and nitrogen gas) was supplied to the reactor and a nitrifying population developed. Besides, a dynamic mathematical model including nitrification, Anammox, COD oxidation and denitrification was proposed for the simulation of the performance of deammonification. Research results showed that autotrophic granules was cultivated successfully by controlling the dissolved oxygen in the reactor between 0.3 and 0.5 mg/L, and an total inorganic nitrogen (TIN) removal efficiency of 63.7% was obtained with a higher nitrogen load increased by reducing HRT to 3 days. Moreover, a set of experiments and simulations were carried out to analyze the effects of denitrification process, substrate nitrite and DO on SBR system, and to validate the model. Heterotrophic denitrifiers has some influence on.the Anammox process during the initial cultivation, and the influence decrease gradually during the following operation period. The biological processes could be inhibited by a certain nitrite concentration 20-30mg/L, a total nitrogen removal efficiency drop. The high or low DO concentration was not in favor of the operation of SBR system. In addition, the simulation results were consistent with the experimental results, which illuminated that the mathematical model was appropriate for the modelling of deammonification in a single reactor, thus it could estimate the impact of specific parameters and predict the efficiency of system. |
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