Mathematical Simulation And Control Of Denitrification Integrated With Methanogenesis

In the simultaneous denitrification and methanogenesis process, organic carbon and nitrogen in wastewater can be removed and energy can be recycled at the same time. In this paper, batch and continuous flow assays were used to study SDM process in a single anaerobic reactor. With sodium acetate as electron donor, mathematical simulation of SDM process in batch reactor was adapted to clear the mechanism of integration and competition between denitrification and methanogenesis. Besides, the appropriate electron donor was selected by batch experiment. Based on the results of batch experiments, continuous flow system was used to construct SDM process in the upflow anaerobic sludge blanket (UASB) reactor, thus the suitable COD/N, load and hydraulic retention time (HRT) were investigated, the main conclusions are as follows:(1) The multiplicative Monod and non-competitive Monod equation were integrated with theoretical equations determined by stoichiometry and bioenergetics to establishthe SDM model, the results show that the model could analyze the SDM process quite well.(2) With sucrose, sodium acetate and methanol as an electron donor, the potential of anaerobic granular sludge to carry out SDM process under different COD/N was investigated. It was confirmed that a better removal of COD and N could be achieved at COD/N of 10 with sodium acetate and sucrose as an electron donor.(3) The operating conditionsof UASB reactor were set at a temperature of (35±1)℃ and HRT of 38.4h to build SDM system in a single reactor with sodium acetate and sucrose as electron donor. The results showed that integration of denitrification and methanogenesis could be achieved at COD/N>4 and COD/N>10 with sucrose and sodium acetate as an electron donor, respectively.(4) The effect of the load on SDM process in a single reactor was investigated by gradually increasing the organic loading rate (OLR) and nitrogen loading rate (NLR).With sucrose and sodium acetate as the electron donor, the maximum OLR carried by the reactor was 6.25 and 3.125 kg/(m3·d) respectively, the corresponding NLR was 0.625 and 0.3125 kgN/(m3·d).(5) The effects of HRT on SDM system in a single reactor were studied. The results showed that the minimum HRT to achieve the SDM process with sucrose and sodium acetate as the electron donor was 6.4h and 9.6h, respectively.