The Study On Simultaneous Nitrification And Denitrification Of Domestic Sewage

For the disadvantage of long process flows, large covering area, high central cost and needing extra carbon source, traditional techniques usually could not be used. Simultaneously nitrification and denitrification (SND) overcomes these problems and seriously reduce the operation costs, gained broad application prospect around the world.Self-made aerobic-anoxic-anaerobic integral water treatment device was used to treat simulated domestic wastewater. Impact of DO, C/N, HRT and pH on SND and mechanism were investigated. Simultaneously, pilot scale experiment was conducted in the scene to investigate the efficiency and operation cost on sewage wastewater. Results show that:(1) The results show that SND exists in both small-sized experiment and pilot scale experiment, without accumulation of nitrite, indicating that SND in the experiments were not short-cut nitrification and denitrification.(2) Results of small-sized experiment show that DO, C/N, HRT and pH have great impact on SND. Optimal condition of DO, C/N, HRT and pH were gained at1.4～1.6mg/L,C/N=5, HRT=20h and pH=7.5, with ammonia, TN, COD removal rate at85.89%,92.76%and80.75%respectively.(3) Aerodynamic model of SND in aerobic-anoxic-anaerobic integral water treatment device was derived based on normal SND aerodynamic model. A saturated contents (KNO3) of nitrate of1.55mg/L was calculated, which far more surpassed that of monopole denitrification, explaining SND quantitatively.(4) Results of pilot scale experiment show that optimal condition of DO, HRT were3.0mg/L and48h (inlet flow is6m3/d), with ammonia, TN, COD removal rate at85.19%,69.28%and69.96%respectively.(5)There are no sludge accumulation happened in the experiment at lab and pilot test, and no discharged sludge existed also, the sludge at the bottom of the reactor exist in the form of granulated, it could indicate that the research of the reactor produce less sludge and decrease the sludge treatment cost,the reactor also could remove the P by the way of adding lime(6) The economic benefit analysis for a10m3/d handing capacity was investigated, capital cost of15905(1,590RMB/m3) and operating cost of0.55RMB/m was calculated.In conclusion, high removal efficiency SND was maintained on sewage wastewater using aerobic-anoxic-anaerobic integral water treatment device, the process flows was shortened, covering area shrieked and the costs was saved without extra carbon source. It is estimated that this technology will be the most important technology in small sewage wastewater.