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Efficient urban wastewater denitrification to achieve a low-carbon and nitrogen than for the bottom of the time aeration BAF (Biological Aerated Filter, BAF) unit has been transformed secondary aeration mode period by optimizing the filter layer dissolved oxygen distribution and to improve the environmental conditions of the degradation of organic matter and ammonia, promote nitrification to inhibit carbon source consumption, to retain carbon source for subsequent denitrification unit. First, the paper as a reference to the time aeration BAF process optimization study. Including: hanging film to start, aeration amount of pollutants along the way to remove the law, anti-shock loading capability of pollutants backwash, get the best amount of aeration, to determine the position of the filter layer needed supplemental oxygen for behind the secondary aeration BAF test provides a reference. For secondary aeration BAF the total gas aeration BAF equivalent conditions, adjusting the distribution of the gas of the two aeration point, removal of pollutants, DO along the range distribution of pollutant along removal of law, anti-shock loading capability of pollutants and backwash; comparative study with aeration BAF process. Primary aeration BAF study results showed that the best air-water ratio range of 4:1 6 : 1. When the air-water ratio about 4:1, an aeration BAF COD, NH 4 - N and TN removal rates 72.67%, 71.92% and 44.97%; gas-water ratio is greater than 6:1, the removal of COD and NH 4 - N The rate has improved greatly, but the TN removal efficiency decreased and aeration power consumption. Reactor COD removed region 0 2 25cm segment; NH 4 - N main degradation area in 175 4 10cm segment to improve the area at the junction of DO concentration determined in the the 180cm Department set two aeration components. The secondary aeration BAF primary aeration BAF process optimization. The results showed that under the conditions of the total gas-water ratio equal, secondary aeration by changing the conventional aeration BAF DO distribution, significantly improve the NH 4 - < / sub> N removal, moderately reduce the COD removal efficiency, to retain carbon source for the subsequent denitrification process. In the gas-water ratio 4:1,3:1 and 2:1, 1:1 and 2:1 conditions, COD average removal rate were 68%, 71% and 58%; NH 4 - N average removal rate were 74.76%, 94.04%, 87.94%; the TN average removal rates were 41.31%, 36.34%, and 44.49%, respectively. Secondary aeration BAF improve the ability of the reactor volume load impact resistance, gas-water ratio of 2:1, 3:1, 3:1, 6:1,4:1 COD removal efficiency of 75.68%, 76.90% and 73.52%; NH 4 - N removal rates were 43.48%, 51.64% and 54.56%. However, secondary aeration BAF accelerated aerated filter head loss, shorten the backwash cycle. To solve this problem, it is recommended that the internal reflux, added to the reactor the enhanced water flushing of the filter in the lower part of the gas as well as accelerate the degradation of refractory organics.
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