Startup And Influence Factors And N₂O Emission From An Anaerobic/Oxygen-limited Sequencing Batch Reactor Performing Simultaneous Nitrogen And Phosphorus Removal

Simultaneous nitrification denitrification and phosphorus removal?SNDPR?refers to remove both nitrogen and phosphorus under condition of anaerobic/ oxygen-limited,it is a new type of simultaneous nitrogen and phosphorus removal process,Compared with conventional biological nitrogen removal process,it has the advantages of lower oxygen demand,less carbon source and lower sludge yield.In addition,it was found that the emission of strong greenhouse gases N₂O in the process of nitrogen removal,therefore,the study of the emission and control of N₂O in the process has attracted much attention in recent years.Inoculated with nitritation sludge,the simultaneous nitrification,denitrification and phosphorus removal?SNDPR?process was successfully developed in an anaerobic/oxygen-limited?DO concentration of 0.3⁰.8 mg·L-1?lab-scale sequencing batch reactor fed with synthetic wastewater.on the basis of this,the effects of influent pH,DO concentration and COD concentration on simultaneous nitrogen and phosphorus removal and N₂O emissions characteristics in SNDPR were studied,and obtained the optimum operating conditions of the reactor,and the factors affecting N₂O accumulation,aimed to provide the basis for improving the effect of simultaneous nitrogen and phosphorus removal and the reduction of N₂O emission in this process.The main results are as follows:?1?The lab-scale SBR reactor,Inoculated with nitritation sludge,using synthetic wastewater with ammonia and phosphorus as influent,by gradually increasing the influent COD and PO43--P concentration,adjust the influent ammonia concentration and control of anaerobic/ oxygen-limited?DO 0.3¹.0 mg L-1?,in a relatively short period of time to achieve SNDPR.The removal rates of nitrogen and phosphorus were 76.1±5% and 98.4±1%,respectively.?2?The effects of different DO concentration?<0.3 mg·L-1,0.3¹.0 mg·L-1,>1.5 mg·L-1?on nitrogen and phosphorus removal,and N₂O emission were studied,results showed that,with the increased of DO concentration,the phosphorus removal efficiencies were 74.2%,82.6% and 88.5%,respectively.The nitrogen removal efficiencies were 47.8%,76.3%,and 31.3%,respectively.The amounts of N₂O emission were 5.5,7.4 and 2.0 mg·L-1,and the corresponding conversion rates were 58.2%,50.4% and 34.1%,respectively.This study revealed that,when the concentration of DO was controlled around 0.3¹.0 mg L-1,the system could achieve a good performance of simultaneous nitrogen and phosphorus removal,but it would increase the emission of N₂O.?3?The effects of different pH?6.0?7.0?8.0?9.0?on nitrogen and phosphorus removal,and N₂O emission were studied,results showed that,with the increased of pH values,the phosphorus removal efficiencies were 84.0%,74.7%,79.6% and 87.7%,respectively,phosphorus were well removed at pH 9.0 and 6.0.The nitrogen removal efficiencies were 83.9%,77.5%,64.9% and 67.8%,respectively.The emission of nitrous oxide decreased with the increase of pH.Specifically,the nitrous oxide emission at pH 6.0 was 3.5 times of that at pH 9.0.This study revealed that,in order to get well removal efficiency of nitrogen and phosphorus and reduced the emission of N₂O,the initial pH value should be neutral.?4?The effects of different COD concentration?46?100?200 mg·L-1?on nitrogen and phosphorus removal,and N₂O emission were studied,results showed that,with the increased of COD concentration,the phosphorus removal efficiencies were 62.3%,70.53% and 86.73%,respectively.The nitrogen removal efficiencies were 55.2%,67.6%,and 74.6%,respectively.The amounts of N₂O emission were 4.9,5.0 and 2.7 mg·L-1,and the corresponding conversion rates were 45.0% ? 37.3% ? 20.0%,respectively.This study revealed that,the increase of COD concentration could improve the removal efficiency of nitrogen and phosphorus and reduce the emission of N₂O.?5?The effects of NO3--N and NO2--N?9.8 and 18.3 mg·L-1 NO3--N?10.7 mg·L-1 NO2--N?on nitrogen and phosphorus removal were studied by anoxic batch experiments used the anaerobic sludge,results showed that,P uptake rates were 6.0,7.2,6.7 mg P·L-1·h-1,P uptake and denitrification ratios were 1.1,1.3 and 0.9,respectively,indicating that there was obvious denitrifying nitrogen and phosphorus removal in the system.But the rate of P uptake was only about 1/4 under the condition of anaerobic/ oxygen-limited,which indicated that there were two kinds of phosphorus removal methods in the system,the former is the main way of phosphorus removal.moreover,found that N₂O was mainly accumulated at the NO2--N as electron acceptor,indicating that N₂O emission was mainly affected by the concentration of NO2--N,with limited oxygen NO2--N accumulation of nitrogen removal routes phenomenon inference system for nitrification and denitrification.Combining with the NO2--N accumulation in SBR in the condition of anaerobic/oxygen-limited,showed that the nitrogen removal by the way of shortcut nitrification denitrification.