Nitrogen Removal Performance And Simultaneous Nitrification And Denitrification In A Fine Bubbleaeration Oxidation Ditch With Varied Flow Velocities

With the increasing of eutrophication in (the water bodies of) China, how toremove nitrogen and phosphorus effectively and efficiently from sewage to ruducenutrient discharging becomes an important step to control water pollution. This study tooka fine bubble aeration speed oxidation ditch system as the object, explored the removalcharacteristics of the nitrogen in the oxidation ditch，and analysised the influence of DOon SND. The conclusions can be made as follows:(1) Firstly, we continuously operated the fine bubble aeration speed oxidation ditchsystem about370days, and found that it could remove nitrogen effectively. The totalnitrogen could be removed by80%, which made the81.08%water samples of the effluentreached the high standard. The ammonia removal rate was about98%(except lowtemperature in winter), which means97.30%of the effluent reached the standard. At thesame time, this system also had a good ability to remove COD and TP, the rate wereabove88.08%and88.20%, respectively.(2) Secondly, we detailedly discussed an important kinetic parameters--KO(namely denitrification dissolved oxygen inhibition coefficient), which had greatinfluence on the processes of simultaneous nitrification-denitrification. We measuredthe KOthrough some aerobic denitrification batch experiments. The activated sludge weused were from an oxidation ditch in the xi’an fourth sewage plant. The results showedthat, when dosed easily degradable organic matter(SCOD) as the substrate in the sewage,the value of KOwas0.7801mg/L; and when dosed sodium acetate, the KOwas 0.9205mg/L. Provides a reference for the determination of value in other waterconditions of KO.(3) Thirdly, we utilized the determined value of KOto analysis the contribution ofSND’s on the process for removing nitrogen in low oxygen conditions by themicroporous aeration oxidation ditch. The results showed that, when the concentrationsof DO in the reactor were1.2mg/L,1.0mg/L and0.8mg/L, the theoretical efficiencies ofSND were38.75%,43.1%,48.56%, respectively; while the actual efficiency of SNDwhich determined by calculating the concentration balance of nitrogen throughexperiments were37.06%,41.33%,47.86%, respectively. The relative standarddeviation was within5%.