Phosphorus Removal Effectiveness Of A₂n/baf Process

Phosphorus removal was the key to solve eutrophication, the goals of dephosphorization technology researchs were that developing stable and efficient dephosphatation processes and realizing sustainable development. A₂N/BAF process was a new technology based on two-sludge process, its advantages were good effecting, low energy consumption, small occupied area, and effectively solved contradiction problem of dephosphorization and denitrifying in the traditional biological dephosphorization process. However, the study of its principle and influence factors were still in the initial stage, and the craft of strengthening technology needed to be further explored.This thesis mainly researched phosphorus removal efficiency of A₂N/BAF process. At the first, the way of quick startup of A₂N/BAF process was studied. Then, through Long-term successively operation of A₂N/BAF process, its long-termstability and feasibility was determined, at the same time, phosphorus removal capacity of each unit were analyzed. On the base of stable operation of process, through a beaker on the experimental and analysis of practical process system, biological dephosphorization characteristic of A₂N/BAF process was researched, and biological dephosphorization dynamic model was established. Finally, in view of the effluent TP did not be stable to achieve level A standard, and put forward the enhanced biological dephosphatation technology.A consequent cultivation of DPBs followed by nitrifying bacteria was studied to accelerate the startup of A₂N/BAF process. Researches showed that, after 11 days, nitrification biofilm was cultivated successfully, after 12 days, DPBs domesticated successfully. The cultivation method achieved quick startup of DPBs sludge by reducing organic matters in anoxic stage, and consequently provided DPBs, instead of other denitrifying bacteria, with more favorite growth environment.In 112 days'operation of A₂N/BAF process, removal rate of TP maintained above 80%, and effluent TP concentrations of the secondary settling were below 1mg/L. The key units for dephosphorization were anaerobic pool, anaerobic segment and phosphorus uptake section. the primary BAF and the secondary BAF relyed on interception effect to remove phosphorus, Eventual effluent COD, NH₄⁺-N, NO₃^--N, TN and SS achieved level standard A of GB18918-2002.COD and NO₃^--N were the key effect factors of phosphorus removal, if they existed at the same pool, would happenned reaction of phosphorus release, denitrifying, and denitrifying phosphorus uptake. In the phosphorus release stage, the best value of organic loading is 0.11⁰.16gCOD/gMLSS, in the phosphorus uptake stage, the bestΔNO₃^--N/ΔP=1.95gNO₃^--N/gP. Avoiding inhibitory effect of COD and NO₃^--N to phosphorus release and phosphorus uptake was necessary condition to guarantee the stable and long-term operation of process.In the stable operation period of A₂N/BAF process, DPBs could remove 80% of PO₄^3--P of biological dephosphatatin system; COD/NO₃^--N=3.70¹3.38, the relation equation of phosphorus release and uptake volume was y=0.8403x-0.4757, in the phosphorus uptake stage,ΔNO₃^--N/ΔPO43--P=1.5³.9mg/L; Through the study of phosphorus model, obtained that mathematical model of phosphorus removal for anaerobic pool was:P_h=(P_i+rP_e-0.0004626×0.0752912C_hX_ht_h)/(1+r), for anaerobic segment was: P_y=P_j+0.385399×0.000048X_yC_yt_y, for phosphrus uptake stage was: P_q=P_a(1+r)/(0.0033269X_qt_q+1+r).Dephosphorization way which chemicals was added in the supernatant liquefaction of anaerobia pool, not only saved chemicals doses, but also benefit to the premary BAF. After combined with chemical way, removal efficiency of COD, NH₄⁺-N, NO₃^--N, TN and SS had no opparent changes what compared with the initial craft, and effluent TP of the secondary settling stably reached the level A standard of GB18918-2002.