Kinetics of Nitrification/Denitrification in Single-Sludge Reactor System(Involving Distributed Fractions of Nitrifying Bacteria and Denitrifying Reductases)

• Main Authors: Chen Tsai-Chien, 蔡建成
• Other Authors: Huang Ju-Sheng
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/23542471492228297297

碩士 === 國立成功大學 === 環境工程學系 === 89 === A nitrification-denitrification kinetic model of a single-sludge reactor system (an anoxic denitrification reactor followed by an aerobic nitrification reactor), accounting for the distributed fractions of Nitrosomonas, Nitrobacter, nitrate-reductase and nitrite-reductase, was proposed. By using sludge taken from each bioreactor of the steady-state single-sludge reactor system, independent batch experiments were also performed to estimate the distributed fractions of nitrifying bacteria and denitrifying reductases. When treating nitrogen-containing wastewater (i.e., similar to chemical- coagulation/dissolved-air-flotation pretreated slaughterhouse wastewater; COD = 220 — 450 mg/L, NH4+-N = 120 mg/L, TP = 20 mg/L), the single-sludge reactor system was very effective for nitrification-denitrification under proper operating conditions (NH4+-N loading, sludge recycle ratio, mixed-liquor recycle ratio, and MCRT). According to material-balance calculations using operating conditions and performance data of the single-sludge reactor system (eight test runs), the specific nitrification rate of the aerobic nitrification reactor and the specific denitrification rate of the anoxic denitrification reactor were 0.18 — 0.21 mg NH4+-N/mg VSS-d and 0.23 — 0.30 mg NOx--N/mg VSS-d, respectively. The ratio of CODutili/NOx--Nred and the phosphorus content of waste sludge determined from the operating conditions and performance data of the single-sludge reactor system were 3.9 — 5.2 and 4.29% — 8.16%. In addition, the measured alkalinity changes in the single-sludge reactor system were close to the theoretical, indicating that the measurement of alkalinity changes can be adequately used for monitoring the single-sludge reactor system. From independent batch experiments (enrichment culture), two-step nitrification followed Monod-type kinetics with biokinetic constants kn1, Ks,n1, kn2, and Ks,n2 of 1.73 mg NH4+-N/mg VSS-d, 1.71 mg NH4+-N/L, 2.27 mg NO2--N/mg VSS-d, and 12.7 mg NO2--N/L, respectively. Meanwhile, two-step denitrification followed zero-order and Monod-type kinetics, respectively, with biokinetic constants kdn1, kdn2, and Ks,dn2 of 3.56 NO3--N/mg VSS-d, 0.74 mg NO2--N/mg VSS-d, 0.14 mg NO2--N /L. When steady states were reached in the single-sludge reactor system, sludges were respectively removed from the anoxic denitrification reactor and the aerobic nitrification reactor. From independent batch experiments using such sludges, the estimated distributed fractions of Nitrosomonas, Nitrobacter, nitrate-reductase and nitrite-reductase were 0.14 — 0.34, 0.16 — 0.31, 0.06 — 0.14, and 0.32 — 0.47, respectively. Obviously, the distributed fraction of nitrite-reductase was the greatest. This finding confirms further our previous performance data that the accumulation of NO2--N did not occur in the single-sludge reactor system during the entire period of operation. By placing biological parameter values and operating conditions of the single-sludge reactor system into the kinetic model, the calculated NH4+-N, NO2--N and NO3--N concentrations in the effluent of the anoxic denitrification reactor and the aerobic nitrification reactor as well as the calculated NH4+-N and TN removal efficiencies were all in fairly good agreement with the experimental data. Accordingly, the proposed kinetic model can be adequately used to predict treatment performance of the single-sludge reactor system. Finally, according to simulated results using the verified kinetic model, an optimal design and operation of the single-sludge reactor system is inevitably necessary to result in proper distributed fractions of Nitrosomonas, Nitrobacter, nitrate-reductase and nitrite-reductase, and thus effective NH4+-N and TN removal efficiencies can then be achieved.