污泥浓度对双重后置反硝化工艺脱氮除磷的影响

利用城市实际污水考察了ρ(MLSS)在2 400、3 350、4 300和5 250 mg/L 4种工况下SBR反应器(厌氧/好氧/缺氧/再好氧/沉淀/排水/预缺氧运行模式)的脱氮除磷效果,并分析了反应器单个周期内有机物、氮和磷的转化过程及污泥产量. 结果表明:ρ(MLSS)由2 400 mg/L升至5 250 mg/L时,系统TN去除率由52.5%升至66.6%；后续缺氧及预缺氧工序的脱氮比例(该工序TN去除量占系统TN总去除量的比例)由12.7%增至23.1%；ρ(MLSS)为4 300 mg/L时系统TP去除率(75.6%)达到最大. 后续缺氧及预缺氧工序中,ρ(MLSS)与内源反硝化速率呈正相关(R2=0.703 7)；提高ρ(MLSS)可使PAOs(聚磷菌)在下一个周期内获得更多的碳源,使厌氧释磷量由1.62 mg/L升至9.10 mg/L,但PAOs吸磷动力会减弱,对除磷不利. 在后置反硝化、污泥衰减、能量解偶联等减量机制共同作用下,ρ(MLSS)为4 300 mg/L时系统污泥减量可提高24.4%. 从脱氮除磷及污泥减量效果综合考虑,ρ(MLSS)是双重后置反硝化工艺重要的控制参数,在该研究条件下控制在4 300 mg/L最优. 

Characteristics of Nitrogen and Phosphorus Removal in Multiple Post-Denitrification Processes with Different Sludge Concentrations

The performance of biological nitrogen and phosphorus removal on the treatment of municipal sewage in SBR process was investigated with sludge concentrations (ρ(MLSS)) of 2400,0, 4300 and 5250 mg/L, and with an SBR reactor operation mode of anaerobic/aerobic/anoxic/aerobic/precipitation/drainage/pre-anoxic for recycled sludge. The transformation process of organic matter, nitrogen and phosphorus, and sludge production were also analyzed over a single cycle. The investigation results showed that the total nitrogen removal efficiencies varied from 52.5% to 66.6% when ρ(MLSS) increased from 2400 mg/L to 5300 mg/L, while the percentages of TN removal in anoxic and pre-anoxic processes varied from 12.7% to 23.1%. The total phosphorus removal efficiencies reached a maximum of 75.6% when the ρ(MLSS) was 4300 mg/L. There was a positive correlation between ρ(MLSS) and endogenous denitrification rate (R2=0.7037) in the post-denitrification process. With the increase of ρ(MLSS), the PAOs could obtain more carbon in the next cycle, and the phosphorus release capacities increased from 1.62 to 9.10 mg/L. It also could lower the ability of the absorption power of phosphorus, which could cause unfavorable influence on phosphorus removal. Under the mechanism of postposition denitrification process, the sludge decay and energy uncoupled, and the sludge reduction reached 24.4% when the sludge concentration was 4300 mg/L. Based on the comprehensive consideration of biological nutrient removal and sludge reduction, ρ(MLSS) was an important control parameter in the multiple post-denitrification process, and the optimum ρ(MLSS) was 4300 mg/L under the experimental conditions.