北京某大型市政污水厂超负荷运行能力的模拟评估

Model-based Evaluation of Overload Treatment Capability for a Large Municipal WWTP in Beijing

为最大限度地减少非处理水的直排量,北京某大型市政污水处理厂在进行升级改造时,将只改造1个系列(总处理量的25%),同时保留另外3个系列以超负荷运行。因此,预先了解和掌握超负荷运行时的出水水质以及相应的工艺参数对实际运行控制甚为关键。运用数学模拟技术对该厂A/O工艺的最佳工况及超负荷运行能力进行评估,结果显示:现状工艺在常规运行条件下的最佳内回流比为100%,最佳MLSS为4000mg/L;超负荷运行时,夏季能够承受的总处理水量为设计值的90%,而冬季所能承受的总水量不宜超过设计值的80%。控制适宜的内回流比、提高DO与MLSS浓度均可强化工艺在超负荷运行时的硝化能力。当进水NH4+-N浓度出现脉冲峰值时,选取适宜的内回流比、提高DO值及增加好氧区体积均可削弱其对出水NH4+-N值的影响。当进水流量出现脉冲峰值时,曝气池中随后会出现NH4+-N峰值和NO3--N谷值,氨氮峰值的传递速度与廊道中的水流速度基本一致。

To minimize the direct discharge of wastewater, an upgrade of a large municipal wastewater treatment plant （WWTP） in Beijing will only deal with a parallel process line （25% of the to- tal treatment capacity） while the other three lines operate in an overload mode. It is essential to under- stand the effluent quality and the corresponding process parameters in advance. Model-based evaluation of the A/O process reveals that the optimal internal recycle ratio is 100% and the optimal MLSS is around 4 000 mg/L under the conventional operation condition. When the plant operates in the overload mode, at least 90% of the total design inflow is accepted in summer; and 80% of the total design inflow is toler- ated in winter. Applying appropriate internal recycle ratio and increasing DO and MLSS can enhance the capacity of nitrification in the overload mode. When a pulse of the influent NH4 - N concentration appears, applying appropriate internal recycle ratio and increasing DO and aerobic zone volume can weaken impact on the effluent. After a pulse influent peak, a NH4 - N peak and a NO3- - N valley may occur in the aeration tanks, and the transmission rate of the NH4 - N peak is basically equivalent to the flow ve- locity in the aeration tanks.