A/A/O污水处理工艺脱氮效果模拟及优化

Simulation of Denitrification of A/A/O Process and Its Optimization

针对武汉某污水处理厂因进水总氮浓度高、碳氮比值低而导致脱氮效果不稳定的问题,基于ASDM模型建立了该污水处理厂A/A/O工艺模型,并利用历史数据对脱氮效果进行了优化模拟。分别对硝化液回流比(0~600%)、好氧段DO(1~6 mg/L)、缺氧段DO(0.005~0.2 mg/L)、温度(16~29℃)等工艺运行参数进行了模拟分析,通过模型模拟筛选出的最优运行参数如下:硝化液回流比为100%,好氧段DO为1 mg/L,污泥回流比为65%,排泥量为550 m3/d,且缺氧段DO浓度越低越有利于脱氮。根据以上结论并结合该污水处理厂实际情况,确定如下优化实施方案:硝化液回流比为300%,好氧段DO为3 mg/L以下,同时关闭硝化液回流点前的曝气头以降低缺氧段DO,并按90kg/d投加碳源(以COD计)。该污水处理厂按照上述方案实际运行2个月,脱氮效果明显提高,出水总氮达标率达到100%。

To solve unstable denitrification caused by high total nitrogen and low BOD5/TN ratio in influent of a wastewater treatment plant(WWTP) in Wuhan,an A/A/O process model was established based on activated sludge/anaerobic digestion model(ASDM),and the denitrification was optimized and simulated by using historical data.The influencing factors,such as reflux ratio of nitrifying liquid(0-600%),dissolved oxygen(DO) in aerobic zone(1-6 mg/L),DO in anoxic zone(0.005-0.2 mg/L) and temperature(16-29 ℃),were simulated and analyzed.The optimal operational parameters were as follows:reflux ratio of nitrification liquid of 100%,DO in aerobic zone of 1 mg/L,sludge reflux ratio of65%,and sludge discharge amount of 550 m3/d.It was found that low DO in the anoxic zone was more conducive to nitrogen removal.According to the above conclusions and the actual situation of the WWTP,the optimized plan was determined as follows:nitrifying liquid reflux ratio of 300%,DO in the aerobic zone of less than 3 mg/L,closing aerator before the nitrifying liquid reflux point to reduce DO in anoxic zone,and carbon source dosage(calculated by COD) of 90 kg/d.After two months of actual operation,the denitrification performance was improved obviously,and 100% of the total nitrogen samples reached the discharge standard.