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为防止自然水体出现富营养化现象,我国提高了污水处理厂氮磷排放标准[1-2]。排放标准的提高即对传统脱氮除磷工艺的处理效率提出了更高要求。生物脱氮工艺包括硝化和反硝化2个阶段:氨氧化菌和亚硝酸菌先后将氨氮氧化为亚硝态氮及硝态氮;反硝化细菌利用有机碳提供电子供体将硝态氮还原为氮气,从水中溢出以实现脱氮[3]。污水中的磷则通过消化污泥和水两条路线实现去除或回收,而从水线中去除或回收磷更为稳定,也更为经济[4-5]。
在传统活性污泥法系统中,生物脱氮和生物除磷在污泥龄、碳源、硝酸盐的存在与转化等方面存在一定矛盾[6],且实现生物脱氮除磷的效率普遍较低。在常规 A2/O 工艺中,污水依次通过厌氧池、缺氧池和好氧池,而回流污泥会将一部分硝酸盐带回厌氧区,硝酸盐的存在使得反硝化菌优先争夺了进水的碳源,因而严重影响了聚磷菌(phosphorus accumulating bacteria,PAO)的释磷效率,进而影响系统除磷效率[7-8]。我国污水处理厂的进水普遍呈现C/N、C/P均较低的状态,80%以上的进水BOD5/TN小于3.6,BOD5/TP平均为27,生物脱氮除磷的效果不甚理想[9]。因此,为提高脱氮除磷效率,确保出水氮磷指标达标,往往需要投加药剂[10],这使得污水处理厂处理成本增加。
污水处理厂是个复杂系统,涉及诸多影响污水处理效率及运行成本的不可控因素(如水质、水温等),以及可控因素(曝气量、加药量、污泥浓度等)。在污水处理厂运行中,应充分发挥可控因素的主导作用,挖掘工艺潜力,促进优势菌种代谢活力,以提升污染物去除效率并降低处理成本。反硝化除磷菌(denitrifying phosphorus accumulating bacteria,DPAO)具有“一碳两用”的“技能”,能节省碳源、减少污泥产量,因而一直是研究热点[11-13]。在实际运行中,应注重工艺优化调控对DPAO的影响,发挥其重要作用,进而促进活性污泥系统同步脱氮除磷效率的提升及系统运行管理的优化。
本研究以我国西南地区某污水处理厂(处理规模为10×104 m3·d−1)为例,对污水处理工艺进行优化调控,考察调控措施对系统运行性能的影响,解析优化后系统同步脱氮除磷的过程,并探讨工艺优化后的运行特点,以期为提高同类污水处理厂的运行效率提供参考。
Process optimization regulation scheme of a full-scale modified A2/O wastewater treatment plant and its improvement of simultaneous nitrogen and phosphorus removal efficiency
- Received Date: 09/01/2021
- Available Online: 10/02/2022
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Key words:
- modified A2/O process /
- municipal wastewater /
- denitrifying phosphorus removal /
- operating cost
Abstract: The influence of optimal control parameters on processing effect and the contribution of main structures to nitrogen and phosphorus removal were analyzed by taking a municipal wastewater treatment plant (WWTP) with a treatment capacity of 10×104 m3·d−1 as the research object. The results showed that the total nitrogen (TN) and total phosphorus (TP) in the effluent decreased simultaneously after changing the aeration and reflux modes. Anaerobic tank was the main place for nitrogen and phosphorus removal since the reduction of TN and TP in anaerobic tank accounted for 70.8% and 89.5% respectively. The biological phosphorus removal experiments showed that the anaerobic phosphorus release rate (measured by VSS) was 3.35 mg·h-1 on average. Aerobic and anoxic phosphorus uptake experiments confirmed that denitrifying phosphate accumulating organisms (DPAO) accounted for over 90% of phosphate accumulating organisms (PAO), and DPAO could also absorb phosphorus in the aerobic stage. After optimizing and regulating the process, the effluent quality of treatment system could meet the class 1A standard of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918–2002), and at the same time, energy saving and consumption reduction can be realized to reduce the cost of wastewater treatment. The result of this study can provide a reference for the performance improvement of similar municipal WWTPs.