阶梯曝气对城市污水好氧颗粒污泥系统的影响

为实现低C/N城市污水的同步脱氮除磷,采用SBR反应器以厌氧/好氧(A/O)为运行方式,在保持总曝气量900 L不变的条件下调整曝气策略将均匀曝气2. 81 L·(h·L)-1改为先高强度4. 22 L·(h·L)-1后低强度1. 88 L·(h·L)-1的"高/低曝气"和先低强度1. 88 L·(h·L)-1后高强度4. 22 L·(h·L)-1的"低/高曝气"].试验考察了不同曝气策略下系统的脱氮除磷性能及污泥特性.结果表明,高/低曝气下系统的脱氮除磷效果最佳,出水NH_4+-N、NO_2--N、NO_3--N和TP浓度分别为0、0. 15、8. 12和0. 04 mg·L~(-1),总氮(TN)和总磷(TP)去除率分别为78. 33%和99. 19%,同步硝化内源反硝化(SNED)作用明显,SNED率为77. 08%.且相比于均匀曝气,系统硝化速率及反硝化速率均增加,反硝化速率(以N/VSS计)达到整个运行过程中的最大值,为14. 33 mg·(g·h)-1,同时颗粒污泥密实度、沉降性能及稳定性提高,污泥容积指数(SVI)为23. 49 m L·g~(-1).调整曝气策略为低/高曝气后,系统脱氮除磷性能变差,TN和TP去除率均降至最低,分别为51. 26%和58. 32%,但此时系统硝化性能最佳,氨氧化速率和硝酸盐生成速率均达到整个运行过程中的最大值,分别为14. 92 mg·(g·h)-1和7. 50 mg·(g·h)-1,同时颗粒污泥中丝状菌大量繁殖、结构松散、沉降性及稳定性均变差,SVI升至40. 76 m L·g~(-1).故采取高/低阶梯曝气策略有利于AGS系统高效脱氮除磷及提高稳定性.

Effect of Step Aeration on a Municipal Sewage Aerobic Granular Sludge System

In order to achieve simultaneous nitrogen and phosphorus removal in low-C/N urban sewage, a sequencing batch reactor (SBR) was operated in anaerobic/aerobic (A/O) mode. Keeping the total aeration volume at 900 L, the aeration strategy was adjusted. The uniform aeration of 2.81 L·(h·L)^-1 was changed to "high/low aeration" with high strength 4.22 L·(h·L)^-1before low strength 1.88 L·(h·L)^-1, and "low/high aeration" with low strength 1.88 L·(h·L)^-1 before high strength 4.22 L·(h·L)^-1. The experiment investigated the nitrogen and phosphorus removal performance and sludge characteristics of the system under different aeration strategies. The results showed that the nitrogen and phosphorus removal performances of the system under high/low aeration were the best. The effluent concentrations of NH₄⁺-N, NO₂^--N, NO₃^--N, and TP were 0, 0.15, 8.12, and 0.04 mg·L^-1, respectively. The removal rates of total nitrogen (TN) and total phosphorus (TP) were as high as 78.33% and 99.19%, respectively. Simultaneous nitrification endogenous denitrification (SNED) was clear, with the SNED ratio at 77.08%. Compared with uniform aeration, the system nitrification rate and denitrification rate increased, and the denitrification rate reached 14.33 mg·(g·h)^-1, which was the maximum value during the whole operation; the solidity, sedimentation performance, and stability of granular sludge were improved, and the sludge volume index (SVI) was 23.49 mL·g^-1. After adjusting the aeration strategy to low/high aeration, the nitrogen and phosphorus removal performance of the system deteriorated, and the removal rates of TN and TP were reduced to 51.26% and 58.32%, respectively. However, the system had the best nitrification performance with ammonia oxidation rate and nitrate production rate at 14.92 mg·(g·h)^-1and 7.50 mg·(g·h)^-1, respectively, which were their maximum values during the whole operation. Simultaneously, the filamentous bacteria in the granular sludge multiplied, the granular structure became loose, the sedimentation and stability all worsened, and the SVI rose to 40.76 mL·g^-1.