Ma Yong, Peng Yongzhen, Wang Shuying, Yuan Zhiguo, Wang Xiaolian
Key Laboratory of Beijing for Water Environment Recovery, Beijing University of Technology, Beijing 100022, China.
Water Res. 2009 Feb;43(3):563-72. doi: 10.1016/j.watres.2008.08.025. Epub 2008 Sep 6.
Nitrogen removal via nitrite (the nitrite pathway) is beneficial for carbon-limited biological wastewater treatment plants. However, partial nitrification to nitrite has proven difficult in continuous processes treating domestic wastewater. The nitrite pathway is achieved in this study in a pilot-scale continuous pre-denitrification plant (V=300 L) treating domestic wastewater by controlling the dissolved oxygen (DO) concentration at 0.4-0.7 mg/L. It is demonstrated that the nitrite pathway could be repeatedly and reliably achieved, with over 95% of the oxidized nitrogen compounds at the end of the aerobic zone being nitrite. The nitrite pathway improved the total nitrogen (TN) removal by about 20% in comparison to the nitrate pathway, and also reduced aeration costs by 24%. FISH analysis showed that the nitrite oxidizing bacteria (NOB) population gradually reduced at low DO levels, and reached negligible levels when stable nitrite pathway was established. It is hypothesized that NOB was washed out due to its relatively lower affinity with oxygen. A lag phase was observed in the establishment of the nitrite pathway. Several sludge ages were required for the onset of the nitrite pathway after the application of low DO levels. However, nitrite accumulation increased rapidly after that. A similar lag phase was observed for the upset of the nitrite pathway when a DO concentration of 2-3 mg/L was applied. The nitrite pathway negatively impacted on the sludge settleability. A strong correlation between the sludge volume index and the degree of nitrite accumulation was observed.
通过亚硝酸盐进行氮去除（亚硝酸盐途径）对碳受限的生物废水处理厂有益。然而，在处理生活污水的连续工艺中，实现部分硝化至亚硝酸盐已被证明具有难度。在本研究中，通过将溶解氧（DO）浓度控制在0.4 - 0.7 mg/L，在一座中试规模的连续前置反硝化处理厂（V = 300 L）中实现了亚硝酸盐途径，该厂用于处理生活污水。结果表明，亚硝酸盐途径能够反复且可靠地实现，在好氧区末端超过95%的氧化态氮化合物为亚硝酸盐。与硝酸盐途径相比，亚硝酸盐途径使总氮（TN）去除率提高了约20%，同时曝气成本降低了24%。荧光原位杂交（FISH）分析表明，在低溶解氧水平下，亚硝酸盐氧化菌（NOB）数量逐渐减少，当稳定的亚硝酸盐途径建立时，其数量达到可忽略不计的水平。据推测，NOB因对氧的亲和力相对较低而被洗出。在亚硝酸盐途径的建立过程中观察到一个滞后期。在应用低溶解氧水平后，需要几个污泥龄才能开始亚硝酸盐途径。然而，此后亚硝酸盐积累迅速增加。当溶解氧浓度为2 - 3 mg/L时，在亚硝酸盐途径被破坏时也观察到类似的滞后期。亚硝酸盐途径对污泥沉降性能有负面影响。观察到污泥体积指数与亚硝酸盐积累程度之间存在很强的相关性。
