This work presents the novel application of hydrocyclones for mixed liquor recirculation (MLR) treatment in the anoxic/aerobic (A/O) process to enhance the denitrification process. An exhaustive investigation on treated activated sludge and A/O effluents was conducted in batch and continuous operation tests. The median diameter of the sludge flocs was decreased from 78.82 μm to 15.77∼23.31 μm, and the extracellular polymeric substances (EPS) desorption was observed, thus leading to the release of the soluble chemical oxygen demand (SCOD). A marked increase in the BOD₅/TN ratio was consequently achieved, which supplied the carbon source and improved the biodegradability of the MLR. The hydrocyclone treatment also enabled a 7.17% ± 0.93% specific oxygen utilization rate (SOUR) increase at the optimal hydrocyclone intensity of 0.13 MPa, owing to the desorption of positioned microbial secretion from the microorganism cells. The nitrate reductase and nitrite reductase were also improved by 15.13% ± 1.16% and 17.61% ± 1.55%, respectively. The nitrate removal efficiency was enhanced by 13.6%, and the nitrogen oxide gases varied slightly; this behavior was consistent with the variations in the key enzymes involved in denitrification. The A/O process operated in the mode of hydrocyclone-treated MLR, compared with in the conventional mode, resulted in a 15.56% higher TN removal, and the other effluent parameters remained stable. Hydrocyclone disruption is thus a convenient and energy-efficient process with broad implications in denitrification development.

中文翻译：

---

在缺氧/好氧过程中，通过水力旋流器处理混合液再循环实现增强的反硝化作用

这项工作提出了水力旋流器在缺氧/好氧（A / O）工艺中增强混合反硝化工艺的水力旋流器在混合液再循环（MLR）处理中的新应用。分批和连续运行测试对处理过的活性污泥和A / O废水进行了详尽的研究。污泥絮凝物的中值直径从78.82μm减小到15.77-23.31μm，并观察到胞外聚合物（EPS）的解吸，从而释放了可溶性化学需氧量（SCOD）。BOD ₅明显增加因此获得了/ TN比，这提供了碳源并改善了MLR的生物降解能力。水力旋流器处理还可以在最佳水力旋流器强度为0.13 MPa的情况下使比氧利用率（SOUR）提高7.17％±0.93％，这是由于微生物细胞中定位的微生物分泌物解吸所致。硝酸盐还原酶和亚硝酸盐还原酶也分别提高了15.13％±1.16％和17.61％±1.55％。硝酸盐去除效率提高了13.6％，氮氧化物气体变化不大；这种行为与反硝化过程中关键酶的变化是一致的。与传统模式相比，以水力旋流器处理的MLR模式运行的A / O过程可将TN去除率提高15.56％，其他出水参数保持稳定。因此，旋液分离器是一种方便且节能的方法，对反硝化的发展具有广泛的意义。