Achieving nitrite accumulation via partial denitrification (PD) is a novel technique to supply sufficient nitrite for the anammox process which is used to treat carbon-limited wastewater. Rapid initiation of PD through pH control was developed in this pilot-scale study and the optimum C/N ratio was investigated. The start-up strategy is proposed based on a lab-scale experiment reported in this work in which a high rate of nitrate reduction and an efficient nitrate-to-nitrite transformation ratio (NTR) could be simultaneously achieved at the pH of 9.0. Two pilot-scale reactors (100 L), with one serving as an experimental reactor and the other as a control, were used to determine the pH effect on the start-up of the PD process. In the experimental reactor, the initial pH of 9.0 was applied at the beginning of mixing in each cycle. Results showed that the PD process was rapidly established within 100 cycles with an average NTR of 83.86%, whereas the control reactor achieved PD after 250 cycles. Moreover, the effect of C/N ratios on the PD process was investigated and the result showed that the optimum C/N ratio was 2.5 with both the NTR and nitrate reduction ratio (NRR) exceeding 80%. High-throughput sequencing results demonstrated that Thauera, possibly a functional bacterium for the partial denitrification process, was dominant on the genus level and accounted for over 65% of the microbial community in both PD reactors. The strategy for establishing the partial denitrification process can be easily achieved through long-term stable nitrite accumulation. PD can be integrated with anammox to improve nitrogen removal in an energy-saving mode.

中文翻译：

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通过部分反硝化作用 快速生产亚硝酸盐：中试规模操作和微生物群落分析†

通过实现亚硝酸盐积累部分反硝化（PD）是一种新颖的技术，可为厌氧氨氧化工艺提供足够的亚硝酸盐，用于处理含碳量有限的废水。通过该中试研究开发了通过pH控制快速引发PD的方法，并研究了最佳的C / N比。根据这项工作中报告的实验室规模的实验提出了启动策略，其中在9.0的pH值下可以同时实现高硝酸盐还原速率和有效的硝酸盐-亚硝酸盐转化率（NTR）。使用两个中试规模的反应器（100升），其中一个用作实验反应器，另一个用作对照，以确定pH对PD工艺启动的影响。在实验反应器中，在每个循环的混合开始时施加的初始pH值为9.0。结果表明，PD过程在100个循环内迅速建立，平均NTR为83.86％，而对照反应器在250个循环后达到PD。此外，研究了C / N比对PD工艺的影响，结果表明，当NTR和硝酸盐还原率（NRR）均超过80％时，最佳C / N比为2.5。高通量测序结果表明Thauera，可能是部分反硝化过程的功能细菌，在属水平上占主导地位，占两个PD反应器中微生物群落的65％以上。通过长期稳定的亚硝酸盐积累，可以轻松实现建立部分反硝化过程的策略。PD可以与厌氧氨气结合使用，以节能模式提高脱氮率。