硫自养反硝化技术（SADeN）兼具经济、低碳优势，适用于有机物匮乏型污水的深度脱氮处理，但目前工程应用案例仍较少。作为典型的生物处理工艺，SADeN技术长期运行效性能、低温响应特征及相应的调控策略仍需在实际工程条件下进行系统研究。本文对两座并联运行的下向流SADeN生物滤池（单池设计处理能力均为8000 m3·d⁻1）开展了连续400余天的研究。结果表明，滤池的脱氮效能具有明显的季节性差异，夏季平均脱氮负荷较冬季高出近2倍。投加硫代硫酸盐（S2O32⁻）可有效强化滤池的冬季运行性能，并表现出超化学计量强化效应（OSEE），即实际脱氮量较基于S2O32⁻投加量计算的理论值高24.79%–331.50%。通过剖析污染物浓度和电子转移通量沿滤床高度的变化，发现OSEE效应主要源于S2O32⁻在滤床上部快速消耗溶解氧，并激活下部床层中固相硫基活性填料（SReF）的电子通量。微生物群落分析进一步表明，SReF电子通量的增加可能与S2O32⁻促进了硫自养反硝化菌丰度回升以及微生物生态网络稳定性恢复有关。本研究为SADeN技术在实际污水处理厂中的工程应用提供了范例，并深化了对S2O32⁻强化低温反硝化作用机制的认识。

Sulfur-based denitrification (SADeN) technology is a cost-saving and low-carbon alternative for treating organic-deficient wastewater. However, the use of this technology in full-scale applications is still limited. Crucial concerns for biological processes, such as changes in seasonal performance and the ways in which it responds to low temperatures, have yet to be studied in real SADeN processes. Herein, two SADeN biofilters in parallel (downflow, with a design water treatment capacity of 8000 m³·d⁻¹ each) were systematically investigated over a period of more than 400 days. Seasonal variations in denitrification rates were observed, with an average difference of up to 2 times between summer and winter. The use of thiosulfate was verified as an efficient strategy to improve the performance of SADeN biofilters in winter, which was found to have an overstoichiometric enhancement effect (OSEE), with 24.79–331.50 % more nitrate removal than that calculated according to thiosulfate dosages. Analyzing the biofilter vertically revealed that the OSEE occurred because thiosulfate rapidly consumed dissolved oxygen in the upper zone of the bed and activated the electron flux of the sulfur-based reactive filler (SReF) in the lower zone. Microbial community analysis further suggested that this increase in electron flux may be associated with the abundance recovery of sulfur autotrophic denitrifiers and the stability recovery of the microbial eco-networks. This study offers a paradigm for the full-scale application of SADeN technology in real wastewater treatment plants, providing an in-depth understanding of the role of dosing thiosulfate in tackling low-temperature challenges.