Induction and consolidation of granulation enable rapid start-up and robust maintenance of thiosulfate-driven partial denitrification coupling with anammox.

Amid the global imperative for sustainable development, thiosulfate-driven partial denitrification coupling with anammox (TDDA) stands out as a low-carbon wastewater treatment technology; however, its practical applications pose challenges, particularly given the cumbersome start-up and difficult long-term maintenance. Here, strategic induction and consolidation of granulation are proposed to break through these technological bottlenecks. Initial operation with conventional flocculent sludge failed to establish the TDDA fprocess, even with sufficient substrate. By systematically shortening the sludge settling time, sludge granulation was successfully induced, increasing the average particle size from 90.2 μm to 233.3 μm within 60 days. This morphological shift provided a robust carrier for slow-growing anammox bacteria (Candidatus Brocadia), which significantly enriched to (1.1 ± 0.1)×1010 copies/g-VSS, elevating the anammox contribution to nitrogen removal beyond 80%, marking the successful rapid start-up of the TDDA biosystem. Subsequent upregulation of nitrogen loading rate further consolidated the granular sludge, which not only increased the average particle size to 359.2 μm but also stabilized the nitrogen removal performance, with efficiency and rate reaching 91.4 ± 3.2% and 0.40±0.02 kg-N/(m3·d), respectively. These findings demonstrate that granulation, as a dual-functional strategy for biomass enhancement and performance stabilization, provides a viable pathway for the high-efficiency implementation of sustainable nitrogen removal technologies.