Abstract: An engineering case of rapid recovery using the “commissioning under load” strategy for a denitrification-nitrification (DN) system treating leachate at a waste incineration plant in Zhejiang province was introduced, following system collapse due to high-load shock. Faced with the operational constraints of a DN system failure caused by high ammonia nitrogen load (NH3-N concentration: 600-800 mg/L) in the leachate treatment system and the lack of an off-site transportation option, a progressive on-load debugging scheme was implemented. Key factors including water quality indicators (CODCr，NH3-N，pH) and environmental parameters (dissolved oxygen, temperature) were intensively monitored. The results demonstrated that the collapsed DN system could successfully regained functionality within 20-30 days using this strategy and progressively achieved stable operation (NH3-N removal rate>95%). This study provides a replicable technical reference for the rapid recovery of biological systems subjected to high ammonia nitrogen shock under similar operating conditions.

Key words: waste leachate, denitrification-nitrification system, high ammonia nitrogen load, commissioning under load