Pilot-scale demonstration of an integrated process for efficient management of kitchen waste digestion liquid

This is the authors' abstract. We don't add key points for this paper.

Recovering organic waste as bioenergy from source-separated kitchen and food waste via anaerobic digestion is a sustainable approach; however, this process often generates large volumes of high-strength kitchen waste digestion liquid (KWDL) that require further treatment. This study proposes an integrated treatment train consisting of dissolved air flotation (DAF) pretreatment followed by a two-stage partial nitrification/anammox (PN/A) process. Results from long-term pilot-scale operation showed that the DAF process reduced chemical oxygen demand (COD) and suspended solids (SS) from 8204 ± 605 mg COD/L and 7317 ± 831 mg SS/L to 5580 ± 395 mg COD/L and 2424 ± 415 mg SS/L, respectively. In the subsequent PN reactor, a stable average nitrite accumulation ratio of 75.7% was achieved under low dissolved oxygen (<2 mg O 2 /L) and elevated free ammonia concentrations (45.0 ± 47.2 mg N/L). The PN effluent, with an NO 2 − /NH 4 + ratio of approximately 1.74, was then treated in the anammox reactor, where about 77.5% of total nitrogen (TN) was removed through the combined action of anammox and heterotrophic denitrification. Microbial community assessment revealed that Candidatus_Brocadia was the dominant anammox bacterial genus. Overall, the combined process achieved removal efficiencies of 91% COD, 98% SS, and 85% TN under pilot-scale operation, with overall COD and TN loading rates of 0.63 kg COD/m 3 /d and 0.12 kg N/m 3 /d, respectively, demonstrating a practical and controllable treatment route for high-strength food waste digestate and providing operational insights for future full-scale implementation.