Optimization of Preparation Conditions for a Novel Composite Slow-Release Carbon Source and Its Denitrification Performance

• • Optimal preparation conditions: PVA 8.64 g, SA 2.41 g, rice husk 3.82 g, corncob 4.47 g, reed straw 6.06 g, freezing time 19.11 h, crosslinking time 12 h, yielding a 7-day cumulative carbon release of 43.38 mg·g−1, which ensures stable long-term carbon supply for denitrification. • • The carbon release kinetics fit first-order, Higuchi, Ritger-Peppas, and Weibull models, confirming a dual-mechanism control (diffusion and skeleton erosion) that prevents rapid carbon depletion and supports sustained denitrification. • • Under static conditions, the composite achieved a maximum NO3−-N removal rate of 90.8% at an influent concentration of 50 mg·L−1, with a removal rate of 0.079 mg·(g·h)−1, demonstrating high efficiency in batch reactors. • • Under dynamic conditions with HRT = 3 h, the average NO3−-N removal rate remained at 88.1%, indicating robust performance in continuous-flow systems and suitability for practical wastewater treatment.