Effects of treatment with iron-based precipitate on the long-term leaching of nitrogen and phosphorus from livestock manure compost

This study evaluated the applicability of iron-based precipitate (IBP), primarily composed of ferric hydroxide, as a stabilizing agent to reduce the leaching of nitrogen (T-N) and phosphorus (T-P) from livestock manure compost.The mineralogical properties of IBP include an amorphous structure with a high Fe 2 O 3 content (71.7%), a specific surface area of 266.17 m 2 g -1 , and mesopores with an average pore size of 3.93 nm.Results from the toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) tests indicated a low environmental risk, showing undetectable or minimal concentrations of heavy metals, T-N, and T-P.Column experiments were conducted using cow and pig manure composts amended with 5wt% and 10wt% IBP.A synthetic acid rain solution, based on the SPLP method, was continuously applied for five years to simulate rainfall conditions.The results demonstrated that the addition of IBP generally reduced the leaching concentrations of both T-N and T-P.In pig manure compost, T-N was reduced by up to 11.1% and T-P by 47.9% with the 10 wt% IBP addition.On the other hand, cow manure compost exhibited a relatively lower reduction efficiency.These findings were consistent with previous batch test results, particularly for phosphorus stabilization.Overall, this study demonstrates that iron-based precipitate is effective in reducing the leaching of nutrients (N and P) from livestock manure compost and poses minimal environmental risk.Therefore, IBP is expected to be utilized as an eco-friendly stabilization strategy to mitigate agricultural non-point source pollution and prevent eutrophication in adjacent water systems.