Agricultural runoff significantly contributes to eutrophication events around the world. In the Chesapeake Bay watershed, poultry litter serves as a major source of nutrients. To address this problem, we have developed technologies to extract phosphate from poultry litter. Farmers can apply the nutrient-deficient poultry litter to their fields without contributing to nutrient loads. At the same time, the extracted phosphate can be recovered in the form of struvite, a slow-release fertilizer. The objective of this work was to investigate the addition of green coagulants, such as bentonite, chitosan, potato starch, and sodium alginate, to generate flocs of struvite particles that quickly settle. These natural coagulants are more cost-effective than conventional options, such as alum and ferric chloride. In addition, phosphate strongly interacts with aluminum and iron oxyhydroxides, decreasing the agricultural value of particles recovered with conventional coagulants. We hypothesized that natural coagulants would also provide better control of phosphate release, allowing generation of fertilizers with moderately customized time-release. The optimum dose of the individual natural coagulants, and select mixtures, was determined using jar tests conducted with extracts from 20 g/L poultry litter slurries. For example, the size of suspended particles was reduced from 33.9 µm (no coagulant addition) to 8.5 µm with addition of 500 mg/L of chitosan and 100 mg/L of bentonite. This change in particle size distribution caused the optical density to decrease by 57%, indicating better settling and recovery of struvite. The volume concentration of recovered particles increased with bentonite addition up to 100 mg/L. Scanning electron microscopy with energy dispersive x-ray spectroscopy was applied to confirm the impacts of individual and mixed coagulant use on the morphology and composition of recovered struvite particles. Overall, the use of green coagulants improved phosphorus recovery from agricultural waste.<br/>

Green coagulants for improved struvite recovery from agricultural waste

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.