PREVENTING NUTRIENT INFLUX INTO COASTAL WATERSHEDS BY RECOVERING NUTRIENTS FROM POULTRY LITTER

For the past few decades, nutrients have been in the spotlight because of their adverse environmental impacts on inland and coastal water bodies. The role of excessive nutrients in eutrophication of water bodies has been fairly well established. Therefore, controlling the influx of nutrients into environmentally sensitive water bodies is crucial. Recently, phosphorus loading has dramatically increased in the Chesapeake Bay watershed through heavy land application of poultry litter. Land application of poultry litter is a traditional waste management strategy on the Delmarva Peninsula due to the high density of poultry operations. Previous studies have shown that poultry litter contains a high fraction of water leachable phosphorus; therefore, phosphorus leaches from manure into water bodies in agricultural run-off. Due to increasing regulations by the US EPA to establish Chesapeake Bay Total Maximum Daily Loads and the State of Maryland to reduce phosphorus runoff (Phosphorus Management Tool), farmers have been facing pressure to find alternative ways of managing poultry waste.

The goal of this work was to recover nutrients, especially phosphorus, from poultry litter to (1) produce a P-laden product that can be exported from sensitive watersheds and (2) generate a low-P manure that can be land applied. Using an innovative process that exploits acid-base chemistry and solid-liquid equilibrium, up to 90% of the phosphorus was removed from the poultry litter and recovered as struvite (MgNH₄PO₄) or potassium struvite (MgKPO₄). Furthermore, the reactor was operated at high effective poultry litter doses (i.e., mass of poultry litter per volume of water) by recycling process effluent, thereby, reducing fresh water usage; this recycling scheme did not compromise phosphorus recovery. Another important improvement to the system involved lowering the acid demand through utilization of (synthetic) CO₂-rich flue gas. Overall, the nutrient recovery process represents a low cost technology that allows farmers to land-apply the low-P manures, while generating a valuable product that facilitates phosphorus export from agriculturally-impacted watersheds. Implementation of the fully developed technology will decrease influx of nutrients into environmentally-sensitive coastal watersheds of Chesapeake Bay.