(753c) Modular Electrochemical Treatment of Concentrated Animal Feeding Operations Waste for Simultaneous Nutrient Reduction and Recovery

Land application of manure is a beneficial practice which improves soil quality by adding important nutrients, with Concentrated Animal Feeding Operations (CAFOs) being the largest users of land-applied manure as a management practice for animal waste. Although CAFOs are subject to state and federal regulations requiring approved Manure Management Plans, agricultural runoff is still a widespread issue due to the complexity of controlling this distributed source of excess nutrients. This land application has led to significant pollution of water systems due to nutrient runoff in the form of phosphorus (P) and nitrogen (N) causing harmful algal blooms in water bodies such as the Great Lakes[1]. Therefore, the reduction of P and N present in manure and the recovery of these species as solid form could serve as a viable approach to reducing environmental impact of runoff, providing an additional source of revenue for farm operations and providing a less variable form of fertilizer for land application.

Ohio University (OHIO) is developing an electrochemical technology, via funding from the Ohio Water Development Authority, to enhance manure management practices for farming operations. Specifically, the technology – the e-CAFO – controls solution pH at the electrode interface and can recover phosphorous and nitrogen species as struvite (MgNH₄PO₄) or reduce phosphorous content through crystallization of multiple phosphate species. This offers an opportunity to operate the technology with a primary sustainability focus on wastewater remediation and a secondary economically lucrative focus on fertilizer generation. Furthermore, the modularity of the e-CAFO provides an opportunity to evaluate deployment as a distributed treatment technology depending on farm size and density in the geographical region. This distributed option would provide better control over non-point sources that lead to harmful algal blooms.

The utility of this e-CAFO has been demonstrated by OHIO [2], with maximum phosphorous recovery dependent on cell voltage, temperature, flow conditions and calcium content. This previous study showed reduced phosphorous recovery in the presence of calcium and highlighted the need for multi-factor analyses with additional variables. Furthermore, process simulations have been developed in ASPEN Plus to understand the equilibrium conditions that maximize nutrient recovery as struvite or nutrient reduction in solution. These simulations provide further insight into the operating window for the e-CAFO technology and will accompany the multi-factor analyses to be presented at the meeting.

References

[1] S. Basu, “Controlling Nitrogen and Phosphorous in Wastewater,” Chemical Engineering Progress, vol. 116, no. 4, pp. 41–47, Apr. 2020.

[2] Z. Belarbi and J. P. Trembly, “Electrochemical Processing to Capture Phosphorus from Simulated Concentrated Animal Feeding Operations Waste,” J. Electrochem. Soc., vol. 165, no. 13, pp. E685–E693, Jan. 2018, doi: 10.1149/2.0891813jes.