Break | AIChE


In order to recover nitrogen and phosphorous from concentrated animal feeding operations (CAFO) waste as a solid slow release fertilizer product, and to remove a large part of these pollutants from the supernatant, an efficient solution consists in forcing the precipitation of struvite. However, the formation of struvite (MgNH4PO4·6H2O) in animal wastewater treatment plants can lead to scaling and thus operational problems reducing the treatment efficiency. Therefore, controlled struvite formation in animal wastewater treatment plants not only presents an opportunity to recover nutrients but also corresponds to the valorization of wastes. The overall objective of the present research is to demonstrate that it is possible to use an electrochemical reactor with rotating cylinder electrode to recover phosphorus and nitrogen from CAFO waste as a solid fertilizer product (MgNH4PO4∙6H2O). The effect of applied potential to the cathode, turbulent flow, Ca2+, and temperature on the kinetic of precipitation of struvite was evaluated. Struvite electrochemical precipitation appears as an alternative method to recover nitrogen and phosphorous from waste waters. This approach could offer CAFO a modular technology which smoothly integrates into current manure lagoon systems. Key parameters controlling the electrochemical precipitation process of struvite are: solution pH, temperature, rate of stirring, and the presence of foreign ions including calcium.