Struvite control in flush water recycle components of livestock waste management systems

The research conducted in this study was to address the problem of recycling livestock-waste-lagoon effluent back through the waste management system. The goal of the recycle concept is to reduce the amount of water required for waste disposal, thus reducing the amount of water that must be treated. Since the recycle approach continuously reuses the effluent, a supersaturation of nutrients from the metabolic waste produces crystalline precipitates which deposit within the recycle components. The primary crystalline species has been identified as magnesium ammonium phosphate hexahydrate, commonly known as struvite.

The approach taken in this research was to determine if struvite can be inhibited by chemical treatment. An analytical solution containing the typical concentration of struvite ions found in lagoons was developed for bench-top evaluation of potential inhibitors. The testing protocol included agitation to simulate pump and pipe turbulence and an extended settling period to allow for equilibrium. Potential inhibitors were chosen from other industries that experience scale control problems. Inhibitors were judged by any delay in formation and by the concentration of struvite ions still in solution after the settling period. Twenty products were tested, out of which seven products showed potential to prevent struvite formation. From this group, inhibitors will be selected on the basis of cost to the producer, danger in handling the product, and any environmental negative impacts that may arise when the treated lagoon contents are land applied.