Removal of Solids and Phosphorus From Liquid Swine Manure by Gravitational Settling: Chemical Amendment Effects.

Manure management and disposal are major challenges for pork producers in Manitoba due to the high phosphorus (P) concentration in swine manure, which presents a risk to surface water quality. Chemical treatment of liquid swine manure, in conjunction with gravity settling (sedimentation), has the potential to enhance both the solid/liquid separation of manure and the removal of most of the P bound to fine suspended particles. The P-rich separated solid fraction can be hauled more economically over longer distances for application on low-P cropland. In this laboratory column study, we examined the efficacy of four chemical amendments [calcium carbonate, magnesium sulfate, aluminum sulfate, and polyacrylamide (PAM)] for gravity solid/liquid separation of swine manure slurries containing 1%, 5%, and 8% solids by weight. Manure treated with each amendment was allowed to settle for up to 24 h in 120-cm high, 15-cm diameter sedimentation columns. Samples were collected from sampling ports at the 30-, 60- and 90-cm depths after 0.5, 1, 2, 4, 8 and 24 h of settling and characterized for solids content and for N and P concentrations. Preliminary results indicate that PAM was the most effective amendment for removal of suspended solids. For all treatments, most of the solids were removed within the first 4 h of settling. Results on solids and P removal will be presented.