Chemically Enhanced Solids and Phosphorus Removal from Liquid Swine Manure

Abstract

Abstract. Pig producers are under pressure to comply with increasingly stringent regulations aimed at protecting surface water quality. This study investigated the effectiveness of four chemical amendments [calcium carbonate (CaCO3), magnesium sulfate (MgSO4), aluminum sulfate (alum), and the polyacrylaminde (PAM) Superfloc C494] at enhancing solids settling in swine manure slurries containing 10, 50, and 80 g L-1 total solids (TS). Amendment manure was placed in 21 L settling columns (15 cm diameter and 120 cm height) and allowed to settle. Samples collected from the 15 to 45 cm, 45 to 75 cm, and 75 to 105 cm depth intervals during 24 h of settling were analyzed for TS and phosphorus (P) concentration. Polyacrylamide was the most effective amendment for removing solids from the 15 to 45 cm layer in manure containing 10 g L-1 TS during the first 4 h of sampling. Calcium carbonate was the second most effective at the same TS concentration and slightly outperformed PAM at 80 g L-1 initial TS. Alum and MgSO4 did not significantly (p < 0.1) improve solids removal when compared with the control at all initial TS concentrations and sampling times. The effectiveness of PAM at removing solids decreased at initial TS concentrations of 50 and 80 g L-1 due to resuspension of solids at settling times beyond 4 h. These results indicate that treatment of swine manure with chemical amendments at the concentrations tested enhances gravitational settling of solids, particularly at low TS concentration (10 g L-1), but has minimal effect on P removal. Keywords: Coagulant, Flocculant, Manure management, Nutrients, Solid-liquid separation, Total solids.