Submitted to: Transactions of the ASAE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/13/2005
Publication Date: 8/9/2005
Citation: Vanotti, M.B., Rice, J.M., Ellison, A.Q., Hunt, P.G., Humenik, F.J., Baird, C.L. 2005. Solid-liquid separation of swine manure with polymer treatment and sand filtration. Transactions of the American Society of Agricultural Engineers. 48(4):1567-1574. Interpretive Summary: Organic polymers are useful to increase separation of suspended solids and carbon compounds from liquid swine manure. With the polymer, the small particles in swine wastewater are agglomerated into larger particles or flocs. We evaluated if the use of polymer flocculants could improve the drainage characteristics of sand filter beds and prevent typical clogging with repeated applications of liquid swine manure. The test was done at pilot scale. Results showed that flocculation improved drainage characteristics of the sand filter and prevented clogging and surface sealing during the 20-month evaluation period; the sand filter beds drained quickly, usually within one to two hours after pouring. Polymer flocculation and sand filtration removed 98% of TSS and VSS, 86% of BOD and 85% of COD from the flushed swine manure. Along with the solids, there was a capture of 63% TKN and 77% TP; most of the nutrients removed in the solids were organic forms. We also found that drying time to produce removable cakes was affected by solids loading rate, and that sand bed size required per pig may range from 1.8 to 3 square meters per pig.
Technical Abstract: Small particles typical of liquid swine manure often clog sand filter beds and fine filters. We evaluated the effectiveness of polymer flocculants to improve drainage and filtration performance of sand filter beds by increasing the effective particle size. A pilot separation unit was evaluated at the Swine Unit of the NCSU Lake Wheeler Rd. Laboratory in Raleigh, N.C., in 40 consecutive cycles during a 20-month period. The unit consisted of a homogenization tank that mixed the flushed swine manure, an in-line polymer mixer, and two sand filter beds (29.7 sq m) designed to receive 30.5 cm (1-ft) depth of the polymer treated effluent. Flocculation treatment using PAM improved drainage characteristics of the sand filter and prevented clogging and surface sealing. The treatment removed 98% of total suspended solids (TSS) and volatile suspended solids (VSS), 86% of BOD, and 85% of COD from the flushed manure. Along with the solids, there was a capture of 63% TKN and 77% TP. Most of the nutrients removed in the solids were organic forms. Drying time to produce removable cakes varied with the loading rate of solids applied to the sand filter bed. A load of 2 kg TSS/sq m per drying cycle provided a balance between bed size and drying time.