Use of a solids-liquid separator in the manegement of dairy cattle wastes may (a) reduce labor requirements, (b) make mechanical handling more feasible, (c) improve automation, (d) produce solids with economic value, and (e) produce a liquid that may be handled by ordinary equipment and treated to produce potable water and fertilizer. In solids-liquid separation of dairy cattle wastes, macro-colloidal (> 5μ) and larger solid particles are partially removed from the liquid portion by screens, sieves, and compressors. The two products produced, are (a) wet solids and (b) a dilute liquid. The solids contain about 45 to 80% water depending on the systems used and are stable in nature. The solids have little or no odor and may be dried and used for bedding, refeeding, or mulch, thus having economic value. The liquid is dark brown in color and contains about 85–90% of the 5-day BOD and only about 1–3% suspended and dissolved solids. It may be handled by ordinary equipment and does not require special liquid pumps and high-powered tractors for mixing, pumping, and conveying. The liquid may be irrigated directly onto crops and soils or it may be treated to make potable water and a more concentrated fertilizer.
1The author expresses his appreciation to Lee G. Carlson and Roger Swanson, Environmental Division, Babson Bros., Inc., 2100 S. York Rd., Oak Brook, Illinois 60521, and to Don D. Jones, Graduate Assistant, Dept. of Agricultural Engineering, Purdue University, Lafayette, Indiana 47907 for their assistance in the preparation of this paper.
2Presented at the 59th Annual Meeting of the International Association of Milk, Food, and Environmental Sanitarians, Milwaukee, Wisconsin, August 21–24, 1972.