REMOVAL OF SOLIDS AND MAJOR PLANT NUTRIENTS FROM SWINE MANURE USING A SCREW PRESS SEPARATOR

Abstract

A screw press separator was temporarily installed on a commercial swine farm in Horry County, South Carolina. The separator had a 0.5 mm screen and was operated with a single 40 kg weight on each pressure plate arm. Prediction equations were developed from the data to describe the removal of total solids (TS), total volatile solids (VS), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammonium nitrogen (NH4 –N), organic nitrogen (organic–N), and total phosphorus (TP). Separated solids were analyzed to determine the percent total solids and the concentration of major plant nutrients. The concentration of total potassium (TK) in the separator influent and effluent was the same within measurement error. The removal of TS, VS, N, and P was found to vary significantly with the TS concentration of the influent manure. Therefore, building management and the methods used to implement the machine in the manure handling system would have a significant impact on separator performance. The prediction equations were used to calculate separator performance for a typical pit–recharge swine building based on observed characteristics on the cooperator’s farm. The screw press would be capable of removing 14.9% of the TS, 19.6% of the VS, 34.9% of the COD, 9.2% of the TKN, 16.0% of the organic–N, and 14.8% of the TP from the manure added by housed swine.