Design and performance evaluation of a screw press separator for separating dairy cattle manure.

Separation of solids from liquid manure is a common method in the management of cattle manure slurries, but it is also important to recognise its limitations. Despite the large number of industrial farms in Iran and 2.7 million heads of cattle, still the traditional approach is used in dealing with animal manure and its accumulation in surrounding land. In this study, in order to promote the use of manure separators, a screw press separator with a volumetric capacity of 14 per day (200 dairy cows) was designed and developed. In order to determine the optimal separation conditions, the effects of concentrations of input manure, pressure, and screw speed on the percent removal of solids and total solids content (TS%) of the separated solids were evaluated for sandladen dairy manure in a factorial test with completely randomized design. Maximum throughput capacity of the machine for a manure with 14 %TS was equivalent to 557.5kg/h. The triple interactions between variables in both efficiencies were significant at the probability level of 1 and 5%, respectively. Increasing the concentrations of input manure and applied pressure increases degree of dryness of solids stream, but reduces removal of solids. An optimum state could be obtained based on a tradeoff between the two efficiencies at 20% TS, 6 kg weight on the compression mechanism and screw speed of 30 rpm.