Rheological Properties of Sand-Laden Dairy Manure: Modeling by Concentration and Temperature

Liquid dairy manure is applied with irrigation water or injected into the soil, as well as being used for the production of biogas. One of the problems facing dairy operations is the slurry manure transportation and pumping through pipelines to distant locations of the farm, especially when the sand content (used as bedding material) increases. In this study, rheological properties of sand-laden dairy manure (SLDM) including total solids (TS%), density and apparent viscosity were determined at four levels of manure solids (7, 10, 13 and 16 %TS) as well as the liquid manure taken from a manure separator tested at shear rates of 1.76 to 225.28 using a concentric cylindrical rheometer. Effect of temperature on the apparent viscosity at five levels (10, 21, 30, 40 and 50 °C) and various shear rates was investigated. Fresh manure collected with a scraper contained 36% sand. Results of the study showed that sand-laden manure is a non-Newtonian fluid, and behaves as a shear thinning material (pseudoplastic), but approaches Newtonian fluid when concentration decreases. Increasing the sand content, will increase density and reduce the viscosity of the slurry manure. Apparent viscosity at a shear rate of 112.64 and ambient temperature of 21°C, for 7,10,13,16 TS% and effluent of separator was 37.1, 101.5, 352.9, 773.4 and 147.4 mPa.s, respectively. The relationship between temperature, concentration (TS%) and shear rate with apparent viscosity was represented by an exponential model