Wind Tunnel Experiments on the Effects of Olives Mill Wastewaters Spray on the Reduction of the Entrainment of Sand by Wind

Abstract

The degradation of physical characteristic of soils by wind erosion is one of major problem in the southern Tunisian arid regions. To find a remedy for these soils changes, studies were conducted, since many years, to reuse olives mill wastewaters, liquid waste produced in the process of olive oil extraction, like a simple and efficient practices for combating desertification. Wind-tunnel experiments were conducted on pre-treated soils with applied doses of 50 m³.ha^-1, 100 m³.ha^-1 and 200 m³.ha^-1 next to an a witness soil sample in order to investigate the effect of the mulching of olives mill wastewaters on reduction of wind erosion. Sand samples were exposed to different wind speeds for 2 min. Shear velocities were deduced from the wind speed profiles and saltation of sand particles was recorded electronically with a saltiphone©.

Within the 2-min test runs, changes in wind erosion aerodynamic parameters were detected. The aerodynamic roughness lenght, _z0, and the threshold shear velocity, u_*t, increase is proportional to the applied doses. The roughness lengths derived from the wind profile measurements measured over the various tested ranged from 1.78 E-04 and 3.92 E-04 m for 0 m³.ha^-1 and 200 m³.ha^-1, respectively. The results in wind tunnel tests on the soil treated with these different doses showed that u_*t was raised from 8.65 m.s^-1 to 12.15 m.s^-1 for 50 m³.ha^-1 and 200 m³.ha^-1, respectively. These results strongly suggest that the mulching of olives mill wastewaters reduces soil erosion by wind.