Phosphogypsum Management Challenges in Tunisia

Abstract

The accumulation of phosphogypsum (PG) produced till 2015 makes its management a real challenge to the Tunisian authorities and put the Chemical Tunisian Group (TCG) to face a challenge at large scale as the specified storage embankments knew considerable extensions in terms of heights and areas. Several studies were elaborated subsequently in 2007, 2012 and 2013 to focus on the stability of Sfax and Skhira Phosphogypsum embankments’ and showed two different chemical and mechanical behaviors according to the experienced deposition process. In 2012, it was revealed that the wet PG embankment of Sfax City with 56 m height, 53Ha area and 32° slope can only be of 70 m height maximum. This embankment can reach 100 m in height if a reinforcement technique will be used. This deposition process is well recommended to ensure better interaction between the embankment and the existing ground surface. Using the dry deposited process, the area of the PG embankment of the Skhira City covers 112Ha and presents two elevation levels of 25 m and 55 m in 2013. However, the dry deposited process results in a damaged embankment profile, excessive settlements and lateral displacements. Therefore, a PG embankment of 100 m height cannot be achieved. A reinforcement of the embankment by High Density Polyethylene geotextile (HDPE) layers at increments of 4 m from 55 m elevation allows reaching 130 m of height. Comparative study was raised between the wet and the dry process and resulted in favoring of the wet process from both industrial and geotechnical perspective. Thus, the TCG expects turning all its deposition processes to the wet one.