Development of an eco-friendly bio-based granular geomaterial for the environmental restoration of Ichkeul Lake, Tunisia

Abstract

Ichkeul Lake in northern Tunisia is a UNESCO World Heritage site. During the 1990s, its role as a nesting site for birds migrating between Europe and Africa became less prominent due to the increase in salinity due to the inflow of seawater from the Bay of Bizerte. This seawater inflow with increasing saline concentration was enhanced by lake-bed subsidence due to a reduction in sediment supply as a result of reservoir development. This phenomenon occurred by decreasing lake-bed elevation, which was accelerated by the draining from Ichkeul Lake to the Bay of Bizerte, with the resuspension of lake-bed sediments due to wind disturbance. In this study, self-medicating granular geomaterial with in situ microorganisms was proposed to raise or maintain the lake-bed elevation. This geomaterial can enhance urease-producing bacterial activity in the lake and accelerate calcite precipitation onto the surface of the lake bed, thus improving the benthos’ living conditions. Further, nitrogen resources are released from this geomaterial, which enhances the lake ecosystem by promoting aquatic plant growth. Filed column exposure tests were conducted to evaluate the proposed method’s effectiveness. Results were as expected. Therefore, this new geomaterial should help restore the function of Ichkeul Lake as a habitat for migratory birds while also recovering lake-bed elevation and aquatic plant conditions.