Testing microwave dewatering as a solution for reducing clay disposal pond areas

Phosphate processing plants produce an excessive amount of phosphatic clay. This clay represents a serious environmental problem due to their disposal in huge ponds. Finding a feasible method to reduce the clay disposal area is needed. Although the flocculation process, in the presence of fibrous material, seems to be a good dewatering process for phosphatic clay wastes, the maximum solid percentage of flocculated clay does not exceed 18% (starting from 3 to 4%). Recently, the microwave proved a better performance in several research areas as compared to the conventional drying. In this study, clay dewatering by microwave was investigated. Several factors affecting the dewatering process were studied such as heating time, microwave power efficiency, and fiber percentage. Using the microwave, the solid content significantly increases in a reasonably short time. The time and power are the most significant among the studied factors. In addition, sand–clay mix was tested to improve the solid percentage to be used as a filling material. The results showed that the presence of sand enhances the clay drying due to the transparency of sand to the microwave irradiation as well as increasing the clay bed porosity, which facilitates migration of liquid water and/or water vapor toward the surface of dried material.