A new natural method for sludge drying of wastewater treatment stationThe case of Algeria

This paper presents an experimental application aiming at reducing the sludge drying time in the STEP drying beds of domestic wastewater. This method works with the mixtures of sludge from the Souk Ahras city STEP at different percentages, and with natural material wastes such as scrap limestone flour (SLF) and/or refractory bricks flour based on magnesia (RBFM) from Hadjar Essoud (north eastern Algeria) cement furnaces. The applied experiment focused on mixtures testing for mud-flour varying between 12.5 and 100%. The achieved results for mixtures of 25% SLF and RBFM can be noted as: for the mud blindness from 0 to 20%, in the dry season (August, average temperature 34 degrees C), a globally estimated drying time of 1.5d; for the mud blindness from 0 to 30% in the wet season (December, average temperature 16 degrees C), a substantial drying time in the range between 4 and 5d. In a mixture of 25%, the sludge has been reduced to more than 95% of their initial weight (a reduction from 400 to 17g). The results show two strong desirable aims of STEP sludge management; on the one hand the drying time reduction and its corollary of drying areas and deposit, and on the other hand the recycling of the waste limestone of cement plants.