Environmental pollution from silica sand washing in Algeria: physico-chemical analysis

This study addresses the lack of quantitative data linking silica sand washing efficiency to environmental pollutant emissions at an industrial scale in Sig (Algeria). The novelty lies in integrating multi-analytical characterization with a mass balance approach to quantify pollutant releases from a 300 t/day processing unit. Raw and washed sand were analyzed using particle size distribution analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic absorption spectroscopy (AAS). Washing wastewater, sludge, soils, and airborne dust were also characterized to assess environmental contamination. A mass balance approach was applied to estimate daily emissions. Results show that SiO₂ increased from 96.98% to 98.24%, while iron oxide (Fe₂O₃), one of the main chromophoric impurities, was reduced by 93%. However, significant emissions were identified, including 321 kg/day of Fe₂O₃ and approximately 25 t/day of clay. Wastewater exhibited high TSS (35.66 g/L) and TDS (2800 mg/L), while soils showed alkaline pH (9.57) and elevated metal concentrations. Dust contained high crystalline silica, indicating respiratory risks. These findings demonstrate that, despite improved sand quality, the washing process generates substantial environmental impacts. Therefore, integrated wastewater treatment, sludge valorization, and dust control are required for sustainable processing.