Proof-of-concept evaluation of a modified sand–gravel filtration system incorporating discarded cigarette filters and surgical masks for wastewater treatment

Global water crises are being driven by microbial and heavy metal pollution from industrial and domestic waste, particularly in resource-strained regions. In reaction, this paper designs and evaluates a low-cost filtration system that incorporates reused surgical masks and cigarette filters into traditional sand-gravel columns to treat wastewater. Surface water of the Dhaleshwari River, Bangladesh was taken as samples to evaluate the performance of four filtration chambers with four filter layer thicknesses of 0, 5, 10, and 15 mm. The number of microbial contaminants was identified using colony-forming units (CFU/100 mL) and Pb, Cd, Cr, and Cu were analyzed using standard analysis procedures. The performance of treatment increased steadily with filter thickness, and the best removal efficiency was found in the 15 mm setup. Bacterial loads reduced from 8.5 × 10¹⁰ to 0.25 × 10¹⁰ CFU/100 mL, while Pb, Cd, Cr, and Cu concentrations decreased by 84.7%, 72.61%, 66.7%, and 62.21%, respectively. The adsorption kinetics followed the Langmuir isotherm with incredibly good correlations of Pb (R 2 = 0.9994) and Cr (R 2 = 0.877). Significant treatment effects and interaction between filtration settings and metal removal were confirmed with statistical tests, ANOVA ( p < 0.001), and linear mixed-effects modeling (LMM). The results indicate that waste-based filtration media may enhance water quality under controlled laboratory conditions, suggesting potential for further study in cost-effective wastewater treatment systems.