Investigation of a modified multi soil layering system performance in the supplementary treatment of municipal wastewater

The discharge of untreated municipal wastewater poses significant risks to surface and groundwater resources, highlighting the need for sustainable treatment technologies. The Multi Soil Layering (MSL) system consists of soil block units and enclosed by permeable layers. The present study introduces a Modified Multi Soil Layering (MMSL) system, contain the soil blocks with geotextile cover and a composite of nano-alumina layer. The performance of six experimental treatments was evaluated using a split-plot factorial design with two replications. The first factor was the type of soil block covering (jute, geotextile, and geotextile with a nano-alumina layer), and the second factor was aeration condition (aerated vs. non-aerated). Effluent samples were collected at 2–3-weekly and analyzed for BOD, COD, TSS, TDS, nitrate, and phosphate. Aerated systems exhibited higher BOD and COD removal, with the aerated geotextile cover achieving the highest efficiencies (77% and 78%, respectively). Non-aerated systems showed superior TSS and TDS removal due to stable sedimentation and reduced resuspension, with the geotextile cover reaching 52% and 79%, respectively. Aeration enhanced aerobic activity and nitrate removal, whereas non-aerated conditions favored denitrification, suggesting that coupling aerobic and anaerobic zones may optimize nitrate removal. The geotextile with nano-alumina cover under non-aerated conditions achieved the highest phosphate and nitrate removal (78% and 57%, respectively). FESEM and EDS analyses confirmed that geotextile-based coverings provided more porous and reactive structures that improved pollutant capture, while jute supported primarily surface-level removal. Mineral deposition observed via EDS contributed to sustained system performance.