Background Global progress toward the Millennium Development Goal target of halving the proportion of people without safe water and sanitation remains incomplete, and the challenge persists under Sustainable Development Goal 6 (SDG 6), which seeks universal access to safe water and sanitation by 2030. In Nigeria, more than 60 million people lack access to safely managed water, while untreated agro-industrial effluents continue to degrade surface and groundwater resources. Cassava (Manihot esculenta Crantz) peel, generated in excess of 12 million tonnes annually in Nigeria as a by-product of cassava processing, contains a lignocellulosic matrix rich in functional groups capable of binding microbial contaminants, heavy metals, and cyanogenic compounds.Methods This study evaluated the purification efficiency of dried M. esculenta peel flour for treating domestic wastewater (DW) from a university dormitory and industrial wastewater (IW) from a cassava-garri processing facility in Oyo State, Nigeria. Two treatment configurations, static adsorption and gravity filtration, were compared. Total heterotrophic bacterial count (THBC), physicochemical parameters (pH, temperature, dissolved oxygen, BOD₅, electrical conductivity, total dissolved solids, total suspended solids, and total solids), heavy metals (Zn, Pb, Cu via atomic absorption spectrophotometry), and cyanide concentrations (colorimetric method) were measured at 0, 72, and 144 h during adsorption experiments and before and after filtration.Results THBC declined by 99.2% in IW during adsorption and by 98.8% following filtration. BOD₅ decreased by 71.9% in DW during adsorption treatment. Zinc removal reached 23.0%, while cyanide concentration decreased by 41.1% under filtration. Dominant bacterial isolates included Bacillus spp. (37%), Vibrio spp. (24%), and Corynebacterium spp. (18%). Overall, gravity filtration consistently outperformed adsorption across contaminant classes.Conclusions These findings demonstrate that cassava peel flour is an effective, low-cost biosorbent suitable for decentralised wastewater pre-treatment in low-resource communities.