Characterization of cassava mill effluent under different environmental conditions and its suitability as a biostimulant for soil remediation

Abstract

Cassava mill effluent (CME) is a high-volume byproduct of cassava processing in Nigeria, posing environmental hazards but also offering potential as a low-cost biostimulant for soil remediation. This study characterized fresh CME and monitored its physicochemical evolution over seven days under three storage regimes: covered at room temperature, uncovered at room temperature, and uncovered under sunlight. Parameters including pH, cyanide, electrical conductivity (EC), total suspended solids (TSS), organic carbon, macronutrients (N, P, K, Ca, Mg, Na), cation exchange capacity (CEC), and heavy metals were analyzed using standard methods. Fresh CME was moderately acidic (pH 6.23) with high cyanide (437.67 µg/mL), EC (3506.33 µS/cm), and organic matter (233.64 g/L). Storage conditions significantly altered effluent properties. Exposed storage increased pH (6.70–6.87), cyanide (up to 884.67 µg/mL), EC (up to 9884.33 µS/cm), and TSS (4657 mg/L), while covered storage promoted acidification (pH 3.53) and reduced cyanide (230.67 µg/mL). Nutrient analysis revealed exceptionally high potassium (65,519 mg/L) and moderate nitrogen (121 mg/L) and phosphorus (16.99 mg/L). Heavy metals were within regulatory limits. These findings confirm that CME is a nutrient-dense organic amendment, but its application must be carefully managed particularly for cyanide and salinity under optimized storage conditions to ensure safe and effective bioremediation.