Physico-chemical and geotechnical properties of greywater-polluted soils treated with cereal gruel supernatant

Greywater in direct contact with virgin soil for several years has tendency to pollute and altered its properties. The present study investigates the potential of Cereal Gruel Supernatant (CGS) as sustainable stabilizer for sandy loam Greywater Contaminated Soils (GCS) in parts of southwest Nigeria. The GCSs and Control Soils (CSs) were collected from two sampling locations within Basement Complex geological formation at depths of 0.5, 1.0, and 1.5 m from the surface. The experiment consists of four treatments: CS with no presence of greywater, GCS, CS with 50 ml of CGS, and GCS with 50 ml of CGS. Results showed that addition of CGS enhanced the Isolu GCS properties, with reductions in liquid limit (LL) (up to 19.35%), plasticity index (PI) (up to 19.27%), clay particles (up to 36.1%) but increased sand particles (up to 15.31%) at upper 1.0 m depth. However, shear strength (SS) and cation exchange capacity (CEC) of treated Isolu GCS at 0.5 m depth increased from 116.25 kN/m2 to 180.74 kN/m2 and 1.40 to 3.86 cmol/kg, respectively after 30 days of mixing. Addition of 50 ml CGS to Ibadan GCS resulted in slight increase in LL and PI but appreciable increase in SS (up to15.08%) and bearing ratio (up to 10%) at all sampling depths. These findings suggest CGS can serves as potential soil stabilizer, offering both performance enhancement and ecological advantages. Further investigation is needed to identify the optimum dosage of CGS that will produce low atterberg limits and enhanced SS with less permeability.