Assessment of sand and hearth ash filtration for wastewater treatment and novel monitoring via complex conductivity

The main objective of this study was to develop a cost-effective wastewater treatment system suitable for household use, utilizing sand and hearth ash sourced from industrial waste as filtering materials. The treatment method involved passing untreated domestic wastewater through a vertical cylindrical column using the infiltration percolation technique. Various parameters such as chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), suspended solids (SS), and pH were measured both before and after treatment. The findings demonstrated significant reductions in COD (88%), BOD₅ (78%), and SS (74%), along with a considerable decrease (85–98%) in heavy metal content. To assess treatment efficiency, we introduced complex conductivity σ*(ω) as a novel primary indicator, revealing a strong correlation between electrical parameters and the aforementioned parameters. Furthermore, the study investigated the relationship between wastewater and treated water frequencies and their respective relative permittivity. Wastewater exhibited higher relative permittivity due to dissolved solids and organic compounds, whereas treated water showed decreased relative permittivity, indicating successful pollutant removal throughout the treatment process.