Efficacy of Slow Sand Filtration System Embedded with Activated Carbon for Agro-Industrial Wastewater Treatment

Abstract

Indiscriminate disposal of untreated cassava wastewater is a major environmental challenge faced by communities hosting indigenous cassava processors in Nigeria. This study is therefore aimed at assessing the effectiveness of a simple slow sand filtration system embedded with activated carbon layer for cassava wastewater treatment. The filters were loaded in layers with graded sand, gravel, and varying thickness of activated carbon bed. Cassava wastewater was obtained from a processing site at Ibogun, Ogun State, Nigeria. The filters were filled and left for about two weeks for “schmutzdecke” to form on the top surface of the sand bed and then operated at room temperature (28-34 °C) at hydraulic retention times of 6, 12, and 24 h. The result showed that collected wastewater had a mean value of 1357 NTU, 385, 31.87, and 716 mg/L of turbidity, biochemical oxygen demand (BOD), hydrogen cyanide (HCN) content, and chemical oxygen demand (COD), respectively. These values were above the permissible limit set by the local and international regulatory agencies. The filters with activated carbon showed a drastic reduction in the pollutants load (BOD: 38%-57%, COD: 26%-46%, HCN: 79%, and NTU: 96.5%-98%). This is corroborated by P-values