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 processorsin Nigeria. This study is therefore aimed at assessing theeffectiveness 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 thatcollected wastewater hada mean value of 1357NTU, 385, 31.87, and 716mg/L ofturbidity, biochemical oxygen demand(BOD), hydrogen cyanide (HCN)content, and chemical oxygen demand (COD), respectively. These values wereabove the permissible limit set by the local and international regulatory agencies. The filters with activated carbon showeda 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 <0.05 of 2.84 x 10-32and 1.69x10-29 for COD and BOD,respectively. The obtained result alsodisclosedthat some parameters did not conform to the acceptable limitbut there was a reduction in key pollutants of cassava wastewater. Therefore,the filter can be used as a low-cost treatment mechanism for cassava wastewater prior to disposal.