Removal of toxic substances from cassava effluent using alum and Moringa oleifera seeds as coagulants: a comparative study towards improved agricultural practice

Abstract

Cassava as a food is widely eaten in nearly all tropical countries. This has led to the emergence of many cassava processing centres, which consequently results in extensive ecological pollution due to the release of cassava processing wastewater into the environment. Wastewater treatment is mostly carried out using chemical coagulants, which are not environmental friendly. This study aims at providing non-chemical based alternative treatment procedures for cassava wastewater. The treatment procedures involved the use of alum and Moringa oleifera seeds as coagulants. The coagulants were used in combination with sodium hypochlorite at 25 and 50 mg/L for coagulation periods of 24 h and 48 h. Physicochemical parameters including, pH, biological oxygen demand (BOD), cyanide, coliform count and heavy metals [Ni, Zn, and Cr] were evaluated for both raw and treated wastewaters using standard methods. The data obtained were subjected to descriptive and inferential statistics. At 50 mg/L dose and 48 h coagulation period, the removal efficiencies of cyanide were 98.91% and 99.63% for alum and M. oleifera seeds, respectively. M. oleifera seeds reduced coliform in the effluent by 96.73% and decontaminated heavy metals [Ni, Zn, and Cr]. However, none of the two treatments could reduce BOD to a permissible level. The study concluded that M. oleifera seed is a potential coagulant, and could therefore be used as a substitute to synthetic coagulants.