Evaluation of plantain peelings ash extract as coagulant aid in the coagulation of colloidal particles in low pH aqua system

Abstract

The use of plantain peelings ash extract (PPAE) as a coagulant aid in a low pH water was evaluated in the present studies. Plantain peelings were collected, washed, dried, and ashed in a furnace. The ash was extracted using deionized water, and the chemical composition was examined using an atomic absorption spectrophotometer. Synthetic turbid water of varying turbidities (50, 100, 300 NTU) and varying pHs (2, 3, 4) were prepared by clay dispersion in deionized water. The optimum alum dosages for the coagulation of colloidal particles in different turbid waters of varying pHs were determined by method of continuous variation using the jar test procedure. The residual turbidities of the treated waters were determined, and the alum doses that gave the minimum residual turbidities were taken as the optimum dosage for the removal of colloidal particles. The use of PPAE as a coagulant aid with alum showed an improvement in the value of residual turbidities of the treated waters. Results obtained from the different studies showed that treated waters of lower residual turbidities were obtained from synthetic waters of higher initial turbidities and pHs. The pH of the treated water decreased with an increase in alum dosage, whereas an increase in the pH value was observed with the addition of PPAE as a coagulant aid. High correlation coefficient values (r2) were obtained when the changes in pH (i.e., ΔpH = pHf -pH) of the treated waters were correlated with alum and PPAE additions, and mathematical relationships were derived from the linear graph. Studies on the effect of flocculation time on residual turbidity showed that an optimum flocculation time of 30 minutes was attained, when alum was used alone, before redistribution and redispersion of the flocs was noticed. This phenomenon did not occur when PPAE was used as a coagulant aid. © 2008, CAWQ.