Influence of Operating Factors on Turbidity Removal of Water Surface by Natural Coagulant Indigenous to Tunisia Using Experimental Design

Abstract

A systematic study of the influence of operating conditions on clarification process efficiency using Tunisian cactus cladodes powder (Opuntia ficus indica) was performed. A model of turbid water, using fibrous clay such as palygorskite, ranging from 50 to 500 NTU was investigated. The turbidity removal ability was assessed by the use of standard jar test measurements. A screening experimental design 3⁷//16 was implemented to screen 7 experimental input factors at 3 levels each in 16 experimental runs. Initial turbidity, pH, particle size and mass of sorbent-coagulant added, as well as the type of cactus treatment, the stirring speed and the settling time on turbidity removal were tested. With Starks screening matrix, this work demonstrated that turbidity removal is affected by 5 input factors: initial turbidity, settling time, powder size, slow stirring and pH. Cladode powder acts positively on the turbidity removal.