Abstract
This work aims to control the efficiency of water softening as an inherent phenomenon in the coagulation process or, in other words, to evaluate the softening process as a secondary reaction which is producing simultaneously with the main reaction as the coagulation process. Ghrib Dam water is well-known for its high hardness ranging from 750 to 900 mg/L as CaCO3. That is, this water is unpleasant to the domestic consumption. Conventional water treatment at the Ghrib Station is based on coagulation using aluminum sulfate [Al-2 (SO4)(3)center dot 18H(2)O] (alum) as a single coagulant. Alum has a minimal effect on the total hardness and its human toxicity is not yet doubtful. This research introduces the concept of the replacement of alum by lime and sodium hydroxide (NaOH) in coagulation process at the Ghrib Station. Coagulation experiments on jar test using the three reagents (alum, lime, and NaOH) are performed and physicochemical analyses are conducted to evaluate the possibility of alum partial or total replacement for improving the treatment effectiveness in hardness reducing. The obtained results show that hardness is decreased at its half by combining simultaneously the three chemical products: alum = 15, lime = 100, NaOH = 100 mg/L. Additional survey is required to examine the complicated interaction in the Ca2+/Mg2+-DOM-Al ternary system to comprehensively define the contributions of the two mechanisms - lime softening and coagulation - to organic matter removal by coagulation. (C) 2018 The Authors. Published by IASE. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)