No 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 wellknown 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 [Al2 (SO4)3.18H2O] (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 Ca 2+ /Mg 2+ -DOM-Al ternary system to comprehensively define the contributions of the two mechanisms -lime softening and coagulation -to organic matter removal by coagulation.

Nowadays, reverse osmosis (RO) is the most largely utilized desalination process at the World level. During the three last decades, amazing progress has been realized in the manufacturing of RO membranes using different materials. However, what is astonishing here is the fact that a new research field was open in a relatively short time with hundreds of scientific publications and patents which are made on membrane post-synthesis modifications in order to improve the structural properties and desalination performance opening a large debate about the membrane fabrication techniques and membranes capacities to deal with various water pollutants. This review aims to discuss this extra technological field dedicated to membranes modifications following their fabrication. As conclusions, membrane fabrication methods are a well-established and developed technology which however needs more technical improvements to overcome the needs of a post-synthesis industry and satisfy quantitatively and qualitatively the water guidelines. On the other hand, the large chemical products use in both membranes synthesis and post-synthesis should be avoided or at least reduced, since monomers, alcohols, acids and bases risk to be realized into drinking water. That is said because RO process has been presented hopefully as a promising powerful and green technology instead of chlorination and coagulation/flocculation which are proven highly polluting with their toxic metal salts injection and poisonous disinfection by-products formation.