Combining lime softening with alum coagulation for hard Ghrib dam water conventional treatment

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.

Upgrading Wastewater Treatment Plant to Obtain Drinking Water

“…The proposed plan for this substitutional treatment employing biodegradation is illustrated in Figure 3. The plan presents the simplified treatment method for an effluent inflow, where the effluent firstly passes through preliminary and traditional treatment [83] [84] (primary decanter, activated biological reactor and secondary decanter). In addition to such stages, the effluent would undergo a post-treatment stage termed "final polishing" (Figure 3), which implies the biological filter.…”

Water Reuse: Extenuating Membrane Fouling in Membrane Processes

“…Convenient pre-treatment techniques are chosen following the constituents to be eliminated and the level of their elimination. Frequent pre-treatment techniques for MF and UF comprise [23,110,111]: 1) Coagulation (habitually with lime, alum, or ferric salts) and flocculation [112][113][114][115][116][117][118][119][120], 2) Adsorption (most frequently employed material is powdered activated carbon (PAC)), 3) Pre-oxidation (utilizing ozone) [121], 4) Pre-filtration (employing large pore size membranes, granular media, filter cloth, etc.). Practically, these processes [1] may be used in integration, as an illustration, coagulation followed by pre-filtration, coagulation followed by adsorption with PAC [122,123], and ozonation followed by coagulation [124].…”

The Lethal Water Tri-Therapy: Chlorine, Alum, and Polyelectrolyte

“…For polydiallyldimethyl-ammonium chloride (PDADMAC), the monomer amount limit is 0.5% in Europe and 2% in the USA [54,55]. For potable water treatment [56][57][58][59], the National Sanitation Foundation has suggested limit injections for usually employed commercial polymers in the USA. The maximums are frequently < 50 mg/L for PDADMAC, < 20 mg/L for epichlorohydrin and dimethylamine (ECH/DMA) polymers and < 1 mg/L for polyacrylamides (PAMs), irrespective of the PAM charge kind [50].…”