Softening of Hamma drinking water by nanofiltration and by lime in the presence of heavy metals

The paper presents results of a study investigating softening by nanofiltration of the Hamma underground water resource. The Hamma wells supply the City of Constantine with hard drinking water containing calcium bicarbonate. The main parameters investigated were pressure, cross-flow velocity and water temperature. Nanofiltration was found to be a very efficient process for partial reduction of the temporary hardness, within the pressure limits considered, the calcium and bicarbonates retentions reaching 34% and 30%, respectively. Experiments were also conducted to modify the furring capacity of the water by doping the Hamma water with metal cations. Addition of Zn2+ and Cu2+ induced some inhibition, but no effect was observed in the cases of Fe2+ and Mn2+.

This study confirms that NF is an interesting possibility for eliminating temporary hardness from drinking water. Data are presented showing the effect of various parameters on the flux and ion retention of Hamma water. The paper also presents data characterizing the inhibitory effect induced by the presence of Cu2+, Fe2+, Zn2+ and Mn2+ ions in temporary hardness reduction by lime addition. Relatively high inhibition effects were exerted by Zn2+ and Cu2+ while Fe2+ and Mn2+ did not exhibit an inhibitory influence.