Enhancement of suspended matter sedimentation in the process of chemical softening of natural water

Summary

The kinetics of water clarification in process flow schemes with separate processes of chemical softening and water sedimentation during softening with sodium hydroxide in the presence of mineral additives (loam, calcium carbonate, generated sludge), as well as with the use of flocculants is considered. It was demonstrated that adding calcium carbonate or sludge from the settling tank at the stage of the chemical reaction provided for the increase of the hydraulic size of the resulting suspension and, accordingly, for the 2–3 times reduction of the subsequent water clarification time by settling. The maximum reduction in turbidity of purified water (1.34 mg/dm³) by settling is achieved using calcium carbonate. Adding anionic or nonionic flocculants after the completion of the precipitation reaction of hardness salts with sodium hydroxide provides for reducing the turbidity of water during settling
to 4–4.7 mg/dm³. The total hardness of treated water is 0.55–0.7 degrees.

Key words

flocculants , settling , turbidity , softening , hydraulic size , natural water , hardness , alkalinity , sodium hydroxide method , mineral additives