NW2830 - Various Chemicals

These chemicals are used in various stages of the Water and Wastewater treatment process. Caustic Soda (Sodium hydroxide) - used to increase the pH of water, for example for metals removal and final water pH correction. Increased pH makes the water less corrosive to plumbing and reduces the amount of lead, copper and other toxic metals that can dissolve into drinking water. Caustic is preferred on final water rather than lime as lime can increase the turbidity of the water. Sulphuric Acid - used to decrease the pH of water and is most commonly used to reduce the raw water pH to condition the water prior to the addition of coagulant and polymer. Where the source water is very alkaline, coagulant dosing may not reduce the pH to optimum levels for coagulation. Sodium Hypochlorite - alkaline when added to water for disinfection. Disinfection removes, de-activates or kills pathogenic microorganisms. Phosphoric acid - acid dosed for plumbosolvency control; Plumbosolvency is the ability for water to dissolve lead. To control and prevent this, the addition of phosphate is required. Continuous dosing of low levels of phosphate into drinking water causes build-up of a thin scale on the inner walls of pipework. This scale prevents water from coming into direct contact with the walls of any lead pipework. Provided that the dose is applied continuously and without interruption this scale remains in place, thereby protecting customers from any harm associated with lead in drinking water. Ammonium Sulphate - Chloramination is the treatment of drinking water with a chloramine disinfectant. Both chlorine and small amounts of ammonia are added to the water one at a time which react together to form chloramine (also called combined chlorine), a long-lasting disinfectant. Used at smaller WTWs in the Suffolk region.