Sourcewater coag/settling filtration storage elevated tank consumer Optimizing the chemistry in a water treatment plant

Sourcewater coag/sett ing filtration storage elevated tank consumer Sourcewater Temperature 32 – 85 o F pH 6.5 to 8.5 Alkalinity TOC (chlorine demand and DBP formation) 1.5 to 5 mg/l bacteria

Sourcewater coag/settling filtration storage elevated tank consumer Pre-oxidation Chlorine, chlorine dioxide, potassium permanganate pH likely is decreased

Sourcewater coag/settling filtration storage elevated tank consumer Coagulation/flocculation/sedimentation Addition of alum (wants pH low) or ferric coagulant, polymers, pH decreases Alkalinity decreases Lime addition may be necessary

Sourcewater coag/settling filtration storage elevated tank consumer Disinfection Addition of chlorine (low pH favored for HOCl formation) pH decreases Alkalinity decreases (slightly) DBP reaction starts Reaction time with microorganisms is critically important IN SUNLIGHT, UV REACTS WITH FREE CHLORINE

Sourcewater coag/settling filtration storage elevated tank consumer Disinfection Addition of chlorine (low pH favored) pH decreases Alkalinity decreases (slightly) DBP reaction starts Reaction time with microorganisms is critically important Lime addition may be necessary IF DONE IN SUNLIGHT, UV REACTS WITH FREE CHLORINE DBP Control Reduce pH for slower reaction Reaction time is critical Chlorine feed in plant Flushing in DS Temperature is critical Reaction can be modified by changing reactants (chloramine)

Sourcewater coag/setting filtration storage elevated tank consumer Corrosion Control Increase pH (pH 8.5 typical) with lime or caustic Use corrosion inhibitors (pH 7.5 typical)

Sourcewater coag/settling filtration storage elevated tank consumer Optimized Process Pre-oxidant that doesn’t form DBPs Coagulant at lower pH Chlorine at low pH lime to raise pH and ammonia to change DBP reaction Chlorine “trim” dose for monochloramines Flushing to minimize water age