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Use of mixed oxidant solution in pretreatment can achieve both lower turbidity levels and reductions of up to 40 percent in alum and polymer required. Customers report faster floc formation and improved settling due to the quality of the formed floc. Typically, disinfection by-product (DBP) formation is also reduced with the corresponding reduction in organics.

Customers report:

• larger floc that forms more rapidly, even at colder temperatures
• reduced fluffiness, leading to good settling
• formation of a vortex around the rotating paddle
• high degree of clarity in both the supernatant and the water between the floc particles
• very low turbidity of the supernatant (typically < 0.1 ntu) nearly drinking water quality

The microflocculation effect with mixed oxidant solution is relatively insensitive in magnitude to the free available chlorine (FAC) dose in pretreatment over a broad dose range. However, since any chlorine residual remaining will form disinfection by-products, logic dictates dosing the mixed-oxidant solution to cause the microflocculation effect, while leaving nil chlorine residual to minimize DBP formation. Note that the microflocculation effect will not occur in all waters. The best way to test the possibility of occurrence at your site is to perform a jar test.