How can the disinfection process be optimized using monochloramine?

Document ID

Document ID TE185

Published Date

Published Date 04/02/2019
How can the disinfection process be optimized using monochloramine?
Optimizing monochloramine formation
Chloramination involves mixing chlorine and ammonia together at a controlled ratio to form monochloramine. The ideal mix is five parts chlorine to one part ammonia, but this can vary depending on the pH, chlorine demand, and ammonia in the source water. If too much chlorine is added, dichloramine will form, which creates taste and odor problems. If too much ammonia is added, bacteria may grow, which can lead to biofilms or nitrification. To make sure you are feeding chlorine and ammonia at the optimum ratio, monitor the concentration of monochloramine, total chlorine, and free ammonia.

The monochloramine and total chlorine concentrations (as Cl2) should be equal. If total chlorine is higher than monochloramine, your system has formed dichloramine in addition to monochloramine. Free ammonia in an optimized process should be very low but have some measurable concentration (Free ammonia is ammonia in the form of NH3 or NH4+ that has not combined with chlorine.). A small but measurable concentration of free ammonia ensures that you are feeding a ratio of chlorine to ammonia that is optimal. If the free ammonia concentration is too high, nitrifying bacteria may form and form biofilms or convert excess ammonia to nitrite. Biofilms and nitrite will consume your monochloramine disinfectant. Measure nitrite to determine if your system is undergoing nitrification.

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