AWWA ACE71075

In this study, the effect of mixing was examined by conducting breakpoint chlorination experimentsunder different levels of mixing, represented by the average velocity gradient, G in s^-1. A ratherunique way of plotting breakpoint chlorination curve was utilized to analyze the data, whichallowed a clear delineation if the monochloramine formation was according to the stoichiometry.A quantitative comparison between experimental data and stoichiometry can clearly indicate theimpact of non-uniform mixing. The experimental data showed that as the G value increased from35 to 500 s^-1, the monochloramine formation increased from 75 to 87 percent of thestoichiometric value. The location of the breakpoint, correspondingly, increased from a molarratio of 1.25 to 1.75.Comparison of 50- and 200-rpm experimental data was conducted and a breakpoint curve wasplotted imposing one over the other. It has been observed from previous literature that in idealconditions, breakpoint occurs at chlorine to ammonia nitrogen molar ratio of 1.5:1, and the peakof monochloramine is expected at a molar ratio of 1:1. Hence, breakpoint curve was plotted atmixing speed of 50 and 200 rpm, indicating free chlorine, monochloramine, dichloramine,trichloramine, and total chlorine concentration at contact time of 45 minutes.In conclusion, when chlorine and ammonia are combined to produce monochloramine, thedegree of mixing indeed has significant impact on the performance of the chloraminationprocess, and therefore must be a critical consideration in its design and operation. Includes 12 references, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2009

Number of Pages:

47

File Size:

1 file , 2.4 MB