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Current IssueAugust 28, 2015
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Ask The Expert: Determining proper chlorine levels
Question: Editor's Note: The following request was received in Spanish and translated for "Ask the Expert" by Agua Latinoamérica editor Ingvi Kallen—the editors.

Q: Allow me to congratulate you for publishing Agua Latinoamérica, which is a very useful source of information.

Some time ago I had the opportunity of reading your magazine in a friend’s business, and took advantage of the free subscription offer, and later paid for a long-term subscription. I would like to know where I can find information about the limitations of drinking water disinfection with chlorine and its byproducts (hypochlorites) specifically, if there is a table available that shows the effects of chlorine on virus, bacteria, parasites (protozoa), algae and fungi spores.

This information is extremely important to me, since in these Latin American countries chlorine is used with the belief that it eliminates any type of microbiological contamination. It would be very interesting to know the levels of residual chlorine that present a germicidal effect on each one of the microorganism groups previously mentioned.

Déborah Pellecer

Answer: A: The following website (for the Wilkes University Center for Environmental Quality in Pennsylvania) has some information related to the data you're seeking:

• http://wilkes.edu/~eqc/chlorinecontact.htm*

The table here also was found at a webpage for a "Water Sanitation" course at Kansas State University:

Table 3. Effective Chlorine Levels Microorganisms Concentration (ppm) Algae 2.0 Bacteria (gram-negative cells) 0.2-5.0 Spores 150-250 Mold (hyphae) 100 Spores 135-500 Viruses 0.2-3.25

SOURCE: www.oznet.ksu.edu/grsc_subi/Teaching/GRSC651/GRSC651_Courses_Material/lecture_slides/GRSC651_lect_32_Water_Sanitation.ppt

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