Bactericidal Properties of Chloramines and Free Chlorine in Water

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Abstract
A comparison of chloramines and free Cl as bactericidal agents was made under varying conditions of time, temperature and pH against Escherichia coli, Aerobacter aerogenes, Pseudomonas pyocyaneae, Eberthella typhosa and Shigella dysenteriae The criterion used was 100% killing. Increased time caused increased effectiveness; lowered temps. decreased activity; and increased pH reduced effectiveness. Residual free Cl of 0.04 p.p.m. killed in 1 min. at a pH of 7 and a temp. of 20 -25 C. Under the same conditions a chloramine residual of 1.2 p.p-m. did not kill in 10 min. but did kill in 20 min. Using a similar contact period, 25 times as much chloramine was required as for free Cl. With the same amt. of residual, the necessary contact period for chloramines was 100 times that for free Cl.