Chlorine Dosage Rates And Residuals

Table 3 gives recommended ranges of chlorine dosages for disinfection of various wastewaters. Recommended minimum bactericidal chlorine residuals are given in Table 4. Data in Table 4 are based on water temperatures between 20° C to 25° C after a 10-minute contact for free chlorine and a 60 minute contact for combined available chlorine.

The minimum residuals required for cyst destruction and inactivation of viruses are much greater. Although chlorine residuals in Table 4 are generally adequate, surface waters from polluted waterways are usually treated with much heavier chlorine dosages. Ordinary chlorination will destroy all strains of coli, aerogenes, pyocyaneae, typhsa, and dysenteria.

In addition to these microorganisms, three other types are readily destroyed: Enteric vegetative bacteria (Eberthella, Shigella, Salmonella and Vibrio species); Worms such as the block flukes (Schistosoma, species); Viruses (for example, the virus of infectious hepatitis). Each of these groups of organisms differs in its reaction with chlorine.

There is evidence that the comparative reaction of different organisms to one form of chlorine is not necessarily maintained relative to other forms.

Table 3. Recommended Chlorine Dosage Ranges

Wastewater Type

Chlorine Dosage (mg/1)

Raw Sewage

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  • Melvin
    WHO recommended chlorine dosage?
    8 years ago

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