15 Water Purification: Chemical Treatment: Methods of chlorinetreatment: Calcium Hypochlorite:
Description
This article is from the Water Treatment FAQ, by Patton Turner with numerous contributions by others.
15 Water Purification: Chemical Treatment: Methods of chlorinetreatment: Calcium Hypochlorite:
Also known as High Test Hypochlorite. Supplied
in crystal form, it is nearly 70 % available chlorine. One product,
the Sanitizer (formally the Sierra Water Purifier) uses these crystals
to super chlorinate the water to insure pathogens were killed off,
then hydrogen peroxide is added to drive off the residual chlorine.
This is the most effective method of field chlorine treatment. The US
military
and most aid agencies also use HTH to treat their water, though a test
kit, rather than superchlorination, is used to insure enough chlorine
is added. This is preferable for large scale systems as the residual
chlorine will prevent recontamination
Usually bulk water treatment plants first dilute to HTH to make a 1%
working solution at the rate of 14g HTH per liter of water. While
testing to determine exact chlorine needs are preferable, the solution
can be used at the dose rate of 8 drops/gallon, or for
larger quantities, 1 part of 1% solution to 10,000 parts clear water.
Either of these doses will result in 1 PPM chlorine and may need to be
increased if the water wasn't already filtered by other means.
When test kits are available, the WHO standard is a residual chlorine
level of 0.2 to 0.5 mg/l after a 30 min. contact time. The may
require as much as 5 mg/l of chlorine to be added to the raw water.
Continue to:
My Books
