Geoscience Reference
In-Depth Information
between containers, adding a pinch of salt, or adding some lemon juice. A pinch of powdered
vitamin C (available at health food stores) in a quart of treated water will react with free chlor-
ine or iodine and totally remove the bad taste. Running the water through an activated carbon
filter will also remove free chlorine, iodine, and bad tastes.
Caution:
Do not remove free chlorine or iodine until the water has set for the proper steril-
ization time (see
table 8-1
, below), and do not remove traces of chlorine or iodine from water
that is to be stored for long periods of time.
Chlorine Bleach
Liquid chlorine bleaches, such as Purex and Clorox, contain a chlorine compound in solution
that will effectively disinfect water. There are some products on the market sold as “bleach” for
laundry use that do not contain chlorine and could be harmful,
so be sure to read the label.
The
procedure for disinfecting drinking water is usually written on the labels of Purex and Clorox
brand chlorine bleaches. When the procedure is not given, use the following percentage of
available chlorine as a guide (see
table 8-1
)
. Chlorine bleach is not as stable and reliable as the
recommended iodine treatments. Chlorine is very pH sensitive, and alkaline waters signific-
antly reduce its antimicrobial effectiveness (Wilkerson 1992, 72).
Caution:
Do not use powdered bleach or bleach with conditioning additives, scents, or col-
orfast additives.
To purify, add four drops of standard liquid chlorine bleach (5 percent concentration) per
quart of water, and double that amount for turbid or colored water. The treated water should be
mixed thoroughly and allowed to stand for thirty minutes. The water should have a slight chlor-
ine odor. If it doesn't, repeat the dosage and allow it to stand for an additional fifteen minutes.
The slight chlorine taste of treated water is additional evidence of safety. Chlorine bleach loses
strength over time, so if your bleach is over one year old, the amount used to disinfect should
be doubled, and if it is a few years old, it is probably worthless. If you are counting on stored
chlorine bleach for your emergency water purification, it is best to rotate your bleach stock
once a year.
Chlorine Dioxide
With the discovery that
Cryptosporidium
cysts pose a significant health threat and often survive
traditional chlorine water-disinfection treatments, many municipalities have included chlorine
dioxide in their water treatment process. Much like ozone water treatments, chlorine dioxide is
a powerful oxidizing agent that can kill C
ryptosporidium
cysts and rapidly purify water. It does
