Drinking water disinfection in the USA
For decades, chlorine has played an
important role in water treatment. Chlorine is the most widely applied
disinfectant. The advantage of chlorine is that is can easily be
produced and that it is relatively cheap. Chlorine effectively kills
pathogens. It contributes to the reliability of drinking water produced from
surface water. Chlorine tablets are used to disinfect water on locations
where no collective drinking water treatment takes place. After the
discovery of chlorinated byproducts, the use of alternative disinfectants
has increased.
In the United States of America, 50% of the drinking water is produced from
groundwater. In some cases surface water from rivers and lakes is used.
Chlorine is mainly used for the disinfection of drinking water in the USA.
In the past few years alternative disinfectants, for example chloramines,
have been used to reduce the amount of disinfection byproducts.
Standards for drinking water disinfection in the USA
In 1914 the first drinking water standard was accepted. The standard
concerned the maximum amount of bacteria that should not exceed 100
microorganisms per liter water. Less than 2 coliform bacteria per 100
milliliter water were allowed. In the following years more drinking water
standards were established, for example for lead,
copper and zinc.
Existing standards were intensified. In 1962 there were 28 standards for
substances found in drinking water. For health threatening chemical and
biological pollutants, obliged maximum pollution values were formulated. For
pollutions altering the looks, taste and smell of water, directing values
were formulated.
Clean Water Act
The Clean Water Act (CWA, 1972) is an amendment on the Federal
Water Pollution Control Act (1948) which contains the basic rules for
pollution discharge into water. The CWA was established to repair and
preserve the chemical, biological and physical quality of all water
(including oceans, lakes, rivers, streams, groundwater and wetlands) in the
United States of America. Through the CWA, EPA has gained the authority to
establish standards for water pollutions.
Safe Drinking Water Act
The Safe Drinking Water Act (SDWA) was established in 1974. Its purpose is
to maintain a safe drinking water quality. The attention for the drinking
water quality increased in the United States of America after the discovery
of various (industrial) pollutants in drinking water and the discovery of
disinfection byproducts.
The EPA establishes drinking water standards to protect public health. To
attain these standards, drinking water is treated to remove pollutants and
is subsequently tested. Drinking water quality in the USA has improved after
the implementation of the SDWA.
Stage I and Stage II Disinfectant / Disinfectant Byproducts Standard
In 1998 the Stage I and Stage II Disinfectant / Disinfectant Byproducts
Standard was established. Stage II contains maximum pollution values for
disinfection byproducts that can harm human health. The byproducts that are
regulated are found in drinking water networks in concentrations which can
be harmful (table 1).
Table 1: maximum concentrations of disinfectants and disinfection
byproducts according to Stage I and II Disinfectants and Disinfectant
Byproducts rules.
|
|
Stage I |
Stage II |
| Disinfectant |
Chlorine |
4 ppm |
|
|
Chloramines |
4 ppm |
|
|
Chlorine dioxide |
0.8 ppm |
|
|
|
|
|
| Byproducts |
Total trihalomethanes |
80 ppb |
40 ppb |
|
Halogenic acetic acids |
60 ppb |
30 ppb |
|
Bromate |
10 ppb |
5 ppb |
|
Chlorite |
1 ppm |
|
(EPA 2001) |
