By Dr. Hans Peterson and Dr. Colin Fricker
Insert: If engineers and water treatment process manufacturers
have guidelines for what qualities safe drinking water should have,
they can work towards finding effective solutions.
The question of what needs to be done to move toward safe drinking
water is not as simple as most people assume. It is a question that
can have both a political and a technical answer.
First, if we look at the Canadian Drinking Water Quality Guidelines,
it is the result of negotiations between provincial and federal
agencies and the guidelines are really a mix of political and technical
solutions.
When Health Canada studied the effects of cancer-causing trihalomethanes
(THMs) it was concluded that the level should be decreased from
350 to 50 micrograms/litre (mg/L). But, several provinces balked
at this and a compromise level of 100 mg/L was set. The United States
Environmental Protection Agency (USEPA) set the level at 80 mg/L.
Several agencies are now considering below 50 mg/L levels. Political
or technical?
Arsenic in drinking water has also hit a downward spiral moving
from 50 to 25 to 10 mg/L in Canada. Some provinces remain at 25
mg/L, including Saskatchewan as it needs more time to get its treatment
plants to meet the 10 mg/L guideline. The USEPA stated more than
a decade ago that the level should really be below two mg/L. Health
Canada wanted to set it to five mg/L, but again some provinces balked
and the level was set to 10 mg/L. The Safe Water Drinking Foundation
(SDWF), in a 2006 review of effects of arsenic, stated that communities
that supply its residents with arsenic levels above five mg/L should
have its residents tested for the ill effects of arsenic. Political
or technical?
The dilemma is that many water sources have high levels of natural
organic material (NOM) giving rise to high levels of THMs when the
water is chlorinated. The removal of NOM often requires specialized
treatment techniques which are not widely applied. The situation
is further complicated by the fact that the most suitable treatment
technique for NOM removal varies according to the chemistry of the
source water. Arsenic too requires targeted water treatment processes,
especially if the guideline level drops to five mg/L or less.
Government agencies may, however, not look at the production of
truly safe drinking water, but, instead, means of circumventing
particular guidelines.
For example, when chlorine reacts with organic material a myriad
of chlorination by-products are generated and the THMs are only
one group. But they are the only group with a guideline in Canada.
Regulated elsewhere, haloacetic acids (HAAs) have similar carcinogenic
potential as the THMs. One way to reduce the THMs is to lower the
pH, which works well in Canada because we don’t look at the HAAs.
This is a recipe to increase the HAAs and the total carcinogenic
potential may stay the same or indeed increase, yet the water may
now meet the Canadian Drinking Water Quality Guidelines. Similarly,
the use of monochloramine as a secondary disinfectant has been widely
adopted to reduce the formation of THMs. However, chloramines actually
increase the formation of nitrogenous by-products, such as N-nitrosodimethylamine,
which is highly toxic and a suspected human carcinogen. However,
these compounds are not regulated. Political or technical?
A large concern with drinking water safety is the need to have low
or no disease-causing microbes in the water. In Canada this is mainly
measured through the use of "indicator bacteria" — specifically
E. coli and total coliforms. Parasites (including cryptosporidium
and giardia), while regulated elsewhere, have not become mandatory
in Canada. Indeed, the North Battleford outbreak of cryptosporidiosis
was caused by a water meeting the Canadian and Saskatchewan Drinking
Water Quality Guidelines. Difficulties in measuring the parasites
have been used as an excuse to not introduce them into the guidelines,
yet in other countries, such as the United Kingdom, continuous monitoring
of these parasites has been a requirement for years.
Are E. coli and total coliforms good indicators of protozoan parasites?
In one word, no. Measuring E. coli and coliforms in chlorinated
water can be misleading as these organisms usually die at low chlorine
exposures while protozoa, such as cryptosporidium, giardia, and
some bacterial and viral pathogens, are far more difficult to kill
using chlorine. In fact, measuring E. coli and total coliforms simply
means that you have met a regulatory requirement. Monitoring of
public water supplies for the presence of indicator organisms does
little to protect public health.
Microbial safety of drinking water has become tightly associated
with liability. In Milwaukee a 1993 cryptosporidiasis outbreak caused
some 400,000 people to become infected and around 100 people died.
The cost was estimated to be more than US$25 billion according to
the U.S. National Research Council. Cities are therefore not so
concerned about Canadian guidelines, but about potentially devastating
lawsuits should they supply unsafe drinking water. So, expect major
Canadian cities to do everything they can to remove protozoan parasites
and any other disease-causing microbes.
SDWF found E. coli, total coliforms and campylobacter in all raw
water sources, but it was only campylobacter that showed up in treated
drinking water in some of the rural water treatment plants. The
dilemma for rural water treatment plants is that they typically
have much poorer quality water sources than cities yet need to treat
their water in minutes while cities take hours.
Also cities have typically many water treatment processes. The
Canadian Medical Journal recognized this in an article titled,
"Safe Water? Depends on where you live!" Indeed, in the United States,
communities smaller than 10,000 people were responsible for 96 per
cent of the violations of U.S. Environmental Protection Agency’s
Total Coliform Rule.
Rural water treatment plants need better treatment processes than
cities to be able to deal with the poorer quality water and limited
resources in rural communities. There are many other examples of
how politics is interfering with technical drinking water issues
in Canada, such as allowable pesticide residues, but isn’t it time
that we instead started to think about the provision of safe drinking
water?
To help move towards truly safe drinking water, the SDWF is working
on a Framework for Safe Drinking Water where problems and solutions
are highlighted by using science rather than what is politically
expedient. If engineers and water treatment process manufacturers
have guidelines for what qualities safe drinking water should have,
they can work towards finding effective solutions. They would then
truly start living up to their number one priority: protecting public
health.
Dr. Hans Peterson is the executive director of the Safe Drinking
Water Foundation.
Dr. Colin Fricker is a board member of the SDWF. He runs a consulting
company that troubleshoots water quality problems for large and
small water treatment plants in Europe, North America, Africa, Australasia
and Latin America. He has a specific interest in the role of water
in dissemination of infectious disease.
The article was provided by Safe Drinking Water Foundation and
Canadian
Water Treatment magazine.
Go to www.safewater.org.
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