Environmental Engineering Reference
In-Depth Information
hazardous substances by the Directive 2000/60/EC (Council of the European Union 2000).
They are also included in Decision 2455/2001/EC, which establishes a list of priority sub-
stances in the field of water policy (Council of the European Union 2001).
9.4 Removal of Pesticide Residues During Drinking Water Production
Drinking water comes from two main sources: surface water and groundwater. Profound
groundwater from restrained aquifers is usually free of direct contamination with pesti-
cides. However, shallow aquifers are accessible to contamination from agricultural wastes.
The treatment used to produce drinking water from surface water and groundwater must
guarantee the removal of pesticides or at least reduce their concentration below the estab-
lished limits. Pesticide detection rates in treated groundwater were generally much lower
than detection rates in treated surface water, but the gap between them steadily decreased
in the last 20 years (McInnis 2010).
Intensive studies have been carried out in an attempt to determine what levels of pes-
ticides are acceptable in water supplies. The first effort was made in 1969 when permis-
sible limits for 10 pesticides in public water supplies in the United States were established
and used as guidelines (Edwards 1973). Since then, standards for drinking water have
been revised several times. As an example, the recommended maximum value for aldrin
in drinking water has been reduced, through a number of revisions during the last 50
years, from 17 μg/L (Edwards 1973) to 0.03 μg/L (World Health Organization 2008). A lot
of progress in pesticide legislative has been made but for most pesticides, drinking water
standards have yet to be set.
The US EPA has the authority to develop nationwide standards, and some of the states are
setting local standards as well. Organic pesticides are covered by a guideline limiting the
concentration of any single organic chemical to no more than 50 mg/L and the combined
concentration of all organics found to no higher than 100 mg/L. Under the Safe Drinking
Water Act (US EPA 1996), EPA establishes maximum contaminant levels (MCLs) for pesticides
in water delivered to users of a public water system. However, drinking water standards for
all pesticides found in water have not been established. EPA has established MCLs for only 21
pesticides (
Table 9.5
), 10 of which are no longer approved for use (Hetrick et al. 2000).
In the EU, the so-called Drinking Water Directive, the Directive 98/83/EC (Council of
the European Union 1998), aims to protect human health from the adverse effects of
contamination of water intended for human consumption by ensuring that it is “whole-
some and clean.” This Directive has set limits for pesticides in water intended for human
consumption as 0.1 µg/L for individual pesticides and 0.5 µg/L for the sum of all pesticides.
Moreover, depending on the method used for water treatment, water intended for drinking
water production is also subjected to a maximum limit that varies between 1 and 5 μg/L for
total pesticides (Council of the European Communities 1975).
The complicating factors in setting standards for the individual chemicals is that it is
unknown how a given compound might interact with other chemicals to affect human
health. Health studies have been conducted on people drinking contaminated water sup-
plies, but these studies are limited by the fact that many health problems are difficult to
trace to a specific cause as well as by the fact that the number of such studies is limited.
A survey conducted across India definitely pointed toward high pesticide contamina-
tion (DDT, β-endosulfan, α-endosulfan, and lindane) in drinking water (Shukla et al. 2006).
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