Environmental Engineering Reference
In-Depth Information
standards in this revised edition raised criticism from different sides. Some
researchers considered the new guidelines too lenient (Shelef 1991 , quoted in
Ensink 2006 ) while others criticized them for being too strict (Faruqui et al. 2004 ;
Ensink 2006 ).
Some critics pointed out that a strong focus on microbiological risk implies that
wastewater has to be treated before it can be used for irrigation. This does not take
into account that from a health perspective, it might be more effective to invest
financial resources, in a developing country context, into measures like
improved water supply or health education (cf. Drechsel et al. 2002 ; Faruqui et al.
2004 ). Moreover, the gap between the
apparently inappropriate target of the WHO
standards and existing water quality
(Cornish and Kielen 2004 : 1) might lead urban
planners and politicians either to condemn the practice of wastewater irrigation or to
ignore it (Drechsel et al. 2002 ; Carr 2005 ). What is more, strict requirements for
wastewater irrigation might lead to the paradoxical situation where highly polluted
river water is used instead of better-quality wastewater. Under such circumstances,
the health risks for producers and consumers would be increased by adherence to
the guidelines (Carr et al. 2004b ).
The third edition of the WHO Guidelines from 2006 offers a somewhat new
perspective on wastewater irrigation. Although it still has a strong focus on
microbiological indicators (and some of the criticism mentioned above still seems
valid), it stresses the importance of a holistic approach to risk in accordance with
the Stockholm Framework.
The Stockholm Framework refers to the concept of ' relative risk ' , which requires that one
considers all possible sources of risk and exposure when setting guidelines. These would
include risks related to poor water supply, hygiene and sanitation, and other sources of (e.g.
post-harvest) food contamination. For example, if contaminated drinking water or lack of
toilets is causing high background levels of illness in the population, then a costly treatment
of wastewater for crop application is not likely to improve public health, and should not be
the priority investment in countries where funds are limited. Decision-makers are thus
encouraged to look at the larger nexus of water-sanitation and health and their intercon-
nections (IWMI 2006 : 2).
In other words, there are different entry points for the task of reducing health
risks related to wastewater irrigation besides treatment. For instance, improving
hygiene at markets can be a better way to protect public health than wastewater
treatment (Ensink et al. 2007 ). Thus, broadening the perspective from the farmer/
producer level to include the market and consumer levels is important.
One point for which the 2006 WHO guidelines have been criticized is the
prominent role that they attribute to technical wastewater treatment.
[A]ll different risk reduction scenarios that are presented as a matter of example, include
wastewater treatment technology. This seems to imply that municipalities, where untreated
wastewater is currently being used, have only two alternatives to protect public health: the
removal of farmers from their land, or to turn a blind eye to the practice (Ensink and van der
Hoek 2007 : 576).
Thus, on the one hand, standards on the quality of irrigation water have con-
tinually been modi
ed to take results of new research and a widening of the
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