marginalized communities living around agricultural and aquaculture regions where untreated wastewater is used are also exposed to risks. The impact on health varies depending of location and type of contaminant, however bacteria and in- testinal worm infestations have been shown to pose the great- est risk (Drechsel et al, 2010).

In addition farmers often lack knowledge of water quality, in- cluding nutrient content, so they combine nutrient-rich irriga- tion water with chemical fertilizers. This makes agriculture a source of pollution rather than a step in environmental sanita- tion (Evers et al, 2008).

Whilst some countries have national guidelines for the accept- able use of wastewater for irrigation, many do not. The Guide- lines on the Safe Use of Wastewater, Excreta and Greywater in Agriculture and Aquaculture (WHO/FAO, 2006a) provide a comprehensive framework for risk assessment and manage- ment that can be applied at different levels and in a range of socio-economic circumstances. The main characteristics of the approach proposed by the guidelines are: •

the establishment of health-based targets, which allow local authorities to set risk levels that can be handled under the local socio-economic conditions and with the capacities avail- able in a country;

• •

•

the application of quantitative microbial risk assessment (for pathogenic viruses and bacteria) as a cost-effective way of as- sessing health risks;

the identification of all risk points along the chain of events from the origin of the wastewater to the consumption of the produce (e.g. the farm-to-fork approach of the HAPPC meth- od in food safety);

the design of a combination of health risk management mea- sures, to be applied along the same chain of events, with the aim of ensuring health protection as a result of incremental risk reduction. Such interventions can include partial waste- water treatment;

•

monitoring at all stages to ensure measures are effective, ap- plied correctly and lead to the desired impact on health.

In many countries the capacity to apply these guidelines and best practice recommendations is insufficient and needs sub- stantial strengthening. Yet, this incremental approach to waste- water management is highly compatible with the concept of the sanitation ladder. Both improvements in sanitation and

improvements in wastewater use are mutually re-enforcing ac- tions in support of optimizing wastewater management from the public health perspective (WHO/FAO, 2006).

Optimizing agricultural practices including irrigation tech- niques, fertilization practices, and reducing water evaporation and crop selection can save significant amounts of water with a subsequent reduction in wastewater production. In a similar way, opportunities for appropriate use of wastewater, as well as improvement in fertilization and animal production should continue to be explored. Development and modification of ag- ricultural tools and practices should be promoted as one facet in addressing the management of wastewater.

Sectorally appropriate solutions may however not be benefi- cial across the board. Reuse of wastewater may, for example increase productivity and yield without the need for additional water sources and artificial fertilizers, but carry risks for con- sumer health – creating costs further down the chain. This again highlights the cross-cutting nature of wastewater man- agement that requires collaboration and dialogue between partners who may not usually talk, for example farmers, pub- lic health officials, municipal and waste managers, planners and developers.

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