Utilisation Eaux Usées
10/07/2012 3 min

Reuse of treated wastewater: ANSES supplements its previous studies

With a view to conserving water resources, the reuse of treated wastewater (RTWW) for crop irrigation or green space watering is considered an interesting alternative solution. In the wake of expertise work on the risks of exposure by the oral route, ANSES has just published an assessment of risks due to exposure by the respiratory and cutaneomucosal routes. These recommendations aim to limit exposure by these routes as much as possible.

Employed in certain countries where water resources are scarce (especially in North Africa, Israel, Australia and the United States), the reuse of wastewater is a technique which is considered in France to be an interesting alternative for crop irrigation and green space watering. This practice makes it possible to conserve water resources, especially when climatic conditions are unfavourable (long periods of drought) or in areas where water resources are not available for all the required uses.

However, even when treated in a wastewater treatment plant, urban wastewater contains various pathogenic micro-organisms and potentially toxic organic matter and mineral substances. The conditions for reuse of treated wastewater for crop irrigation and green space watering must therefore be regulated by law in order to prevent the potential health risks of these practices.

Three stages of expertise

In 1991, a structural proposal was made by the Conseil supérieur d’hygiène publique de France (French High Council for Public Hygiene - CSHPF). Based on this, a regulatory project was drafted by the public authorities and submitted to AFSSA (French Food Safety Agency) for delivery of an opinion on it. In 2008, the Agency (1) issued an initial opinion

regarding the health risks for humans and animals of oral route exposure to treated wastewater used for agricultural irrigation or watering.

In 2010, AFSSA completed its analysis with an assessment of the risks of reusing a specific type of wastewater, effluents from animal by-product processing plants, for the irrigation of crops for human or animal consumption (2).

Due to the possibility of exposure of residents, passers-by and workers providing watering services during treated wastewater reuse operations (spray watering of golf courses and green spaces and crop irrigation), AFSSET was asked in 2009 by the Ministries of Health and Ecology to supplement the previously-issued expert assessments by appraising the potential respiratory and\or cutaneomucosal route risks of this practice. The recently-issued expert report examines this topic.

Recommendations to minimise human exposure

The human health risks of treated wastewater spraying via inhalation and cutaneomucosal contact were evaluated by comparing the fate of the water during spraying, the chemical and microbiological composition of the treated wastewater used and the potential exposure of general and worker populations.

In the current state of knowledge, it is impossible to conclude that for the two exposure routes examined no chemical or microbiological risk for exposed populations exists with regard to the reuse of treated wastewater through spraying. Therefore, ANSES deems it necessary to minimize human exposure to treated wastewater as much as possible during spraying operations.

Consequently, ANSES proposes a set of recommendations regarding the qualities of treated wastewater, the regulation of treated wastewater reuse practices by spraying and the minimisation of human exposure of the populations concerned, including residents, passers-by and workers (golf course and green space watering and crop irrigation).

The aim of these recommendations is to supplement current regulations (3) on reuse of treated wastewater and to specify the regulatory framework for crop irrigation and golf course and green space watering by spraying.

Lastly, due to the identification of missing or incomplete data during the expert assessment, ANSES is issuing recommendations regarding studies and research which will enable it to provide a more detailed characterisation of the risks of this practice.

(1) AFSSA (2008). Reuse of treated wastewater for watering or irrigation. 69 p.
(2) AFSSA (2010). Opinion of the French Food Safety Agency on the risk assessment of effluents from processing plants of Category 1, 2 and 3 animal by-products intended to be reused for the irrigation of food and feed crops. 34 p.
(3) Official Journal of the French Republic (2010). Ministerial order of 2 August 2010 regarding use of treated urban wastewater for crop or green space irrigation – NOR : SASP1013629A.