Onema

Home - Mission - A Four Part Strategy

 

 

  • Developing new systems to recover and reuse rainwater

    What are the current practices and available techniques worldwide for the management of rainwater in cities?
    The International office for water (IOWater) drafted a report for Onema on the subject.
    Four approaches with different goals for rainwater management stood out, namely
    1- management of water and pollutant flows,
    2- landscape improvement of urban areas,
    3- the resource itself,
    4- temperature regulation in collective housing and in the city itself. A panorama of current regulations and aids in the Netherlands and Germany concerning the use of rainwater in homes was presented in a second study. It proposes changes taking into account the experience acquired by these two countries that have innovated in the use of rainwater. In the Netherlands, the ministry ran a study on six test projects using water for washing in homes.

Reusing treated wastewater

Reuse of treated wastewater is a common practice worldwide, but very limited in France. It could be a means to reduce draw-offs and be used in particular for irrigation of crops and watering of parks and recreational installations in cities.

"The reuse of treated wastewater raises the issue of health risks and the treatment required to eliminate any pollutants and contaminants", according to Stéphane Garnaud. "We financed a study by Cemagref that identified the components creating the greatest risks for health and the environment".

They are notably micro-organisms, organic (detergents, pesticides, solvents) and inorganic (trace metals) micro-pollutants, and dissolved salts. Thanks to this study, the treatment techniques capable of reducing or even eliminating risks for human health and the environment were identified. For example, disinfection techniques are often a means to avoid risks due to micro-organisms and membrane technologies are effective against dissolved and/or residual pollutions. In France, waste-stabilisation ponds, landfills using membranes and activated-sludge installations coupled with disinfection, filtering and tertiary stabilisation systems would appear to be the technologies best suited to the required level of quality.


Though hydric conditions in France do not currently justify radical changes in management concerning reuse of treated wastewater in the water cycle, it would nonetheless certainly be wise to study innovative projects in the field. That is why Onema supports the REGAL project (Véolia, BRGM, CNRS and two mid-sized companies), which is studying artificial recharge and active management of coastal aquifers, notably using pre-treated urban wastewater. Onema funds two aspects, i.e. work to gain knowledge on the sustainability of a system using treated wastewater and the socio-economic and environmental evaluation of obstacles to social acceptability of integrated measures for active management.

Contact: stephane.garnaud@onema.fr

A panorama of examples in reusing treated wastewater in Mediterranean countries
Reuse of wastewater is common in Mediterranean countries, where water resources are particularly limited. In its efforts to support water policies, Onema commissioned a study on the subject. In Jordan, a country confronted with a population explosion, reuse is a fundamental factor in the national water policy, in terms of protection of public health and of the environment, and for the agricultural sector. Treated wastewater represents 10% of all water resources and should rise to 19% by 2020. Tunisia has progressively set up a system for the reuse of treated wastewater, essentially for agriculture. The program combines a reinforcement of urban sanitation facilities, integration of reuse of treated wastewater in the national strategy for management of water resources, control over health and environmental impacts, research and the establishment of regulations and standards. This approach has, however, encountered certain limits due to climate conditions. In Spain, on Majorca, the reuse of treated wastewater has made it possible, for example, to recover farm land that had been lost for cultivation, to limit the salinity of wells for drinking water, to reduce the cost of treatments for drinking water and to develop parks in cities without reducing the availability of drinking water.