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THE OVERSEAS TERRITORIES UPGRADE THEIR SANITATION INFRASTRUCTURE

Le développement des infrastructures d’assainissement et d’approvisionnement en eau potable dans les départements d’outre-mer, réaffirmé comme une priorité par la dernière conférence environnementale, fait l’objet depuis 2008 d’un important soutien financier de l’Onema, ainsi que d’actions de recherche spécifiques. Bilan d’étape.


photo Bernard Le Guennec – Onema

Following three years of work, the new wastewater-treatment plant will be inaugurated in Cayenne in January. An active-sludge process will be used treat the wastewater of 60 000 population equivalents (PE), in compliance with the European urban-wastewater directive. The new plant is a key step in upgrading the sanitation infrastructure in Guiana, though it must be said that all overseas territories are lacking in this respect given that less than half of their overall population is currently served by wastewater-treatment plants up to European standards. The reasons for that situation are the difficult access, a hot and humid climate, narrow coastal strips subject to intense real-estate pressures, ageing infrastructure, etc. The project in Guiana was confirmed as a priority by the Environmental conference and has received continuous support from Onema, ranging from funding to on-site research.

108.5 million euros over five years

Between 2008 and 2013, no less than 103 projects (upgrading of plants and networks, supply of drinking water, etc.) were funded by Onema in the framework of its solidarity mission. Representing a total of 108.5 million euros, the various projects were split among the territories as follows, Reunion Island 27.6 million, Martinique 21.1 million, Guiana 20.6 million, Guadeloupe 19.2 million, Mayotte 17.6 million, New Caledonia 1.8 million and Wallis-et-Futuna 85 thousand. Examples? On Reunion Island, Onema contributed to the construction of five networks and ten treatment plants, including the Grand Prado plant in Saint-Denis, with a capacity of 160 000 PE. On Guadeloupe, 12 plants representing 10 000 PE each are currently under construction. On Mayotte, two plants are now in operation and one other plant plus five networks are under construction.

Full-scale studies on reed-bed filters

At the same time, Onema has managed a series of research projects to adapt sanitation techniques to the overseas environmental context. The projects deal notably with reed-bed filters, a technique developed by Irstea in continental France since the 1980s for small to mid-sized towns and suitable for overseas applications, and sludge treatments using drying beds planted with reeds. Full-scale, experimental facilities are now being monitored scientifically to check sizing criteria and determine precisely their capacity to reduce pollutants. That is the case on Mayotte, where since 2010 three facilities have been experimenting with different plants and layouts, e.g. reed-bed filters with vertical and horizontal flow, combined with a settling tank/digester or with a baffled reactor, etc. In Guiana, two treatment plants with vertical-flow reed-bed filters, representing a total of 780 PE, have also been monitored since 2010 and 2012. Finally, starting in 2014, the Attentive study will look at adapting the technique to two treatment plants on Martinique and to a third on Guadeloupe.

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