Advances of a doctoral research on "The value of plants in the strategies of development of constructed wetland for wastewater treatment – Biodiversity, technology, society, culture – the case of Pondicherry area"
Speaker : Mr Franz Fardin, PhD candidate, Department of Geography, University of Paris 8, in collaboration with the Department of Social Science, French Institute of Pondicherry.
Pondicherry area can be considered as a pilot zone in India, because of the multiplicity of ecotechnologies used to treat wastewater, especially constructed wetlands (CWS). In order to determine the environmental and socio-economic values of plants species, as well as other CWs resources, naturalist and social sciences methods have been undertaken. Plants species used in CWs are chosen according to the techniques. A comparative study of three sites has been undertaken, namely north Pondicherry sewage treatment plant (STP), Auroville, and the village of Alankuppam.
Among the 226 taxons used in CWs all over the world, 76 grow in India and 67 in Tamil Nadu and Pondicherry area. 13 are planted in Aurovillian CWs, and a single one in north Pondicherry STP. These plants are used as resources in only few different ways, whereas a wide range of utilizations could be developed. Furthermore, the local wetland species which represent a major economic role are not used in CWs. The same remark can be done about the uses of treated wastewater (reclaimed wastewater), which are limited to land irrigation. The quantity and the quality of wastewater are different for each site, characteristics which can be considered as a major factor in the choice of technique. While in Pondicherry urban zone the wastewater treatment is centralized, Auroville has chosen to decentralize it. In Alankuppam, wastewater still does not have a proper mode of management and treatment, however, one can consider that wastewater is managed and, in a part, treated, in a "traditional" way. Indeed, a test of physico-chemical parameters points out that the pond which receives domestic wastewater through the drainage network can be considered as a system of wastewater treatment.
However, even if the data analysis is still going on, the first results point out that the sanitary issues have to be taken into account. Indeed, the Alankuppam pond is used for aquaculture purposes. In Pondicherry STP, a part of treated wastewater irrigates agricultural lands, and Auroville develops the same utilization in some of its community. Because of a possible bioaccumulation and/or biomagnifications of some pollutants, more investigations have to be undertaken in order to determine the sanitary risk of such practices.
Organizers : Department of Social sciences, French Institute of Pondicherry; Department of Ecology, French Institute of Pondicherry; Department of Ecology and Environmental Sciences, Pondicherry University.