Évolution de l'impact environnemental de lixiviats d'ordures ménagères sur les eaux superficielles et souterraines, approche hydrobiologique et hydrogéologique. Site d'étude : décharge d'Étueffont (Territoire de Belfort – France)

摘要

A multi approach study, using geophysics, tracing tests, water balance, geology, hydrogeology and statistics analyses on physico-chemicals data, shows (1) leachate's infiltrations between 31 and 43% accross a shaly natural interface and superior to 45% accross an artificial geomembrane interface and (2) a localized physico-chemical impact on the existing piezometer network. Collected leachates are treated by a natural lagooning system. After the suspension of waste deposits, biodegradation activity reduces and generates a decrease in leachates noxiousness, thus changing the lagoons hydrobiologic mechanisms. We note a diversification of all the microbial loop components allowing the re-use of the organic material. The new trophic pyramid organization allowed to attain a viable ecosystem for fish fauna, in the last lagoon. Treated leachates undergo a second purification by natural attenuation in the receiving stream. A bacteriological approach on leachates, lagoons and groundwater quality allowed to assess presence and survival of faecal bacteria in these various environments. This landfill doesn't represent an important source of faecal bacteria. This studied site, where landfill's leachates and septic tank sewage are mixed together, confirms the use of Escherichia coli and Entoroccocus as markers of recent faecal contaminations. The shaly aquifer resembles more in a fractured area than in an impervious zone, with a preferential circulation along cracks and fractures which doesn't assure the natural filtration and lead to a vulnerable aquifer to bacterial contaminations.