Présentations Colloques

    Oral Presentation
    Session 7.03: Agricultural and sanitation contaminants and implications for water services and health
    Seidl Martin
    Transfert of Pollutants from an on-site waste water treatment to the groundwater - a case study
    On site waste water treatment (OWWT) is implemented where the population density is too low to make a collective disposal affordable. In France the OWWT concerns 20% of the population and is submitted to a recent regulation in terms of means. Usually household water is settled and digested in a septic tank, followed by an aerobic sand filter. If the filter is not drained, the soil is acting as post treatment. As the effluent will reach the ground water it's necessary to evaluate how the OWWT and the underlying soil mitigate the pollution.**In order to study the impact of an OWWT, a real scale system of one family in a small rural community south-east of Paris, was followed during one and half year. The system, composed of a septic tank and a 25 mC non-drained sand-filter, was equipped during the construction for quantitative and qualitative hydrological monitoring. Volumetric water content, water tension and quality of interstitial liquid were followed at several depths, ranging from 70 to 160 cm, inside the filter and the underlying soil. In parallel the household water consumption was recorded, as well local precipitation, evapotranspiration and ground water level. Hydrological data were collected at 10-min interval from March 2012 to June 2013, together with monthly water samples. The water quality parameters followed were nutrients, carbon, parabens and triclosan. **The hydrological parameters made it possible to follow specific hydric fluxes like morning shower across the treatment system towards the groundwater. The analysis of specific household tracers nitrogen and parabens allowed to estimate their elimination rate and the residual flux towards groundwater. The presentation will detail the impact of precipitation, groundwater level etc. on the elimination rate and the pollutant transfer, as well the limits of the experimental set-up used. The results show that domestic health care products, frequently considered as risk for the surface water quality, should also be considered as threat for areas with OWWT and vulnerable ground water resources.


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