Tracing the influx of sewage from a leaky sewer into a very thin and fast-flowing aquifer

Water parcels of different chemical composition were detected in a 1 m thick and up to 17 m/d fast-flowing groundwater system using a multi-layer sampler based on the dialysis cell technique. The parcels result from the infiltration of sewage effluents and also probably due to the leaching of sewage sludge from the agricultural land surface. Samples obtained at depth intervals as small as 3 cm in a natural gradient flow field revealed relative high concentrations and variable vertical profiles of Na⁺, NO₃^-, HCO₃^-, SO₄^2- and DOC 9 m downstream of the infiltration pipe. A pump used to obtain water samples during a 2 year period, in the same research field, proved to be an inadequate sampling technique to trace the movement of sewage effluent.