ABSTRACT
Many substances show a strong tendency to sorb readily to the solid phase of an aquifer. Commonly they are regarded to be immobile or retarded. However, colloidal and suspended microparticles may be mobile also in the subsurface environment. Thus, microparticles should be taken into account to predict contaminant transport. A particle load at the “Hengsen-Island” test site (Dortmund, Germany) of less than 20 µg/l inorganic microparticles was observed, compared to 1.2–3.6 mg/l of macromolecular organic carbon. These values can increase by several orders of magnitude at the bankfiltration site during hydraulic mobilisation. No or only little mobilisation was observed at the slow sand filter site, where hydraulic changes are frequent due to the operating water works. There was a very good correlation between data from particle analysis and microbiology.
