Quantification of aquatic nano particles after, different steps of Bodensee water purification with laser-induced breakdown detection (LIBD)

The laser-induced breakdown detection (LIBD) is a very sensitive method for the direct detection of colloids based on the plasma generation on single particles by a focused, pulsed laser beam and the detection of the produced shock wave or plasma light emission. For the determination of colloid size s the light emission of single plasmas is detected by a microscope CCD-came ra system. With known mean particle diameter and breakdown probability the particle concentration can be calculated. The application of the LIBD to mo nitor the change of colloid concentration and size during the purification steps of drinking water at the Bodensee (Lake Constance, Germany) water pur ification plant is shown. The breakdown probability, correlating to colloid number density, decreases with every purification step. By addition of FeC l3 as a precipitating agent and with an additional filtration step, not onl y suspended matter, but also colloids are effectively removed. After this p rocess a remaining particle concentration of 50 ng/L and a mean particle di ameter of 27 nm are found.