The structure of hydrous flocs prepared by batch and continuous flow water treatment systems and obtained by optical, electron and atomic force microscopy

This paper concerns the imaging of hydrous floc particles by Light Microscopy (LM), Scanning Election Microscopy (SEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The use of a microscope technique means that visual structural information is obtained, in contrast with other techniques measuring particle characteristics. It was found that when a preparation technique was used that involves cryogenic freezing of the sample, before observation in the SEM, larger (1-100 mu m) flee particles could be imaged without the loss of structural information normally caused by drying the sample; Damage caused by drying was not apparent with the TEM technique used. It was shown that the various microscope techniques produced compatible results, together covering a wide size range (10 nm-5mm). This indicates that major artefact formation due to sample preparation is unlikely. It was furthermore shown that when a micro-scale continuous flow system was used the reproducibility of the floc structure observed increased. (C) 1997 IAWQ. Published by Elsevier Science Ltd.