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 Mic roscopy (LM), Scanning Election Microscopy (SEM), Transmission Electro n Microscopy (TEM) and Atomic Force Microscopy (AFM). The use of a mic roscope 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 involve s cryogenic freezing of the sample, before observation in the SEM, lar ger (1-100 mu m) flee particles could be imaged without the loss of st ructural information normally caused by drying the sample; Damage caus ed by drying was not apparent with the TEM technique used. It was show n that the various microscope techniques produced compatible results, together covering a wide size range (10 nm-5mm). This indicates that m ajor artefact formation due to sample preparation is unlikely. It was furthermore shown that when a micro-scale continuous flow system was u sed the reproducibility of the floc structure observed increased. (C) 1997 IAWQ. Published by Elsevier Science Ltd.