EFFECTS OF ADSORBED ORGANIC-MATTER ON SIZE, STRUCTURE AND FILTERABILITY OF IRON OXYHYDROXIDE FLOCS

In this study, the effects of adsorbed fulvic acid, a naturally occurr ing organic acid, on the aggregation and filtration of hematite partic les are investigated. The study of aggregate structure shows that the fractal dimensions of hematite aggregates which are partially coated w ith fulvic acid molecules are higher than those obtained with no adsor bed fulvic acid. The high fractal dimensions are, due to restructuring within the aggregates, which only occurred at low coverage by the org anic acid. In the filtration experiments, high clean filter efficiency was obtained for particles with the net charge opposite to the filter media. During ripening period, however, the particle sizes played a m ore important role than the surface charges. Particles of a micron siz e seemed to have less capture efficiency during this period, since the y are controlled neither by diffusion nor interception.