CHARACTERIZATION AND REMOVAL OF HUMIC SUBSTANCES IN ULTRA-FILTRATION AND NANOFILTRATION

Sixty percent of the Finnish lakes can be described as humic waters. H umic-free water is required in industry; for instance, in the paper ma king process the brightness may decrease because of humic water. One a im of this investigation was to study the removal of humic substances from different waters with ultrafiltration (UF) and nanofiltration (NF ) using salts and retention aids as pretreatments. The other aim was t o characterize humic acids with different methods. In both UF and NF o f moorland water, retention was good without any pretreatment, but a s mall positive effect was obtained with AlCl3, NaCl, KCl and FeCl3. Ret ention aids did not improve the retention, but the cationic ones were affected slightly positively. In NF a higher pressure evidently improv ed retention. In every case pH had a great influence because at a low pH the structure of humic acid is more compact and no fouling occurs. Humic acid was analyzed using GOD, TOC, UV/VIS, SEM-EDAX, FTIR and zet a potential methods. Adsorption of humic acid was tested with polymer films using contact angle measurements and also with active carbon and carrot adsorbents. Adsorption was strongest at pH 3 in every trial an d active carbon adsorbed humic acid much more than carrot adsorbents.